Population Structure and Male Melanism in the Reeves' Turtle, <i>Chinemys reevesii</i>

Abstract

Mark-recapture study on a population of Reeves' turtle, Chinemys reevesii, was conducted at two adjacent ponds in the southwestern part of Gifu Prefecture. A total of 111 turtles was marked during the period from 1986 to 1987, comprising 42 males, 68 females, and one young individual. It was speculated from the age structure that females lived longer on average than males. The females were larger than the males, growing to more than 200mm in carapace length (CL), whereas the males grew to about 160mm in CL. Melanistic individuals occurred only in males. Submelanistic males were six to nine years old and their mean CL was 140.3mm. Melanistic males were older than six years and larger than 120mm in CL. The mean CL of melanistic males was 149.6mm.

Radiotelemetric Study of Movement Patterns of Lotic Freshwater Turtles during Breeding and Hibernation Seasons

“…Several ecological aspects, such as movement pattern (Yabe 1992), population structure (Yabe 1989(Yabe , 1994, and population dynamics (Nakajima et al 2000, Takenaka andHasegawa 2001), have been studied for these species. These studies have been conducted mainly in lentic habitats, such as ponds, where population density of turtles tends to be high.…”

Mauremys reevesii (Gray 1831) – Reeves' Turtle, Chinese Three-Keeled Pond Turtle

“…Adult male M. reevesii tend to become melanistic as they grow older and larger, and large males occasionally lose all light markings on the shell and soft parts. Females do not exhibit this trend in coloration (Mao 1971;Sachsse 1975a;Sengoku 1979;Lovich et al 1990;Yabe 1994). Yabe (1994) reported an extreme case of male melanism in a central Honshu population, in which males, including an individual of 120 mm CL and all those greater than 145 mm CL, lost all light markings.…”

“…Females do not exhibit this trend in coloration (Mao 1971;Sachsse 1975a;Sengoku 1979;Lovich et al 1990;Yabe 1994). Yabe (1994) reported an extreme case of male melanism in a central Honshu population, in which males, including an individual of 120 mm CL and all those greater than 145 mm CL, lost all light markings. He assumed that the degree of the melanistic change in this species is correlated more with body size than with age.…”

“…This figure is much larger than those reviewed by Pritchard (1994) for the record size of M. reevesii, including the megalocephalic form (previously recognized as C. megalocephala: Iverson et al 1989). Males are much smaller than females, attaining a CL of 200 mm at most (Yabe 1994;Yasukawa, pers. obs.).…”

Impacts of river alteration for flood control on freshwater turtle populations

“…Age was determined by counting the number of plastron growth rings (Sexton 1959); turtles whose growth rings could not be identified were placed in the oldest age category. For the Reeve's turtle, Chinemys reevesii, melanic males were classified as mature, and males that were not completely melanic were classified as immature (Yabe 1994). Likewise, females aged C9 or those assigned to the old category were classified as mature because the youngest gravid female was 9 years old in C. reevesii (Kosuge, personal communication).…”