Reproductive cycle of Pacifastacus leniusculus (Dana) (Crustacea: Decapoda) from the Brugneto Lake (Liguria, northwest Italy)

This paper investigates the reproductive biology of the signal crayfish Pacifastacus leniusculus (Dana). This North American species was introduced around the year 2002 in the Brugneto Lake (NW Italy), an oligotrophic artificial lake lying 780m above sea level. Various aspects essential to understanding reproductive biology were examined. P. leniusculus exhibits obvious sexual dimorphism, but previous studies have only identified juvenile and adult males and did not indicate the presence of adolescent specimens (according to the literature, physiologically mature but morphometrically immature specimens). The analyses of the morphological characters of the male chelae, performed in the present work, instead suggest the presence of a more robust (and possibly dominant) male morphotype. It is therefore possible that even adolescents of this species (whose cephalothorax length at sexual maturity was estimated at 47.4mm) are morphologically adult individuals, and that the specimens considered in the present work as adults (cephalothorax length, CTL, 63.6mm) are morphotypes stemming from particular environmental conditions. In P. leniusculus of the Brugneto Lake, ovaries mature progressively between July and January and oviposition occurs between October and February; young hatch from May to July. The smallest ovigerous females collected during the present investigation were 36mm CTL, while the estimated CTL at sexual maturity for females was about 40.3mm, at an age of 3years. Reproductive output increased with body size, as larger females produced more eggs.