Synalpheus Spence Bate 1888

Synalpheus diversity in the study area Of the 27 species that have been recorded from Northeast Brazil, 20 were analyzed in the present study. We have not examined material of S. cf. africanus, S. bousfieldi, S. filidigitus, S. longicarpus, S. maxillispinus, S. paraneptunus and S. rathbunae (Table 1). The present study provides six new records for the southwestern Atlantic (S. barahonensis, S. belizensis, S. brevidactylus, S. corallinus, S. hoetjesi, and S. kensleyi) and 13 range extensions/new records from Brazil (S. agelas, S. androsi, S. antillensis, S. dardeaui, S. fritzmuelleri, S. hemphilli, S. herricki, S. pandionis, S. ruetzleri, S. tenuispina, S. townsendi, S. ubatuba, and S. yano) (Figs. 20, 21), increasing the known diversity of Synalpheus in the study area, excluding the four doubtful records (see below), to 29 species. Most of the new records in this study involve species collected from calcareous substrates on the outer continental shelf off Recife, Pernambuco (S. androsi, S. barahonensis, S. belizensis, S. brevidactylus, S. corallinus, S. herricki, S. kensleyi, S. pandionis, S. ruetzleri, and S. yano), the majority of which are sponge-associated. Sampling in underexplored areas and substrates, particularly on the continental shelf, often yields new records, extensions of known bathymetric distributions, as demonstrated in this study, and the discovery of new taxa (e.g., Soledade et al. 2019). Additionally, new records for species inhabiting shallow coastal waters (S. dardeaui, S. hoetjesi, S. kensleyi, S. pandionis, S. tenuispina, and S. yano) were also documented. These findings are attributed to the scarcity of studies focusing on the genus in the region and the taxonomic challenges associated with identifying certain species, besides the employment of advanced sampling techniques such as artificial refuge structures (ARS), diving, and dredging (Hultgren et al. 2010; Anker et al. 2012, 2016). With the addition of six new records from the southwestern Atlantic and excluding the misidentifications and doubtful records discussed below, the number of Synalpheus species currently known from the Brazilian coast is 31 (Table 1). Sequences of the 16S gene for S. barahonensis, S. hoetjesi, and S. ul were compared with other Synalpheus sequences available in GenBank to confirm their identification (Fig. 19). The sequence for S. barahonensis represents the first of this gene to be deposited in GenBank, rendering comparisons with other populations unfeasible at the moment. Conversely, the 16S sequences for S. hoetjesi and S. ul are the first reported from the southwestern Atlantic. As noted earlier, the sequences of S. ul specimens from Brazil (PE) were found to be identical to those from the southern Caribbean (Barbados and Panama), suggesting recent connectivity between Brazil and the Caribbean Sea (Fig. 19). In the case of S. hoetjesi, although the two sequences from Praia dos Carneiros (S. hoetjesi – Brazil, PE) clustered with those from the Caribbean (Panama, Barbados, and Curaçao) in a well-supported clade, a subdivision within the clade was observed. This subdivision separated the Brazilian specimens from their Caribbean counterparts into two distinct lineages. Furthermore, a genetic difference of 0.5% between these lineages was detected, suggesting small genetic variations between S. hoetjesi populations (Kimura & Weiss 1964; Avise 2000).