Chinemys reevesii

(Gray, 1831b)
Chinese three-keeled pond turtle

The elongated (to 23.6 cm) oval to oblong carapace is slightly arched, unserrated, but medially notched posteriorly, and has three keels: a pronounced medial vertebral keel flanked on each side by a lower keel extending along the dorsal portions of the pleural scutes. The lateral keels are more pronounced in juveniles. Vertebral 1 is broader anteriorly than posteriorly; it is broader than long in younger individuals, but becomes elongated with age until it may be slightly longer than broad in old turtles. Vertebrals 2-5 are broader than long. Lateral marginals may be upturned; posterior marginals are smooth to only slightly serrated. The carapace ranges from light to dark brown with darker pigment along the keels, and, in some, light seams. The posterior plastral lobe is broader than the anterior lobe. The plastron is notched posteriorly; the plastral formula is: abd >< pect >< fem > gul >< an > hum. Both plastron and bridge are yellow with a large brown blotch on each scute; these blotches may be smooth edged, or have extending dark radiations which give the blotch a spiky appearance, or the plastron is dark brown or black. The head is moderate to broad (megalocephala -form) in size with a projecting snout and a slight medial to no notch on the upper jaw. It is dark brown to black with a series of elongated, broken, or curved yellow stripes on the sides. The tympanum is often ringed with yellow, and both chin and lower jaw may contain mottled yellow marks. The neck is grayish brown to black with several solid or broken, narrow yellow stripes. The limbs and tail are uniformly olive to brown. Melanism occurs very rarely in females (Lovich et al., 1985), but is common in older males. Yabe (1994) reported that submelanistic males are 6-9 years old (mean carapace length 14.0 cm), while melanistic males are older than six years and longer that 14.9 cm. In submelanistic males the yellow markings are fading and the body color is becoming darker. In melanistic males all exterior parts, including the iris of the eye are completely black.
The diploid chromosome number is 52: 26 macrochromosomes (16 metacentric, 6 submetacentric, 4 telocentric) and 26 microchromosomes (Sasaki and Itoh, 1967; Killebrew, 1977a); however, Gao and Bingying (1986) reported the 52 chromosomes are divided into 22 macrochromosomes (14 metacentric, 4 submetacentric, 4 subtelocentric) and 30 microchromosomes, whereas (Carr and Bickham, 1986) counted 28 macrochromosome (18 metacentric or submetacentric, 10 telocentric or subtelocentric) and 24 microchromosomes; also see Geographic Variation.
Females are larger than males, but males have tails with very thick bases and the vent beyond the carapacial rim. The adult male plastron may also be slightly concave; that of the female is always flat. Age and size at attainment of sexual maturity are unknown, but males develop the enlarged tail early at carapace lengths as short as 60 mm.

Chinemys reevesii occurs in Japan on Honshu and Kyushu, Korea, Taiwan, Hong Kong, and on mainland China south of the Yangtze River west to Guangzhou; it has been introduced in the USA and Canada. C. reevesii has also been reported from the Philippines and the Bering Islands of the USSR. We have examined these specimens, and they are C. reevesii; however, since this species is unknown from the Philippines we feel the specimens have wrong locality data. The Bering Island specimen was found washed up onto a beach, and we agree with Nikolskii (1915) that it probably drifted there from Japan.

Geographic Variation
No subspecies are currently recognized, but variation exists (Lovich et al., 1985). Japanese Chinemys reevesii average greater carapace lengths than do mainland populations; however, the largest of more than 200 specimens we examined was a 23.6 cm female from Szechwan Province, China. Pritchard (1979) states that Japanese specimens may reach well over 30 cm and possibly to 38 cm, but this is unsubstantiated. Taiwanese specimens often have more neck stripes than turtles from other populations.
The broad-headed form Chinemys megalocephala Fang, 1934 was synonymized with C. reevesii by Iverson and McCord (1989). However, Guo et al. (1997) found variations in the karyotypes of C. reevesii and "C. megalocephala". Both had a diploid compliment of 52 chromosomes; 28 macrochromosomes, and 24 microchromosomes. C. reevesii had a fundamental number of 74, with two pairs of subtelocentric macrochromosomes, and a constriction on the short arm of the third macrochromosome. In contrast, the broad-headed megalocephala -variant had a fundamental number of 78, with 4 pairs of subtelocentric macrochromosomes, and no constriction on the short arm of the third macrochromosome. With such genetic variation, perhaps these forms represent valid subspecies.

Chinemys reevesii lives in shallow, soft-bottomed waters of ponds, marshes, canals and streams, but may also enter rivers.

Natural History
Courtship and mating occur in the spring, with the males pursuing and swimming around the females in an effort to make snout contact (Pope, 1935).
Nesting occurs in June and July. Three clutches of four to nine eggs are laid each season (Fukada, 1965). The white eggs are elongated (40 x 23 mm). The duration of incubation depends on the incubation temperature: clutches incubated at 28°C have an average incubation period of 66.9 days, those incubated at 30°C average 62.3 days, and eggs incubated at 33°C hatch in about 56.6 days (Wang et al., 1995). Incubation temperature also affects hatchling mass, as those incubated at high temperatures that hatch more quickly weigh less that those that have gone through longer incubation periods at lower temperatures (Wang et al., 1995).
Fukada (1965) stated that in the Japanese wild newly hatched young overwinter in the nest and emerge in March or April. Hatchlings have three prominent carapacial keels, long tails, and large heads. Their shells are about 22 mm long.
Chinemys reevesii is fond of basking. An omnivore, it feeds on aquatic plants, fruits, and lettuce, as well as worms, aquatic insects, frogs, and fishes.

IUCN Red List Status (1996)
Not listed. This species is a hardy captive with much personality; it breeds well and makes a good pet. Unfortunately, this has led to much collecting in China, where the turtle is also eaten, that has resulted in a drastic decline the population until the species is threatened with extinction in that country. Currently, Chinemys reevesii in Japan and Taiwan are assumed to be under little or no risk.