Deirochelys reticularia (Latreille 1801)

Die Langhalsschmuckschildkröte (Deirochelys reticularia) ist eine Art der Familie Neuwelt-Sumpfschildkröten (Emydidae). Sie kommt in drei Unterarten in Nordamerika vor.

Erscheinungsbild

Weibliche Langhalsschmuckschildkröten erreichen bis zu 25 cm Panzerlänge. Die Carapaxlänge beträgt gewöhnlich aber nur zwischen 15 und 18 Zentimeter. Männchen sind in der Regel etwas kleiner als die Weibchen. Der meist olivfarbene Panzer ist fein gerunzelt und zeigt ein gelbgrünes Netzmuster, das auch dazu dient, die drei Unterarten voneinander zu unterscheiden. Mit zunehmendem Alter verschwindet diese Panzerfärbung jedoch zunehmend und ältere Tiere weisen einen zunehmend dunkeloliven bis fast schwarzen Rückenpanzer auf. Das Randschild des Panzers sowie der Bauchpanzer sind gelb.

Wie der Name "Langhalsschmuckschildkröte" bereits andeutet, haben sie einen außergewöhnlich langen Hals. Er erreicht 80 Prozent der Carapaxlänge.^[1] Die orangegelben Streifen, mit denen der Hals gezeichnet ist. Am Rumpf finden sich vertikale helle Streifen. Am Vorderbein ist ein breiter Streifen vorhanden.

Verbreitung und Lebensraum

Die Art besitzt drei Unterarten, die jeweils ein sich nicht überlappendes Verbreitungsgebiet haben.

• Die Östliche Langhalsschmuckschildkröte (Deirochelys reticularia reticularia) kommt entlang des Atlantik und der Golfküste von Virginia bis zum Mississippi River vor.
• Florida Langhalsschmuckschildkröte (Deirochelys reticularia chrysea) kommt aus Florida.
• Westliche Langhalsschmuckschildkröte (Deirochelys reticularia miaria) tritt von West-Mississippi über Südost-Missouri und Südost-Oklahoma südwärts bis zum Golf von Mexiko auf.

Die Langhalsschmuckschildkröte bewohnt flache Teiche, Seen, Tümpel und Zypressensümpfe. Sie ist nur sehr selten in Fließgewässern zu finden. Sie hält sich jedoch auch häufig außerhalb des Wassers und kann sich dabei recht weit vom nächsten Gewässer entfernen.

Lebensweise

Langhals-Schmuckschildkröten nehmen die übliche animalische Nahrung zu sich, wie sie auch für andere Neuwelt-Sumpfschildkröten charakteristisch ist. Daneben frisst sie aber auch erhebliche Mengen pflanzlicher Nahrung. Die Fortpflanzungszeit ist vom jeweiligen Verbreitungsgebiet abhängig. Die Populationen in Süd-Carolina paaren sich üblicherweise im März. In Florida sind Paarung ganzjährig zu beobachten. Das Gelege besteht aus fünf bis 15 Eiern. Die Zeit bis zum Schlupf ist temperaturabhängig, sie beträgt bei einer Temperatur von 25 bis 30 Grad etwa 60 bis 70 Tage.

Nachweise

Literatur

• Manfred Rogner: Schildkröten – Biologie, Haltung, Vermehrung, Eugen Ulmer KG, Stuttgart 2008, ISBN 978-3-8001-5440-1.

Einzelnachweise

1. ↑ Rogner, S. 61

Weblinks

– Sammlung von Bildern, Videos und Audiodateien

• Deirochelys reticularia In: The Reptile Database
• Fotos der Florida Langhalsschmuckschildkröte
• enature.com

The chicken turtle (Deirochelys reticularia) is a turtle native to the southeastern United States. It is the only extant member of the genus Deirochelys and is a member of the freshwater marsh turtle family Emydidae. The chicken turtle's scientific name refers to its extremely long neck and distinctive net-like pattern on its upper shell. There are three regionally distinct subspecies (eastern, western and Florida), which are thought to have evolved when populations became separated during periods of glaciation. These subspecies can be distinguished by their appearance; the western chicken turtle displays dark markings along the seams of its plastron (lower shell), while the plastron of the Florida subspecies is a bright yellow or orange color. Fossil records show that the chicken turtle has been present in the region for up to five million years.

Chicken turtles inhabit shallow, still or slow-moving bodies of water with plenty of vegetation and a muddy substrate. They are not found in rivers or deeper lakes that may be home to predators such as alligators and large fish. The chicken turtle is predominantly carnivorous and feeds mostly on invertebrates such as crayfish, dragonflies and spiders, but is also known to eat tadpoles, carrion and occasionally plant material. It is an active hunter and its long neck allows it to catch fast-moving prey. Although feeding and mating take place in aquatic environments, the chicken turtle is very well adapted to living on land and may spend more than half the year out of the water. Like many reptiles, it spends much of the day basking in the sun to regulate its body temperature, but unlike most other aquatic turtles, it hibernates over the winter months except in the warmer, southernmost reaches of its range.

The chicken turtle is relatively small compared to other related turtles, with males measuring up to around 16.5 cm (6.5 in) and females around 26.0 cm (10.2 in). It is also one of the world's shortest-lived turtles, reaching a maximum age of 20–24 years. There are thought to be around 100,000 adult chicken turtles in the wild. Although the population as a whole is considered secure, its status in some areas is less certain and several states have listed it as threatened or introduced regulations to manage hunting or taking. The word "chicken" in the turtle's vernacular name is apparently a reference to the taste of its meat, which was once popular in turtle soup and commonly sold in southern markets.

Taxonomy and evolution

Drawing accompanying Latreille's 1801 description of Testudo reticularia

The species was first described in 1801 independently by two French zoologists: as Testudo reticularia by Pierre André Latreille,^[7] and as Testudo reticulata by François Marie Daudin.^[8] Both descriptions were based on drawings and a single specimen collected by Louis Augustin Guillaume Bosc in the vicinity of Charleston, South Carolina some years previously.^[9] Subsequent studies placed the chicken turtle into various related genera (Emys, Clemmys and Terrapene)^[5][10] before Louis Agassiz assigned it to the current genus in 1857.^[11] He distinguished D. reticularia from other North American members of the family Emydidae by the length of its neck, and from the Australian Chelodina by the articulation of the neck vertebrae.^[12] In his 1940 comparison of Latreille and Daudin's original descriptions, naturalist Francis Harper determined that Latreille's had been published first, hence the currently accepted specific name.^[13]

The chicken turtle is the only extant species in the genus Deirochelys.^[1][14] Its parent family is Emydidae, the freshwater marsh turtles, which are found on every continent except Australia and Antarctica.^[15] The name of the genus is derived from the Ancient Greek words for "neck" (deirḗ) and "tortoise" (khélūs), a reference to the species' particularly long neck. The species name reticularia comes from the Latin for "net-like" or "reticulated" (reticulatus), probably alluding to the turtle's patterned carapace (top shell).^[16]

Subspecies

There are three distinct subspecies of chicken turtle, as described by Albert Schwartz in 1956 from a study of 325 specimens:^[10][17]

