Delphinus Linnaeus 1758

Els dofins comuns (Delphinus) són un gènere de cetacis que conté dues espècies de dofí. Abans de mitjans de la dècada del 1990, la majoria de taxonomistes només en reconeixien una espècie, el dofí comú (Delphins delphis). Els cetòlegs actuals solen reconèixer dues espècies: el dofí comú de musell curt, que conserva el nom sistemàtic Delphinus delphis i el dofí comú de musell llarg, Delphinus capensis. Malgrat el seu nom, el dofí comú no és el dofí de la imaginació popular; aquesta distinció pertany al dofí mular, gràcies principalment al seu ús estès en parcs marins, així com la seva aparició a la sèrie de televisió Flipper.

Referències

A Wikimedia Commons hi ha contingut multimèdia relatiu a: Dofí comú

De almindelige delfiner (Delphinus) er en slægt i familien delfiner med to arter, almindelig delfin og langnæbbet almindelig delfin.

Taksonomi

Før midten af 1990'erne accepterede de fleste taksonomer kun en art i slægten, almindelig delfin (Delphinus delphis), men man regner nu med to arter – almindelig delfin (også kaldet kortnæbbet almindelig delfin), der beholder det systematiske navn Delphinus delphis og langnæbbet almindelig delfin (D. capensis). På trods af sit navn er det ikke den almindelige delfin, der er den mest velkendte delfin. Det er derimod øresvinet, primært på grund af tv-serien Flipper og dens optræden i delfinarier.

Variation i slægten

På trods af den historiske praksis med at samle hele Delphinus-slægten i en enkelt art, udviser disse enormt vidtudbredte delfiner en stor variation i størrelse, form og farve. I de sidste par årtier er over 20 forskellige arter i slægten blevet foreslået. Forskere i 1960'erne konkluderede, at der var to arter – den kortnæbbede og den langnæbbede. Deres konklusion blev senere bekræftet af dybdegående genetiske undersøgelser i 1990'erne. Dette studie kom også frem til, at en tredje art (D. tropicalis, ofte kaldet arabisk almindelig delfin) muligvis eksisterede. Den karakteriseres ved et endnu tyndere og længere næb end den langnæbbede art. De nuværende taksonomiske værker betragter den dog som en regional variation.

Udbredelse

De almindelige delfiner er vidt udbredt i tempererede, subtropiske og tropiske vande i hele verden, i et bånd, der strækker sig fra 40 grader syd, til 50 grader nord. Variationen i udseendet i de forskellige grupper antyder, at grupperne ikke blandes. Arten foretrækker typisk lukkede vandområder, som Rødehavet eller Middelhavet. Dybt vand foretrækkes dog frem for lavt vand. Nogle flokke er lokale for ét område, mens andre bevæger sig mellem flere områder. Den foretrukne vandoverfladetemperatur er 10-28° Celsius. Den totale bestandsstørrelse er ukendt, men skal tælles i millioner.

Opførsel

Almindelige delfiner lever i grupper af 10-50, og samles ofte i supergrupper på mellem 100 og 2000 individer. Disse grupper er meget aktive – gruppen stiger ofte op til overfladen, hopper og splasker sammen.

Delfiner er set i blandede flokke med andre delfiner, eller flokke af store hvaler. En interessant teori går på, at delfinernes 'bov-ridning' på store hvaler var grundlaget for, at de nu ofte rider på skibes bovbølger.

Drægtighedsperioden er på ca. 11 måneder, og kalven bliver hos moderen i et til tre år. Kønsmodenhed sker efter fem år, og varer i tyve til femogtyve år. Disse tal varierer dog betydeligt blandt de enkelte bestande.

Trusler

Almindelige delfiner står over for en række trusler fra mennesker. Bestande er blevet jaget ud for Perus kyst, for mad og til hajmadding. I de fleste andre områder er delfinerne ikke blevet jaget direkte. Mange tusinde individer er dog blevet fanget af industrielle trawlere. Almindelige delfiner var vidt udbredt i det vestlige Middelhav indtil 1960'erne, men ses sjældent i dag. Grunden til det er ikke identificeret, men menes at være den store menneskelige aktivitet i området.

Kilder

• Rice, Dale W. (1998). Marine mammals of the world: systematics and distribution. Society of Marine Mammalogy Special Publication Number 4. 231 pp.
• National Audubon Society Guide to Marine Mammals of the World ISBN 0-375-41141-0
• Encyclopedia of Marine Mammals ISBN 0-12-551340-2
• Whales, Dolphins and Porpoises, Mark Carwardine, ISBN 0-7513-2781-6

Delphinus ist eine Gattung der Delfine (Delphinidae). Zu der Gattung gehören zwei sehr ähnliche Arten, der Gemeine Delfin (Delphinus delphis) und der Langschnäuzige Gemeine Delfin (Delphinus capensis). Der Gemeine Delfin bewohnt vor allem die küstenferne Hochsee und kommt auch in der Nordsee und im Mittelmeer vor, nicht jedoch im Indischen Ozean. Der Langschnäuzige Gemeine Delfin ist dagegen vor allem in tropischen Küstengewässern über dem Kontinentalschelf anzutreffen.

Der Gemeine Delfin ist eine hochvariable Art und der schon 1828 beschriebene Langschnäuzige Gemeine Delfin wurde ursprünglich dem Gemeinen Delfin zugerechnet. Erst in den 1990er Jahren wurde die Art anerkannt.

Merkmale

Delphinus-Arten werden maximal 2,5 bis 2,70 Meter lang, Weibchen bleiben in der Regel etwas kleiner. Im Unterschied zu den vielen anderen Delfinen sind die Delphinus-Arten sehr auffällig gezeichnet. Sie besitzen an den Körperseiten ein charakteristisches „Stundenglasmuster“ mit einem ockerfarbenen großen Brust- und Seitenfleck auf dem Rumpf, der durch eine V-förmige Ausbuchtung der dunklen Rückenfarbe unterhalb der Finne von der hellgrauen Färbung der hinteren Seiten abgeschnürt wird. Ein weiteres für die Gattung typisches Merkmal ist ein dunkler Streifen, der sich auf jeder Unterkieferseite von deren Spitze bis zum Ansatz der dunklen Flipper erstreckt. Die Melone ist bei beiden Arten gut ausgeprägt und führt zum typischen Kopfprofil.

Lebensweise

Während der Gemeine Delfin die Hochsee bevorzugt, lebt der Langschnäuzige Gemeine Delfin küstennah in den Tropen. Beide Arten leben in großen Schulen, sind sehr lebhaft, schnelle Schwimmer und zeigen oft Sprünge, manchmal Salti und „reiten“ in den Bugwellen von Schiffen. Sie ernähren sich von Schwarmfischen, Kalmaren und Krill. Das einzelne Junge wird nach einer Tragzeit von 10 bis 11 Monaten geboren.

Literatur

• Hadoram Shirihai: Meeressäuger. Alle 129 Arten weltweit. Illustriert von Brett Jarett. Franckh-Kosmos Verlags GmbH, Stuttgart 2008, ISBN 978-3-440-11277-9.

Weblinks

The common dolphin (Delphinus delphis) is the most abundant cetacean in the world, with a global population of about six million.^[3] Despite this fact and its vernacular name, the common dolphin is not thought of as the archetypal dolphin, with that distinction belonging to the bottlenose dolphin due to its popular appearances in aquaria and the media. However, the common dolphin is often depicted in Ancient Greek and Roman art and culture, most notably in a mural painted by the Greek Minoan civilization.^[4]

It is presently the only member of the genus Delphinus. The common dolphin belongs to the subfamily Delphininae, making this dolphin closely related to the three different species of bottlenose dolphins, humpback dolphins, striped dolphins, spinner dolphins, clymene dolphin, spotted dolphins, fraser's dolphin and the tucuxi and guiana dolphin.^[5] The common dolphin was originally categorized into two different species (now thought to be ecotypes), the short-beaked common dolphin and the long-beaked common dolphin. However, recent evidence has shown that many populations of long-beaked common dolphins around the world are not closely related to one another and are often derived from a short-beaked ancestor and do not always share common derived characteristics. For this reason, they are no longer considered different species.^[6]

Physical characteristics

Common dolphin are medium-sized dolphins; adults range between 1.9 and 2.5 m (6.2 and 8.2 ft) long, and can weigh between 80–235 kg (176–518 lb), although the range between 80–150 kg (180–330 lb) is more common.^[7] Males are generally longer and heavier.^[7] The color pattern on the body is unusual. The back is dark and the belly is white, while on each side is an hourglass pattern colored light grey, yellow, or gold in front and dirty grey in back.^[8] They have long, thin rostra with up to 50–60 small, sharp, interlocking teeth on each side of each jaw.^[9]

Taxonomy

Despite the historic practice of lumping the entire genus Delphinus into a single species, these widely distributed dolphins exhibit a wide variety of sizes, shapes and colors. Indeed, over the past few decades, over 20 distinct species in the genus have been proposed. Scientists in California in the 1960s concluded there were two species — the long-beaked and short-beaked. The long-beaked common dolphin was thought to have a disjointed range in coastal areas in tropical and warmer temperate oceans. The range included parts of western and southern Africa, much of western South America, central California to central Mexico, coastal Peru, areas around Japan, Korea and Taiwan, and possibly near Oman.^[10] Vagrants have been recorded as far north as Vancouver Island.

This analysis was seemingly confirmed by a more in-depth genetic study in the 1990s. This study also suggested a third species (D. tropicalis, common name usually Arabian common dolphin or Indo-Pacific common dolphin), characterized by an extremely long and thin beak and found in the Red Sea and Indian Ocean, might be distinguished from the long-beaked species. The current standard taxonomic works recognize this as a subspecies of D. delphis rather than a separate species.

