Morphometric changes at terminal molt and reproductive capacity in the kelp crab Pugettia ferox Ohtsuchi & Kawamura, 2019 (Decapoda: Brachyura: Majoidea)

Abstract

Abstract It has been assumed that functional maturity and terminal molt occur simultaneously in majoid crabs. Although this assumption seems to be accurate in females, males of some majoids can mate with females even before their terminal molt. Here we describe the morphometric changes at terminal molt and test the reproductive capacity of pre-terminal molt males in the kelp crab Pugettia feroxOhtsuchi & Kawamura, 2019 (Majoidea, Epialtidae, Epialtinae). We measured the post-pseudorostral carapace length (PCL), claw length (CL), claw height (CH), and pleon (abdomen) width (AW) of crabs to estimate the morphological features distinguishing pre- and post-terminal molt individuals, namely relative claw length (CL/PCL) ≥ 0.660 in males and relative abdominal width (AW/PCL) ≥ 0.487 in females. Males with pre-terminal molt morphological features were observed for behavioral maturity through encounters with mature virgin females under laboratory conditions. More than half of the males copulated with a female and then underwent terminal molt. These females bred clutches, and larvae hatched. These results indicate that pre-terminal molt males of P. ferox can be functionally mature.