The Pacific blue-eye (Pseudomugil signifer) is a species of fish in the subfamily Pseudomugilinae native to eastern Australia. Described by Austrian naturalist Rudolf Kner in 1866, it comprises two subspecies that have been regarded as separate species in the past and may be once again with further study. It is a common fish of rivers and estuaries along the eastern seaboard from Cape York in North Queensland to southern New South Wales, the Burdekin Gap in central-north Queensland dividing the ranges of the two subspecies.
A small silvery fish averaging around 3.25 cm in total length (1+1⁄8–1+3⁄8 in), the Pacific blue-eye is recognisable by its blue eye-ring and two dorsal fins. It forms loose schools of tens to thousands of individuals. It eats water-borne insects as well as flying insects that land on the water's surface, foraging for them by sight. The Pacific blue-eye adapts readily to captivity.
Austrian naturalist Rudolf Kner described the species in 1866,[2] from a specimen collected in Sydney in 1858 during the course of the Novara Expedition and taken to Vienna by the SMS Novara.[3] German–British zoologist Albert Günther described Atherina signata from collections in Cape York in 1867.[4] British entomologist William Sharp Macleay named a "curious little fish" collected from the Bremer River, a tributary of the Brisbane River, by one Mr Jameson of Ipswich, Atherinosoma jamesonii in 1884; it was later classified as the same species by Australian ichthyologist James Douglas Ogilby in 1908.[3] Variable across its range, the Pacific blue-eye is considered to be a single species, though it has been split by some into northern signata and southern signifer, with the former found from Ross River northwards and the southern from the Calliope River. The division occurs at a biogeographic barrier known as the Burdekin Gap.[4] In their 1919 monograph of the family Atherinidae, David Starr Jordan and Carl Leavitt Hubbs maintained the two as separate species—P. signifer and P. signata—based on the number of rays in the dorsal fins and differences in the filaments of males.[5] Gilbert Whitley examined the species from the Low Isles off Cairns and maintained them as separate in 1935. In 1979, Hadfield and colleagues analysed the two species and felt that the variations within both species were greater than those between them and that no characteristics let people to distinguish either species. Hence, they recommended combining the species again.[6] However, a 2002[7] and a further 2004 molecular study showed the two populations were genetically distinct and suggested that they may be once again reclassified as species.[8] Species from the northern and southern extremes of the range do not appear to interbreed in hostile environment, suggesting that there may be two separate species within the current concept of the species.[9] Alternative names include southern blue-eye and northern blue-eye.[10]
Within the northern population, five distinct lineages (or subclades) have been identified: one from Ross River and Herbert River, a second from Johnstone, Barron and Tully Rivers, a third from Mulgrave/Russell River and Trinity Inlet, a fourth from Daintree and Mossman Rivers and a fifth from Low Isles and Cape Melville. Four subclades have been identified in the southern population: the first from the Don, Calliope, Pioneer and Kolan Rivers, the second from Burnett and Mary Rivers, the third from Pine River and the fourth from Clarence River southwards.[4]
The Pacific blue-eye generally reaches a total length of around 3–3.5 cm (1+1⁄8–1+3⁄8 in) long; males can reach 8.8 cm (3+1⁄2 in) and females 6.3 cm (2+1⁄2 in).[4] The size of Pacific blue-eyes found north of the Burdekin Gap increases directly with distance from the gap, males and females being the same size. South of the Burdekin Gap, the species exhibits marked size difference between sexes, which becomes more pronounced as the distance from the gap increases.[11] The elongate body is partly transparent and pale yellow or olive with a silver operculum and belly. The scales are relatively large and longer vertically than horizontally. The eye is large and has a blue iris. There are two dorsal fins, the first arising in line with or just posterior to the longest pectoral fin ray. The forked tail fin has rounded tips. The bottom and top edges of the tail fin are edged with white.[4] The male has extended filaments on its dorsal, anal, and pelvic fins. There are black markings at the base of the anterior rays of the anal and rear dorsal fins, and the front (anterior edge) is sometimes white and the rear (posterior) edge greyish in colour. The male's fins may turn orange during the breeding season.[4] Preserved specimens generally discolour to yellow or tan.[4] The Pacific blue-eye can be distinguished from the highly invasive and noxious introduced eastern mosquitofish (Gambusia holbrooki) by its forked tail fin.[12]
The Pacific blue-eye is found from Narooma in southern New South Wales north to the Rocky River in Cape York, though it is uncommon in eastern Cape York. It lives in small, generally slow-moving, streams to estuaries, as well as dune lagoons and salt marshes. It is also found in brackish and marine waters on some Queensland offshore islands such as Hinchinbrook Island, Lizard Island, Low Island, and Dunk Island. It has been recorded as far as 300 km (185 mi) upstream in the Mary and Dawson Rivers in Queensland. Numbers can be prolific in some locations, such as the Mary River. Conversely, it is uncommon in the Elliott and Kolan Rivers. Fish species it is commonly found with include Marjorie's hardyhead (Craterocephalus marjoriae), crimson-spotted rainbowfish (Melanotaenia duboulayi), Australian smelt (Retropinna semoni) and western carp gudgeon (Hypseleotris klunzingeri).[4]