Recent evidence has demonstrated that different populations of long-beaked common dolphins around the world are not closely related to one another and are often derived from a short-beaked ancestor (as well as not sharing common derived characters). Therefore, long-beaked and short-beaked common dolphins are now listed as the same species under the scientific name of Delphinus delphis.^[11][12][13] Currently, the common dolphin is divided into four subspecies:^[11][14]

• D. d. delphis, the nominate subspecies
• D. d. bairdii, the Eastern North Pacific long-beaked common dolphin
• D. d. ponticus, the Black Sea common dolphin
• D. d. tropicalis, the Indo-Pacific common dolphin

Fossil record

Many extinct cetacean species were once lumped into Delphinus, but have since been placed in other genera. In the late 19th century several fossil species were described, including taxa: Delphinus baltringii, Delphinus delannoy and Delphinus domeykoi. However, these species are no longer considered valid.^[15] Another species known as Delphinus brevidens was reassigned to the genus Stereodelphis which is now generally considered synonymous with Squalodon.^[16]

Natural history

Common dolphins live in both warm-temperate and tropical waters ranging from 40–60°N to 50°S. Long-beaked common dolphins mostly inhabit shallow, warm coastal water.^[10] Short-beaked common dolphins are common "along shelf edges and in areas with sharp bottom relief such as seamounts and escarpments".^[8] Common dolphins have a varied diet consisting of many species of fish and squid. This includes both mesopelagic species and epipelagic schooling species. They have been recorded to make dives up to 200 metres (660 ft) deep.

Common dolphins are a widely distributed species. They can be found around the world in both offshore and coastal waters. In the Northwest Atlantic, they can be found from Cape Hatteras North Carolina, to Newfoundland and are strongly associated with the Gulf Stream. Dolphins in this region can often be found in areas that have certain geological factors like underwater canyons and ridges because this is where up-welling occurs which result in greater nutrients. In the Eastern Pacific, common dolphins are found along the coast of California and are associated with the California current. Short-beaked Common dolphins can also be found in Europe, particularly the Scotian shelf, the Black Sea and the Mediterranean. In the Southern Hemisphere, they are abundant in the southwestern Pacific, around New Zealand and southern Australia. They are generally a pelagic species that are often found in waters 650–6,500 feet deep, with the short-beaked type preferring deeper waters than the long-beaked type^[17] Temperature also plays a large role in the congregation of dolphins. For example, in the Western North Atlantic, almost all sightings of Common dolphins took place in waters from 16 to 20 °C. However, there were common dolphin sightings in waters as low as 5 °C.^[17]

Common dolphins can live in aggregations of hundreds or even thousands of dolphins.^[10] Common dolphins are often seen in groups numbering several hundred individuals (with subgroups consisting of 20-30 individuals). Occasionally, different groups will come together to form mega-pods which can consist of over 10,000 dolphins. Genetic studies in the Northeast Atlantic suggest that common dolphin pods generally do not consist of close kin, but rather of members that are not closely related. Unlike many delphinids, common dolphins do not live in a matriarchal society. That being said, closely related individuals are usually found in similar geographical locations fairly consistently, providing evidence that this species displays site fidelity (at least in the Northeastern Atlantic). Male common dolphins display greater site fidelity in relation to their kin than females.^[18] Common dolphin pod structure often consists of nursery pods (which includes females and calves), bachelor pods (consisting of all males) and mixed groups of males and females, including sub-adults and calves. Genetic evidence seems to indicate that common dolphins live in fission-fusion societies, where dolphins form pods that are not necessarily stable and do not necessarily consist of related individuals. It is not known if common dolphins form lifelong bonds with other individuals like the long-term male alliances seen in bottlenose dolphins.^[19]

There is some evidence that common dolphins use signature whistles, similar to that of the bottlenose dolphin. These whistles are believed to serve as an acoustic label, and provide identification information similar to that of a name. It takes approximately 1 year for a calf to learn its signature whistle after which it remains stable for the rest of a dolphin's life. In South Africa, as many as 29 common dolphin signature whistle types were detected. However, it was difficult to determine if each dolphin had its own signature whistle due to the vast number of dolphins present (over 1,000) and anthropogenic background noise. Additionally, considering the vast number of dolphins present and taking into account their feeding and diving behavior, it appears that common dolphin signature whistles are also used for group cohesion. Another hypothesis for the function of signature whistles, is that they serve as a beacon for lost individuals.^[20]

Common dolphins sometimes associate with other dolphin species, such as pilot whales.^[10] In the Gulf of Corinth, common dolphins frequently display mixed species association, especially with striped and Rissos’ dolphins.^[21] Over one third of all dolphin sightings in the gulf consisted of mixed species associations that partially consisted of common dolphins. In mixed species associations, the ratio of striped to common dolphins ranged from 6-11:1. When Rissos’ dolphins were present (there would usually be only one or two individuals), it appeared that much of their scars were the result of interactions between striped and spinner dolphins. In much of the interactions, the Rissos’ dolphins would chase and herd the common dolphins toward the boat, while the common dolphins would try and swim under the Rissos’ dolphin. When groups of common and striped dolphins would charge at each other, the Rissos’ dolphin would chase the striped dolphins. Sometimes these interactions appeared to be playful, and at other times aggressive. Synchronized swimming and surfacing was commonly observed. These interactions take place in the deepest part of the Gulf, furthest from shore and usually consist of a total of 60 dolphins from all three species.

There have been confirmed cases of hybridization between striped and common dolphins in this region. There have been 15 cases of common dolphin and striped dolphin hybrids. Genetic and observational evidence has demonstrated that the hybrids are fertile and are capable of not only reproducing with other hybrids, but are capable of reproducing with each of the parent species.^[22] Striped dolphins have been known to mate with other dolphins, as the Clymene dolphin is the result of hybrid speciation between striped and spinner dolphins. However, this is unlikely to happen with common dolphins, as their population in the Gulf of Corinth is too low.^[23] Common dolphins and bottlenose dolphins have been known to interbreed in captivity. There is one confirmed case of a hybrid between a bottlenose and common dolphin in Southern Spain, an important feeding ground for both species. The mother was a female bottlenose dolphin (dubbed as Billie) who has spent 10 years within a common dolphin pod. Billie was observed assisting common calves reach the surface at three different intervals and would babysit the calves after the mother went through labor. The length of the calf was similar to a bottlenose dolphin calf, with the lateral stripes and coloration of a common dolphin. The calf was spotted with its mother, almost daily on dolphin watching tours among a nursery pod of common dolphins which also contained some immature striped dolphins. Sightings of the calf took place when temperatures were between 14 and 26 °C. The calf was mainly observed swimming in the echelon position (swimming alongside the mother). The calf was found rubbing its head on its mother, jumping backwards over its mother and flipper-to flipper, belly-to flipper and belly-to belly contact was observed.^[24] They have also been observed bow riding on baleen whales, and they also bow ride on boats.^[10] They are fast swimmers and breaching behavior and aerial acrobatics are common with this species.^[7] They are also known to display altruistic behaviors to support injured members.^[25][26]

The short-beaked common dolphin has a gestation period of 10 to 11 months.^[10] The newborn calf has a length of 70 to 100 centimetres (2.3 to 3.3 ft) and weighs about 10 kilograms (22 lb).^[7] For the Black Sea population, weaning occurs at between five and six months, but occurs later (up to about 19 months) in other areas.^[7][10] Typical interbirth interval ranges from one year for the Black Sea population to three years for eastern Pacific Ocean populations.^[10] Age of sexual maturity also varies by location, but can range between two and seven years for females and three and 12 years for males.^[7][10] No evidence exists of any major reproductive differences between the two species.^[8] In captivity, the long-beaked common dolphin has hybridized with the common bottlenose dolphin (Tursiops truncatus).^[10] One of the hybrids has been bred back to a bottlenose dolphin, demonstrating such hybrids are fertile.^[27]

Human interactions

Conservation

The common dolphin is probably the most abundant cetacean species on the planet, and the overall species is listed as Least Concern on the IUCN Red List,^[28] indicating that it is in no danger of extinction. Abundance has been estimated for most major portions of the species range in the Northern Hemisphere, but only for a few places in the Southern Hemisphere. In the Pacific Ocean, there are an estimated 1,428,000 off Japan and in the temperate central Pacific Ocean,^[29] 969,000 off the U.S. west coast (Carretta et al. 2019); and 2,963,000 in the eastern tropical Pacific.^[30] In the Atlantic Ocean, 70,000 are estimated for the western Atlantic Ocean (Waring et al. 2019); 467,000 for European waters;^[31] more than 19,400 for the Mediterranean Sea; and several tens of thousands for the Black Sea.^[32] In the southern part of the Indo-Pacific Ocean, there are an estimated 20,000-22,000 common dolphins in a small portion of southern Australia (Bilgmann et al. 2017), and 15,000-20,000 off southern Africa.^[33] There are no estimates for the population of dolphins in the northern Indian Ocean. Taken together, these estimates suggest that well over six million common dolphins inhabit the World's oceans.

Common dolphins face a mixture of threats due to human influence. Moderate levels of metal pollutants, which are thought to negatively impact dolphin health,^[34] have been measured in some populations.^[35] Populations have been hunted off the coast of Peru for use as food and shark bait. In most other areas, the dolphins have not been hunted directly. Several thousand individuals have been caught in industrial trawler nets throughout their range.

Bycatch is the main threat that common dolphins face today. Short-beaked common dolphins are taken as cetacean bycatch the most in all of Europe, given that they are the most abundant dolphin in the Eastern Atlantic. About 1000 short-beaked common dolphins are bycaught in the North Atlantic each year by either tuna drift, trawling and gillnetting. The regulation is that only cetacean bycatch can not be longer than 15 meters ^[36] and this can lead to be a problem because short-beaked common dolphins are only about 2.7 meters. Common dolphin bycatch is a particularly important issue in Galicia Spain, via trawler fishing.^[37] The bycatch of short beaked dolphins in Galicia from May to September from 2001 to 2002, consisted of 394 individuals annually. Depth was an important factor in bycatch, as incidental capture mostly took place along the continental shelf in water less than 300 m deep. Very few entrapments took place when the depth exceeded 300 m. Time of day was also important as most dolphins became trapped in trawling nets at night (most active feeding takes place at night). Most of the dolphins captured were males and had a mean age of 13+- 4.4 years. It is believed that the reason why the vast majority of bycatch consisted of males is because bachelor pods appear to be particularly abundant in Galicia from the May–October season. This fact reinforces the hypothesis that common dolphins may be sexually segregated in the Northeast Atlantic. If there was a ban on fishing in Galicia in waters than less than 250 m deep, and if there were seasonal closures, it is estimated that 78% of the dolphins would not have been caught.^[37] In the Western North Atlantic, dolphins are vulnerable to swordfish driftnet fishing, with the number of males being caught as bycatch, doubling the number of females. It was also found from stranding samples that males tend to strand more. This provides evidence of sex-based habitat partitioning or pod congregation. ^[37]

