Texas river cooter
The elliptical carapace (to 33 cm) is somewhat flattened (height only 40% of length), and posteriorly serrated. The vertebrals are broader than long; the 1st is the narrowest; the 5th is expanded. Longitudinal rugose striations are present on the pleural scutes in adults. The carapace is olive-brown with a pattern of fine yellow reticulations, whorls, and ocelli; the 2nd pleural contains 5-6 concentric whorls with dark centers, and each marginal has a narrow yellow vertical bar on its upper surface. The undersides of the marginals are patterned with ocelli. Adult males may become more melanistic with age. The hingeless plastron is approximately the same width throughout, and has a posterior notch. It is yellow with dark seams and a pattern of narrow black lines following the seams. This pattern tends to disappear with age. The bridge bears a pattern of dark transverse wavy lines. The skin is black with white to yellow stripes. Head markings are variable, consisting of narrow and broad yellow stripes which may be broken into spots and dashes. Present also are a prominent postorbital stripe and a broad vertical bar just behind the jaw articulation. The upper jaw has a medial notch flanked by tooth-like cusps; the lower jaw is horizontally flattened, as in P. concinna.
Killebrew (1977a) reported 50 chromosomes: 26 macrochromosomes (16 metacentric, 6 submetacentric, and 4 telocentric) and 24 microchromosomes.
Adult males are slightly shorter (to 25.3 cm) and more flattened than females (to 33 cm), and have longer, thicker tails with the anal vent behind the posterior carapace rim. The foreclaws of adult males are long and very pronounced; those of adult females are much shorter and thicker.
Pseudemys texana lives in the Colorado (Concho, Llano, San Saba), Brazos, Guadalupe, and San Antoinio watersheds of central and south-central Texas.
Dixon (in Etchberger and Iverson, 1990) observed previously undocumented and significant geographic variation in color pattern, even within the Colorado River basin, which makes the relationship between P. texana and P. concinna uncertain. Further study of the closeness of these two species is needed.
It is most often found in rivers, but also may wander into irrigation ditches and canals and cattle tanks.
Males are mature in three years, but it takes six or more years for females to be ready to breed (Vermersch, 1992). Courtship behavior is similar to that of P. nelsoni (Fritz, 1989c).
Nesting takes place in May and June; nests are 10.2-12.7 cm deep (Vermersch, 1992). The eggs are dull white, textured with fine granulations, pliable-shelled, and ellipsoidal (39.2-43.3 x 26.2-29.4 mm). In south-central Texas, hatchlings emerge in August and September (Vermersch, 1992).
Hatchlings and juveniles are more brightly marked than adults with a complex pattern of prominent yellow stripes, whorls, and ocelli on each pleural and vertebral scute. The plastral pattern is also more intense.
Wild adults eat mollusks (Lymnaea, Planorbis, Sphaerium) (Ernst et al., 1994), and Vermersch (1992) reported that young individuals actively pursue aquatic and terrestrial insects, crayfish, snails, and other invertebrates when offered them
IUCN Red List Status (1996)