• The eastern chicken turtle (D. r. reticularia) is the turtle originally described by Latreille in 1801. It is the largest of the chicken turtles, with males measuring up to 16.5 cm (6.5 in) and females up to 26.0 cm (10.2 in).^[18] It is distinguished from the other subspecies by the coloring of its carapace, which is olive to brown with a yellow rim.^[3] The plastron (lower shell) sometimes features a spot or indistinct splotch of color.^[19] Its outstretched neck is especially long, sometimes as long as the carapace itself.^[20]
• The Florida chicken turtle (D. r. chrysea) has the most distinctively patterned carapace of all the chicken turtles, featuring bold, broad yellow-orange reticulation.^[3] The shell is cuneiform (wedge-shaped), especially so in males and juvenile turtles,^[21] and measures up to 16.5 cm (6.5 in) for males and 25.0 cm (9.8 in) for females.^[22] The subspecies name chrysea is taken from the Latin for "golden one" due to the bright yellow or orange color of its plastron.^[23][21]
• The western chicken turtle (D. r. miaria) is the smallest of the three subspecies; males have a maximum carapace length of 16.1 cm (6.3 in) and females 21.0 cm (8.3 in).^[22] The stripes on its head and neck are lighter in color (cream or pale yellow) compared to other chicken turtles,^[24] and its plastron features a dark pattern along the seams.^[25] The subspecies epithet miaria derives from the Greek for "stained", referring to this patterning.^[26] Its carapace is oval in shape and flatter than that of the other subspecies.^[27]

The plastron of the eastern chicken turtle (D. r. reticularia) sometimes features an indistinct splotch of color

Schwartz considered that D. r. reticularia is probably most reminiscent of the ancestors of Deirochelys, and that the other two subspecies most likely developed from it.^[28] The western chicken turtle is the most divergent of the three subspecies, suggesting a longer period of separation, possibly after populations were cut off from one another during a period of glaciation. Similarly, D. r. chrysea developed from a later population separation, a common phenomenon on the geographically diverse Florida peninsula.^[28] Studies of the chicken turtle's mitochondrial DNA support this theory of earlier divergence of the western subspecies from the two eastern ones.^[29] It is thought that the Mississippi River prevents intergradation (the presence of populations sharing characteristics of two subspecies) between D. r. miaria and D. r. reticularia since the chicken turtle does not generally inhabit rivers or moving water.^[28] Intergrades of the eastern and Florida chicken turtles are known, however, with several specimens having been collected in north-central Florida.^[19]

Fossil record

Ancestors of the chicken turtle and related turtles of the genus Chrysemys may have been present in North America for up to 40 million years.^[30] Writing in 1978, Dale Jackson considered D. reticularia to have "one of the most complete evolutionary records of any Recent turtle".^[31] Fossils have been found throughout its current range; examples dating from the Pliocene (roughly 5.33 to 2.58 million years ago) to the sub-Recent (prior to the start of the Holocene, or Recent, epoch around 11,700 years ago) have been discovered in Florida,^[32][33] in addition to fossils in Pleistocene deposits in South Carolina.^[32] A fossil found in Alachua County, Florida dating from the middle Pliocene was originally thought to belong to D. reticularia, but was later identified by Jackson as an extinct relative, D. carri.^[34] This species was somewhat larger than its modern relative and its shell roughly twice as thick.^[35] Other fossil fragments from the Hemingfordian (20.6 to 16.3 million years ago) are considered to belong to even earlier, more primitive members of the genus.^[32]

Description

Large adult chicken turtle with the reticulated pattern on the carapace clearly visible

The chicken turtle resembles the painted turtle (Chrysemys picta) and some species of cooter (genus Pseudemys) in appearance, but has an unusually long neck that is close to the length of its shell.^[36] It often also has black blotches on the underside of the bridge (the part of the shell connecting the carapace and plastron), which are not present in these other species.^[20] The carapace of the chicken turtle is elongated and pear-shaped, with the rear half noticeably wider than the front.^[37][38] It ranges from dark green to brown in color,^[39] and features a distinctive yellowish net-like pattern across its entire upper surface.^[40] The scutes of the upper shell have a ridged or wrinkled texture and are rough to the touch.^[3] Beneath its shell, the chicken turtle has particularly slender ribs, supposedly developed to accommodate its long, muscular neck.^[33] Although the chicken turtle shares morphological features with Blanding's turtle (Emydoidea blandingii), such as these elongated ribs and the shape of the skull, DNA analysis has shown they are not closely related.^[41]

Descriptions of the chicken turtle disagree on the base color of its skin but it is generally reported to be darker than the carapace, varying from olive to brown to black.^[10][20][40] One of the distinguishing features of D. reticularia is a broad yellow stripe on the forelegs.^[36] The skin of the neck and head also has light stripes, although narrower, while the tail and rear legs show vertical yellow markings.^[42] The head itself is elongated with a somewhat pointed snout but no other distinguishing features,^[43] and the digits of the feet are webbed and tipped with claws.^[7]

Compared to other turtles, the chicken turtle is small to medium in size. Adults vary in length from around 10–25 cm (4–10 in),^[3] with an average length of around 13 cm (5 in).^[33] The width of the carapace is roughly 65 percent of its length.^[33] Mature chicken turtles exhibit some degree of sexual dimorphism; the females are larger and heavier than males, although the males have longer, thicker tails.^[10][36] Unlike the painted turtle, there is no difference between the sexes in terms of the length of the foreclaws.^[10]

Chicken turtle hatchlings measure approximately 28–32 mm (1.1–1.3 in) and weigh around 8–9 g (0.28–0.32 oz).^[36] The shell is much rounder than the adults',^[44] and the shell and skin are considerably brighter in color,^[45] with a greater number of light stripes.^[42] The young of the western chicken turtle hatches with the distinctive dark markings on its plastron already present.^[45]

Distribution

Range

The chicken turtle is found throughout the southeastern United States; its range extends from the Atlantic coastal plain and states such as North Carolina, South Carolina, Georgia and Florida westward through the Gulf plain towards the Mississippi River. It tends to remain in coastal areas and is largely absent from the Piedmont plateau and more mountainous regions in the north of these states.^[46] West of the river, its territory reaches as far north as Missouri and as far west as Oklahoma and central Texas.^[47] Across its range, the chicken turtle may inhabit many hundreds or possibly thousands of wetland sites, although populations in any particular location are generally small.^[2]

Eastern chicken turtle

Cypress swamp in First Landing State Park, Virginia—it is unclear whether chicken turtles are still present here

The eastern chicken turtle is the most widespread of the three subspecies, with specimens known from eight states. The main bulk of its territory begins on the eastern banks of the Mississippi River in southeast Louisiana and extends eastward along the coastal plain of the Gulf of Mexico. Apart from the coastal region in the south of the state, it is not present in most of Mississippi, save for a small population in the drainage basin of the Tombigbee River.^[18] In Alabama, it is again commonly found throughout the coastal plain in the southern half of the state. It is also present further north in the Ridge and Valley region of the Appalachian mountain range, although less common.^[20]

Through Georgia, South Carolina and North Carolina, the eastern chicken turtle is again widely found throughout the coastal regions, although specimens have been recorded further inland in North Carolina.^[18] It is abundant in northern Florida, especially in the Panhandle region, where it is the only subspecies present. Its range begins to overlap with the Florida chicken turtle towards the north-central part of the state, with intergrades having been identified in Taylor, Levy, Gilchrist and Clay counties.^[21]