Common dolphins were abundant in the western Mediterranean Sea until the 1960s but occurrences there have tailed off rapidly. The reasons are not well understood, but are believed to be due to extensive human activity in the area. In the US, they are a protected species and sometimes are caught by accident in some trawler nets as by-catch, though despite this they are still quite common throughout their range. Despite these potential threats, the short-beaked common dolphin is considered to be Least Concern by the IUCN Red List, and the long-beaked common dolphin is listed as Data Deficient.^[1]

The short-beaked common dolphin Delphinus delphis is listed globally on Appendix II^[38] of the Convention on the Conservation of Migratory Species of Wild Animals (CMS).^[39] As amended by the Conference of the Parties in 1985, 1988, 1991, 1994, 1997, 1999, 2002, 2005 and 2008. Effective: 5 March 2009 of the Convention on the Conservation of Migratory Species of Wild Animals (CMS) as it has an unfavourable conservation status or would benefit significantly from international co-operation organised by tailored agreements. The Mediterranean population of the short-beaked common dolphin is also listed on Appendix I,^[38] as this population has been categorized as being in danger of extinction throughout all or a significant proportion of their range and CMS Parties strive towards strictly protecting these animals, conserving or restoring the places where they live, mitigating obstacles to migration and controlling other factors that might endanger them. In addition, the species is also covered by the Agreement on the Conservation of Small Cetaceans of the Baltic, North East Atlantic, Irish and North Seas (ASCOBANS)^[40] and the Agreement on the Conservation of Cetaceans in the Black Sea, Mediterranean Sea and Contiguous Atlantic Area (ACCOBAMS).^[41]

Mass stranding events

On June 8, 2009, a mass-stranding event (MSE) occurred in Falmouth Bay, Cornwall, United Kingdom. It is believed the MSE was likely caused by naval involvement, as all other factors which cause MSEs in cetaceans currently appear unlikely to have influenced the event. During the event, twenty-six common dolphins washed ashore, and about the same amount floated back out to sea. There were three other MSEs in the UK before this event, all of unknown cause, from the years 1915 to 1938, but with arguably lower counts of stranded dolphins.^[42]

Captivity

Common dolphins are not common in captivity. But on at least three occasions, a beached common dolphin in California was nursed back to health at SeaWorld San Diego, but deemed unfit to release back to the ocean. These common dolphins remained at SeaWorld with the bottlenose dolphin exhibit. On one occasion, a male common dolphin managed to impregnate one of the female bottlenose dolphins in the exhibit, leading to four hybrid births.^[27] One of the resulting common dolphin/bottlenose dolphin hybrids remained at SeaWorld, San Diego (alternately under the name Cindy or Bullet) while the other (named CJ) was kept at Discovery Cove, and was moved to SeaWorld Orlando in 2016.

Other than at SeaWorld, at least 90 common dolphins are known to have been captured from the wild and kept in captivity. Captured common dolphins are said to be difficult to keep in captivity.^[9]

The behavior of captive common dolphins is not very well studied. However, a study was conducted in New Zealand of common dolphin reacting to swimmers at Marineland.^[43] Unlike bottlenose dolphins (which demonstrated antagonistic or sexual behaviors), the common dolphins retreated to the refuge center of the pool, where swimmers were not allowed. They did not leave the refuge section until the swimmers left. The dolphins also surfaced much more frequently, which is a possible indicator of stress. Aggressive and playful behavior among the dolphins decreased when swimmers were present. This behavior is consistent with wild common dolphins off of New Zealand, as they actively avoid swimmers.^[44]

See also

• List of cetaceans
• Marine biology

References

La komuna delfeno estas la nomo donita al du specioj de delfenoj kiuj formas la genron Delphinus. Taksonomiistoj kaj cetologoj kutime agnoskas du speciojn — nome Ordinara delfeno, kio retenas la sistematikan nomon Delphinus delphis, kaj la Longbeka ordinara delfeno, nome D. capensis.

Spite sian nomon, la komuna delfeno ne estas la delfeno de populara imago; tiu honoro korespondas al la Botelnaza delfeno (genro Tursiops) pro sia disvastigita uzado en marparkoj kaj sia apero en la televida serio Flipper.^[1] Tamen, tiu delfeno estis la plej ofte reprezentata en arto kaj literaturo de antikva Grekio kaj Romia Imperio.^[2]

Fizikaj trajtoj

Ambaŭ specioj de komunaj delfenoj estas mezgrandaj; plenkreskuloj gamas inter 1.9 kaj 2.5 longe, kaj povas pezi inter 80 kaj 235 kg, kvankam la gamo inter 80 kaj 150 kg estas plej ofta.^[3] Maskloj estas ĝenerale pli longaj kaj fortikaj.^[3] La kolormodelo de la korpo estas malkutima. La dorso estas malhela kaj la ventro estas blankaj, dum ambaŭflanke estas bildo kiel akvohorloĝo helgriza, flava aŭ orkolora antaŭ malhelgriza dorse.^[4] Ili havas longajn, fajnajn bekojn kun ĝis 50–60 malgrandaj, akraj, interfermeblaj dentoj ambaŭflanke de ĉiu makzelo.^[5]

Taksonomio

• genro: Delfenoj - Delphinus
  • Ordinara delfeno aŭ delfeno kutima - Delphinus delphis
  • Tropika delfeno - Delphinus tropicalis aŭ Delphinus capensis

Notoj

1. ↑ "American Cetacean Society — Bottlenose Dolphin". Arkivita el la originalo en 2008-07-25. Alirita la 18an de Novembro 2018.
2. ↑ Watson, L. (1981). Sea Guide to Whales of the World. p 270. ISBN 0-17-601535-3.
3. ↑ ^{3,0 3,1} (2006) Whales, Dolphins and Other Marine Mammals of the World, p. 171–176. ISBN 0-691-12757-3.
4. ↑ (2002) Guide to Marine Mammals of the World. ISBN 0-375-41141-0.
5. ↑ The Common Dolphin. Arkivita el la originalo je 2008-06-19. Alirita 2008-07-03.

Bibliografio

• Rice, Dale W. (1998). Marine mammals of the world: systematics and distribution. Society of Marine Mammalogy Special Publication Number 4. 231 pp.
• Encyclopedia of Marine Mammals ISBN 0-12-551340-2
• Whales, Dolphins and Porpoises, Mark Carwardine, ISBN 0-7513-2781-6
• Heptner, V. G.; Nasimovich, A. A; Bannikov, Andrei Grigorevich; Hoffmann, Robert S, Mammals of the Soviet Union, Volume II, part 3 (1996). Washington, D.C. : Smithsonian Institution Libraries and National Science Foundation

Delphinus es un género de cetáceos odontocetos de la familia de los delfínidos.^[1]​ Hasta mediados de la década de 1990, la mayoría de los taxónomos solo reconocían una especie en el género, el delfín común. Actualmente se reconocen dos especies.

Taxonomía

El género fue descrito en 1758 por Carlos Linneo en su obra Systema naturæ, quien designó como especie tipo al delfín común oceánico (Delphinus delphis).^[2]​ Se conocen dos especies:^[2]​^[3]​

• Delphinus capensis Gray, 1828 - delfín común costero o de rostro largo.
• Delphinus delphis Linnaeus, 1758 - delfín común oceánico o de rostro corto.
  • Delphinus delphis delphis Linnaeus, 1758
  • Delphinus delphis ponticus Barabash, 1935

Conducta

Los delfines pertenecientes a este género, huevil viajan en grupos de 10 a 50 individuos, que frecuentemente pueden reunirse en grandes bancos de entre 100 hasta 2000 animales. estos grandes bancos son generalmente muy activos en la superficie del mar, jugando y saltando juntos. El comportamiento típico incluye burlas, golpes con la aleta caudal y golpes de mandíbula.

Se ve frecuentemente a estos delfines mezclarse con otros cetáceos, por ejemplo con otras especies de delfín en los bancos de atún del Pacífico oriental, y también con bancos de calderones. Una interesante teoría sostiene que los delfines hacen sus piruetas jugando con los barcos porque siempre lo hicieron con las grandes ballenas.

El período de gestación es de aproximadamente 11 meses, y el período entre partos es de uno a tres años. La maduración sexual ocurre a los cinco años de edad, y la máxima longevidad es de 25 años. Estos datos están sujetos a variación entre poblaciones según su ubicación geográfica.

Referencias

no entiendo ustedes si

Bibliografía

• Rice, Dale W. (1998). Marine mammals of the world: systematics and distribution. Society of Marine Mammalogy Special Publication Number 4. 231 pp.
• National Audubon Society Guide to Marine Mammals of the World ISBN 0-375-41141-0
• Encyclopedia of Marine Mammals ISBN 0-12-551340-2
• Whales, Dolphins and Porpoises, Mark Carwardine, ISBN 0-7513-2781-6

See artikkel räägib loomade perekonnast; tähtkuju kohta vaata artiklit Delfiin (tähtkuju); sugukonna kohta vaata artiklit Delfiinlased; liigi kohta vaata artiklit Tavadelfiin; Eesti endise ansambli kohta vaata Delfiinid (ansambel)

---

Delfiin (Delphinus) on mereimetajate perekond delfiinlaste sugukonnast.

Eluviis

Delfiin võib vee all viibida 3-4 minutit. Magades hõljub ta umbes 50 cm sügavusel ja tõuseb iga 30 sekundi järel veepinnale hingama, ise sealjuures ärkamata.

Elab kümnetest või sadadest isenditest koosnevas karjas, millel pole kindlat juhti.

Liigid

Delfiini perekonda kuulub kuni kolm liiki.

Enne 1990. aastate keskpaika lugesid süstemaatikud perekonda vaid ühe liigi – tavadelfiini (Delphinus delphis). Tänapäeval loetakse delfiinide perekonda kaks liiki: tavadelfiin ja Delphinus capensis. Tavainimene mõistab "hariliku delfiini" all aga hoopis afaliini ehk laiksilm-delfiini, keda on kujutatud mitmetes filmides ja seriaalides.

The Cove

Kampaania The Cove paljastas rohkem kui 20 000 delfiini tapmise ja selle, kuidas nende liha, mis sisaldab mürgiseid ained, müüdi Jaapanis ja teistes Aasia riikides toiduna, sageli eksponeerides seda kui vaala liha. Suur osa maailmast ei ole selle probleemiga kursis. Sellest on tehtud ka dokumentaalfilm, mis kannab samuti nime The Cove.

