Growth, Sexual Maturity and Dimorphism in Six Species of Snapping Shrimps of the Genus Alpheus (Decapoda: Alpheidae)

This study investigated the sexual dimorphism, allometric growth, and morphological maturity of six sympatric species of Alpheus. The samplings occurred in August 2015, February and August 2016, and February 2017, in the intertidal, during low spring tides, in two localities in the northeastern Brazilian coast. In total, 3038 individuals were captured: 302 A. angulosus, 400 A. bouvieri, 516 A. buckupi, 410 A. carlae, 1002 A. estuariensis, and 408 A. nuttingi. According to our data, the six species lack sexual dimorphism regarding the carapace length. However, the major chelipeds were more robust in males of five species, whereas abdominal structures (pleurae and sternites) were larger in females, both indicatives of sexual dimorphism. The analyses of the relative growth of cheliped dimensions versus body size demonstrate that males of six species invest more energy in the chelipeds during the adult and juvenile phases. On the other hand, in the females the cheliped growth is higher during the juvenile phase. The analysis of energy allocation (calculated using body and chelipeds mass) also confirmed a high energetic investment in this appendage in males (minimum 32% of the body mass). Our results also show that females can also invest a lot of energy in the chelipeds (minimum 22% of the body mass). However, the intraspecific sex differences may be consequences of a trade-off between embryo production and cheliped development. The growth rate of pleura and sternites were higher in the adult females of all species except for A. bouvieri. In the males of the six species the appendix masculina grows faster during the juvenile phase. Lastly, in the six species of Alpheus studied, males and females reach the morphological maturity at very similar sizes, indicating a synchrony of reproduction and growth.