The eastern chicken turtle is also present in Virginia, although it is very rare there. A small colony was known to inhabit First Landing State Park in Virginia, but several studies have only managed to locate one adult female and it is thought this population may be extirpated. Around 40 mi (64 km) to the west, a small group of around 30 adults is present in Isle of Wight County.^[48] Neither of these locations is contiguous with the rest of the turtle's range; it is unclear whether these populations are relics of a native and formerly more widespread group, or whether they were introduced to the area.^[21]

Florida chicken turtle

As its name suggests, the Florida chicken turtle is native to Florida and is only found within the state. It is relatively widespread throughout the central and southern portions of the state, although it is absent from the Florida Keys.^[21]

Western chicken turtle

The western chicken turtle's range is generally restricted to locations west of the Mississippi River, although specimens have been found on the river's eastern banks in northwest Mississippi state.^[21] Its range extends from the coastal plain of the Gulf of Mexico in Texas and Louisiana, northward into the south and east of Oklahoma and through Arkansas towards Missouri. It may once have been common in the swampland of Missouri's Bootheel region, but is now only found in a few small groups in the extreme southeast of the state.^[49] Its territory is also decreasing in Arkansas; diffuse groups are now found only in the northern reaches of the Gulf coastal plain in the south of the state, as well as some regions of the Arkansas River Valley.^[50] The western chicken turtle is reasonably uncommon in Texas but its population there is secure. It inhabits the drainage basins of several rivers in the eastern half of the state, such as the Sabine and the Neches.^[39]

Habitat

Chicken turtles are semiaquatic, equally comfortable in wetland habitats and on land. All three subspecies have similar preferences; they like quiet, still or slow-moving bodies of water such as shallow ponds, oxbow lakes, drainage ditches, borrow pits, marshes, swales, cypress swamps, and Carolina bays.^[2][49][51] Generally, the chicken turtle prefers water with a maximum depth of around 70 cm (2.3 ft), but it is known to inhabit ponds up to 2 m (6.6 ft) deep. It rarely inhabits moving water such as streams or rivers, but may sometimes colonize quieter rivulets or pools in the riparian zone.^[42] Furthermore, it strongly favors fresh water, avoiding brackish water wherever possible.^[29]

The chicken turtle thrives in bodies of water with dense aquatic vegetation and a soft, muddy substrate. Often these are ephemeral or temporary wetlands that readily dry out during the summer or in periods of drought. Such habitats tend to be free both of fish, which would provide competition for food,^[43] and potential predators such as alligators.^[52] When drying occurs, chicken turtles will migrate to the land and burrow into the soil or hide under foliage to avoid dry weather. Although they are well adapted to living terrestrially, they rarely abandon their original habitat even during extended dry spells, and will relocate to the water once it returns.^[53]

Although the chicken turtle does not generally inhabit islands, isolated groups are also known in the Outer Banks chain of barrier islands off North Carolina.^[38] These maritime forest habitats are prone to drying out easily in the summer and can be affected by storms and sea spray, but research into one of these groups found no meaningful differences in longevity, growth rate or sex ratio between members of this population and their mainland counterparts.^[54]

Behavior

Chicken turtle basking

The chicken turtle is diurnal; its main periods of activity, such as feeding and mating, take place in the morning and late afternoon, either side of the warmest hours of the day.^[29][36] Like all reptiles, chicken turtles are cold-blooded and must regulate their body temperature. The main way they do this is through basking; they will spend many hours in the sun and can often be seen sitting on logs or tree stumps with their neck outstretched.^[49] However, they tend to spend less time basking than their herbivorous relatives.^[55] In order to be active, chicken turtles require an internal body temperature of around 25.5 °C (77.9 °F),^[55] therefore they are generally more active on warm, cloudy days than on hot, sunny ones.^[36] Like other turtles, the chicken turtle is extremely wary while basking and can be startled easily. Some have been known to bite and scratch in response to threats while others are more timid and retiring.^[50][56] Males may display particularly hostile behavior towards each other.^[55]

Unusually for an aquatic turtle, the chicken turtle is known to hibernate in winter throughout the northern part of its range.^[2] It leaves the water in late September to find a suitable site for the winter, usually either in mud and vegetation around the edges of the ponds and swamps which it inhabits.^[56] Alternatively, it may bury itself under fallen leaves in surrounding woodlands or in the mud at the bottom of a pond.^[36][46] Hibernating chicken turtles remain out of the water for up to six months before becoming active again in the spring. They are able to spend long periods on land without feeding due to their large stores of body fat.^[57] The first few days of activity following hibernation are generally dedicated to nesting and egg-laying by females, with males emerging slightly later around early April.^[58] In the southernmost part of its range where winters are milder, the chicken turtle remains active all year round apart from on especially cool days.^[55]

Chicken turtles are also frequently encountered on land during the summer months when the temporary wetlands they inhabit dry out. Males especially wander onto the land during this period and may travel great distances in search of alternative water,^[29] whereas gravid females remain in the wetland as long as possible since extra water is needed for egg production.^[59] Turtles unable to find a suitable aquatic habitat during particularly dry years may migrate to higher ground and burrow into the earth to undergo aestivation,^[46] a period of dormancy similar to hibernation. Survivorship rates among small juveniles are lower during this period, possibly because they lack the fat and water reserves required to withstand long periods without feeding.^[59] Individuals are known to return to the same terrestrial refugia from one year to the next.^[59] In total, a chicken turtle may spend up to 285 days per year on the land.^[60]

Life cycle

Mating and nesting

Adult chicken turtle laying eggs, Florida

The mating season of the chicken turtle can be estimated by the times of year in which male testicular volume is greatest, indicating maximum sperm production.^[61] This period varies by location; in Florida, the testes are largest during the hottest months of summer, while in South Carolina and the slightly cooler climate of Missouri this occurs in the late spring and early summer months, roughly May through July.^[49][55] In Texas, courtship may take place in the early spring (February to April) or fall (September to November).^[62] The chicken turtle's mating ritual is initiated by the male, who swims at an angle towards the female turtle until he is facing her head-on. He then attracts the female's attention by making short, rapid swimming motions, gazing at her and vibrating his outstretched foreclaws against her face and neck.^[52][55] Only if the female is receptive does copulation occur.^[52] There is no evidence of forced insemination as sometimes seen in other related turtles.^[63] Chicken turtle mating takes place in shallow waters,^[36] and reproduction can be disrupted by prolonged periods of dry weather.^[55]

Like mating, the timing of the nesting season depends on latitude. For example, in Florida nesting takes place continuously between mid-September and early March, with the possibility of an interruption if the winter weather is particularly cold.^[55] Further north, nesting may begin earlier in the year (around the end of August) but is always paused during the coldest months before resuming in the spring.^[64] In South Carolina and Arkansas, nesting and egg-laying may recommence in February,^[55][50] while in Virginia, in the northernmost reaches of the chicken turtle's range, it may not start again until March.^[36] This pattern of nesting in winter and hatching in spring is highly unusual; the chicken turtle is one of the only native North American turtles to nest at this time of year.^[55][50] Several reasons have been suggested for why this behavior developed. One hypothesis is that it allows the hatchlings to emerge in the spring when there is a good supply of food available and less competition from hatchlings of other turtle species that appear later in the year. Furthermore, predators of turtle eggs may be less likely to hunt for them in the spring when there are generally fewer to be found.^[64] Atypically among North American turtles, the female chicken turtle can retain fertilized, calcified eggs in her oviducts for several months after copulation, especially over the winter; these eggs will be laid in the spring once the nesting season resumes.^[65]