Vaata ka

• Delfinaarium

Delphinus generoko Delphinidae familiako animalia da. Artiodaktiloen barruko sailkatuta dago.

Espeziak

• Delphinus capensis
• Delphinus delphinus

Delfiinit (Delphinus) on delfiinien (Delphinidae) heimoon kuuluva valassuku. Suvun edustajat laskettiin pitkään yhdeksi ja samaksi lajiksi, mutta 1960-luvulta alkaen on katsottu, että kyseessä on kaksi eri lajia: pitempinokkainen "nimilaji" Delphinus delphis eli delfiini ja harvinaisempana pidetty eteläiselle pallonpuoliskolle painottuva Delphinus capensis. On myös esitetty, että Punaisenmeren ja Intian valtameren hyvin pitkänokkainen delfiini olisi oma lajinsa Delphinus tropicalis, mutta kyse voi olla alueellisesta vaihtelusta.

Varsinaiset delfiinit eivät ole maailmanlaajuisesti uhanalaisia.

Suomessa havaittiin syksyllä 2006 kaksi delfiiniä, emo ja poikanen, jotka liikkuivat marraskuun alussa Turun saaristossa ja hukkuivat sitten vapaa-ajankalastajan lohiverkkoon Kemiön saaren tuntumassa.

Levinneisyys

Lähteet

Delphinus est un genre de cétacés comprenant trois espèces de dauphins.

Liste des espèces

• Delphinus capensis Gray, 1828 - Dauphin commun à long bec.
• Delphinus delphis Linnaeus, 1758 - Dauphin commun ou Dauphin commun à bec court.
• Delphinus tropicalis van Bree, 1971 - Dauphin commun d'Arabie (maintenant reconnu comme Delphinus capensis tropicalis).

• Delphinus capensis.

• Delphinus delphis.

• Delphinus tropicalis.

Références taxinomiques

• (en) Référence World Register of Marine Species : taxon Delphinus Linnaeus, 1758 (+ liste espèces)
• (en) Référence Paleobiology Database : Delphinus Linnaeus 1758
• (fr+en) Référence ITIS : Delphinus Linnaeus, 1758
• (en) Référence Mammal Species of the World (3^e éd., 2005) : Delphinus Linnaeus, 1758
• (fr+en) Référence CITES : genre Delphinus (sur le site de l’UNEP-WCMC)
• (en) Référence BioLib : Delphinus Linnaeus, 1758
• (en) Référence Animal Diversity Web : Delphinus
• (en) Référence Catalogue of Life : Delphinus Linnaeus, 1758 (consulté le 11 décembre 2020)
• (en) Référence UICN : taxon Delphinus
• (en) Référence NCBI : Delphinus (taxons inclus)

Notes et références

Ainmhí mara is ea an deilf choiteann.

Delphinus é un xénero de cetáceos odontocetos da familia dos delfínidos que comprende dúas especies coñecidas como golfiños comúns ou delfíns comúms.

Son golfiños oceánicos propios das augas tropicais e subtropicais próximasa ás costas de ambas as beiras do Atlántico norte, do Índico e do Pacífico.^[2]

Etimoloxía

O xénero Delphinus tomouno Linneo do nome latino do golfiño (ou delfín) común, delphīnus, -i,^[3] nome que, á súa vez, deriva do grego δελφίς (delphís), "delfín",^[4] ou δελφύς (delphýs).^[4]

Taxonomía

Ata 1994, cando se recoñeceu como especie diferente a Delphinus capensis, que definira Gray en 1828,^[2][5] críase que era a única especie do xénero Delphinus. Posteriormente, en 1971, Van Bree definiu unha terceira especie, Delphinus tropicalis, pero na actualidade non é admitida pola comunidade científica, e os ictiólogos considérana como unha subespecie de Delphinus capensis, clasificada hoxe como Delphinus capensis tropicalis Jefferson & Van Waerebeek, 2002.^[5]

Especies e subespecies

• Xénero Delphinus
  • Delphinus capensis Gray, 1828
    • Delphinus capensis capensis Jefferson & Van Waerebeek, 2002 — do océano Pacífico e as costas africanas e suramericanas.
    • Delphinus capesis tropicalis Jefferson & Van Waerebeek, 2002 — do mar Vermello e o océano Índico.
  • Delphinus delphis Linnaeus, 1758
    • Delphinus delphis delphis Linnaeus, 1758 — do Atlántico europeo e norteamericano e o Pacífico tropical.
    • Delphinus delphis ponticus Barabash, 1935 — do mar Negro.

Distribución xeográfica

• Distribución de
  Delphinus capensis

• Distribución de
  Delphinus delphis

Características

Teñen unha lonxitude corporal nos adultos que pode oscilar entre os 2 e os 2,6 m, e un peso de entre os 70 e os 135 kg. Os machos son lixeiramente máis grandes que as femias.

O corpo é esvelto, hidrodinámico, delgado, e un fociño longo, máis longo en Delphinus capensis, e de cor gris escura ou negra, aínda que pode ter a punta branca; hai unha pregadura ben marcada entre o bico e a fronte, que descende desde o alto da cabeza en suave declive.^[6] Na boca teñen entre 80 e 120 dentes cónicos, pequenos, simliares (homodonte), en cada maxilar.

Presentan unha aleta dorsal alta, situada no centro do lombo, e de forma que pode variar entre a falciforme á case triangular, e a súa cor pode oscilar entre a negra a practicamente a branca agrisada, cos bordos máis escuros, grises ou negros. As aletas pectorais son relativamente pequenas, anchas, de cor negra ou gris, e cos extremos lixeiramente acabados en punta; os bordos da punta son convexos. O pedúnculo caudal é fino, de cor gris clara, e a aleta caudal é de cor gris escura ou negra, cunha lixeira fendedura separando os dous lobos, que teñen os extremos dirixidos cara a atrás e están rematados en punta.^[6]

A coloración é moi vistosa, máis apagada en Delphiunus capensis, co lombo gris, negro, negro purpúreo ou apardazado, que forma unha "V" ou unha "X" debaixo da aleta dorsal, como debuxando a súa sombra (deseño denominado "en reloxo de area"), que se vai aclarando no pedúnculo caudal. O ventre é branco ou de cor crema, que se ve interrompida por unha ou dúas liñas amarelas ou grises, descontinuas; na rexión torácica dos flancos presenta unha mancha (o chamado parche torácico) de cor amarelada ou crema torrada. Ao redor dos ollos levan un anteface negro, que se prolonga ata o bico. Presentan, tamén, unha estreita banda escura desde a aleta pectoral ata o centro do maxilar inferior.^[6]

Bioloxía

Diferenzas entre as dúas especies

A diferenza máis evidente entre o Delphinus delphis e Delphinus capensis é a lonxitude e a anchura do peteiro. Porén, hai tamén outros trazos distintivos.

D. delphis ten o corpo algo máis repoludo, a cabeza máis arredondada, un debuxo máis complexo no seu bico, o anteface máis chamativo, unha banda máis estreita entre a mandíbula interior e as aletas pectorais e unhas cores máis brillantes, e adoita vivir máis lonxe das costas.

D. capensis ten un perfil máis fino, pouco ou nada de branco entre o ollo e a aleta pectoral, a fronte máis suave, o debuxo do bico moito máis simple e unhas cores máis apagadas, e normalmente vive máis preto da costa. Tamén hai diferenzas de comportamento entre ambas as especies.^[6]

Notas

Véxase tamén

Bibliografía

• Carwardine, Mark (1995): Ballenas, delfines y marsopas. Guía visual de todos los cetáceos del mundo. Barcelona: Ediciones Omega. ISBN 84-282-1037-3.
• Kowalski, Kazimerierz (1981): Mamíferos. Manual de teriología. Madrid: H. Blume Ediciones. ISBN 84-7214-229-9.
• Mead, J. G. and Brownell, R. L., Jr. (2005): "Order Cetacea en: Wilson, D. E. and Reeder, D. M. Mammal Species of the World (3rd ed.) Johns Hopkins University Press. pp. 723–743. ISBN 978-0-8018-8221-0.
• Perrin, William F.; Bernd Wursig and J. G.M. Thewissen (Eds.) (2008): Encyclopedia of Marine Mammals, Second Edition. Academic Press. ISBN 978-0-12-373553-9.
• Rice, Dale W. (1998): Marine mammals of the world: systematics and distribution. Society of Marine Mammalogy / Special Publication Number 4. ISBN 978-1-891276-03-3.
• Stewart, Brent S.; Phillip J. Clapham, James A. Powell and Randall R. Reeves (2002): National Audubon Society Guide to Marine Mammals of the World. ISBN 0-375-41141-0.

Outros artigos

• Cetáceos
• Odontocetos
• Delfínidos
• Delphinus delphis

Hvalategundin hrefna (Balaenoptera acutorostrata) hefur einnig verið nefnd léttir á íslensku

Léttir (fræðiheiti Delphinus delphis) einnig nefndur höfrungur eða eiginlegur höfrungur^[2] er fremur lítill tannhvalur af höfrungaætt og minnsta höfrungategundin við Ísland.

Lýsing

Léttir er grannvaxinn og straumlínulaga, bolurinn sívalur fremst en þynnist aftur. Trýnið er svart, langt og mjótt og afmarkað frá háu enninu. Þeir eru svartir eða dökkgráir að ofan með hvítan kvið. Litamynstur er allbreytilegt milli svæða, bakið er þó svart og ljósar hliðarnar ýmist gulleitar, brúnar eða hvítar. Frá dökkri augnumgjörð er svart strik fram á trýni. Hornið er fremur stórt, á miðju baki og aftursveigt. Bægslin eru meðalstór, breiðust við búkinn og mjókka þaðan fram í endana.

Útbreiðsla og hegðun

Létti er helst að finna á hitabeltis- og heittempruðum hafsvæðum frá 40.-60.°N að 50.°S og er hann algengastur á landgrunnssvæðum en finnst einnig á úthafi.

Fæðan er breytileg eftir svæðum og árstíma en er aðallega ýmsar tegundir uppsjávarfiska og smokkfiska. Léttir kafar allt niður á 200 metra dýpi í leit að fæðu. Þeir eru afar hraðsyndir og hafa þeir mælst á hraða yfir 64 kílómetra á klukkustund.

