Reproduction of two species of freshwater turtle, Chelodina rugosa and Elseya dentata, from the wet–dry tropics of northern Australia

Abstract

Chelodina rugosa is a fast-growing, carnivorous turtle that occupies seasonally ephemeral habitats, whereas Elseya dentata is relatively slow-growing, largely herbivorous and con®ned to permanent water. Ovarian cycles followed an annual cycle of enlargement beginning in December (E. dentata) and January (C. rugosa), followed by ovulation and then follicular regression. Nesting season was determined from presence of gravid females, and for C. rugosa spans some 8 months from the late wet season until mid dry season, during which the turtle lays multiple clutches of eggs in underwater nests. Nesting may continue for longer when waterholes dry later following prolonged wet season rains. Nesting by E. dentata also begins in the late wet season but is complete by May and only one clutch is laid. Females of both species reproduce each year and clutch size and mass are related to female size. Annual spermatogenic cycles are similar in timing to those reported for temperate-zone chelids but would be classi®ed as pre-nuptial because spermatogenesis begins before breeding. Gonial proliferation begins at the start of the wet season and spermiation coincides with the onset of ovulation. Mating was not observed but in C. rugosa probably occurs during December and January soon after turtles emerge from aestivation. Post-mating storage of sperm in the epididymes did not occur in E. denatata but did appear to occur in some C. rugosa. The high reproductive output and extended nesting season of C. rugosa re¯ects its occupation of highly productive but unpredictable habitats and a reproductive strategy which ensures that some hatchlings meet optimal conditions for emergence. In contrast, the comparatively low fecundity and short nesting season of E. dentata, despite year-round warm temperatures and access to permanent water, suggests that its reproductive output may be energetically limited by a largely herbivorous protein-poor diet.

Ecological Aspects of a Wood Turtle, <em>Glyptemys insculpta</em>, Population at the Northern Limit of its Range in Québec

“…However, we believe that annuli counts are at best minimums because annuli were often too small and/or too worn to count. The validity of using scute annuli to determine age has been questioned for all turtles (Cox et al 1991;Kennett 1996;Brooks et al 1997). However, it seems with few exceptions that in temperate climates the counting of scute annuli is a reliable estimator of an individual's age at least to or near the age of maturity (Germano and Bury 1998).…”

Chelodina oblonga Gray 1841 – Northern Snake-Necked Turtle

“…The head is retracted sideways when disturbed and is not fully protected by the edge of the carapace and barely at all by the plastron. When disturbed it releases yellow fluid from inguinal and axillary scent glands, but the secretion lacks the pungent odor typical of some other species of Chelodina (Eisner et al 1978;Kool 1981;Kennett et al 1994a). …”

Spermatogenic cycle of the African sideneck turtlePelusios castaneus(Schweigger, 1812) (Reptilia: Testudines)

“…Reproduction of freshwater turtles in temperate regions is largely constrained by seasonal variation in temperature, with mating, egg development, nesting and hatching confined to warmer months, whereas freshwater turtles in tropical climates generally experience warm temperatures all year round (Kennett 1999). The African sideneck turtle Pelusios castaneus (Schweigger, 1812) (Reptilia: Testudines) is a freshwater turtle of the family Pelomedusidae, widely distributed in West Africa, occurring from Guinea and Senegal to northwestern Angola (Kirkpatrick 1995).…”

“…Spermatogenesis in turtles has been described by several authors as following one of three patterns: prenuptial, postnuptial (dissociated pattern) and acyclic (Georges 1983;Rao & Shaad 1985;Kennett 1999;Meylan et al 2002). In the prenuptial pattern, spermatogenesis immediately precedes mating, while in postnuptial spermatogenesis, spring mating uses spermatozoa produced the previous summer and or fall that have been stored in the epididymides over winter during a sexually quiescent phase (Lofts 1977;Lofts & Tsui 1977;Meylan et al 2002).…”

“…The spermatogenic cycles of various marine and freshwater turtles have been documented, including the Stinkpot, Sternotherus odoratus (McPherson & Marion 1981); the Australian freshwater turtle Emydura krefftii (Georges 1983); the freshwater turtle Trionyx gangeticus (Rao & Shaad 1985); the Loggerhead turtle, Caretta caretta (Wibbles et al 1990); the Kemp's Ridley sea turtle, Lepidochelys kempi (Rostal 1991); the Australian freshwater turtles Chelodina rugosa and Elseya dentata (Kennett 1999) and the Florida Softshell Turtle, Apalone ferox (Meylan et al 2002). With the exception of the recent report of Olukole et al (2011), on the topographical anatomy of the male reproductive organs of the African sideneck turtle, little is known about the reproductive cycle in this family.…”