Effects of male cheliped autotomy on female reproductive traits during successive matings in the porcellanid crab <i>Petrolisthes japonicus</i> (Decapoda: Anomura: Porcellanidae)

Petrolisthes japonicus is an anomuran crab with broad, dorsoventrally flattened chelipeds that readily autotomizes them when grasped by predators, facilitating escape. Although autotomy provides immediate survival benefits, it also imposes costs: loss of both chelipeds reduces growth, female reproductive output, and male mating success when competing with intact males. Because males can copulate with multiple females within a short period, repeated matings may be constrained by sperm limitation, potentially exacerbated by cheliped autotomy. This study tested whether cheliped loss affects male reproductive performance in successive matings under different autotomy conditions: both chelipeds intact, the larger cheliped autotomized, or both chelipeds autotomized (five males per group). Each male was sequentially paired with ten receptive females, and female spawning, fertilization rate, fecundity, and egg size were examined. The male autotomy condition did not significantly affect any female reproductive trait. Fertilization rates were 100% across all broods, and the shortest spawning intervals ranged from 1 to 2 days. These results suggest that males of P. japonicus may retain high reproductive potential regardless of cheliped autotomy condition. However, mating incidence was low and successive matings within 2 days were rare, indicating that further studies are needed to better evaluate male reproductive potential.