Léttir sést oftast í stórum hópum, hundruð eða þúsundir einstaklinga. Þó virðist vaðan vera samsett úr fjölmörgum einingum sem hver um sig inniheldur fáeina tugi einstaklinga. Léttir er oft í slagtogi við aðrar höfrungategundir og fylgir einnig stundum stórhvölum, til dæmis langreyði og steypireyði. Þeir fylgja einnig oft skipum og bátum.^[3]

Veiðar og fjöldi

Stofnstærð léttis í heiminum er óþekkt en rannsóknir á afmörkuðum svæðum benda til að tegundin geti verið algengasta hvalategundin í heiminum. Reglulegir hvalatalningarleiðangrar Hafrannsóknastofnunar við Ísland sýna að þéttleikinn er mestur sunnan við 57°N en tegundin hefur nokkrum sinnum sést vestan við landið.

Veiðar á létti hafa verið stundaðar í Svartahafi, Miðjarðarhafi og við Perú. Léttir er meðal þeirra hvalategunda sem drepast í hvað mestum mæli í veiðarfærum, sérstaklega í hringnót og reknetum á úthafi.

Tilvísanir

Heimildir

• Ásbjörn Björgvinsson og Helmut Lugmayr, Hvalaskoðun við Ísland (Reykjavík: JPV Útgáfan, 2002).
• Hammond, P.S., G. Bearzi, A. Bjørge, K. Forney, L. Karczmarski, T. Kasuya, W.F. Perrin, M.D. Scott, J.Y. Wang, R.S. Wells og B. Wilson, „Delphinus delphis“, 2008 IUCN Red List of Threatened Species (IUCN 2008).
• Jón Már Halldórsson. „Lifa höfrungar við Ísland?“. Vísindavefurinn 19.2.2008. http://visindavefur.is/?id=7077. (Skoðað 13.4.2009).
• Leatherwood og Reeves, The bottlenose dolphin (Academic Press, 1990). ISBN 0-12-440280-1
• Páll Hersteinsson (ritsj.), Íslensk spendýr (Reykjavík: Vaka-Helgafell, 2005). ISBN 9979-2-1721-9
• Perrin, J., „Common Dolphins“ hjá W. Perrin, B. Wursig og J. Thewissen (ritstj.), Encyclopedia of Marine Mammals (Academic Press, 2002): 245–248. ISBN 0-12-551340-2.
• Reeves, R., B. Stewart, P. Clapham og J. Powell, National Audubon Society Guide to Marine Mammals of the World (New York: A.A. Knopf, 2002). ISBN 0-375-41141-0.
• Sigurður Ægisson, Jón Ásgeir í Aðaldal, Jón Baldur Hlíðberg, Íslenskir hvalir fyrr og nú (Forlagið, 1997).
• Stefán Aðalsteinsson, Villtu spendýrin okkar (Reykjavík: Bjallan, 1987).
• Wells, R. og M. Scott, „Bottlenose Dolphins“ hjá W. Perrin, B. Wursig og J. Thewissen (ritstj.), Encyclopedia of Marine Mammals (Academic Press, 2002): 122–127. ISBN 0-12-551340-2.

Parastie delfīni (Delphinus) ir viena no delfīnu dzimtas (Delphinidae) ģintīm, kas saskaņā ar jaunākajiem ģenētiskajiem pētījumiem apvieno 2 mūsdienās dzīvojošas delfīnu sugas. Neskatoties uz ģints nosaukumu, šīs delfīnu sugas ir mazpazīstamas. Populārāki un pazīstamāki ir pudeļdeguna delfīni,^[1] toties parastie delfīni ir attēloti Senās Grieķijas un Senās Romas mākslā un literatūrā.^[2]

Izplatība

Parastie delfīni mājo siltos mērenās joslas un tropu ūdeņos, starp 40—60° ziemeļu paralēli un 50° dienvidu paralēli. Garpurna parastais delfīns galvenokārt uzturas siltās piekrastes jūrās,^[3] bet parastais delfīns uzturas dziļāk atklātā jūrā, vēsākos ūdeņos,^[4] gar sēkļiem vai areālos, kuros ir klinšaina gultne, zemūdens kalni vai kāda krauja.^[5] Uz muguras ir liela, trīsstūrveida spura, kas atrodas apmēram muguras vidusdaļā.^[6]

Izskats

Parastie delfīni ir vidēji lieli, pieaugušam īpatnim sasniedzot 1,7—2,6 m garumu un 70—235 kg svaru,^[4][6][7] lai gan šīs sugas delfīna masa biežāk ir 80—150 kg.^[7] Tēviņi ir nedaudz lielāki nekā mātītes.^[7] Ķermeņa krāsa ir neparasta, salīdzinot ar citiem delfīniem. Mugura ir tumši pelēka, bet vēders balts, uz sāniem ir smilšu pulksteni atgādinošs laukums, kas var būt gaiši pelēks, dzeltenpelēks vai zeltains priekšpusē un tumši pelēks aizmugurē. Purns ir slaids un salīdzinoši tievs, katrā žokļa pusē (gan augšā, gan apakšā) ir 50—60 nelieli, asi zobi.^[8] Parastajiem delfīniem ļoti bieži ir balts purna gals, un tiem ir viena vai divas tumši pelēkas joslas, kas savieno apakšžokli un krūšu spuras.^[6]

Atšķirības starp sugām

Galvenā ārējā atšķirība ir šo delfīnu purna garumā. Garpurna parastajam delfīnam purns ir slaidāks un garāks kā parastajam delfīnam, bet diskutablajai pasugai Arābijas parastajam delfīnam purns ir vēl garāks un vēl slaidāks.

Kopīgās īpašības

Parastie delfīni ir ļoti sabiedriski, tie veido barus, kuros ir simtiem vai pat tūkstošiem īpatņu.^[3] Reizēm tie apvienojas ar grindām vai joslvaļiem, kā arī mēdz pavadīt motorlaivas.^[3] Parastie delfīni ir ātri peldētāji, spējot sasniegt ātrumu 60 km/h, tiem patīk arī lēkāt no jūras viļniem, izpildot dažādas akrobātiskas virāžas.^[6][7] Šīm sugām var novērot altruistisku rīcību, veselajiem bara locekļiem aizsargājot slimos vai ievainotos delfīnus.^[9] Parasto delfīnu diēta ir ļoti daudzveidīgi, tie barojas ar dažādām zivīm, kas uzturas baros, un kalmāriem. Parasto delfīnu maksimālais ieniršanas dziļums ir 200 m.

Grūsnības periods ilgst 10—11 mēneši. Jaundzimušais mazulis ir 70—100 cm garš un sver apmēram 10 kg.^[7] Mazuļi dzimšanas intervāls ir atšķirīgs, atkarībā no izplatības areāla, piemēram, Melnajā jūrā mazuļi dzimst katru gadu, bet Klusā okeāna austrumos ik pēc trīs gadiem.^[3]

Sistemātikas diskusijas

Līdz 1990. gadiem ģintī tika izdalīta tikai viena suga — parastais delfīns (Delphinus delphis). Mūsdienās daži sistemātiķi Indijas okeānā dzīvojošo garpurna parastā delfīna pasugu Delphinus capensis tropicalis izdala kā atsevišķu sugu — Arābijas parasto delfīnu (Delphinus tropicalis),^[10] tomēr lielākā daļa zinātnieku to uzskata par pasugu.^[11]

Sistemātika

• Parasto delfīnu ģints (Delphinus)
  • Garpurna parastais delfīns (Delphinus capensis)
  • Parastais delfīns (Delphinus delphis)

Atsauces

Delphinus is een geslacht van walvisachtigen, en het typegeslacht van de familie der dolfijnen (Delphinidae). De wetenschappelijke naam van het geslacht werd in 1758 gepubliceerd door Carl Linnaeus.^[1] Er worden twee soorten in het geslacht geplaatst, de gewone dolfijn (Delphinus delphis) en de Kaapse dolfijn (Delphinus capensis).

Taxonomie

Tot 1994 werd maar één soort in dit geslacht ondergebracht: de gewone dolfijn (Delphinus delphis). Genetisch en anatomisch onderzoek wees echter uit dat er binnen die oude soort twee echte soorten onderscheiden konden worden. De ene behield de naam Delphinus delphis, de andere kreeg de naam Delphinus capensis, naar Kaap de Goede Hoop, een van de plaatsen waar de soort voorkomt.

Soms wordt nog een derde soort in dit geslacht geplaatst: Delphinus tropicalis. Die wordt echter door sommige auteurs beschouwd als een regionale ondersoort van de Kaapse dolfijn, door andere auteurs zelfs niet eens onderscheiden maar beschouwd als een synoniem.

Soorten en ondersoorten

• Delphinus delphis Linnaeus, 1758 – Gewone dolfijn
  • Delphinus delphis delphis
  • Delphinus delphis ponticus Barabash, 1935 (Zwarte Zee)
• Delphinus capensis Gray, 1828 – Kaapse dolfijn
  • Delphinus capensis capensis
  • Delphinus capensis tropicalis Van Bree, 1971

Gedrag

Beide soorten hebben een gelijkaardige levenswijze. Za zwemmen in groepen van 10 tot 50 exemplaren, maar soms komen ze samen in scholen van honderden tot 2000 exemplaren. Deze scholen zijn vaak erg actief. Ze kunnen tijdens het zwemmen snelheden van meer dan 40 km/u halen, waarmee ze tot de snelste walvissen behoren. Soms mengen ze zich met andere walvissen, zoals grienden en andere dolfijnen. Ze zwemmen soms ook mee op boeggolven veroorzaakt door schepen of grote walvissen.

Bronnen, noten en/of referenties

For stjernebildet, se Delfinen.

Gulflankedelfin eller delfin (Delphinus delphis) er et sjøpattedyr i slekten Delphinus, som er monotypisk. Den kan bli drøyt 2 meter lang og veier om lag 80 kg.

Delfiner lever i flokker. Hovedflokken består av en større grupper hanner og hunner som lever i ulike flokker i kortere tidsrom. Mødre og døtre lever i samme flokk hele livet, mens moren støter fra seg sønnene etter om lag ett år.

