Synalpheus ruetzleri Macdonald & Duffy, 2006

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, Zootaxa 5666 (1), pp. 1-52 : 33

Synalpheus ruetzleri Macdonald & Duffy, 2006

Material examined: Pernambuco—Fernando de Noronha :4M, 1 OV , 2F, Buraco do Inferno , 18.vi.2019, 03°48.968′S 32°23.577′W, 13.0–15.0 m depth, in sponge, DZ / UFRGS 7073 ; 3 M, Ilha do Meio , 18.vi.2019, 03°49.015′S 32°23.549′W, 12.0 m depth, in sponge, DZ / UFRGS 6705 ; 2 M, Ressureta , 19.vi.2019, 03°49.191′S 32°23.847′W, 8.0 m depth, in sponge, DZ / UFRGS 7070 ; 2 M, Ponta da Sapata , 17.vi.2019, 03°51.892′S 32°27.965′W, 8.0 m depth, in sponge, DZ / UFRGS 6707 ; Continental Shelf off Recife: 1 M, 10.v.2018, 08°21′34.9′′S 34°41′53.3′′W, 50.8 m depth, in sponge, MOUFPE 21794 ; 1 F, same data as MOUFPE 21794, MOUFPE 21793 .

Description: Macdonald & Duffy (2006), Ríos & Duffy (2007), and Anker & Pachelle (2014).

Distribution: Belize, Panama, and Brazil (Fernando de Noronha, Ceará, and Pernambuco) ( Macdonald & Duffy 2006; Ríos & Duffy, 2007; Anker & Pachelle 2014; this study).

Ecology: Obligatory symbiont of sponges ( A. dispar , H. cf. caerulea , and unidentified sponge species); in heterosexual pairs; shallow waters to 50.8 m ( Macdonald & Duffy 2006; Ríos & Duffy, 2007; Anker & Pachelle 2014, as S. cf. ruetzleri ; this study). Sampled at Fernando de Noronha (DZ/UFRGS 6705, 6707, 7070, 7073) and continental shelf off Recife (MOUFPE 21793, 21794) in association with sponges (unidentified).

Remarks: Synalpheus ruetzleri is part of the S. brooksi complex ( Macdonald & Duffy 2006) and, as described by Macdonald & Duffy (2006), exhibits an extensive morphological variation, complicating its identification within the complex. The first record of the species from Brazil was provided by Anker & Pachelle (2014), from Ceará, where the material was identified as S. cf. ruetzleri due to differences from the type material (for more details, see Remarks of S. cf. ruetzleri in Anker & Pachelle 2014). Our material agrees with the description provided by Macdonald & Duffy (2006), except for one male (DZ/UFRGS 6710) that exhibited four articles in the carpus of the second pair of pereiopods (vs. five articles in the holotype) (see Macdonald & Duffy 2006, fig. 11G). The present study expands the known range of the species in the southwestern Atlantic, as well as its bathymetric distribution, from less than 20 m ( Anker & Pachelle 2014) to 50.8 m.