Potamalpheops tyrymembe sp. n.: the first southwestern Atlantic species of the shrimp genus Potamalpheops Powell, 1979 (Caridea: Alpheidae).

A new species of the alpheid shrimp genus Potamalpheops Powell, 1979, P. tyrymembe sp. n., is described based on several specimens collected from burrows of the ucidid crab Ucides cordatus (Linnaeus, 1763) and other, unknown burrowing decapods, on a mangrove flat between the Baiano and Serra rivers, Povoado de Tremembé, Maraú, state of Bahia, Brazil (14º08'51.9"S, 39º05'04.4"W). The new species belongs to the P. monodi (Sollaud, 1932) species group, based on the presence of two pairs of spiniform setae on the distal margin of the telson and non-enlarged male chelipeds. It is characterized by a short rostrum and absence of setae on the pterygostomial angle of the carapace.

New record of the sponge-dwelling shrimp Typton distinctus Chace, 1972 (Decapoda: Caridea: Palaemonidae) in São Paulo State, Brazil.

Among the Caridea Infraorder, the palaemonid shrimp from the genus Typton Costa, 1844 are commonly found in association with sponges, frequently feeding on the tissues of their hosts ((Duris et al. 2011; Almeida et al. 2014; Pachelle et al. 2015; Soledade et al. 2017). Typton is mostly characterized by morphological features related to their sponge-dwelling lifestyle, as a simple and compressed rostrum, carapace smooth and antennal spines present, antennae extremely reduced and scaphocerite rudimentary. Mandible without palp, incisor process normal, reduced or absent. Second legs unequal, asymmetrical, without molar process on major chela (Bruce, 1972).

Congruence between morphology and molecular data supports the distinction between the snapping shrimps Alpheus macrocheles and A. amblyonyx (Caridea, Alpheidae).

The snapping shrimp Alpheus macrocheles (Hailstone, 1835b) is widely distributed across the Atlantic Ocean and was originally described from Hastings, England, based on a very brief description with limited morphological details and diagnostic illustrations. The morphologically similar A. amblyonyx Chace, 1972, type locality Quintana Roo, Mexico, is a western Atlantic taxon. The superficial description of A. macrocheles by Hailstone and the high similarity with A. amblyonyx has led to taxonomic confusion regarding the precise identification of these species. Thus, our objective was to reexamine these two species, based on a combined analysis of morphological-including a redescription for A. macrocheles and new morphological characterization of A. amblyonyx-and molecular data. In total, 42 morphological characters were analyzed, in addition to a phylogenetic analysis of 16S ribosomal RNA (rRNA) gene sequences. A Bayesian Inference analysis recovered A. macrocheles and A. amblyonyx as distinct clades supporting the taxonomic distinction between them. The tree topology suggests that A. macrocheles is more closely related to A. crockeri (Armstrong, 1941) and A. puapeba (Christoffersen, 1979) than to A. amblyonyx, which forms the sister group to a well-supported clade containing these three species. This contribution conclusively distinguishes between A. macrocheles and A. amblyonyx and points out the need for a comprehensive review involving all species of the larger A. macrocheles group.

Shallow-water stenopodidean and caridean shrimps from Abrolhos Archipelago, Brazil: new records and updated checklist.

This study deals with a recent collection of stenopodidean and caridean shrimps made in the Abrolhos Archipelago, Bahia, Brazil, in July and August 2013. Sampling was carried out in the vicinity of Ilha de Santa Bárbara (17°57'49"S 38°41'53"W). Specimens were obtained by hand or using small hand nets in tide pools or under rocks in the intertidal zone. Part of the material was collected by scuba diving in the shallow subtidal, to a maximum depth of 11 m. We obtained a total of 18 species, 12 of which are reported for the first time for the Abrolhos and 4 as new records for the state of Bahia. The distributions of Microprosthema semilaeve (von Martens, 1872), Typton gnathophylloides Holthuis, 1951, Alpheus verrilli (Schmitt, 1924) and Alpheopsis cf. trigona (Rathbun, 1901) are extended from their previously known ranges. The occurrence of Automate cf. rectifrons Chace, 1972 on the Brazilian coast is confirmed. We thus provide an updated checklist of stenopodidean (2 species) and caridean (29 species) shrimps from the Abrolhos Archipelago, incorporating and critically evaluating previous records.