The female nests on land, often in loose soil,^[49][62] but sometimes in heavier ground.^[66] She digs out a cylindrical cavity with a depth of around 10 cm (4 in) and a diameter at the opening of approximately 8 cm (3 in).^[44] Nests are usually built close to the water,^[50] although females are known to wander up to 280 m (306 yd) in search of suitable sites.^[64] Once the nest is ready, the female deposits a clutch of between one and nineteen eggs.^{[nb 1]} The eggs are white with a leathery or parchment-like shell,^[38][50] and elliptical in shape, measuring approximately 28–41 mm (1.10–1.61 in) by 17–25 mm (0.67–0.98 in).^[64] Egg mass varies considerably; a review of eight studies found reported averages between 9.0 g (0.3 oz) and 11.0 g (0.4 oz).^[68] The mass appears to be positively correlated with female body size and eggs laid in fall are significantly heavier than those laid in spring.^[69] Several minutes after laying, the female will fill in her nest, sweeping the dirt over the eggs with her hind legs until they are covered.^[64] Chicken turtles commonly lay two clutches of eggs per year,^[67] although in the uninterrupted nesting season of Florida, females have been known to produce as many as four.^[38]

Growth and lifespan

The incubation period of chicken turtle eggs is again dependent on location and temperature. In the warmer climate of Florida, incubation takes 78–89 days in the wild, while in South Carolina it may last up to 152 days.^[67] Under laboratory conditions, which aimed to recreate the very cool soil temperatures (as low as 4 °C (39 °F)) experienced further north, incubation was extended up to 194 days.^[57] The egg's yolk contains a very high proportion of fats, on average 32.5% of dry matter, which help to nourish the hatchling during this long period in the nest.^[69] Inside the egg, the embryo goes through a period of little to no development (diapause) in the late gastrula stage. It must experience a period of cool temperatures, around 15–22 °C (59–72 °F), before development proceeds when the temperature increases to 24 °C (75 °F). The temperature during this time strongly influences the sex of the hatchling; in one study, 100% of eggs kept at 25 °C (77 °F) produced male turtles, whereas at 30 °C (86 °F), 89% were female.^[67]

When it is ready to emerge from the egg, the hatchling breaks through the shell using its egg tooth, a sharp, thornlike projection on its beak.^[70] Chicken turtles born in the fall commonly remain in the nest over winter before emerging in the spring,^[50] meaning that hatchlings from eggs laid in February or March may not leave the nest for over a year.^[46] Very young hatchlings are almost circular, although as they grow their shell becomes less rounded and more elongated.^[71] Young chicken turtles grow rapidly, approximately 25–44 mm (0.98–1.73 in) in the first year depending on conditions; in drought years growth may be slower.^[67] The rate of growth is highly variable between regions and populations.^[72] Growth continues until the turtle reaches sexual maturity, which occurs after approximately 2–3 years (or at a plastron length of 75–80 mm (2.95–3.15 in)) for males, and around 6–8 years (plastron length 141–155 mm (5.55–6.10 in)) for females.^[2] The turtle continues to grow after reaching maturity, although considerably more slowly. Females that reach a length of around 180 mm (7.09 in) appear to become much less reproductively active; they may only lay eggs every second or third nesting season, or they may cease to ovulate altogether.^[50]

The chicken turtle is one of the shortest-lived turtles in the world.^[37] Wild chicken turtles have been recaptured up to 15 years after their first capture, with some reaching an estimated maximum age of 20–24 years.^[67] A study by herpetologist Whit Gibbons suggested that less than 1% of chicken turtles live past the age of 15.^[67] In captivity, they may only live for as little as 13 years.^[1] This short lifespan means that the average female chicken turtle is active for fewer than ten breeding seasons.^[57] Determining the age of a turtle becomes increasingly difficult as the animal ages; in the first few years of its life the turtle's shell may show visible growth rings (annuli) that can be used to approximate its age.^[73] Annuli in the turtle's claws can sometimes be seen up to the age of around 14.^[67]

Ecology

Diet

Dragonfly nymphs are a favorite food of the chicken turtle

Like many emydids, chicken turtles are almost completely carnivorous during the first year of their lives. However, they are unusual in preferring a carnivorous diet into adulthood.^[74] It has been suggested that this explains the smaller local populations of D. reticularia compared to other related turtles due to competition with fish for food, especially insects.^[75] In the wild they are known to prey on crayfish, invertebrates, tadpoles, vegetation and carrion,^[76] including dead fish and other animals.^[38] Carr described having seen a chicken turtle eating Nuphar (bonnet-lily) buds,^[66] while captive adults have been observed feeding on gopher frog tadpoles,^[77] lettuce, and canned fish.^[45]

In a 1997 study of chicken turtle fecal matter collected during the summer months in South Carolina, dragonfly nymphs were the most commonly observed food, along with snails, spiders and insects such as backswimmers and water bugs. Only six out of forty-three specimens had ingested plant material.^[75] Investigations into the digestive tract contents of chicken turtles in north-central Florida, where the eastern and Florida subspecies coexist, found similar results. Decapods (including crayfish and shrimp), dragonflies and beetles were the most frequently encountered foods; six out of twenty-five turtles had consumed trace amounts of plants or algae.^[78] Research in Oklahoma found evidence that adults of the western subspecies follow a more omnivorous diet than their relatives. While crayfish and bugs were still present in the majority of fecal samples, 92.6 percent of samples also contained material or seeds of various plants, including the common rush and broadleaf cattail.^[79]

The chicken turtle is an aquatic hunter. It waits in the water and strikes its long neck out quickly with its mouth open to catch live food,^[80] relying on sight to detect its prey.^[81] The length of the neck allows it to capture fast-moving prey such as fish and spiders, which would otherwise be able to escape.^[38] Like Blanding's turtle, the chicken turtle uses a sucking motion when feeding;^[74] any water taken in during the process is expelled before the food is swallowed whole.^[80] The Florida chicken turtle is known to feed passively, swimming along with its long neck extended and foraging in clumps of vegetation.^[74]

Predators

Information regarding predation of the chicken turtle is scarce, but it is presumed that common predators such as raccoons, skunks and snakes feed on eggs and juvenile turtles.^[45][74] Fire ants are also known to attack nests and kill hatchlings of D. reticularia and other turtles.^[82] Hibbitts and Hibbitts suggest humans and alligators to be the main predators of the western subspecies,^[62] while a study in Florida found evidence of red-shouldered hawks preying on various turtles including the Florida chicken turtle.^[83] Otters, herons and snapping turtles are also listed as possible predators.^[48][74][82]

The meat of the chicken turtle is considered palatable and was once widely sold at markets throughout the southern United States for use in turtle soup;^[36][66] it is thought that the vernacular name is a reference to the flavor of its meat.^[49] It is still sometimes eaten today in rural areas, although this is uncommon.^[45] Consumption by humans is no longer considered to be a significant threat to the chicken turtle population.^[84]

Parasites

Various parasites have been identified during examinations of chicken turtle specimens. In 1968, Fain described a new species of cheyletoid mite, Caminacarus deirochelys, found in the rectum of a chicken turtle collected in Englewood, Florida, thirty years earlier.^[85] The trematode Neopolystoma orbiculare has been reported from the bladder of D. reticularia,^[86] while Telorchis corti is known to parasitize chicken turtles and various other emydids.^[87] A 2016 study of two chicken turtle specimens captured in Alabama identified a previously unknown species of blood fluke, Spirorchis collinsi.^[88]

