Unknown facts of the biology of Polybius henslowii – Effect of gender on claw morphology and diet

Abstract

Polybius henslowii is known for both its unusual swimming behaviour and for forming large shoals during its pelagic phase. Although being a common species, many aspects of its biology remain unknown. In this work, P. henslowii's sexual dimorphism was examined in both dietary composition and morphologies of carapace and claw. Males were generally larger than females both on carapace and claw sizes. Claw morphology differed between males and females. Diet was similar between genders. Hence, we suggest that the sexual dimorphism in claw morphology results from gender-specific behaviours instead of diet. The most common dietary items were sand (51.2%), squid (34.1%) and crustaceans (26.8%). The same items were also the most important in volume, but with squids being more important than sand. The diet composition of P. henslowii was consistent with previous studies but also presenting sediment as an important item.