Referanser

Eksterne lenker

• (sv) Gulflankedelfin hos Dyntaxa
• (en) Gulflankedelfin – oversikt og omtale av artene i WORMS-databasen
• (en) Gulflankedelfin i Encyclopedia of Life
• (en) Gulflankedelfin i Global Biodiversity Information Facility
• (en) Gulflankedelfin hos Fossilworks
• (en) Gulflankedelfin hos NCBI
• (en) Gulflankedelfin hos ITIS
• (en) Kategori:Delphinus delphis – bilder, video eller lyd på Wikimedia Commons
• (en) Delphinus delphis – galleri av bilder, video eller lyd på Wikimedia Commons
• Delphinus delphis – detaljert informasjon på Wikispecies

Multimedia w Wikimedia Commons

Delfin^[5] (Delphinus) – rodzaj ssaka z rodziny delfinowatych (Delphinidae).

Występowanie

Rodzaj obejmuje gatunki występujące we wszystkich oceanach świata^[6].

Systematyka

Nazewnictwo

Nazwa rodzajowa pochodzi od greckiego słowa δελφίς delphís, δελφίνος delphínos – „delfin”^[7].

Gatunek typowy

Delphinus delphis Linnaeus, 1758

Podział systematyczny

Do rodzaju należą następujące gatunki^[5][6]:

• Delphinus capensis – delfin długopyski
• Delphinus delphis – delfin zwyczajny

Uwagi

Przypisy

Delphinus é um gênero de golfinhos cosmopolita. Duas espécies são reconhecidas por Mead e Brownell (2005), três são possíveis, entretanto, por se tratar de um gênero polimórfico, novos estudos deverão definir a quantidade de espécies.

• Delphinus capensis Gray, 1828 - Golfinho-comum-de-bico-longo
• Delphinus delphis Linnaeus, 1758 - Golfinho-comum-de-bico-curto

Referências

• MEAD, J. G.; BROWNELL, R. L. (2005). Order Cetacea. In: WILSON, D. E.; REEDER, D. M. (Eds.) Mammal Species of the World: A Taxonomic and Geographic Reference. 3ª edição. Baltimore: Johns Hopkins University Press. p. 723-743.

Denna artikel handlar om släktet vanliga delfiner, Delphinus. Generell information om familjen delfiner finns på Delfiner.

Vanliga delfiner (Delphinus) är ett släkte däggdjur av familjen delfiner som lever i haven. Trots namnet är vanliga delfiner inte de delfiner som människan mest förknippar med delfiner. Den rollen har istället flasknosdelfin eller öresvin som brukar hållas på delfinarier och som blev världskänd genom TV-serien Flipper^[1].

Kännetecken

Individerna är på ryggen mörkgrå till svart eller brun och på buken vitaktig. På sidorna finns timglasformiga markeringar i ljusgul till ljusgrå. Vid stjärtfenan är kroppen svartaktig. Färgsättningen skiljer sig mellan olika populationer, i vissa regioner saknas markeringarna på sidan helt. De kan bli mellan 1,70 och 2,40 meter långa och väger omkring 80 kg.

Utbredning och habitat

Vanliga delfiner förekommer i flera från varandra avskilda havsregioner i tropiska och tempererade områden. En större sammanhängande population lever i Svarta havet, Medelhavet och nordöstra Atlanten. En annan större population finns i östra Stilla havet vid Amerikas västra kustlinje. Dessutom förekommer arten vid Nord- och Sydamerikas östra kustlinje (men saknas i Karibien), söder om Afrika samt kring Madagaskar, vid Omans, Tasmaniens och Nya Zeelands kustlinje samt i hav kring Japan, Koreahalvön och Taiwan (se kartor).

Vanliga delfiner visas främst i det öppna havet och de syns sällan vid kusten. De föredrar vattentemperaturen mellan 10 och 20 °C.

Levnadssätt

Liksom andra delfiner livnär sig vanliga delfiner främst av fiskar och ibland av bläckfiskar.^[2] De har snabba rörelser och simmar eller hoppar ofta omkring fartyg. Liksom andra medlemmar av familjen bildar de ofta stora flockar med upp till flera tusen individer som uppvisar ett komplext socialt beteende.^[2] Under sommaren är flockarna vanligen mindre. Ibland bildar de grupper med andra tandvalar som grindvalar. Medlemmar i en grupp hjälper varandra. Till exempel iakttogs vanliga delfiner som hjälpte skadade individer att når vattenytan för att andas.

Dräktigheten varar i ungefär 11 månader.^[2] Födelsen av ungarna kan vara i två timmar. Ungdjuren föds med stjärtfenan framåt så att den inte drunknar vid födelsen. Modern hjälper sedan ungdjuret att komma till vattenytan. Andra delfiner i gruppen skyddar honan och ungdjuret för möjliga hajattacker. Tvillingar föds mycket sällan och i dessa fall dör vanligen ett av ungdjuren då modersmjölken inte räcker till. Ungdjuret dias ungefär ett år och sedan stannar ungen cirka två år till vid modern.

Hot

I vissa delar av utbredningsområdet jagas vanliga delfiner. Till exempel fångas de av peruanska fiskare. Även i Svarta havet var tidigare jakt på vanliga delfiner vanlig. Det största hotet är numera kollisioner med fartyg och deras propeller samt vattenföroreningar^[3]. Sedan 1960-talet minskar populationen i Medelhavet och Svarta havet oroväckande snabb men orsaken är inte helt utredd. Troligen beror beståndets minskning på överfiskning så att delfinerna har brist på föda, eller de fick ett svagare immunsystem på grund av vattenföroreningar. IUCN listar populationen kring Medelhavet sedan 2003 som stark hotad (endangered).^[4]

Systematik

Fram till mitten av 1990-talet betraktades Delphinus delphis som en enda art men idag delas släktet Delphinus av några zoologer upp i sadeldelfin eller kortnosad vanlig delfin (som fortfarande bär det vetenskapliga namnet Delphinus delphis) och i kapspringare eller långnosad vanlig delfin (Delphinus capensis).^[5]

Tidigare fanns upp till 20 förslag för isolerade populationer som skulle få artstatus, bland annat Delphinus bairdii i östra Stilla havet och Delphinus tropicalis i Indiska oceanen.

Referenser

Den här artikeln är helt eller delvis baserad på material från tyskspråkiga Wikipedia, Gemeiner Delfin, 3 juni 2010.

Noter

1. ^ ”American Cetacean Society - Bottlenose Dolphin”. Arkiverad från originalet den 25 juli 2008. https://web.archive.org/web/20080725121057/http://acsonline.org/factpack/btlnose.htm. Läst 31 augusti 2008.
2. ^ [a b c] Delphinus delphis på Animal Diversity Web (engelska), besökt 18 september 2010.
3. ^ Lavery, T.J., Butterfield, N., Kemper, C.M., Reid, R.J., and Sanderson, K. 2008. Metals and selenium in the liver and bone of three dolphin species from South Australia, 1988 - 2004. Science of the Total Environment, 390: 77 - 85.
4. ^ Delphinus delphis (Mediterranean subpopulation) på IUCN:s rödlista, auktor: Bearzi, G. 2003, besökt 18 september 2010.
5. ^ Wilson & Reeder, red (2005). ”Delphinus” (på engelska). Mammal Species of the World. Baltimore: Johns Hopkins University Press. ISBN 0-8018-8221-4

Externa länkar

• Wikimedia Commons har media som rör Vanliga delfiner.
  Bilder & media

? Bayağı yunus Bayağı yunus (Delphinus) cinsinin bir üyesi ve yunusgiller (Delphinidae) familyasının tipik türü olan kısa burunlu bayağı yunus ya da tırtak (Delphinus delphis). Bilimsel sınıflandırma Âlem: Animalia - Hayvanlar Şube: Chordata - Kordalılar Sınıf: Mammalia - Memeliler Takım: Cetacea - Balinalar Alt takım: Odontoceti - Dişli balinalar Familya: Delphinidae - Yunusgiller
Cins: Delphinus
Linnaeus, 1758 Türler

• Delphinus capensis -
  Uzun burunlu bayağı yunus
• Delphinus delphis -
  Kısa burunlu bayağı yunus, tırtak

'Bayağı yunus, yunusgiller (Delphinidae) familyasının tipik cinsi Delphinusu oluşturan iki yunus türünün ortak adıdır.

1990'lardan önce, taksonomi bilimcilerinin çoğunluğu tarafından, Delphinus cinsi içinde yalnıca Delphinus delphis türünün varlığı tanınmış ve "bayağı yunus" genel adı ile anılmıştır. Daha sonra yürütülen genetik araştırmalara bağlı olaraksa, günümüz balina bilimcileri bu cins içinde iki ayrı tür olduğunu genellikle kabul etmektedir. Bahsi geçen türler şunlardır:

• Delphinus capensis - Uzun burunlu bayağı yunus
• Delphinus delphis - Kısa burunlu bayağı yunus

Yunusgiller familyasının tipik türü kısa burunlu bayağı yunus olsa da hem en sık rastlanan yunus türü olma hem de özellikle 1970'li yıllarda Türkiye'de de yayınlanan ABD televizyon dizisi Flipper'ın popülerleştirmesi nedeniyle "yunus" denildiğinde ilk akla gelen canlı olma unvanları, Türkçede "şişe burunlu yunus" ya da "afalina" olarak anılan Tursiops truncatus'a aittir. Kısa burunlu bayağı yunus, Türkçede esasen "tırtak" adı ile anılır.

Farklı türlerin tanınması

Tüm Delphinus cinsini tek bir türe indirgeme yaklaşımının tarihsel bir geçmişi olsa da oldukça geniş bir dağılım alanına sahip bu yunusların geniş aralıkta bir büyüklük, biçim ve renk çeşitliliği gösterdiği izlenir. Öyle ki, son birkaç on yıllık dönemde, bu cins içinde sınıflanmak üzere yirmiden fazla tür önerilmiştir. Ancak 1960'larda Kaliforniya'dan bilim insanları, daha sonra 1990'larda yürütülen ayrıntılı bir genetik çalışma ile de doğrulanacağı üzere, uzun burunlu (D. capensis) ve kısa burunlu (D. delphinus) olmak üzere iki farklı bayağı yunus türünün olduğu sonucuna varmıştır.

