Biologia populacional e reprodutiva de três espécies de porcelanídeos (CRUSTACEA: DECAPODA: PORCELLANIDAE) em uma praia do semiárido brasileiro

Abstract

The population and reproductive biology of three species of porcelanids crabs (Pachycheles greeley, Petrolisthes armatus and Petrolisthes galathinus) were studied for the first time in a semi-arid tropical beach of northeastern Brazil. A catch-per-unit-effort (CPUE) technique was used to sample the crabs along linear transects, for 2-hours sampling periods by two persons on a monthly basis during spring low tide periods from December 2015 to December 2016 in Baixa Grande beach. A total of 739 porcelanids crabs were collected, of which 371 were P. greeleyi (187 males, 104 non-ovigerous females, and 47 ovigerous females), 253 P. galathinus (117 males, 89 non-ovigerous females, and 47 ovigerous females) and 115 P. armatus (55 males, and 32 non-ovigerous females). The population presented a normal and unimodal size frequency distribution to P. greeleyi and P. galathinus, and non-normal and unimodal to P. galathinus. The abundance of porcelanids, including ovigerous females, was higher during the dry season. Pachycheles greeleyi was the most abundant specie, followed by P. galathinus and P. armatus. The low abundance of P. armatus is possible related to to the competitive exclusion of the congener specie founded in this present study. The specimens sizes are similar to those reported for other populations. The sexual ratio did not differ from the expected 1:1 proportion, typical of species that occupy environments in equilibrium. The fecundity index of the porcelanids found on Baixa Grande beach is relatively low (P. greeleyi: 4,1 eggs, P. galathinus: 8,4 eggs and P. armatus: 12,5 eggs) when compared to other populations.