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Tropical island environments are considered hotspots due to their high diversity, endemism and ecological importance. However, reports that discuss the composition and ecology of planktonic decapods in these environments are still very few. In order to ascertain the composition, abundance and spatial-temporal distribution of planktonic decapods, zooplankton samples were taken by means of sub-surface hauls with a standard plankton net of 300 µm mesh size. Sampling was carried out at five stations in the nearshore leeward area of the Fernando de Noronha archipelago, in July and December 2013 and June and November 2014. A total of 22 decapod taxa were recorded, among which the most abundant were Brachyura (zoeae), Clibanarius sp., Caridea and Callianassidae. Characteristic annual distribution and temporal tendencies were observed for the larvae of the hermit crab Clibanarius sp. and for the larvae of burrowing shrimps (Callianassidae). Some taxa showed differences between sampling stations. In general, higher abundances were observed in the southern (downstream) stations of the island (Baía dos Golfinhos and Cacimba do Padre), and lower abundances in the northernmost (upstream) station (Porto de Santo Antônio), indicating the existence of larval retention in the nearshore coastal zone of this oceanic island ecosystem.

The current biogeographic and taxonomic knowledge on decapod larvae in tropical oceans is still very incomplete, in spite of their huge ecological and socio-economic importance. The present study reports two new records for decapod larval forms in pelagic environments off oceanic islands in the western tropical Atlantic, and provides detailed diagnoses and images of these larvae. Samples were taken from July 2010 to November 2014 using neuston, bongo and WP-2 nets at three localities: St. Peter and St. Paul's Archipelago (SPSP), Rocas Atoll (RA) and Fernando de Noronha Archipelago (FN). The larval forms Cerataspis monstrosa (Gray, 1828) and Amphionides reynaudii (H. Milne Edwards, 1832) were recorded around these areas, constituting the first record for these oceanic islands. Out of 121 samples analyzed, one specimen of C. monstrosa (Mysis II) was found off FN, and 20 specimens of A. reynaudii in nine distinct stages (Mysis II, IV, VI, VII, VIII, IX, X, XI, XII) were found off SPSP, RA and FN.