Saint Peter and Saint Paul's Archipelago (SPSPA), one of the smallest and most isolated island groups in the world, is situated on the Mid-Atlantic Ridge, between Brazil and the African continent. SPSPA has low species richness and high endemism; nonetheless, the diversity of fishes from deep habitats (>30 m depth) had not been previously studied in detail. Several expeditions conducted between 2009 and 2018 explored the shallow and deep reefs of SPSPA using scuba, closed-circuit rebreathers, manned submersibles, baited remote underwater stereo-videos (stereo-BRUV) and fishing between 0 and 1050 m depth. These expeditions yielded 41 new records of fishes for SPSPA: 9 in open waters, 9 in shallow waters (0-30 m), 8 in mesophotic ecosystems (30-150 m) and 15 in deeper reefs (>150 m). Combined with literature records of adult pelagic, shallow and deep-reef species, as well as larvae, the database of the fish biodiversity for SPSPA currently comprises 225 species (169 recorded as adult fishes and 79 as larvae, with 23 species found in both stages). Most of them (112) are pelagic, 86 are reef-associated species and 27 are deep-water specialists. Species accumulation curves show that the number of fish species has not yet * These authors contributed equally to this study.

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Three valid species of the genus Physiculus are known from the Brazilian marinewaters. A fourth, new species, Physiculus cirm n. sp.., is described based on seventeen specimens collected in the surroundings of Saint Peter and Saint Paul Archipelago, equatorial Atlantic. A review of the Brazilian species of Physiculus is provided, as well as a key to the species of the genus reported from the Atlantic Ocean. The new species is distinguished from all its congeners, except P. cynodon and P. karrerae, by the large number of longitudinal series of scales (156–189 vs. 70–150). P. cynodon from the Northern Pacific has about 200 longitudinal series of scales, and it differs from the new species by the number of rays of the first dorsal fin (6–8 vs. 10 in P. cynodon), pectoral-fin rays (20–25 vs. 27 in P. cynodon), and the presence of an outer row of large canine teeth on upper and lower jaw. From P. karrerae, which has 134–160 longitudinal series of scales, the new species differs by the presence of scales on the tip of the snout and dorsal-fin membrane, and the number of pectoral-fin rays (20–25 vs. 24–27 in P. karrerae). [Zoobank URL: urn:lsid:zoobank.org:act:1AFBC251-2BB1-4479-98A4-307188EC5D66]

ABSTRACT. Several studies conducted in Brazilian oceanic islands have generated many results of great significance for the understanding of these ecosystems. However, most of these studies have been restricted to shallow waters, not going beyond 200 m depth. In this work, seven exploratory deep-water fishing surveys were carried out with bottom traps at Saint Peter and Saint Paul Archipelago, between 2012 and 2014, at depths ranging from 300 to 700 m. During these surveys the presence of a deep-sea crab, identified as Chaceon gordonae was recorded, with 458 specimens being caught. Of the sampled specimens, 252 were males and 206 were females. The carapace length (CL) of sampled crabs measured, on the average, 110.81 ± 14.52 mm for males and 102.00 ± 16.55 mm for females. In general, the β1 parameter of the length-weight relationship indicates a positive allometric growth. A comparison of linear regression between the carapace length and right chela length and width for males suggested a morphological maturity of 108.90 and 110.10 mm CL, respectively, whereas the regression between carapace length and abdomen width in females indicated a size at morphological maturity of 84.00 mm CL.

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