Reproductive biology of two species of semiterrestrial crabs of the genus Armases (Brachyura, Sesarmidae) living in sympatry in a southern Caribbean coastal stream

What is it about?

We investigated the reproductive biology of two semi-terrestrial crab species, Armases americanum and A. roberti, in the San Miguel stream in the southern Caribbean. The species are generally allopatrically distributed on islands and the mainland of the Caribbean Sea coastal streams but were found living in sympatry in the present study. For these two species we addressed the question whether there will be differences in their reproductive traits that would allow us to understand their coexistence. Reproductive parameters included sex ratio, maturity size, frequency of mature individuals, fecundity, embryo size, and reproductive output. We collected 1,417 individuals, with A. americanum females maturing at smaller sizes than males and producing numerous small embryos. A. roberti females matured at larger sizes than males and produced fewer and larger embryos. Reproductive output was slightly higher for A. roberti compared to A. americanum. The results revealed distinct reproductive strategies, underscoring the importance of species-specific differences in understanding their coexistence. Future studies involving allopatric populations of both species will help determine if differences in reproductive strategies are less pronounced compared to sympatric populations.

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