Synalpheus hoetjesi Hultgren, Macdonald & Duffy, 2010 (Figs. 15, 16)

Material examined: Pernambuco —Goiana: 2 M, 2 OV, Praia de Catuama, 20.i.2023, 7°39′18.6′′S 34°49′28.1′′W, 1.5 m depth, in sponge, DZ / UFRGS 7057; Cabo de Santo Agostinho: 4 M, Baía de Suape, 16.viii.2019, 8°21′54′′S 34°56′50′′W, 3.5 m depth, in sponge, MOUFPE 21521; 8 M, 1 OV, same data as MOUFPE 21521, associated with Echinodictyum dendroides Hechtel, 1983, MOUFPE 21513; 2 M, same data as MOUFPE 21521, MOUFPE 21510; 2 M, same data as MOUFPE 21521, in sponge, MOUFPE 21523; 5 M, same data as MOUFPE 21521, in sponge, MOUFPE 21508; 6 M, same data as MOUFPE 21521, in sponge, MOUFPE 21522; 5 M, same data as MOUFPE 21521, in sponge, MOUFPE 21509; 8 M, Baía de Suape, 21.iii.2019, 8°21′54′′S 34°56′50′′W, 3.5 m depth, associated with E. dendroides, MOUFPE 21581; 2 M, same data as MOUFPE 21581, MOUFPE 21585; 6 M, 2 OV, same data as MOUFPE 21581, DZ / UFRGS 7056; 1 M, 1 OV, same data as MOUFPE 21581, DZ / UFRGS 7056; 6 M, same data as MOUFPE 21581, MOUFPE 21589; 4 M, 1 OV, Baía de Suape, 26.x.2018, 8°21′54′′S 34°56′50′′W, 3.5 m depth, associated with E. dendroides, MOUFPE 21579; 6 M, same data as MOUFPE 21579, MOUFPE 21583; 1 M, same data as MOUFPE 21579, MOUFPE 21584; 2 M, same data as MOUFPE 21579, MOUFPE 21587; 35 M, 4 OV, 1 F, same data as MOUFPE 21579, in unindentified sponge, MOUFPE 21603; 1 OV, same data as MOUFPE 21579, MOUFPE 21526; 1 OV, same data as MOUFPE 21579, MOUFPE 21528; 1 OV, same data as MOUFPE 21579, MOUFPE 21530; 9 M, 2 OV, Baía de Suape, 26.iv.2018, 8°21′54′′S 34°56′50′′W, 3.5 m depth, associated with E. dendroides, MOUFPE 21861; Tamandaré: 1 M, 1 OV, Praia de Carneiros, 06.vi.2019, 8°41′32′′S 35°4′25′′W, 2.0 m depth, in sponge, MOUFPE 21595; 1 OV, same data as MOUFPE 21595, in rocks, MOUFPE 21596; 1 M, 1 OV, same data as MOUFPE 21595, in rocks, MOUFPE 21597; 2 M, Praia de Carneiros, 20.vii.2019, 8°41′32′′S 35°4′25′′W, 3.5 m depth, associated with E. dendroides, MOUFPE 21610; 5 M, Praia de Carneiros, 20.vii.2019, 8°41′32′′S 35°4′25′′W, 3.5 m depth, associated with E. dendroides, MOUFPE 21612; 1 M, same data as MOUFPE 21612, MOUFPE 21619; 1 M, 1 OV, same data as MOUFPE 21612, MOUFPE 21622; 2 M, same data as MOUFPE 21612, MOUFPE 21611; 37 M, 3 OV, Praia de Carneiros, 22.iii.2019, 8°41′32′′S 35°4′25′′W, 3.5 m depth, associated with E. dendroides, DZ / UFRGS 7058 (genetic voucher, genbank access PV273116, PV 273117); 2 M, 3 OV, 1 F, same data as DZ / UFRGS 7058, MOUFPE 21860.

Description: Hultgren, Macdonald & Duffy (2010).

Distribution: Panama (Bocas del Toro), Curaçao, Barbados, Venezuela, and Brazil (Pernambuco) (Hultgren et al. 2010, 2011; Hultgren & Duffy 2011; Anker et al. 2012; Rodríguez et al. 2020).

Ecology: Shallow regions of coral reefs, on rocks or in sponges (e.g., Agelas sp., Hyattella sp., Xestospongia sp.); in heterosexual pairs; shallow waters to 15 m (Hultgren et al. 2010; Anker et al. 2012; this study). Here, we record S. hoetjesi for the first time in association with the sponge E. dendroides. Ecological notes regarding our material are provided in the Remarks and in the Discussion section.

Remarks: Synalpheus hoetjesi is characterized by the rostrum subequal in length although narrower than the orbital teeth, by the orbital teeth rounded to triangular (Fig. 15A), by the ventrolateral tooth of the basicerite and the distolateral tooth of the scaphocerite being subequal in length (Fig. 15A), by the lateral margin of the uropodal exopod with four to six teeth (in addition to the spiniform setae) (Fig. 16B) and by the mesial spiniform setae on the posterior margin of the telson much thicker than the lateral (Fig. 16D) (Hultgren et al. 2010). Although previous studies (e.g., Hultgren et al. 2010; Anker et al. 2012) have reported S. hoetjesi in heterosexual pairs, we observed S. hoetjesi in aggregations ranging from 3 to 46 individuals by host sponge, with varying proportions of males and females. It is also noteworthy that, as reported by Anker et al. (2012), specimens of S. ul, a species very similar to S. hoetjesi, were found at the same collection site and in the same species of sponge (Fig. 3D). Synalpheus hoetjesi differs from S. ul by the thickness of the spiniform setae on the posterior margin of the telson, with the mesial more robust than lateral in S. hoetjesi (vs. mesial and lateral with approximately the same thickness in S. ul) (see Hultgren et al. 2010, Fig. 9). Hultgren et al. (2010) reported morphological variations in the spiniform setae of S. hoetjesi according to the sponge species in which these individuals were found, with mesial and lateral approximately the same thickness (see Hultgren et al. 2010, Fig. 9). In this study, one male specimen from Praia de Carneiros, Tamandaré (MOUFPE 21619), have four articles in both carpus of the second pereiopod, instead of five, as described for the species (Hultgren et al. 2010). This variation may suggest morphological plasticity in S. hoetjesi, although the potential influence of the host sponge on shrimp morphology was not evaluated in this study. Here, we report the first record and provide 16S gene sequences for the species in the southwestern Atlantic, showing a 99.5% similarity to sequences from individuals found in the Caribbean Sea (Barbados, Curaçao, and Panama) (phylogram Fig. 19) (see more details in the discussion).