Synalpheus tenuispina Coutière, 1909

Anker, Arthur & Pachelle, Paulo P. G., 2014, Taxonomic notes on some Brazilian species of Synalpheus Spence Bate, 1888, with new records and description of a new species (Decapoda, Alpheidae), Zootaxa 3815 (2), pp. 215-232 : 223-226

Synalpheus tenuispina Coutière, 1909

( Figs. 5 , 6 )

Synalpheus latastei tenuispina Coutière 1909: 26 , fig. 8; Chace 1972: 93; Coelho & Ramos 1972: 150; Christoffersen 1980: 171; Christoffersen 1998: 362.

(?) Synalpheus latastei tenuispina— Abele 1976: 273; Martínez-Iglesias et al. 1993: 12; Martínez-Iglesias et al. 1996: 35. Synalpheus tenuispina— Crosnier & Forest 1965: 364; Ríos & Duffy 2007: 78 (key); Anker et al. 2012: 9, 86 (table), 90 (key).

Material examined. 1 male (cl 7.1 mm), Brazil, São Paulo, São Sebastião, Pier da Petrobras, 12.XII.2009 [ MZUSP 31503]; 1 male (cl 6.9 mm, major P1 missing), 1 heavily damaged specimen (only major P1, P2-P5 and sternal portion of cephalothorax), Brazil, Rio de Janeiro, Niteroi, Baia de Guanabara, Praia de Boa Viagem, scuba diving, fauna associated with Polychaeta, coll. J.B. Mendonça Jr., 04.X.2006 [ MZUSP 22133].

Description. Rostrum with base clearly delimited from anteromesial margin of orbital hoods, much longer than wide at base, arrow-shaped in dorsal view, longer than orbital teeth, acute distally, tip overreaching mid-length of first article of antennular peduncle; orbital teeth large, triangular, acute distally, about as long as wide at base; anteromesial margin between orbital teeth and rostrum abruptly sloping ventrally, forming deep V-shaped notch in dorsal view; rostro-orbital process well developed ( Fig. 5 A, B).

Pleuron of first abdominal somite pointed posteroventrally, forming feeble hook; pleura of third to fifth somites also rounded, fifth slightly more angular ( Fig. 5 C). Telson broad, about 1.3 times as long as anterior width, slightly tapering distally; dorsal surface with shallow, longitudinal, median depression and two pairs of stout spiniform setae inserted at about 0.45 and 0.75 length of telson, respectively; posterior margin broadly rounded, about 0.6 length of anterior width, with two stout spiniform setae, mesial much longer than lateral ( Fig. 5 D).

Antennular peduncle with second article 1.5 times as long as wide; stylocerite very strong, reaching far beyond distal margin of first article, with acute tip ( Fig. 5 A). Antennal basicerite with acutely projecting distodorsal tooth and much stronger distolateral tooth, latter reaching well into first third of second article of antennular peduncle and almost equalling tip of stylocerite; scaphocerite with very strong distolateral tooth reaching beyond end of antennular peduncle; blade well-developed, moderately broad, reaching to about 0.7 length of scaphocerite, fringed with long setae; carpocerite reaching slightly beyond end of antennular peduncle but not beyond distolateral tooth of scaphocerite ( Fig. 5 A, B).

Mouthparts typical for genus. Third maxilliped with very short penultimate article; ultimate article with crown of about six stout spiniform setae on apex ( Fig. 5 E, F).

Major cheliped with merus about 2.3 times as long as wide; palm ovoid, 2.3–2.4 as long as dactylus; distodorsal margin of palm slightly protruding, forming low blunt protuberance, without acute tooth; dactylus subequal to pollex ( Fig. 6 A, B). Minor cheliped with merus about 2.3 times as long as greatest width, with convex dorsal and ventral margins, distodorsal margin projecting as sharp tooth; carpus cup-shaped; palm about 1.2 times as long as fingers; dactylus and pollex with sharp cutting edges, laterodorsal surface of pollex slightly depressed ( Fig. 6 C, D).

Second pereiopod with five-articulated carpus, first carpal article about four times length of second, equal to sum of second to fifth articles ( Fig. 5 G). Third pereiopod with merus almost four times as long as wide; carpus with stout spiniform seta distoventrally; propodus with eight spiniform setae on ventral margin and one pair of spiniform setae on distoventral margin; dactylus biunguiculate, moderately stout, secondary unguis subparallel to and shorter than terminal unguis ( Fig. 5 H, I). Fifth pereiopod with propodus armed with four spiniform setae on ventral margin and one pair of spiniform setae on distoventral margin, and with well-developed grooming brush laterally, consisting of at least six rows of serrulate setae ( Fig. 5 J, K).

