Painted turtle
The painted turtle is the most widespread native turtle of North America. It lives in relatively slow-moving fresh waters, from southern Canada to northern Mexico, and from the Atlantic to the Pacific. They have been shown to prefer large wetlands with long periods of inundation and emergent vegetation. This species is one of the few that is specially adapted to tolerate freezing temperatures for extended periods of time due to an antifreeze-like substance in their blood that keeps their cells from freezing. This turtle is a member of the genus Chrysemys, which is part of the pond turtle family Emydidae. Fossils show that the painted turtle existed 15 million years ago. Three regionally based subspecies evolved during the last ice age. The southern painted turtle is alternately considered the only other species in Chrysemys, or another subspecies of C. picta.
The adult painted turtle is long; the male is smaller than the female. The turtle's top shell is dark and smooth, without a ridge. Its skin is olive to black with red, orange, or yellow stripes on its extremities. The subspecies can be distinguished by their shells: the eastern has straight-aligned top shell segments; the midland has a large gray mark on the bottom shell; the western has a red pattern on the bottom shell.
The turtle eats aquatic vegetation, algae, and small water creatures including insects, crustaceans, and fish. Painted turtles primarily feed while in water and are able to locate and subdue prey even in heavily clouded conditions. Although they are frequently consumed as eggs or hatchlings by rodents, canines, and snakes, the adult turtles' hard shells protect them from most predators. Reliant on warmth from its surroundings, the painted turtle is active only during the day when it basks for hours on logs or rocks. During winter, the turtle hibernates, usually in the mud at the bottom of water bodies. The turtles mate in spring and autumn. Females dig nests on land and lay eggs between late spring and mid-summer. Hatched turtles grow until sexual maturity: 2–9 years for males, 6–16 for females.
In the traditional tales of Algonquian tribes, the colorful turtle played the part of a trickster. In modern times, four U.S. states have named the painted turtle their official reptile. While habitat loss and road killings have reduced the turtle's population, its ability to live in human-disturbed settings has helped it remain the most abundant turtle in North America. Adults in the wild can live for more than 55 years.
Taxonomy and evolution
The painted turtle is one of two species in the genus Chrysemys.The parent family for Chrysemys is Emydidae: the pond turtles. Emydidae is split into two sub families; Chrysemys is part of the Deirochelyinae branch. The three subspecies of the painted turtle are the eastern, midland, and western.
The southern painted turtle used to be considered a sub-species of C. picta, but is now generally considered a different species.
The painted turtle's generic name is derived from the Ancient Greek words for "gold" and "freshwater tortoise" ; the species name originates from the Latin for "colored". The subspecies name, marginata, derives from the Latin for "border" and refers to the red markings on the outer part of the upper shell; dorsalis is from the Latin for "back", referring to the prominent dorsal stripe; and bellii honors English zoologist Thomas Bell, a collaborator of Charles Darwin. An alternate East Coast common name for the painted turtle is "skilpot", from the Dutch for turtle, schildpad.
Biologists have long debated the genera of closely related subfamily-mates Chrysemys, ''Pseudemys, and Trachemys. After 1952, some combined Pseudemys and Chrysemys because of similar appearance. In 1964, based on measurements of the skull and feet, Samuel B. McDowell proposed all three genera be merged into one. However, further measurements, in 1967, contradicted this taxonomic arrangement. Also in 1967, J. Alan Holman, a paleontologist and herpetologist, pointed out that, although the three turtles were often found together in nature and had similar mating patterns, they did not crossbreed. In the 1980s, studies of turtles' cell structures, biochemistries, and parasites further indicated that Chrysemys, Pseudemys, and Trachemys'' should remain in separate genera.
Classification
Originally described in 1783 by Johann Gottlob Schneider as Testudo picta, the painted turtle was called Chrysemys picta first by John Edward Gray in 1855. Four subspecies were then recognized: the eastern by Schneider in 1783, the western by Gray in 1831, and the midland and southern by Louis Agassiz in 1857, though the southern painted turtle is now generally considered a full species.Subspecies
Although the subspecies of painted turtle intergrade at range boundaries they are distinct within the hearts of their ranges.- The male eastern painted turtle is long, while the female is. The upper shell is olive green to black and may possess a pale stripe down the middle and red markings on the periphery. The segments of the top shell have pale leading edges and occur in straight rows across the back, unlike all other North American turtles, including the other three subspecies of painted turtle, which have alternating segments. The bottom shell is plain yellow or lightly spotted. Sometimes as few as one dark grey spot near the lower center of the shell.
