This study investigated the composition and spatial distribution of the sublittoral decapods on the reefs of Porto de Galinhas Beach, southern coast of Pernambuco, Brazil, through the Underwater Visual Census technique. Data were collected monthly, at night during full-moon tides in low tide periods from June 2004 to May 2005, using SCUBA diving and a visual census with a fixed belt transect (20 m long). Three sampling areas were defined: Confined Waters (low hydrodynamics) with shallow sites (up to 2.5 m deep); Semi-open Water (3 to 6 m deep), influenced by waves and tidal currents (moderate hydrodynamics); and Open Water (7 to 10 m deep), in the breaker zone (high hydrodynamics). A total of 6,287 individuals of 34 species belonging to the infraorders Brachyura (19 species), Achelata and Anomura (5 species each), Caridea (3 species), and Stenopodidea and Astacidea (1 species each) were collected. Two decapod assemblages were distinguished: in a habitat with low hydrodynamics and shallow (Confined) water; and in a habitat with moderate to high hydrodynamics and depths of 3 to 10 m (Semi-open and Open water). At the sites with high hydrodynamics, i.e., the Open-water Area in the breaker zone, decapod diversity was significantly lower than in the other, protected areas on the reef bench. These results suggest that the distribution of subtidal decapods on coastal reefs is influenced by depth and exposure to water stress caused by waves and currents (hydrodynamics). The visual census technique with SCUBA proved to be suitable for ecological studies on subtidal decapods.

The barbouriid shrimp Janicea antiguesis (Chace, 1972) is reported from Porto de Galinhas and Tamandaré in Pernambuco and Guarapari in Espírito Santo, Brazil. These records confirm the presence of J. antiguensis in northeastern and eastern Brazil, considerably extending its Brazilian range from Fernando de Noronha to southern Espírito Santo and also representing the first record of this species from mainland coastal reefs. In Brazil, J. antiguensis occurs in or near marine reef caves, typically at depths between 5 and 15 m, and can be most easily observed while scuba diving at night. Colour photographs of J. antiguensis from various Atlantic localities are provided and its colour pattern is compared to that of the closely related Indo-West Pacific barbouriid shrimp, Parhippolyte misticia (Clark, 1989). Some in situ observations are provided for the Porto de Galinhas population of J. antiguensis. Multiple observations of pairs with both individuals brooding embryos at different developmental stages suggest protandric simultaneous hermaphroditism in J. antiguensis.