Bu süreç sonunda, önerilen diğer türlerin bir kısmı Stenella cinsi içine kaydırılmıştır ama bahsi geçen genetik çalışmaya dayanarak, Delphinus cinsi içinde Delphinus tropicalis bilimsel adı ve sıklıkla da Arap ya da Malabar bayağı yunusu genel adları ile anılan üçüncü bir türün olduğu da ileri sürülmüştür.^[1] D. capensis'e göre daha da uzun bir burnu olan bu canlı, Kızıldeniz ve Hint Okyanusu'nda bulunur. Bun karşın, yakın tarihli morfolojik incelemelerde D. capensis ve D. tropicalis arasındaki farkların tür seviyesinde olmadığı gösterilmiştir^[2] ve D. tropicalis, güncel standart taksonomik çalışmalarda D. capensis'in bölgesel bir varyasyonu olarak değerlendirilmektedir.

Fiziksel özellikler

Renk

Bayağı yunuslar oldukça renkli canlılardır ve derileri, balinalar (Cetacea) takımının tüm üyeleri içindeki en ayrıntılı renk desenlerini içerir. Yanlarında, boğum yeri sırt yüzgecinin hizasına denk gelecek şekilde yan yatmış bir kum saati deseni vardır ve bu desenin sırt yüzgecinden önde olan kısmı sarımsı kahverengi, arkada olan kısmı ise açık gridir. Sırtları, başlarının üstünden kuyruğa kadar ve sırt yüzgeci hizasında da yanlardaki kum sati deseninin boğumuna doğru V şeklinde uzanmak üzere, koyu gri-siyah renktedir. Karınları beyaz olan bayağı yunusların gözlerini koyu renkli halkalar çevreler ve bu halkalar, burunlarının arkasından geçen koyu renkli bir çizgi ile birbirine bağlanır. Ayrıca, siyah bir bant da çeneden göğüs yüzgeçlerine uzanır. İki bayağı yunus türünden uzun burunlu olan (D. capensis) daha soluk, kısa burunlu olan (D.delphinus) ise daha koyu renklidir.^[3]

Cinsel organ bölgesindeki renk biçemine bakılarak, bir bayağı yunusun cinsiyetini ayırmak olasıdır:^[4]

• Erkek bireyde, cinsel bölgenin hemen üzerinde siyah ve alev benzeri bir leke bulunur.
• Dişi bireydeyse, aynı bölgede, çevresi gri tonla çevrili ve dar bir siyah bant izlenir.

Baş

Genel adlarının burunları ile ilgili olarak ifade ettiğinden başka, uzun ve kısa burunlu bayağı yunusların birbirinden ayrılabilmesini sağlayan başa ait bir başka nitelik de bu türlere özellikle yandan bakıldığında izlenebilir: kısa burunlu bayağı yunusun melon yapısı daha yuvarlak ve hayvanın alnı burnuna daha dik bir açı ile birleşiyorken, uzun burunlu yunusta daha yassı bir melon vardır ve alnı da burnuna daha dar bir açı ile birleşir.^[3]

Bayağı yunusların her iki çenesinde de 40-55 çift küçük ve sivri diş bulunur.^[5]

• Erkekler dişilerden biraz daha büyüktür ve en küçük formlar Karadeniz'de (erkekler 1,7-1,8 m, dişilerse 1,5-1,7 m arasında), en büyük formlar ise Hint Okyanusu'nda (erkekler 2,42 metreye, dişilerse 2,12 metreye kadar) yaşar.^[4]
• Kısa burunlu bayağı yunus görece daha ağır olan türdür.^[3]

Yaşam döngüsü ve davranış

Üreme ve ömür

3-4 yaşında ya da 1,8-2,1 m uzunluğa ulaştıklarında cinsel olgunluğa erişen bayağı yunuslarda gebelik süresi yaklaşık 10-11 aydır ve 76–86 cm uzunluğa sahip bir yavru doğururlar.^[3] Yavrunun anne ile olan birlikteliği 1-3 yıl gibi bir süreyi kapsar. 20-25 yıllık bir ömre sahip olan bayağı yunuslar için burada ifade edilen rakamların farklı topluluklar arasında büyük çeşitlilik gösterdiği göz önünde bulundurulmalıdır.

Toplumsal yapı

Bayağı yunuslar 10-50 üyelik gruplar halinde seyrederler ve sıklıkla da 100-2000 üyelik sürüler halinde toplanırlar. Bu sürüler genellikle çok hareketlidir: sürüyü oluşturan gruplar birlikte yüzeye çıkar, sıçrar ve su sıçratırlar. Su üstüne sıçramak, yüzeye kuyruk ya da çene çarpmak tipik davranışlardır.

Bayağı yunusların, balinalar (Cetacea) takımının pilot balinası gibi türlerinin sürüleriyle karıştıkları gözlenmiştir. Benzeri bir karışmanın, Büyük Okyanus'un doğusundaki sarı yüzgeçli ton balığı bölgelerinde, başka yunus türü sürüleri ile de gerçekleştiği izlenmiştir. İlginç bir teoriye göre, yunuslarda sık gözlenen "pruva yüzüşü" davranışının kökeninde balinaların önünden pruva yüzüşü yapmaları yatmaktadır.

Beslenme

Bayağı yunusların temel gıdası mürekkep balıkları ve sürüler halinde bulunan küçük balıklardır. Bu yunusların, ekip olarak çalışıp, balıkları yoğun sürüler haline sıkıştırdıkları gözlenmiştir. Dünyanın bazı bölgelerinde, geceleri yüzeye doğru hareketlenen derin yansıtıcı tabaka canlılarıyla da beslenirler. Ayrıca, çoğu diğer yunus türü gibi bayağı yunuslar da fırsat buldukça insanların trolle avlanma benzeri balıkçılık etkinliklerinden faydalanır ve ağlardan kaçan ya da balıkçıların denize attığı balıklar ile beslenirler.^[3]

Nüfus ve dağılım

Toplam nüfuslarının kesin olarak bilinmediği ve yüzbinlerce olduğu tahmin edilen bayağı yunuslar, 10-28 °C'lık yüzey suyu sıcaklıklarını tercih ederler. Bununla paralel olarak da tüm dünya denizlerinde, kabaca 50° kuzey ile 40° güney enlemleri arasında kalan ılıman, tropik altı ve tropik sularda bulunurlar. Türler, tipik olarak, Kızıldeniz ve Akdeniz gibi ara denizler ile kıyıdan açıktaki ve daha az olarak da kıta sahanlıkları üzerindeki derin suları tercih ederler. Bazı topluluklar tüm yıl boyunca yerleşimlerini korurken, diğerleri göçer bir davranış gösterir.

Uzun ve kısa burunlu yunusların dünya denizlerindeki kabaca dağılımları aşağıdaki şekillerde mavi renk ile sunulmuştur.

Şekillerden de yorumlanabileceği üzere, uzun burunlu bayağı yunus iç denizlerde bulunmaz ve kıyıya daha yakın suları tercih ederken, kısa burunlu bayağı yunus Karadeniz ve Akdeniz gibi iç denizlerde bulunur ve kıyılardan görece uzak suları tercih eder.^[3] Basra Körfezi'nde de bulunan bayağı yunusların Atlas Okyanusu'ndaki kuzey sınırı Yeni İskoçya ve İzlanda iken, Büyük Okyanus'ta ise Kaliforniya'nın kuzeyi ile Japonya'dır; bazen, Arktik Okyanus'ta da görülebilirler. Güney sınırları ise Arjantin'in Valdéz Yarımadası, Afrika'nın güney ucu, Avustralya'nın güneyi ve Yeni Zelanda'dır.^[6]

Kaynakça

Дельфі́н (Delphinus) — рід морських ссавців з родини дельфінових (Delphinidae).

Назва

У перекладі з давньогрецької δελφίς, δελφύς дослівно означає «утроб», «матка», тобто «риба з маткою».

Нерідко словом «дельфін» позначають всіх зубатих представників ряду китоподібних (підряд дельфіноподібні, або «зубаті кити»). Зокрема, це стосується трьох різних родів родини дельфінових, поширених у морських акваторіях України: фоцени, афаліни і власне дельфіна.

Систематика

Дельфін (Delphinus) — типовий рід родини Дельфінові (Delphinidae).

• рід Delphinus — Дельфін
  • Delphinus capensis — Дельфін довгомордий
  • Delphinus delphis — Дельфін білобокий
  • Delphinus tropicalis — Дельфін тропічний

• Delphinus delphis

• Delphinus capensis

• Delphinus tropicalis

• Дельфін звичайний біля берегів Ірландії

• Дельфін капський у затоці Баха-Каліфорнії

• Дельфін на гербі департаменту Луара, Франція

Див. також

• Дельфін (сузір'я)
• Тварини-символи
• Афродіта (дельфін — один з її атрибутів)

Джерела

Рід Дельфін (Delphunus) // Види ссавців світу, 2005 (англ.).

Chi Cá heo mỏ, tên khoa học Delphinus, là một chi động vật có vú trong họ Delphinidae, bộ Cetacea. Chi này được Linnaeus miêu tả năm 1758.^[1] Loài điển hình của chi này là Delphinus delphis Linnaeus, 1758.

Các loài

Chi này gồm các loài:

• Delphinus capensis
• Delphinus delphis
• Delphinus tropicalis

Hình ảnh

• 
• 
• 
• 

Chú thích

Tham khảo

Phương tiện liên quan tới Delphinus tại Wikimedia Commons

Латинское название Delphinus Linnaeus, 1758

Систематика
на Викивидах

Изображения
на Викискладе

ITIS 180437 NCBI 9727

Дельфины-белобочки^[1] (лат. Delphinus) — род морских млекопитающих из семейства дельфиновых.

В переводе с древнегреческого δελφίς, δελφύς дословно означает «утроба», «матка», то есть «рыба с маткой». Нередко словом «дельфин» обозначают всех некрупных зубатых представителей отряда китообразных.