In the wet tropics, the Pacific blue-eye is mostly found in streams flowing up to 30 cm (12 in) per second, or rarely 90 cm (35 in) per second. Within fast-flowing areas, it shelters in areas of slower-moving water—less than 20 cm (8 in) per second—sometimes in the lower half of the water column or in the lee of underwater rocks. Further south in southeastern Queensland it is mostly found in water flowing more slowly than 10 cm (4 in) per second.[4] It can also be found in tidal pools that become isolated from rivers at low tide.[13] The Pacific blue-eye also forages in mangroves; a field study in the waters around Hinchinbrook Island and near Ingham on mainland Queensland nearby found that the species entered mangroves with the incoming tide as soon as the water was deep enough to swim in but left again an hour later as they kept to areas of shallow water.[14] A field study in two lakes polluted by coal mine runoff in central Queensland found that the Pacific blue-eye was more resistant than tadpoles of the striped marsh frog (Limnodynastes peronii) to adverse health effects. The fish species did not suffer acutely but showed markers of compromised health in the long term.[15]
The Pacific blue-eye is found in loose schools of tens to thousands of fish. They are generally found in the middle to upper water column within 1 metre (3 ft) of the riverbank and often close to underwater cover.[4] The Pacific blue-eye is euryhaline—it can survive in a wide range of water salinities from fresh-water to marine environments. It responds to changes in salinity (and the resulting change in buoyancy) by changing the volume of its swim bladder, which takes up to 6 hours and 40 minutes when salinity is reduced and around 5 hours when it is increased. In the meantime, the fish can swim with a head-up or head-down posture, which either increases or decreases buoyancy respectively. This adaptation helps the fish in the range of salinities it encounters in its estuarine environment.[16]
In a school of Pacific blue-eyes that is threatened, a few individuals accelerate and change direction, which initiates an escape wave that spreads through the whole cohort.[17] Animals are known to dart in random directions and speeds as an escape response when threatened. Pacific blue-eyes on their own dart in this manner for up to ten seconds after being faced with a threat at close range. This period is briefer when faced with more distant threats or for fish in schools.[18]
Female Pacific blue-eyes are sexually mature at six months of age or when they have reached 2.3 cm (7⁄8 in) in standard length. Males are mature at 2.8 cm (1+1⁄8 in) standard length.[4] A study published in 2003 showed that males will preferentially choose larger females—who are more fecund as a rule—unless more energy is required to do so, such as swimming further against a current.[19] Fish can breed in fresh and saltwater. The life span of the species is around 1–2 years in the wild, and around 2–3 years in aquariums, though some males may reach 4 years of age.[4] In an aquarium, Pacific blue-eyes spawn in gravel or moss at the base of aquatic plants.[4] An experiment housing Pacific blue-eyes and mosquitofish together showed that the growth and breeding of the former fish were severely affected by the presence of the latter. The mechanism was unclear—there were some signs of direct aggression (bite marks on fins of Pacific blue-eyes) but stress from contact was thought to be a major factor.[20]
The diet consists of water-based and terrestrial insects, flying insects, such as various types of fly, and, to a lesser extent, tiny crustaceans and algae.[4] Field work on Narrabeen Lakes showed that Pacific blue-eyes spent time near the surface looking for dead flying insects, consuming anything below their mouth gape size. This varied from around 2.5 to 3.5 mm, and was proportional to the length of the fish. The Pacific blue-eye forages using vision, and the turbidity of the water affects its ability to find food.[21]
The Pacific blue-eye (Pseudomugil signifer) is a species of fish in the subfamily Pseudomugilinae native to eastern Australia. Described by Austrian naturalist Rudolf Kner in 1866, it comprises two subspecies that have been regarded as separate species in the past and may be once again with further study. It is a common fish of rivers and estuaries along the eastern seaboard from Cape York in North Queensland to southern New South Wales, the Burdekin Gap in central-north Queensland dividing the ranges of the two subspecies.
A small silvery fish averaging around 3.25 cm in total length (1+1⁄8–1+3⁄8 in), the Pacific blue-eye is recognisable by its blue eye-ring and two dorsal fins. It forms loose schools of tens to thousands of individuals. It eats water-borne insects as well as flying insects that land on the water's surface, foraging for them by sight. The Pacific blue-eye adapts readily to captivity.
Pseudomugil signifer Pseudomugil generoko animalia da. Arrainen barruko Pseudomugilidae familian sailkatzen da.