Uropod with protopod ending in large subacute tooth laterally; distolateral margin of exopod with two strong teeth (including lateral tooth of diaeresis) and one stout spiniform seta ( Fig. 5 L).

Colour in life unknown.

Distribution. Southwestern Atlantic: Brazil (Rio de Janeiro, São Paulo, Santa Catarina). Records of S. tenuispina from the Caribbean Sea ( Abele 1976; Martínez-Iglesias et al. 1993, 1996) most likely refer to a species currently known as Synalpheus cf. africanus Crosnier & Forest, 1965 , and not to S. tenuispina (see below).

Ecology. Synalpheus tenuispina appears to be a non-symbiotic species, dwelling in pier growth or in crevices of polychaete reefs.

Remarks. Coutière's (1909) original description of Synalpheus latastei tenuispina was based on a single large female (tl 30 mm) from Desterro, now Florianópolis, Santa Catarina, Brazil. The description is actually a short paragraph with comparisons of proportions and lengths between the new form and the supposedly closely related, eastern Pacific Synalpheus latastei Coutière, 1909 (now junior synonym of Synalpheus spinifrons (H. Milne Edwards, 1837)) and Synalpheus lockingtoni Coutière, 1909 , accompanied by a few figures. The holotype of S. latastei tenuispina was deposited in the Muséum National d'Histoire Naturelle in Paris, France (MNHN), where, however, it was missing already in the 1960s ( Crosnier & Forest 1965) and was also not found during a more recent search in 2007 (A. Anker, pers. obs.). Based on the morphological differences between S. latastei tenuispina and S. spinifrons in Coutière's (1909) account, Crosnier & Forest (1965) elevated the Brazilian form to full species, as S. tenuispina .

The most complete specimen of the present material is an adult male (cl 7.1 mm, tl ~ 25 mm) from São Sebastião ( Figs. 5 , 6 ). This male agrees well with figures of the missing female holotype in Coutière (1909), except for the slightly broader rostrum and stouter merus of the third pereiopod (cf. Fig. 5 A, H and Coutière 1909: fig. 8a, m). Obviously more fresh material is needed to understand the range of morphological variation of S. tenuispina and also to document the colour pattern of the species.

The Caribbean records of S. latastei tenuispina ( Abele 1976; Martínez-Iglesias et al. 1993, 1996, all as S. latastei tenuispina ) are difficult to assess without examining the material. They most probably refer to a problematic amphi-Atlantic taxon (possibly more than one species) currently known as Synalpheus cf. africanus (cf. Anker et al. 2012: fig. 3) and not to S. tenuispina . The differences between S. cf. africanus and S. tenuispina are rather slight. Anker et al. (2012) noted that the specimens tentatively identified as S. cf. africanus from Atol das Rocas, Aruba and Panama were closer to S. africanus than to S. tenuispina in the length of the scaphocerite and shape of the rostrum, and were also much smaller than S. tenuispina (maximum tl ~ 15 mm compared to 30 mm for the female holotype of S. tenuispina ). As Anker et al. (2012) pointed out, the entire S. africanus — S. tenuispina complex needs a molecular analysis, but for the time being it is more sensible to treat the larger southern Brazilian form as S. tenuspina .

Figures

FIGURE 5. Synalpheus tenuispina Coutière, 1909, male (cl 7.1 mm) from São Sebastião, Brazil [MZUSP 31503]: A—frontal region, dorsal; B—same, lateral; C—abdomen, lateral; D—telson, dorsal; E—third maxilliped, lateral; F—same, tip of ultimate article, mesial; G—second pereiopod, lateral; H—third pereiopod, lateral; I—same, distal propodus and dactylus, lateral; J—fifth pereiopod, lateral; K—same, propodus and dactylus; L—uropod, dorsal.

FIGURE 6. Synalpheus tenuispina Coutière, 1909, male (cl 7.1 mm) from São Sebastião, Brazil [MZUSP 31503]: A—major (left) cheliped, lateral; B—same, chela, mesial; C—minor (right) cheliped, lateral; D—same, carpus and chela, mesial.