Synalpheus cf. ruetzleri Macdonald & Duffy, 2006

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 : 221-223

Synalpheus cf. ruetzleri Macdonald & Duffy, 2006

( Fig. 4 )

Synalpheus ruetzleri Macdonald & Duffy 2006: 8 , figs. 8–13; Anker et al. 2012: 85 (table), 88 (key). Zuzalpheus ruetzleri — Ríos & Duffy 2007: 61, pl. 4.

1. Anker & Tóth (2008, p. 21) obviously made a type-error in the diagnosis of Synalpheus belizensis by stating that the antennal scaphocerite has no blade. Their illustration of the frontal region of the holotype of S. belizensis (fig. 12A) clearly shows both scaphocerites having a narrow blade and the presence / absence of a scaphocerite blade is also used to distinguish S. belizensis from S. bocas under remarks (p. 24) and in the key (p. 27). However, an aberrant specimen of S. belizensis in Anker & Tóth's fig. 13H has no blade on the left scaphocerite and a reduced blade on the right scaphocerite.

Material examined. 1 male (cl 4.1 mm), Brazil, Ceará, off Fortaleza, Parque Estadual Marinho da Pedra da Risca do Meio, station Dive II, in Agelas dispar , leg. L.E.A. Bezerra, 14.VII.2004 [ MZUSP 31501].

Description. See Macdonald & Duffy (2006) for description and illustrations and Ríos & Duffy (2007, under Zuzalpheus ruetzleri ) for diagnosis and colour photograph; comparative illustrations of the Brazilian specimen are provided in Fig. 4 .

Distribution. Western Atlantic: Caribbean Sea ( Panama: San Blas Islands, Belize: Carrie Bow Cay); possibly Brazil (Ceará) (Macdonald & Duffy 2006; Ríos & Duffy 2007; present study).

Ecology. In Belize, Synalpheus ruetzleri was found exclusively in the demosponge Hymeniacidon cf. caerulea Pulitzer-Finali , in very shallow water, 1–2 m ( Ríos & Duffy 2007). In contrast, the Ceará material was found inside a different sponge, Agelas dispar Duchassaing & Michelotti , collected by scuba diving in less than 20 m, whereas in Panama, S. ruetzleri appears to associate with various sponges, including H. cf. caerulea (Macdonald & Duffy 2006) .

Remarks. The present material, if confirmed to be conspecific with the Caribbean Synalpheus ruetzleri , may represent the first record of this species in the southwestern Atlantic and Brazilian waters. Like most other species of the taxonomically difficult Synalpheus brooksi Coutière, 1909 species complex, S. ruetzleri appears to be morphologically highly variable, as exemplified by differences in the shape of the orbital teeth (Macdonald & Duffy 2006: figs. 8A, 13A) and distodorsal protuberance of the major chela (idem., figs. 10A, D, G, 13C). The presence of a small scaphocerite blade separates this species from the otherwise almost identical Synalpheus bousfieldi Chace, 1972 and Synalpheus idios ( Ríos & Duffy, 2007) . It also differs from the supposedly variable S. brooksi , for instance, by the shape and direction of the distodorsal protuberance of the major chela (more pointed and directed somewhat upward in S. brooksi ) in addition to the absence of a scaphocerite blade (Macdonald & Duffy 2006).

The single male specimen from Ceará matches only partly the description and illustrations provided by Macdonald & Duffy (2006). The shape of the frontal margin of the carapace is rather similar as are most features of the antennular and antennal peduncles (cf. Fig. 4 A and Macdonald & Duffy 2006: fig. 8A, D). The telson of the Ceará male is rather different from those of the male holotype and female allotype from Belize, especially in the narrower posterior half (cf. Fig. 4 C and Macdonald & Duffy 2006: fig. 8B, G). However, in the number (4 + 5) and position of dorsal spiniform setae, the telson of the Ceará specimen is clearly aberrant ( Fig. 4 C). Another important difference with the type material is the shape of the distodorsal protuberance of the major chela, which is relatively short and straight in the Brazilian specimen compared to the dorsally slightly swollen and ending in a small, downward directed point in both the holotype and allotype (cf. Fig. 4 E, F and Macdonald & Duffy 2006: fig. 10A, D, F, G). However, in this last feature, the Ceará specimen approaches the non-type male of S. ruetzleri from Panama (cf. Fig. 4 E, F and Macdonald & Duffy 2006: fig. 13C). Noteworthy, the armature of the distolateral margin of the uropodal exopod is variable (one or two teeth) in the Ceará specimen ( Fig. 4 L, M).

The paucity of the Brazilian material (presently one single male specimen) does not allow to evaluate the importance of these morphological differences. Sequencing of the barcoding gene segment (COI) of the Ceará specimen is highly desirable to test the correctness of the present identification.

Figures

FIGURE 4. Synalpheus cf. ruetzleri Macdonald & Duffy, 2006, male (cl 4.1 mm) from off Fortaleza, Brazil [MZUSP 31501]: A—frontal region, dorsal; B—abdomen, lateral; C—telson, dorsal; D—third maxilliped, lateral; E—major (right) cheliped, lateral; F—same, chela, mesial; G—minor (left) cheliped, lateral; H—same, carpus and chela, mesial; I—second pereiopod, lateral; J—third pereiopod, lateral; K—same, distal propodus and dactylus, lateral; L—left uropod, dorsal; M—right uropod, distolateral margin of exopod, dorsal.