- The midland painted turtle is long. The centrally located midland is the hardest to distinguish from the other three subspecies. Its bottom shell has a characteristic symmetrical dark shadow in the center which varies in size and prominence.
- The largest subspecies is the western painted turtle, which grows up to long. Its top shell has a mesh-like pattern of light lines, and the top stripe present in other subspecies is missing or faint. Its bottom shell has a large colored splotch that spreads to the edges and often has red hues.
| Eastern painted turtle C. p. picta | Midland painted turtle C. p. marginata | Western painted turtle C. p. bellii |
Until the 1930s, many of the subspecies of the painted turtle were labeled by biologists as full species within Chrysemys, but this varied by the researcher. The painted turtles in the border region between the western and midland subspecies were sometimes considered a full species, treleasei. In 1931, Bishop and Schmidt defined the current "four in one" taxonomy of species and subspecies. Based on comparative measurements of turtles from throughout the range, they subordinated species to subspecies and eliminated treleasei.
Since at least 1958, the subspecies were thought to have evolved in response to geographic isolation during the last ice age, 100,000 to 11,000 years ago. At that time painted turtles were divided into three different populations: eastern painted turtles along the southeastern Atlantic coast; southern painted turtles around the southern Mississippi River; and western painted turtles in the southwestern United States. The populations were not completely isolated for sufficiently long, hence wholly different species never evolved. When the glaciers retreated, about 11,000 years ago, all three subspecies moved north. One theory about the origin of the subspecies is that the western and southern subspecies met in Missouri and hybridized to produce the midland painted turtle, which then moved east and north through the Ohio and Tennessee river basins. However, morphological evidence does not support this theory. Instead, it was found that if the midland turtle is a hybrid, it would more likely be a hybrid of the eastern and western subspecies
In 2003, Starkey et al. proposed that Chrysemys dorsalis, formerly considered a subspecies of C. picta, to be a distinct species sister to all subspecies in C. picta. Although this proposal was largely unrecognized at the time due to evidence of hybridization between dorsalis and picta, the Turtle Taxonomy Working Group and the Reptile Database have since followed through with it, although both the subspecific and specific names have been recognized.
Fossils
Although its evolutionary history—what the forerunner to the species was and how the close relatives branched off—is not well understood, the painted turtle is common in the fossil record. The oldest samples, found in Nebraska, date to about 15 million years ago. Fossils from 15 million to about 5 million years ago are restricted to the Nebraska-Kansas area, but more recent fossils are gradually more widely distributed. Fossils newer than 300,000 years old are found in almost all the United States and southern Canada.DNA
The turtle's karyotype consists of 50 chromosomes, the same number as the rest of its subfamily-mates and the most common number for Emydidae turtles in general. Less well-related turtles have from 26 to 66 chromosomes. Little systematic study of variations of the painted turtle's karotype among populations has been done.Comparison of subspecies chromosomal DNA has been discussed, to help address the debate over Starkey's proposed taxonomy, but as of 2009 had not been reported. The complete sequencing of the genetic code for the painted turtle was at a "draft assembled" state in 2010. The turtle was one of two reptiles chosen to be first sequenced.
Description
Adult painted turtles can grow to long, with males being smaller. The shell is oval, smooth with little grooves where the large scale-like plates overlap, and flat-bottomed. The color of the top shell varies from olive to black. Darker specimens are more common where the bottom of the water body is darker. The bottom shell is yellow, sometimes red, sometimes with dark markings in the center. Similar to the top shell, the turtle's skin is olive to black, but with red and yellow stripes on its neck, legs, and tail. As with other pond turtles, such as the bog turtle, the painted turtle's feet are webbed to aid swimming.The head of the turtle is distinctive. The face has only yellow stripes, with a large yellow spot and streak behind each eye, and on the chin two wide yellow stripes that meet at the tip of the jaw. The turtle's upper jaw is shaped into an inverted "V", with a downward-facing, tooth-like projection on each side.
The hatchling has a proportionally larger head, eyes, and tail, and a more circular shell than the adult. The adult female is generally longer than the male, versus. For a given length, the female has a higher top shell. The female weighs around on average, against the males' average adult weight of roughly. The female's greater body volume supports her egg-production. The male has longer foreclaws and a longer, thicker tail, with the anus located further out on the tail.