Виды

• Длиннорылая белобочка (Delphinus capensis)
• Белобочка (Delphinus delphis)

Примечания

Источник — https://ru.wikipedia.org/w/index.php?title=Дельфины-белобочки&oldid=87357162

模式種 短吻真海豚
Delphinus delphis
Linnaeus, 1758

長吻真海豚的分布

短吻真海豚的分布

种

• 長吻真海豚 D. capensis
  Gray, 1828
• 短吻真海豚 D. delphis
  Linnaeus, 1758

海豚属（学名：Delphinus）是海豚科中的一个属，在历史上它是海豚科中最为人所知的海豚。不过通过海豚馆和电影等今天大多数人知道的海豚是宽吻海豚。

外形

海豚属动物的背部黑色或者棕色，腹部白色。在侧面有一块长形的，颜色从浅黄色向灰色过渡的地区。不过不同地区的动物的颜色有所不同，在有些地区的动物缺乏这个过渡区。总的来说海豚属的动物是所有鲸目动物中颜色最丰富的。海豚属动物体长在1.7至2.4米之间，重60至75千克。

分布

海豚属动物在地球许多热带和温带地区有地区性的分布。比如在地中海、黑海和北大西洋有一个大的族群。另一个大的族群生活在东太平洋。除此之外在南北美洲的东海岸、南非沿海、阿曼沿海、塔斯馬尼亞和新西兰周边、日本、朝鲜和台湾之间的海域里也有海豚属动物生活。

海豚属动物一般生活在开放的海洋中，很少到海岸附近。它们喜欢水温在10至20°C的水域。

习性

海豚属动物主要以鱼为食，有时也吃乌贼。海豚属动物速度相当高，又是会在船首前的弓形波上冲浪般地游泳。与其它海豚一样它们形成非常复杂的社群，这样的群可以有上千头动物。夏季这些大群分开为小群。群内的动物互相帮助。比如人们观察到受伤的动物在游泳时会受到群内其它动物的协助，其它动物会帮助它们浮到水面上来呼吸。

海豚属的出生过程可以持续到两个小时。它们的尾鳍首先出生，这样它们在出生时不会窒息。出生后母兽将幼兽推到水面来呼吸。群内的其它动物在出生时保护母兽和幼兽，防止鲨鱼袭击。双胞胎很少见，而且双胞胎一般无法生存，因为母兽的奶不够喂两头幼兽。幼兽跟随母兽约三年的时间，其中一年是哺乳期。

保护

在一些地区海豚属动物被捕猎。日本太地町的渔民猎杀海豚并出卖其肉(见纪录片:海豚湾)。长时期里在黑海也有猎杀海豚。在大多数地区海豚不是猎杀的对象，不过它们往往会被渔网缠住，或者被绞入船的螺旋桨。1960年代里在地中海和黑海海豚数量骤降，其原因至今不明，有人怀疑这与当时剧增的行船数量有关。

分类

关于海豚属内部种的分类目前有争议。大多数动物学家仅承认一个种，即短吻真海豚。有些动物学家认为生活在东太平洋的海豚和生活在印度洋的海豚，各自属于独立的种，分別稱作Delphinus bairdii與Delphinus tropicalis。但是大多数动物学家不承认这些种。在历史上海豚属内曾经有过20多个种的建议，但是他们全部都被否认了。

从1990年代开始越来越多的动物学家将海豚属中的动物分为两个不同的种：短吻真海豚（Delphinus delphis）和长吻真海豚（Delphinus capensis）。目前，动物学家们对於这两个种是否的确是不同的种，还是同一种的亚种仍有争议。

參考文獻

维基物种中的分类信息：海豚属 维基共享资源中相关的多媒体资源：海豚属

取自“https://zh.wikipedia.org/w/index.php?title=海豚属&oldid=44868498”

マイルカ属 分類 界 : 動物界 Animalia 門 : 脊索動物門 Chordata 亜門 : 脊椎動物亜門 Vertebrata 綱 : 哺乳綱 Mammalia 目 : 鯨偶蹄目 Cetartiodactyla 亜目 : ハクジラ亜目 Odontoceti 科 : マイルカ科 Delphinidae 属 : マイルカ属 Delphinus 学名 Delphinus 種

• マイルカ D. delphis
  Gray, 1828
• ハセイルカ D. capensis
  Gray, 1828
  • （ネッタイマイルカ D. tropicalis）

マイルカ属（真海豚属、Delphinus）はクジラ目ハクジラ亜目マイルカ科に属する属の一つ。マイルカ属はマイルカ（真海豚、Delphinus delphis）とハセイルカ（Delphinus capensis）の2種で構成される。ネッタイマイルカ（熱帯真海豚、Delphinus tropicalis）を種とする分類もある。詳細は本項の「分類学」を参照。

和名ではマイルカすなわち「真のイルカ」、英名でもCommon Dolphin（普通のイルカ）であるが、多くの人が「イルカ」と聞いた時に初めに思い浮かべるイルカはこのマイルカではなく、ハンドウイルカ（バンドウイルカ）であろう。これはテレビシリーズの『わんぱくフリッパー』（原題 Flipper）で活躍したイルカがハンドウイルカであることや、世界中の水族館で最も多く飼育されているイルカがハンドウイルカであることが主な原因であろう。好奇心旺盛で人懐っこいハンドウイルカに比べて、やや神経質な性格とされ飼育例は少ない。

分類[編集]

マイルカ属 Delphinus

• マイルカ Short-beaked Common Dolphin（単にCommon Dolphinとも）, Delphinus delphis
• ハセイルカ Long-beaked Common Dolphin, Delphinus capensis
• （ネッタイマイルカ Arabian Common Dolphin, Delphinus tropicalis（ハセイルカの亜種とされることが多い。詳細は本項の「分類学」を参照））

分類学[編集]

マイルカ属に属するイルカは、生息域によるサイズ、体型、体色の差異が大きく、過去数十年の間に、20以上もの種が提案されていたが、1990年代半ばまでは、マイルカ属に属するのは通常はマイルカ (Delphinus delphis) のみとされていた。しかし1960年代、カリフォルニア州の生物学者は、マイルカ属に属するのは2種（口吻の短い種と口吻の長い種）であると結論付けた。1990年代になり、遺伝子解析により裏付けられ、現在ではマイルカ（Delphinus delphis、英名 Short-beaked Common Dolphin（口吻の短いマイルカの意））とハセイルカ（Delphinus capensis、英名 Long-beaked Common Dolphin（口吻の長いマイルカの意））との2種に分類されることが多い。

同じく遺伝子解析により、第三の種となる可能性のあるイルカが存在することがわかっている。 このイルカはネッタイマイルカ（Delphinus tropicalis、英名 Arabian Common Dolphin（アラビアのマイルカの意））とも呼ばれ、紅海やインド洋に棲息し、特に細長い口吻が特徴である。 現時点では独立した種ではなくハセイルカの一亜種であって、一部の地域のみに棲息し固有の特徴を有しているものとされることが多い。

分布と生息数[編集]

マイルカ属のイルカは、世界中の温帯から熱帯の海域、緯度で表現すると北緯50度から南緯40度の海域に棲息する。離れた生息域間での相互の関りは少ないと考えられている。

紅海や地中海のような閉ざされた海を好むが、浅瀬の他に深い遠洋や広くない大陸棚を好む事も知られている。日本沿岸では、土佐湾、大阪湾などの瀬戸内海や豊後水道、日向灘、天草灘・有明海などで比較的良く見られる。伊勢湾では確認される限り世界でも最北端の定住群が存在し、大村湾にも定住に近い形の地方群が棲息する。

定住する群も、回遊パターンを有する群も、どちらも知られている。 水温は10℃から28℃を好む。

全生息数は知られていないが、数十万頭であろうと考えられている。

行動[編集]

マイルカ属のイルカは、10頭から50頭程度の群を成して行動することが多いが、100頭から2000頭の群 (School) を成すこともしばしばある。行動は非常に活動的であり、群で浮上したり、ジャンプして水をはねたり、といった行動を行う。またブリーチング（ジャンプしたあと、体の側面を水面にぶつけて水をはね飛ばす行動）、尾びれや下顎で水面を叩いたり、水面をかすめるように跳んだりということも良く行う。

東太平洋においては、他のクジラ目の動物と一緒に行動する様子も観察されており、ゴンドウクジラの群と泳ぐことも知られている。各種のイルカが人間の船が作る船首波を跳ぶことは良く知られているが、大型のクジラが泳ぐ時にできる波を跳ぶことがその行動の起源である、という興味深い説もある。

妊娠期間は11ヶ月であり、出産の間隔は1年から3年である。5年程度で性成熟し、寿命は20年から25年である。ただし、生息域による違いも大きい。

人間との関係[編集]

人間による影響は種々ある。 ペルー沖では、食用あるいはサメ漁用の餌として捕獲されている。 他の多くの海域では、直接にはイルカ漁の対象とはなっていないことが多いが、数千頭がトロール船の魚網による混獲が原因で死んでいる。

西地中海においては、1960年代までは多数が棲息していたが、その後、生息数が急速に減少している。 原因は不明であるが、その海域における人間の何らかの活動が原因となっているのだろうと考えられている。

世界最古の化石[編集]

北海道新十津川町で発見されたイルカの頭骨の化石（道開拓記念館収蔵）が2014年の研究でマイルカ科の中で世界最古の化石であることが判明した^[1]。

参考文献、外部リンク[編集]

1. Dale W. Rice, Marine mammals of the world: systematics and distribution, Society of Marine Mammalogy Special Publication Number 4, pp. 231 (1998).
2. National Audobon Society Guide to Marine Mammals of the World ISBN 0375411410
3. Encyclopedia of Marine Mammals ISBN 0125513402
4. Mark Carwardine, Whales, Dolphins and Porpoises ISBN 0751327816
5. 海棲哺乳類図鑑「マイルカ」 国立科学博物館 動物研究部
6. AQUAHEART AQUAHEARTさんによるハセイルカの説明。イラストと写真付き

脚註[編集]

1. ^ “世界最古のマイルカ化石と判明　北海道・新十津川で発見の頭骨”. 北海道新聞 (北海道新聞社). (http://www.hokkaido-np.co.jp/news/donai/548940.html

この項目は、動物に関連した書きかけの項目です。この項目を加筆・訂正などしてくださる協力者を求めています（Portal:生き物と自然／プロジェクト:生物）。

「https://ja.wikipedia.org/w/index.php?title=マイルカ属&oldid=64999105」から取得

참돌고래(영어: common dolphin)는 참돌고랫과 참돌고래속에 속하는 세 가지 종의 해양 포유류를 일컫는 말이다. 몸의 길이는 2.5미터이며, 몸무게는 235kg까지 나간다. 등은 검은색 또는 어두운 갈색이고 배는 희다. 등지느러미가 크고 주둥이는 뾰족하다. 턱에는 많은 이가 있고 콧구멍은 하나다. 1990년대 중반까지는 참돌고래속에 포함되는 종은 하나로 여겼지만, 현재는 짧은부리참돌고래(Delphinus delphis)와 긴부리참돌고래(Delphinus capensis)로 나뉜다.

각주