Comparative reproductive biology of the Tasmanian freshwater crayfishes Astacopsis gouldi Clark, Astacopsis franklinii, Gray and Parastacoides tasmanicus Clark (Decapoda: parastacidae)

The reproductive biology and life history of the Tasmanian freshwater crayfishes in the endemic genera Astacopsis and Parastacoides were studied in the field and laboratory from April 1985 to May 1987. A. gouldi and A. franklinii are open water species associated with riverine and lacustrine habitats from highlands to coastal plains. The burrowing, semiterrestrial P. tasmanicus occurs in wet heathlands, water courses and highland lakes in the wetter cooler, western half of the state. The three species were studied in representative, relatively undisturbed habitats. The habitats of all three species were typified by low water temperatures, high rainfall and fluctuating water levels. Reproductive morphology and anatomy of Astacopsis and Parastacoides was described in detail. Male and female gonads differ from those of northern hemisphere crayfishes, resembling anatomically the gonads of the Palinuridae. The male gonopores show considerable complexity and variation among genera. Female genitalia undergo significant changes in morphology at the onset of sexual maturity. Sexual dimorphism is developed to a greater degree in Astacopsis than in Parastacoides. Secondary sexual characters are more numerous in females of both genera and perform important functions in spawning and incubation of eggs. Data on seasonal reproduction, growth, population structure and density were obtained from regular sampling and mark recapture programs. Size at maturity and reproductive condition were determined by changes in reproductive morphology and gonad condition. In both genera males reach sexual maturity at a smaller size than females. Females, upon reaching maturity, exhibit a biennial breeding and molting cycle which is a unique strategy, apparently a result of the cooler climate conditions in Tasmania. In Astacopsis, mating and spawning take place in autumn, eggs are carried over winter, hatch mid to late the following summer and young remain attached until late summer to early autumn. Parastacoides mates and spawns in autumn, eggs are carried over winter, hatch early the following summer and postlarvae remain attached until mid summer. The larval development and morphology of Astacopsis and Parastacoides was described. Marked differences between the two genera were found and the \primitive\" larval development of Astacopsis differed significantly from that described for other freshwater crayfishes. Growth rates although faster in juveniles are relatively slow in adults of both genera. In reproductive adults of both sexes molting frequency is low (apparently biennial). This results in maturity being reached late and at a relatively large size as well as in overall longer life spans as compared to most other freshwater crayfishes."