Conservation

Chicken turtle in Virginia, where only around 30 adults are thought to remain

The chicken turtle population as a whole is currently considered secure and is thought to consist of at least 100,000 adults.^[2] Local populations are often small but stable, however the species is designated by NatureServe as S1 (critically imperiled) in Virginia and Missouri and S2 (imperiled) in Arkansas, Louisiana, North Carolina and Oklahoma.^[2] The chicken turtle does not appear on the IUCN's Red List of Threatened Species, although the Tortoise and Freshwater Turtle Specialist Group's own provisional list considers it Near Threatened.^[18] At the state level, the chicken turtle is protected by various local laws. In Virginia, where only around 30 adults are thought to remain, it has been listed as "vulnerable" since 1987.^[48] It is also considered at risk by the Alabama Natural Heritage Program; local regulations state that only two turtles may be kept and these must be for personal use (e.g. as pets).^[80] Along with other native reptiles, removal of chicken turtles from their natural habitat is regulated in several states throughout its range including Texas, Georgia and North Carolina.^[84] The chicken turtle is subject to a ban on commercial taking in Arkansas,^[89] where it is "extremely rare".^[57] In Missouri, where until 1995 no sightings had been recorded for at least 33 years,^{[nb 2]} it is listed as an endangered species, making hunting illegal.^[49]

Habitat loss appears to be the most significant threat to the stability of chicken turtle populations.^[91][84] Human activity is one cause of this; the turtle's preferred wetland habitats are often converted for agriculture, such as rice farming, or building developments. In Missouri and Arkansas in particular, the destruction of swampland and bottomland hardwood forests is a direct threat to the chicken turtle.^[49][57] Man-made obstacles such as fences and road barriers can also lead to populations becoming isolated.^[2] Since it prefers to live in small, shallow bodies of water that can easily dry out during the hotter months, the chicken turtle is also susceptible to the loss of upland habitats surrounding wetlands to which it migrates during periods of drought.^[80] Migration also leads to turtles, especially females in search of suitable nesting sites, walking onto roads where they are killed by traffic.^[62] Fire is a further threat; wildfires are becoming increasingly common and while controlled burns can help to protect wetland habitats by decreasing the risk of wildfire, chicken turtles that are overwintering on land or have been forced onto the land during drier months can be caught up in them.^[80]

Several locations inhabited by chicken turtles are already under protection, having been designated as wildlife reserves or conservation areas. However, further preservation of wetlands, especially temporary ones, would be beneficial in ensuring the continued stability of the population.^[84] In particular, the protections currently in place rarely include the surrounding areas of land that the chicken turtle inhabits for much of the year.^[80] Scientists in Oklahoma have developed quantitative polymerase chain reaction assay tests to enable the presence of four uncommon or vulnerable reptiles, including the chicken turtle, to be identified through environmental DNA.^[92]

References

Wikimedia Commons has media related to Deirochelys reticularia.

Notes

Citations

Bibliography

Deirochelys reticularia es una especie de tortuga de agua dulce poco común del sureste de Estados Unidos. Forma parte del taxón monotípico del género Deirochelys.

El nombre común en inglés de tortuga "Pollo" se refiere al sabor de su carne, que solía ser popular en los mercados del sur de Estados Unidos.

Descripción

Son similares en apariencia a Chrysemys picta, pero tienen un inusualmente largo cuello de rayas que está cerca de la longitud del caparazón, con una raya amarilla en las patas delanteras y en las patas traseras. El caparazón tiene forma de pera, y es de color oliva al marrón oscuro. Las hembras son generalmente más grandes que los machos, y los machos tienen una larga y gruesa cola. Los machos también tienen garras más largas. Al nacer miden una pulgada de diámetro, y los adultos alcanzan de 10,2cm a 25,4 cm. Son de tamaño mediano en comparación con otras tortugas.

Comportamiento

Se encuentran regularmente en tierra, la migración entre los hábitats acuáticos, o la búsqueda de áreas para excavar en el suelo y escapar de las condiciones secas. Los machos en general viajan más que las hembras. Pasan mucho tiempo tomando el sol en los troncos y en las rocas y nadando en pequeños grupos. Pasan la hibernación en el barro blando, pero solo en la parte norte de su rango, y en la vegetación del agua. Son tímidas y muerden con mucha facilidad.

Esperanza de vida

Algunas han sido recapturadas hasta 15 años después de su primera captura. Algunas llegaron a la edad máxima de 20 a 24 años en estado salvaje.

Distribución

La especie está formada por tres subespecies, se encuentran en un hábitat adecuado en todo el sureste de Estados Unidos. Deirochelys reticularia se encuentra en la zona costera de Virginia a Texas y hacia el norte de Oklahoma y Arkansas. La subespecie de Florida, D. r. chrysea, se limita a la península de Florida. En el este por el río Mississippi. Es una tortuga peregrina, y con frecuencia se encuentra vagando lejos del agua.

Hábitat

Son semi-acuáticas, se encuentran tanto en agua como en tierra. Prefieren zonas de agua tranquila: lagos, canales, pantanos, pantanos de cipreses, y bahías de las Carolinas. Prefieren el agua con una densa vegetación y el sustrato blando. Son tolerantes a los hábitats acuáticos efímeros y de fácil acceso a la tierra para excavar en el suelo y escapar de las condiciones secas. Han sido encontradas a una profundidad de unos pocos centímetros hasta más de 2 m.

Reproducción

Los machos se reproducen con tortugas hembras por la vibración de las garras delanteras contra la cara. Una vez que la hembra es receptiva ocurre la cópula. Son diferentes de la mayoría de las otras tortugas de América del Norte, ya que anidan en cualquier día de otoño o invierno. En Carolina del Sur hay dos temporadas de puesta de huevos; del invierno a la primavera (febrero a mayo) y otoño hasta principios de invierno (agosto a noviembre). Las hembras excavan nidos cilíndricos en la tierra en una gran variedad de tipos de suelos, desde arenosos a suelos pesados. Las hembras ponen de 2 a 19 huevos. Los embriones pasan por un período de dispause en la fase de gástrula tardía. Se debe experimentar un período de temperaturas frías antes de que avance el desarrollo. Los huevos eclosionan en 152 días a 29 grados Celsius, algunos huevos pueden pasar el invierno en el nido antes de la eclosión. La temperatura de incubación influye en el sexo de los embriones, con 25 grados Celsius la temperatura de incubación produce machos. Las temperaturas más altas tienen como resultado un aumento en los embriones de sexo femenino, con sólo el 11 por ciento de machos a una temperatura de incubación de 30 grados centígrados.

Alimentación

Son omnívoras, comen cangrejos de río, peces, frutas, insectos, invertebrados, ranas, renacuajos y plantas. Durante el primer año de su vida son casi totalmente carnívoras.

Estado de conservación

Las poblaciones se consideran actualmente estables en toda su extensión, aunque sí se enfrentan a amenazas potenciales. La destrucción del hábitat reduce el hábitat adecuado para la migración y la hibernación. A veces mueren en las carreteras a medida que migran entre hábitats, y también es cazada como alimento.

