Embryonic and juvenile attachment structures in Cherax cainii (Decapoda: Parastacidae): Implications for maternal care

Fertilised eggs, stage one and stage two juveniles of the smooth marron, Cherax cainii, are attached to the pleopods of the gravid female via specialised structures. The eggs are fixed to the maternal pleopods by egg stalks, whereas stage one and stage two juveniles remain attached by recurved spines on the dactyls of their fourth and fifth pereopods. Crayfish of the third juvenile stage are independent of the mother and receive no maternal care; their dactyl spines are straight and cannot grasp the mother's pleopods; the female displays agonistic behaviour toward her young commencing with stage III instars. We suggest that eggs and the first two juvenile stages attached to the mother would experience reduced levels of predation and be secured against strong river flow. We conclude by reviewing, briefly, the potential fitness costs and benefits of maternal care, to the mother and young of freshwater crayfish, from a life-history perspective.