Periclimenes paivai is notable for its symbiotic lifestyle with jellyfish. The objective of this study was to investigate the fecundity and reproductive output of females, and specifically to determine whether females protected in their host have a greater reproductive success than other shrimp species. All anatomical parts of the medusae were analyzed and the P. paivai individuals were separated. Among 83 females analyzed, 65 presented embryos in the first developmental stage, and 18 were in the final stage of development. The mean fecundity was 229.08 ± 120.04 in initial-stage embryos and 191 ± 114.76 in final-stage embryos. We observed a positive relationship between the embryo number and the female size; however, the embryo number was not related to the embryonic stage, which indicates that females did not lose their embryos during the incubation period. The weight of brood mass during production is closely related to the female weight according to the results of linear regression, as fecundity increased with female size. In its symbiosis, P. paivai can increase the amount of energy used to produce embryos (mean reproductive output = 10.38%) and can elevate the reproductive success.

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While previous studies on Alpheus formosus Gibbes, 1850 focused on taxonomic and phylogenetic issues, the present study provides information on the biology and ecology of this snapping shrimp, a representative coral reef species widely distributed in the Atlantic Ocean. We studied A. formosus between 2015 and 2016 on two islands in São Paulo state, Brazil: Laje de Santos and Vitoria Island. We analyzed 47 specimens from Laje de Santos and 44 from Vitoria Island. Individuals ranged in size from 2.0 mm to 13.99 mm CL. The mean number of embryos attached to the pleopods of females was 211.28 ± 312.8 in Laje de Santos and 125.2 ± 177.8 in Vitoria Island. This species should be included in monitoring programs of coral ecosystems they inhabit as A. formosus represents a key element in trophic dynamics of these ecosystems.

This study represents an unprecedented effort to assess the diversity of rocky infralittoral decapod Brachyura and Anomura from the Laje de Santos Marine State Park, a preserved and protected area along the southeastern Brazilian coast. The samples were carried out quarterly for one year, using the combination of artificial refuge substrate for the passive capture of specimens and SCUBA dive for active capture. Specimens sampled were deposited in the Crustacean Collection of the Department of Biology of FFCLRP, University of São Paulo. The abundance and richness is expressive considering the dimension of the area with a total of 987 individuals distributed into 32 species, 22 genera, and 11 families. The hermit crab Pagurus brevidactylus and the crab Mithraculus forceps were the most abundant species of Anomura and Brachyura, respectively. This is the first study focused on carcinofauna inhabiting the park on and we encourage future works focused in the monitoring of species as well as the construction of new robust checklists contents from different offshore regions in order to build biodiversity parameters to serve as baseline for future management and work plans on Brazilian protected areas since decapod crustaceans are key group on fauna composition in any subtidal ecosystem.