| Summary: | Knowledge of the molting cycle in crayfish may contribute (1) to improving a population analysis for monitoring and conservation purposes and (2) to imposing significant constraints on practices involved in culture. Two populations of Austropotamobius pallipes in central Italy were monitored from April to November for five years (2002–2006). Crayfish were collected, sexed, and the carapace length (CL) was measured. Molt cycle stages (premolt, molt, postmolt and intermolt) were identified depending on the exoskeleton hardness and color, and the abdomino-thorax splitting. The molt lasted for 6 minutes in juveniles, and maximally 16 minutes in adults in captivity. Males and females were treated separately, and divided into five age classes (0+; 1+; 2+; 3+; >4+). No significant differences were observed between females and males of the same age class. The molting event mainly occurred in April and May ongoing to November. The molting cycle occurred less frequently between July and August, and during the study period it was rarely observed between the last five days of July and the first week of August. Moreover, we measured and counted the gastrolith layers from a total of 124 crayfish (73 females + 51 males) collected twelve years ago, in order to discuss possible correlations between CL and gastrolith size.
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