Reproductive Dynamics of Pacifastacus leniusculus (Decapoda, Astacidae) in the Clitunno River: A Case Study of the Southernmost Population in Italy

Abstract In this study, the reproduction of the southernmost Italian population of the invasive Pacifastacus leniusculus (Dana, 1852) was analyzed. The species was recorded for the first time in the Clitunno River in 2020, an eradication plan started in June 2022 as part of the LIFE IMAGINE 19 IPE/IT/000015 project and aspects of the reproductive biology were examined from individuals captured. In this population, gonad maturation starts in February in females and in May in males. Spawning begins in October and the incubation lasts approximately four-five months. The smallest ovigerous female recorded had a cephalothorax length (CL) of 3.3 cm at an estimate age of 2+. Ovarian eggs and pleopodal eggs number ranged from 142 to 726 and from one to 481, respectively. A positive significant linear correlation between ovarian egg number and female CL was observed. Pleopodal egg diameter was positively correlated with female CL, indicating that bigger females produce larger eggs. This study shows the species is well adapted to the environmental conditions of the new habitat, exhibiting early sexual maturity, and a high potential fecundity but with a high percentage of egg loss. The reproductive characteristics highlighted in this study could help optimize containment efforts for the signal crayfish.