Pseudomugil signifer Pseudomugil generoko animalia da. Arrainen barruko Pseudomugilidae familian sailkatzen da.
Pseudomugil signifer est une espèce de poissons de la famille Pseudomugilidae. C'est une espèce commune des fleuves et estuaires de l'est de l'Australie.
P signifer mesure généralement entre 3 et 3,5 cm ; le mâle peut atteindre une longueur de 8,8 cm, la femelle 6,3 cm[2]. Le corps élancé est partiellement transparent, de couleur jaune pâle ou olive, l'opercule et la surface ventrale sont argentés[2].
Le poisson se rencontre en bancs de quelques centaines à plusieurs milliers d'individus. La femelle est sexuellement mature à l'âge de six mois. Le poisson vit entre un et deux ans dans la nature, entre deux et trois ans en aquarium, mais quelques mâles vivent jusqu'à quatre ans[2].
Le naturaliste autrichien Rudolf Kner décrit l'espèce en 1866 à partir d'un spécimen pêché à Sydney et transporté jusque Vienne sur la SMS Novara en 1858[3],[4]. En 1867, le zoologiste britannique Albert Günther décrit Atherina signata à partir de collectes effectuées dans la péninsule du cap York[2]. En 1884, le zoologiste britannique William Sharp Macleay décrit un « étrange petit poisson » pêché dans le fleuve Bremer, un affluent du fleuve Brisbane, par un certain M. Jameson ; Macleay nomme ce poisson Atherinosoma jamesonii. Ce n'est qu'en 1908 que l'ichtyologiste australien James Douglas Ogilby affirme que ces espèces sont synonymes[4].
P. signifer se trouve de Rocky River sur la péninsule du cap York jusque Narooma, en Nouvelle-Galles du Sud. Ce poisson habite des estuaires ou des ruisseaux de petite taille et aux eaux calmes, des lagunes et des marais salants. Le poisson vit en eau saumâtre et en eau de mer près de quelques îles situées au large du Queensland, notamment Low Island, Dunk Island, Hinchinbrook Island et Lizard Island. Sa présence a été enregistrée jusqu'à 300 km en amont des fleuves Mary et Dawson, dans le Queensland[2].
Pseudomugil signifer est une espèce de poissons de la famille Pseudomugilidae. C'est une espèce commune des fleuves et estuaires de l'est de l'Australie.
Pseudomugil signifer (dugina riba), malena tropska slatkovodna bentopelagička ribica, australski endem. Zlatne je boje a naraste maksimalno do 7.0 cm, uobičajena dužina 3.5 cm. Pripada porodici Pseudomugilidae, red Atheriniformes[1]. Otkrio ju je Kner 1866.
U Hrvatskoj je poznata kao dugina riba, a u engl. kao Pacific blue-eye[2]. Uzgaja se i u akvarijima i hrani crvima.
Pseudomugil signifer (dugina riba), malena tropska slatkovodna bentopelagička ribica, australski endem. Zlatne je boje a naraste maksimalno do 7.0 cm, uobičajena dužina 3.5 cm. Pripada porodici Pseudomugilidae, red Atheriniformes. Otkrio ju je Kner 1866.
U Hrvatskoj je poznata kao dugina riba, a u engl. kao Pacific blue-eye. Uzgaja se i u akvarijima i hrani crvima.
Pseudomugil signifer is een straalvinnige vissensoort uit de familie van blauwogen (Pseudomugilidae).[1] De wetenschappelijke naam van de soort is voor het eerst geldig gepubliceerd in 1866 door Kner.
Bronnen, noten en/of referenties
本魚體適度延長，側扁；嘴小，略垂直；前主上腭之後部齒較長，於口閉合時會外露；第一背鰭起點在胸鰭末端以前，具3~6棘；第二背鰭具1棘棘6~10枚軟條；臀鰭之起點在第一背鰭末端之下方，具1棘及9~12枚軟條；胸鰭尖形，尾鰭開叉；無側線，一縱列鱗具25~31枚。雌雄異形，雄魚背鰭、臀鰭及腹鰭之前方各鰭條成絲狀延長；在春夏之繁殖季節，體色會變成鮮豔之黃色。雄魚體長可達7公分。
本魚棲息範圍自純海洋至純淡水均有，通常於河口之紅樹林較多。為觀賞性之淡水魚，最適水溫為22℃~26℃，喜好鹼性而偏向略硬之水質，餌料除硬而大之人工飼料外均可。本魚體態優雅，宜單種飼養；繁殖不太困難，成熟的親魚在水草中產下一個個卵並受精，卵會以附著絲著於魚巢，產卵的數目依雌魚之年齡及體狀而異，此產卵行動會持續數周之久。卵在水溫26℃，14日可孵化，剛孵化之仔魚即可進食。
作為觀賞性淡水魚。
