Allometry of rostrum and sexual appendages in Hippolyte sapphica morphotypes (Crustacea: Decapoda: Hippolytidae) during the reproductive period

Abstract

ABSTRACT This study focuses on the post-larval development of Hippolyte sapphica morphotypes, during the late reproductive period. The species is endemic to Central/Eastern Mediterranean and displays morphοtype A with a well-developed rostrum and morphotype B with a short, juvenile-like one. Our results partly confirm the previous findings on the rostral dimorphism, while also providing new, detailed results obtained on pre-ovigerous specimens. In the A-males, two distinct sub-populations were discriminated: the main group with a fast rostral development, and a small one, with a slower rostral growth rate. The rostral growth in A-females was significantly attenuated, without identifiable subgroups. No difference was detected in the negative allometric rostral growth of B-specimens in both sexes. The relative growth of the appendix interna was nearly the same in females of both morphotypes, whereas the growth rate of the appendix masculina was significantly higher in A-males with fast rostral development, attenuated in B-males, and finally being the lowest in A-males with slowly developing rostral. Even within the A-males’ subgroup, a significant partial correlation was detected between the relative growth of the rostrum and that of the appendix masculina. The relationship between growth of the rostrum and sexual appendages raises the question about underlying molecular mechanisms.