Subespecies

Hay tres subespecies:

• reticularia reticularia Deirochelys
• De Florida (Deirochelys reticularia chrysea)
• Occidental (Deirochelys reticularia Miaría)

Referencias

• https://web.archive.org/web/20101104115312/http://www.dgif.virginia.gov/wildlife/virginiatescspecies.pdf
• Turtles of the World, 2010 Update:Annotated Checklist of Taxonomy, Synonymy, Distribution, and Conservation Status (Checklist 000v3), p. 99
• Manfred Rogner: Schildkröten – Biologie, Haltung, Vermehrung, Eugen Ulmer KG, Stuttgart 2008, ISBN 978-3-8001-5440-1

Deirochelys reticularia Deirochelys generoko animalia da. Narrastien barruko Emydidae familian sailkatuta dago.

Erreferentziak

• TIGR Reptile Database in Species 2000 and ITIS Catalogue of Life: 2011 Annual Checklist

Ikus, gainera

• Deirochelys
• Emydidae

Deirochelys reticularia

L'Émyde réticulée, Deirochelys reticularia, unique représentant du genre Deirochelys, est une espèce de tortue de la famille des Emydidae^[1].

Distribution

Cette espèce est endémique des États-Unis^[1] :

• Deirochelys reticularia reticularia se rencontre en Virginie, en Caroline du Nord, en Caroline du Sud, en Géorgie, en Floride, en Alabama, au Mississippi et en Louisiane ;
• Deirochelys reticularia chrysea se rencontre en Floride ;
• Deirochelys reticularia miariase rencontre en Arkansas, en Louisiane, au Mississippi, au Missouri, en Oklahoma et au Texas.

Description

Deirochelys reticularia

Deirochelys reticularia

Deirochelys reticularia peut atteindre 25 cm.

Liste des sous-espèces

Selon TFTSG (27 mai 2011)^[2] :

• Deirochelys reticularia chrysea Schwartz, 1956
• Deirochelys reticularia miaria Schwartz, 1956
• Deirochelys reticularia reticularia (Latreille, 1801)

Publications originales

• Agassiz, 1857 : Contributions to the Natural History of the United States of America. Little, Brown & Co., Boston, vol. 1, p. 1-452 (texte intégral).
• Schwartz, 1956 : Geographic variation in the chicken turtle Deirochelys reticularia Latreille. Fieldiana Zoology, vol. 34, n. 41, p. 461–503 (texte intégral).
• Sonnini de Manoncourt & Latreille, 1801 : Histoire Naturelle des Reptiles, avec Figures Dessinées d'après Nature. Détérville, vol. 1, p. 1-280 (texte intégral).

Notes et références

La tartaruga reticolata (Deirochelys reticularia (Latreille in Sonnini & Latreille, 1802)) è una testuggine palustre americana della famiglia degli Emididi. È l'unica specie del genere Deirochelys Agassiz, 1857.^[1]

Etimologia

Il nome generico Deirochelys, che è una latinizzazione del greco antico δειρή ‑ῆς (deiré ‑ês, «collo») e χέλυς ‑υος (chélys ‑yos, «testuggine»), allude al collo di queste tartarughe, insolitamente lungo per le appartenenti al sottordine Cryptodira.^[2]

Il nome specifico reticularia, d'altro canto, deriva dal Latino rētĭcŭlus, ‑i e fa riferimento ai motivi del carapace.^[3]

Descrizione

Litografia del 1842.

Biologia

Distribuzione e habitat

Tassonomia

Sono note 3 sottospecie^[4]:

• D. r. reticularia (Latreille in Sonnini & Latreille, 1802) – tartaruga reticolata orientale
• D. r. chrysea Schwartz, 1956 – tartaruga reticolata della Florida
• D. r. miaria Schwartz, 1956 – tartaruga reticolata occidentale

Note

Deirochelys reticularia atau Kura-kura Ayam

Kura-kura Ayam dewasa bertelur di Florida

Kura-kura Ayam dewasa di Florida

Deirochelys reticularia juga dikenali sebagai Kura-kura Ayam ialah kura-kura yang dijumpai di tenggara Amerika Syarikat. Ia adalah spesies monotip daripada genus Deirochelys.

Nama "Ayam" pada kura-kura merujuk kepada rasa dagingnya seperti daging ayam, yang popular dijual di pasar-pasar selatan Amerika Syarikat.^{[petikan diperlukan]}

Ciri-ciri

Kura-kura Ayam mempunyai ciri-ciri yang serupa dengan Chrysemys picta picta, namun memiliki leher yang panjang dan berbelang. Belang kuning juga terdapat pada kedua-dua kaki hadapan dan belakangnya. Mempunyai selaput pada setiap kaki bagi membantunya berenang. Terdapat corak seperti jaring pada karapas (tempurungnya). Karapasnya berbentuk seperti buah pear, dan memiliki warna zaitun dan coklat gelap. Kura-kura betina lebih besar daripada jantan, dan jantannya memiliki ekor yang lebih panjang serta kuku kaki depan yang panjang. Bersaiz satu inci ketika menetas, dan kura-kura dewasa mencecah hingga 10.2-25.4 cm.

Kitaran hidup

Umur kura-kura liar boleh mencecah hingga 20 ke 24 tahun.

Habitat

Mendiami kawasan sunyi dan berair seperti tasik, kolam yang berhampiran dengan Teluk Carolina. Kura-kura ini cenderung mengorek tanah mencari kawasan lembap sedalam sehingga 2m.

Pembiakan

Tidak seperti kura-kura lain, kura-kura ini membina sarang pada musim luruh atau musim sejuk. 2 hingga 19 biji telur dilahirkan pada satu-satu musim, dan menetas selepas 152 hari (29 darjah Celsius). Suhu yang lebih rendah seperti 25 darjah Celsius menghasilkan kura-kura jantan berbanding betina.

Diet

Haiwan ini bersifat maserba, makan apa sahaja dari udang krai, ikan, buah-buahan, serangga, invertebrata, katak, berudu, dan tumbuh-tumbuhan. Semasa kecil mereka cenderung bersifat maging berbanding dewasa.

Status Pemuliharaan

Populasi kura-kura Ayam masih stabil walaupun masih lagi terdedah dengan ancaman. Kura-kura Ayam Timur dianggap terancam di Virginia.^[1] Pemusnahan habitat dan pemburuan dagingnya juga mempengaruhi populasi haiwan ini. Kadang-kala mereka mati kerana dilanggar di jalan raya.

Subspesies

Terdapat tiga subspesies Kura-kura Ayam:

• Deirochelys reticularia chrysea (Schwartz, 1956) — Kura-kura Ayam Florida
• Deirochelys reticularia miaria (Schwartz, 1956) — Kura-kura Ayam Barat
• Deirochelys reticularia reticularia (Latreille, 1801) — Kura-kura Ayam Timur

Rujukan

De netschildpad^[1] (Deirochelys reticularia) is een schildpad uit de familie moerasschildpadden (Emydidae), en is de enige soort uit het geslacht Deirochelys.^[2]

Indeling

Vroeger werd gedacht dat de soort nauw verwant was aan het geslacht Emydoidea, dat eveneens maar één soort telt. Later bleek dat Emydoidea juist meer verwant is aan de geslachten Emys en Terrapene dan aan Deirochelys, dat een grotere verwantschap heeft met de geslachten Chrysemys en Pseudemys. Bestudering van fossiele exemplaren heeft dit bevestigd.

