Synalpheus sanctithomae Coutière, 1909 Material examined: Pernambuco—Fernando de Noronha: 1 M, Buraco do Inferno, 26.vi.2022, 03°48.968′S 32°23.577′W, 12.0 m depth, in sponge, DZ / UFRGS 7033; 1 F, Ilha do Meio, 26.vi.2022, 03°49.015′S 32°23.549′W, 11.0 m depth, in sponge, DZ / UFRGS 7039; Continental Shelf off Recife: 3 M, 1 OV, 2 F, 07.ii.2018, 8°08′43.7′′S 34°34′22.6′′W, 54.0 m depth, MOUFPE 21785; 1 M, 1 OV, 07.ii.2018, 8°09′06.8′′S 34°34′28.4′′W, 53.0 m depth, MOUFPE 21786; 1 M, 27.ii.2018, 8°13′33.0′′S 34°37′40.3′′W, 50.6 m depth, in sponge, MOUFPE 21540; 1 F, 10.v.2018, 08°21′34.9′′S 34°41′53.3′′W, 50.8 m depth, in sponge, MOUFPE 21795; 1 F, 10.v.2018, 08°23′04.3′′S 34°40′07′′W, 80.0 m depth, in sediment, MOUFPE 21789; 1 M, same data as MOUFPE 21789, in sponge, MOUFPE 21829; 1 M, 1 NI, same data as MOUFPE 21789, in sponge, MOUFPE 21827; 1 OV, same data as MOUFPE 21789, in sponge, MOUFPE 21828; 1 M, 1 F, same data as MOUFPE 21789, in sponge, MOUFPE 21819; 1 M, same data as MOUFPE 21789, in sponge, MOUFPE 21832; 1 M, same data as MOUFPE 21789, in sponge, MOUFPE 21838; 1 M, 1 F, same data as MOUFPE 21789, in sponge, MOUFPE 21823; 1 OV, same data as MOUFPE 21789, in sponge, MOUFPE 21839; 1 M, same data as MOUFPE 21789, in sponge, MOUFPE 21840; 3 M, 1 F, same data as MOUFPE 21789, in sponge, MOUFPE 21835; 1 M, same data as MOUFPE 21789, in sponge, MOUFPE 21846; 1 M, same data as MOUFPE 21789, in sponge, MOUFPE 21850; 1 M, 1 F, same data as MOUFPE 21789, in sponge, MOUFPE 21841; 1 F, same data as MOUFPE 21789, in sponge, MOUFPE 21843; 1 M, 1 F, same data as MOUFPE 21789, in sponge, MOUFPE 21845. Description: Coutière (1909), Dardeau (1984), and Ríos & Duffy (2007). Distribution: USA (Florida), Caribbean Sea, and Brazil (Rocas Atoll, Almirante Saldanha Seamounts, Trindade Island, and from Pernambuco to Bahia) (Christoffersen 1979; Ríos & Duffy, 2007; Anker et al. 2016). Ecology: Coral reefs or on sea bottom with abundance of perforated rocks and calcareous algae; in association with sponges (e.g., Agelas sp., Hyattella sp., Hymeniacidon sp., and Lissodendoryx sp.) (Ríos & Duffy, 2007); in heterosexual pairs; more commonly from 1–20 m, with records at 80 m (this study) and 105 m (Anker et al. 2012, 2016). Remarks: Synalpheus sanctithomae is morphologically similar to S. mcclendoni Coutière, 1910, differing from the latter species by the fingers of major chela being not curved (vs. curved mesially in S. mcclendoni) (for comparison, see Coutière, 1909, fig. 35K, for S. sanctithomae, and Dardeau 1984, fig. 38L, for S. mcclendoni) (Anker et al. 2012). The record of S. sanctithomae by Bezerra & Coelho (2006) from Ceará has been reassigned to S. townsendi (Anker et al. 2012). Hultgren et al. (2010) documented morphological variations in the species, including the number of setae on distal margin of telson (ranging from 2 to 7) and the presence of a row of setae on the major chela dactyl (vs. major chela dactyl without row of setae) (see Coutière, 1909, fig. 35K). A male specimen from the continental shelf off Recife (MOUFPE 21850) examined in this study fits the diagnostic features in the description, but exhibited three pairs of dorsal spiniform setae on the telson (vs. two pair of dorsal spiniform setae) (see Coutière, 1909, fig. 35T).

Published as part of Paixão, Pedro Henrique, Terossi, Mariana, Pasinatto, Karmine, Bochini, Gabriel Lucas & Almeida, Alexandre Oliveira, 2025, Shrimps of the genus Synalpheus Spence Bate, 1888 (Decapoda: Alpheidae) from Northeast Brazil region, pp. 1-52 in Zootaxa 5666 (1) on pages 33-34, DOI: 10.11646/zootaxa.5666.1.1, http://zenodo.org/record/16610054