A study of the reproduction of Krefft's river tortoise, Emydura krefftii, was conducted in the perched dune lakes of Fraser Island, Queensland. Mature male specimens exhibit a postnuptial pattern of spermatogenesis typical of temperate-zone turtles elsewhere, with a peak in spermatogenic activity in autumn and a cessation of activity during the breeding season in spring and early summer. The spermatogenic cycle is paralleled by seasonal variation in testicular weight (standardized for body size) and in the diameter of the seminiferous tubules. Sperm are abundant in the epididymal canals throughout the year. Mating was observed in autumn, late winter and spring.
Females have a cyclic reproductive pattern, with distinct phases of follicular enlargement, ovulation and oviducal period, and quiescence. Yolk begins to accumulate in the ovaries in late summer, and the accumulation continues unabated through the winter, presumably by the transfer of material from fat stores to the ovaries. Ovulations occur from late winter to mid-summer. Atresia of follicles that fail to ovulate was demonstrated histologically.
Emydura krefftii lay up to three clutches of hard-shelled ellipsoid eggs per season. Each clutch contains between four and 10 eggs; the number is strongly correlated with maternal body size. Reproductive potential ranges from 12 eggs per annum for a female that has recently matured (carapace length c. 150 mm), to 30 eggs per annum for a full-sized female (length c. 250 mm). Selected life-history traits of Emydura krefftii are discussed in the context of findings for other populations of the species and for other species of freshwater turtle.