Uiterlijke kenmerken

De netschildpad heeft een typische lichte nettekening van het rugschild, dat enigszins lijkt op een honingraatmotief . Het schild is peer-vormig en meestal olijfgroen of bruin tot bijna zwart, de tekening is lichter tot geel. De soort lijkt uiterlijk sterk op de sierschildpad (Chrysemys picta), maar is er ook eenvoudig van te onderscheiden door de veel langere en geel gestreepte nek, ook op de voor- en achterpoten zit een gele streep. De schildlengte maximale is ongeveer 25 centimeter.^[3]

Algemeen

De netschildpad leeft in een groot aantal staten in het zuidoostelijke deel van de Verenigde Staten. De schildpad leeft in ondiepe wateren als vijvers, meren, rivieren en greppels, stromend water wordt vermeden. Soms wordt de schildpad massaal in tijdelijke poeltjes aangetroffen maar kan ook kan vrij ver van water worden gevonden. De soort is omnivoor en leeft voor een belangrijk deel van kikkervisjes en kreeftachtigen, maar ook planten worden gegeten. Het vlees van de schildpad werd vroeger gegeten, de Engelse naam is 'kipschildpad'. Tegenwoordig is de schildpad beschermd en mag niet meer worden gevangen.

Levenswijze

De schildpad kent twee voortplantingsseizoenen en zet ten minste twee keer per jaar eitjes af, maar het laatste legsel is meestal kleiner in aantal eitjes, dit varieert van 2 tot 19 per keer. Na ongeveer 80 tot 90 dagen kruipen de juvenielen uit het ei, en zijn dan ongeveer drie centimeter lang, het rugschild is geplooid en heeft een lengtekiel. De eerste vijf jaar zijn de jonge schildpadjes voornamelijk carnivoor, maar gaan later meer planten eten.

Taxonomie en naamgeving

De soort wordt ook wel kuikenschildpad genoemd (in het Engels: chicken turtle), omdat de schildpad vroeger wel werd verwerkt in gerechten en naar kip smaakt. De soort werd voor het eerst wetenschappelijk beschreven door Pierre André Latreille in 1801. Oorspronkelijk werd de wetenschappelijke naam Testudo reticularia gebruikt.

Er zijn drie ondersoorten die een iets ander verspreidingsgebied hebben, zoals de Engelse benamingen al verraden.

• Ondersoort D. r. reticularia (Engels; Eastern Chicken Turtle)
• Ondersoort D. r. chrysea (Engels; Florida Chicken Turtle)
• Ondersoort D. r. miaria (Engels; Western Chicken Turtle)

Bronvermelding

Referenties

Bronnen

• (en) Peter Uetz & Jakob Hallermann - The Reptile Database – Deirochelys reticularia - Website Geconsulteerd 20 mei 2015
• (en) - Peter Paul van Dijk, John B. Iverson, Anders G. J. Rhodin, H. Bradley Shaffer & Roger Bour - Turtles of the World, 7th Edition: Annotated Checklist of Taxonomy, Synonymy, Distribution with Maps, and Conservation Status - ISSN 10887105 (2014) - Website
• (en) C.H. Ernst, R.G.M. Altenburg & R.W. Barbour - Turtles of the World - Website
• (nl) Bernhard Grzimek - Het Leven Der Dieren Deel I: Lagere Dieren - Pagina 103 - 1971 - Kindler Verlag AG - ISBN 902748662X

Kycklingsköldpadda (Deirochelys reticularia)^[3] är en sköldpaddsart som beskrevs av Pierre André Latreille 1801. Kycklingsköldpadda ingår i släktet Deirochelys, och familjen kärrsköldpaddor.^[4][5]

Kycklingsköldpadda förekommer i USA, i sydöstra Virginia, längs med atlantiska kustslätten i södra North Carolina, South Carolina, Georgia, Florida, gulfkusten i Alabama, Mississippi, Louisiana, östra Texas, Oklahoma, Arkansas och sydöstra Missouri.

Den är en sötvattenssköldpadda som lever vid både permanenta och temporära dammar, sjöar, diken och i våtmarker. Som fullvuxen kan en hona mäta upp till 25 centimeter. Hanarna är mindre och mäter upp till 15 centimeter. Ett kännetecken för arten är också att den har en lång hals.

Underarter

Arten delas in i följande underarter:^[4]

• D. r. reticularia - förekommer öster om Mississippifloden
• D. r. chrysea - förekommer i Florida
• D. r. miaria - förekommer väster om Mississippifloden

Källor

1. ^ Gray, J. E. (1863) Notes on American Emydidae, and Professor Agassiz’s observations on my Catalogue of them., Ann. Mag. nat. Hist. (3) 12: 176-183
2. ^ Duméril, A.M.C., and G. Bibron. (1835) Erpétologie Générale ou Histoire Naturelle Complète des Reptiles, Vol. 2., Librairie Encyclopédique de Roret, Paris, 680 p.
3. ^ [a b] Latreille,P.A. (1801) XXII Genre. Hétérodon, Heterodon. In: Sonnini and Latreille, Histoire Naturelle des Reptiles aved figures dessinées d’après nature, Vol. 4: 32-37., Chez Deterville, Paris.
4. ^ [a b] Bisby F.A., Roskov Y.R., Orrell T.M., Nicolson D., Paglinawan L.E., Bailly N., Kirk P.M., Bourgoin T., Baillargeon G., Ouvrard D. (red.) (27 april 2011). ”Species 2000 & ITIS Catalogue of Life: 2011 Annual Checklist.”. Species 2000: Reading, UK. http://www.catalogueoflife.org/annual-checklist/2011/search/all/key/deirochelys+reticularia/match/1. Läst 24 september 2012.
5. ^ TIGR Reptile Database . Uetz P. , 2007-10-02 Deirochelys reticularia

Externa länkar

• Wikimedia Commons har media som rör kycklingsköldpadda.
  Bilder & media

Denna artikel om sköldpaddor saknar väsentlig information. Du kan hjälpa till genom att tillföra sådan.

• 1 Опис
• 2 Спосіб життя
• 3 Розповсюдження
• 4 Підвиди
• 5 Джерела

Deirochelys reticularia là một loài rùa trong họ Emydidae. Loài này được Latreille mô tả khoa học đầu tiên năm 1801.^[1]

Hình ảnh

Chú thích

Tham khảo

Liên kết ngoài

Phương tiện liên quan tới Deirochelys reticularia tại Wikimedia Commons

Bài viết liên quan đến rùa này vẫn còn sơ khai. Bạn có thể giúp Wikipedia bằng cách mở rộng nội dung để bài được hoàn chỉnh hơn.

