Synalpheus brevidactylus Anker & Tóth, 2008

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 : 16

Synalpheus brevidactylus Anker & Tóth, 2008 ( Figs. 9 , 10 )

Material examined: Pernambuco — Continental Shelf off Recife : 1 OV , 27.ii.2018, 8°13′52.1′′S 34°37′42.7′′W, 50.0 m depth, in sponge, DZ / UFRGS 7052 ; 1 OV, same data as DZ/ UFRGS 7052 , MOUFPE 21815 ; 1 M, 27.ii.2018, 8°13′36.8′′S 34°37′41.9′′W, 51.0 m depth, in sponge, MOUFPE 21813 ; 1 M, 27.ii.2018, 8°13′52.1′′S 34°37′41.2′′W, 51.8 m depth, in sponge, DZ / UFRGS 7053 .

Description: Anker & Tóth (2008).

Distribution: Panama and Brazil (Pernambuco) ( Anker & Tóth, 2008; this study).

Ecology: Associated with the sponges Neopetrosia subtriangularis ( Duchassaing, 1850) and Calyx podatypa ( Laubenfels, 1934) , growing on substrates such as coral rubble and seagrass; in heterosexual pairs; 1– 51.8 m ( Anker & Tóth, 2008; this study). Sampled at the continental shelf off Recife (all lots cited above) in association with sponges, on coral rubble and algae bottom, at depths from 50–51.8 m.

Remarks: Synalpheus brevidactylus is characterized by a rostrum distinctly longer than the orbital teeth, broad at the base and tapering to the tip; by the fixed and movable fingers of the minor chela excavated on the cutting edges, with the dactylus bearing scattered gambarelloid setae on dorsal surface; by the uropodal exopod armed with two to three lateral teeth ( Figs. 10B, C ); and by the telson presenting a longitudinal median depression ( Fig. 10D ) ( Anker & Tóth, 2008; Anker et al. 2012; this study). Additional diagnostic characters are: the carpus of the second pair of pereiopods divided into five articles, with the first four times as long as the second ( Fig. 9F ), the third maxilliped ending in a set of six or seven spiniform setae ( Fig. 10E ), and the palm of the major chela is approximately three times as long as the fingers ( Anker & Tóth, 2008). The material examined revealed morphological variations when compared to the original description of the species. For instance, a male specimen (MOUFPE 21813) exhibited a rostrum and orbital teeth that were subequal in length, with the rostrum being narrower (vs. rostrum longer and broader than the orbital teeth) (for comparison, see Fig. 9 A and Anker & Tóth, 2008, Fig. 8A ). The fingers of the major chela were strongly unequal in length, with the dactylus being square/rounded and longer than the fixed finger (vs. dactylus slightly longer and more bulging than the fixed finger) (see Figs. 9B, C , and Anker & Tóth, 2008, Figs. 8C, E ). Additionally, the distodorsal tooth of the basicerite is slightly more acute (vs. distodorsal margin of the basicerite with a subacute point). The blade of the scaphocerite is longer, extending beyond the ventrolateral tooth of the basicerite and reaching the end of the distolateral tooth of the scaphocerite (vs. blade of scaphocerite reaching the end of the ventrolateral tooth of the basicerite and halfway to the distolateral tooth of the scaphocerite) (for comparison, see Fig. 9 A and Anker & Tóth, 2008, Fig. 8A ). In another specimen (1 OV, MOUFPE 21815), the tooth of the right orbital hood is partially fused to the rostrum (vs. typical tridentate front) and the uropodal exopod had three fixed teeth on the right side and two on the left (vs. uropodal exopod with three or four fixed teeth in both sides) (see Anker & Tóth, 2008, Figs. 8I, K ). This study provides the first record of S. brevidactylu s in the southwestern Atlantic and expands its known bathymetric distribution from 3 ( Anker & Tóth, 2008) to 51.8 m.

Figures

FIGURE 8. Synalpheus belizensis Anker & Tóth, 2008: female from the Fernando de Noronha Archipelago, Pernambuco, Brazil [DZ/UFRGS 7041].A, pleon, left view; B, telson, dorsal view; C, left uropod, dorsal view; D, third maxilliped, right side, lateral view. Scale bars: A, 1 mm; B–D, 0.5 mm.

FIGURE 9. Synalpheus brevidactylus Anker & Tóth, 2008: male from the continental shelf off Recife, Pernambuco, Brazil [MOUFPE 21813]. A, frontal region, dorsal view; B, major chela, left side, mesial view; C, same, lateral view; D, minor chela, right side, mesial view; E, same, lateral view; F, second pereiopod, left side, lateral view; G, third pereiopod, left side, lateral view. Scale bars: A, D, E, G, 0.5 mm; B, C, 1 mm; F, 0.3 mm.

FIGURE 10. Synalpheus brevidactylus Anker & Tóth, 2008: male from the continental shelf off Recife, Pernambuco, Brazil [MOUFPE 21813]. A, pleon, left view; B, right uropod, dorsal view; C, left uropod, dorsal view; D, telson, dorsal view; E, third maxilliped, left side, lateral view. Scale bars: A, 1 mm; B–E, 0.3 mm.