• x
• t
• s

雞龜（學名：Deirochelys reticularia）^[1]是泽龟科雞龜亞科下的一種陸棲雜食性龜，而雞龜屬則是單種屬，其下生物分佈于美國南部。其龜肉味道與雞肉很像，也因此得名。

亞種

該種下有三個亞種：

• 東部雞龜（Deirochelys reticularia reticularia）
• 佛羅里達雞龜（Deirochelys reticularia chrysea）
• 西部雞龜（Deirochelys reticularia miaria）

参考文献

アミメガメ（Deirochelys reticularia）は、爬虫綱カメ目ヌマガメ科アミメガメ属に分類されるカメ。本種のみでアミメガメ属を構成する。アミメガメ属はアミメガメ亜科の模式属。

分布[編集]

D. r. reticularia　ヒガシアミメガメ

アメリカ合衆国^[1][2]（アラバマ州、ケンタッキー州西部、サウスカロライナ州南東部、ジョージア州南部、テネシー州西部、ノースカロライナ州東部、バージニア州南東部、フロリダ州北部、ミシシッピ州）^[3]

模式標本の産地（模式産地）はチャールストン周辺（サウスカロライナ州）^[3]。

D. r. chrysea　フロリダアミメガメ

アメリカ合衆国（フロリダ州）^[3]固有亜種

D. r. miaria　ニシアミメガメ

アメリカ合衆国（アーカンソー州、オクラホマ州南東部、テキサス州東部、ミズーリ州南東部、ルイジアナ州）^[3]

形態[編集]

最大甲長25センチメートル^[3]。オスよりもメスの方が大型になり、オスは最大でも甲長15.7センチメートル^[3]。項甲板はやや大型で、後方がやや幅広い等脚台形^[3]。後部縁甲板は鋸状に尖らない^[3]。背甲の色彩は淡黄褐色や暗黄色で、網目状の斑紋が入る^[2][3]。種小名reticulariaは「網目状の」の意で、種小名と和名共に背甲に入る斑紋に由来する^[3]。縁甲板外縁は黄色く縁取られる。腹甲は細長い俵型で、中央部でやや括れる^[3]。

頭部はやや大型かつ扁平^[3]。吻端はわずかに突出し、顎の先端は鉤状に尖ったり凹まない^[3]。顎の外縁は鋸状に尖らず、咬合面はやや狭く稜や突起がない^[3]。頸部は長く^[1]、頭部と頸部を合わせた長さがほぼ腹甲長に等しい^[2][3]。頭部や頸部、四肢、尾の色彩は褐色や暗黄色で、黄色や白の筋模様が入る^[3]。

卵は長径2.8-4センチメートル、短径1.7-2.4センチメートルと楕円形^[3]。殻は白い皮革状^[3]。幼体は成長輪が明瞭で、椎甲板にあまり発達しない筋状の盛りあがり（キール）がある^[3]。成長に伴い成長輪やキールは消失する^[3]。

メスはオスに比べると背甲が幅広く甲高が高い^[3]。オスは尾が太くて長く、尾をまっすぐに伸ばした状態では総排泄口全体が背甲の外側に位置する^[3]。メスは尾が細いうえに短く、尾をまっすぐに伸ばしても総排泄口の大部分が背甲よりも内側にある^[3]。

D. r. reticularia　ヒガシアミメガメ

背甲はやや盛りあがる^[3]。背甲の網目模様や縁甲板の縁取りは細く、成長に伴い不明瞭になる個体もいる^[3]。橋に暗色斑が入る個体が多い^[3]。股甲板や肛甲板のシームに沿って暗色の斑点が入る個体もいる^[3]。下顎から喉に筋模様や破線状の斑紋が明瞭に入る^[3]。

D. r. chrysea　フロリダアミメガメ

背甲の網目模様は縁甲板の縁取りは中程度だが、成体でも明瞭^[3]。橋の色彩は黄色一色だが、暗色の斑点や縦縞が入る個体もいる^[3]。腹甲には斑紋が入らない^[3]。下顎から喉に筋模様や破線状の斑紋が明瞭に入る個体もいる^[3]。

D. r. miaria　ニシアミメガメ

背甲はやや扁平^[3]。背甲の網目模様や縁甲板の縁取りは太いが、成長に伴い消失する傾向が強い^[3]。橋にやや大型の暗色斑が入り、暗色斑が繋がる個体もいる^[3]。腹甲の甲板の継ぎ目（シーム）に沿って暗色斑が入る^[1]。下顎から喉に明瞭な斑紋が入らない^[3]。

分類[編集]

アミメガメ亜科内では他属より最も初期に分化したと考えられている^[3]。ヌマガメ科内では長い頸部や頭骨の一部、肋骨からブランディングガメ属と近縁とする説もあったが、形態やミトコンドリアDNAの塩基配列による分子系統学的解析から本種とブランディングガメ属は近縁ではないとする説が有力^[3]。

• Deirochelys reticularia chrysea　Schwaltz, 1956　フロリダアミメガメ　Florida chicken turtle
• Deirochelys reticularia miaria　Schwaltz, 1956　ニシアミメガメ　Western chicken turtle
• Deirochelys reticularia reticularia　(Latreille, 1801)　ヒガシアミメガメ　Eastern chicken turtle

生態[編集]

湖や池沼、湿原、水たまりなどのほぼ止水域のみに生息し、底質が泥で水生植物の繁茂した環境を好む^[3]。日光浴を好むだけでなく、陸づたいに複数の水場を移動し水場から離れた陸地で見られることもある^[3]。昼行性だが、夏季には夜間に活動することもある^[3]。フロリダ半島南部個体群などは周年活動するが、多くの生息地では冬季に水中で穴や泥中でじっとしているか陸上の落ち葉や泥の中で冬眠することもある^[3]。

食性は動物食傾向の強い雑食で、昆虫、クモ、甲殻類、貝類、両生類やその幼生、動物の死骸、植物質（キビ属、コウホネ属など）などを食べる。幼体は動物食だが、成長に伴い雑食傾向が強くなる^[3]。水中で接近した獲物を頸部を素早く伸ばして捕食するが、水面に落下した獲物も食べる^[3]。

繁殖形態は卵生。オスは前肢をメスの頭部の前で震わせて求愛するが、メスの吻端に自分の吻端を擦りつけたり、メスの総排泄口の臭いを嗅ぐこともある^[3]。2-5月と8-11月（亜種フロリダアミメガメでは9-翌3月）に1回に2-19個の卵を年に2-4回に分けて産む^[3]。発生時の温度により性別が決定（温度依存性決定）し、約25℃ではオス、約30℃ではメスが多く産まれる傾向がある^[3]。飼育下では28-29℃の環境下で78-89日で孵化した例がある^[3]。

人間との関係[編集]

生息地では食用とされることがあるが^[1]、食用の養殖などは行われておらず現在では食用とされることも一般的ではない^[3]。英名は味が鶏肉（chicken=鶏）に似ていることに由来する^[3]。

開発による生息地の破壊、水質汚染などにより生息数は減少している可能性もあるが、バージニア州やミズーリ州の地域個体群を除いて絶滅の危険性は低いと考えられている^[3]。

ペットとして飼育されることもあり、日本にも輸入されている。主に飼育下繁殖個体が流通する^[3]。アクアリウムかアクアテラリウムで飼育される。長い頸部を伸ばして獲物を捕食するためケージの大きさはゆとりを持たせ、レイアウトにはあまり尖った物は用いないようにする^[3]。日光浴を好むため、暖房器具などを照射して体を乾かすことができる広い陸地を用意する^[3]。腹甲が薄く腫瘍や潰瘍にかかりやすい傾向があるため、水質の悪化には注意する^[3]。野生個体は生きた餌を好むが、飼育下では死んだ餌や配合飼料や乾燥飼料などにも餌付く^[3]。頸部を伸ばして捕食するため餌を食べるのに時間がかかることや、同種他種問わず他個体に噛みつくおそれがあることから基本的には単独で飼育する^[3]。

参考文献[編集]

関連項目[編集]

• ヌマガメ科
  • アミメガメ亜科