Talorchestia

Serejo, Cristiana S., 2004, Talitridae (Amphipoda, Gammaridea) from the Brazilian coastline, Zootaxa 646, pp. 1-29 : 21-26

“ Talorchestia ” tucurauna ( Müller, 1864) (Figs 11–13)

Orchestia tucurauna Müller, 1864: 54 ; 1869: 79, figs 50–51 [also printed as O. tucuratinga ]; Stebbing, 1906: 534; Chilton, 1919: 379, figs 1–14 (= Talorchestia dentata (Filhol, 1885) non Muller, 1864).

Talorchestia fritzi — Schellenberg, 1938: 211 (non T. fritzi of Stebbing, 1903).

Material examined. Rio Grande do Norte — Rocas Atoll, Farol Island, RN, 87 males, 100 females, S. Brandão et al. col., 10/VII/2001, MNRJ 18739; Golfinhos Bay, Pipa, RN, 7 males, 3 females, C. Serejo & M.C. Rayol col, 11/11/2001, MNRJ 18741; Between Barreira d'agua beach and Roxa beach, Natal, RN, 1 male and 1 female, 27/I/1964, MNRJ 18740. Pernambuco — Jaguaribe, Itamaracá Island, PE, 13 males and 40 females, 12/IX/ 1976, MNRJ 9770. Alagoas — Graça Torta beach, Maceió, AL, 1 male, 2 females, 06/III/ 1980, MNRJ 4646. Bahia — Yemanjá beach, Caravelas, BA, 25 males, 60 females, P.S. Young col., 21/IX/2001, MNRJ 18742; Rio do Peixe beach, Cumuruxatiba, Prado, BA, 18 males, 70 females, P.S. Young, col. 16/IV/2003, MNRJ 18746. Rio de Janeiro — São João da Barra, RJ, 4 males, A. Lemos de Castro col. 31/X/1973, MNRJ 9766; Barra do Una, Búzios, RJ, V. Veloso col. 2/IV/2003, MNRJ 19141.

“ Talorchestia ” tucurauna ( Müller, 1864) , male, 9.2 mm, MNRJ 18739. A, head; B, gnathopod 1; C, ventral view of coxa 1; D, gnathopod 2; E, pereopod 3; F, pereopod 4. Scale bars: A, 1 mm; B–E, 0.5 mm; F, 0.2 mm.

Diagnosis. Male antenna 2 with articles 4–5 long and slender, article 5 slightly longer than article 4. Male gnathopod 2, propodus about 1/4 longer than wide, palm with a large proximal concavity that fits in a projection of the dactylus. Female gnathopod 2, basis enlarged anteriorly, propodus posteriorly rounded. Outer ramus of uropod 1 with marginal robust setae. Telson slightly cleft.

Description. Male, 9.2 mm. Antenna 1 reaching half way of article 4 of peduncle of antenna 2, flagellum with 5 articles. Antenna 2, peduncle long and slender, article 5 slightly longer than article 4, article 4 about 4 times longer than wide, article 5 about 5 times longer than wide; flagellum with 24 articles (Fig. 11A). Mandible with left lacinia mobilis 5­dentate; right lacinia mobilis bifid. Maxilla 1, inner plate with two distal plumose setae; outer plate with 9 dentate robust setae, palp reduced and 1­articulate. Maxilla 2, inner plate with several distal setae and a larger proximal plumose seta; outer plate a little larger than inner plate. Maxilliped palp robust, 3­articulate, article 2 with well developed inner setose distal lobe.

Gnathopod 1 subchelate (Fig. 11B), coxa 1 with a ventral groove, inner margin tipped with slender setae (Fig. 11C), carpus and propodus with well developed posterior lobe. Gnathopod 2 robust and sexually dimorphic (Fig. 11D), palm with a large proximal concavity that fits in a projection of the dactylus. Pereopod 4 a little shorter than pereopod 3, dactylus enlarged (Fig. 11E, F). Dactylus of pereopods 3–7 cuspidactylate. Pereopods 5–7 increasing in length ( Fig. 12 A–C). Posterior lobe of coxa 6 rounded, about 1.7 the length of anterior lobe. Pleopods not modified. Uropods 1–2 with robust setae on peduncles and rami ( Fig. 12 D, E). Peduncle of uropod 3 a little longer than ramus ( Fig. 12 F). Telson longer than wide, slightly cleft distally, each side with 8–9 sub­marginal and marginal robust setae ( Fig. 12 G).

Female, 9.5 mm Antenna 2 ( Fig. 13 A), peduncle articles 4–5 not so long as in males, article 4 about 3 times longer than wide and article 5 about 4 times longer than wide. Gnathopod 1 simple ( Fig. 13 B). Gnathopod 2 ( Fig. 13 C), basis enlarged anteriorly, propodus posteriorly rounded. Oostegites 2–5 oval shaped and slightly tapering distally, oostegite 5 a little shorter than the others ( Fig. 13 D–G).

Type locality. Brazil, probably Santa Catarina.

Distribution. Brazil: from Rio Grande do Norte to?Santa Catarina, including Rocas Atoll (03º 52' S; 033º 48' W), an oceanic Island distant about 70 km off the Rio Grande do Norte coast.

Ecology. Often inhabiting exposed sand­beaches, found together with Atlantorchestoidea brasiliesis at Rio de Janeiro. This is the single species that colonized the Rocas Atoll.

Remarks. Müller (1864) briefly described and illustrated T. tucurauna , which makes its identification a little uncertain. As mentioned before, Mullers types are probably lost and material from the possible type locality, Santa Catarina, have not been found. For these reasons, the necessity of describing a neotype is still needed.

Compared with the observed material, the gnathopod 2 propodus illustrated by Müller (1869) is slightly more rounded (Figs. 11D and 13I). Furthermore, Müller (1869) described a sexual dimorphism in old males (fusion of 1 to 4 first articles in the flagellum of antenna 2 and the enlargement of intermediary articles of pereopod 7), which was not observed in the present material.

Talorchestes tucurauna resembles T. fritzi Stebbing (1903) , which was described originally for the Pacific coast of Costa Rica. Stebbing (1903) commented on the similarities of these species as the palm of gnathopod 2 bearing a proximal excavation, and a corresponding prominence of the dactylus that fits in this excavation. Stebbing (1903) also noticed some distinctions between T. fritzi and T. tucurauna , as the propodus of male gnathopod 2 is 2/5 longer than wide, and not 1/4 to 1/5 longer than wide; the female gnathopod 2, basis has a sinuous anterior margin, not anteriorly rounded; carpus and propodus are distinctly narrower than in T. tucurauna , and the propodus has a sinuous posterior margin, not rounded.

Shoemaker (1932), who worked with Costa Rica samples, also noticed the similarities between T. fritzi and T. tucurauna , but as the description of the latter did not have the condition of female gnathopod 1, he just suggested a possible synonymy between these taxa. Schellenberg (1938), who worked with material from the northeastern Brazilian coast, identified it as T. fritzi . However, Schellenberg's specimens are clearly T. tucurauna by the shape of propodus of male gnathopod 2 (1/4 longer than wide) and by the carpus and propodus of female gnathopod 2 not elongated as in T. fritzi . Furthermore, Schellenberg (1938) described the characteristic development of male gnathopod 2 in this species.

Genus status. The concept of Talorchestia as applied by Stebbing (1906a), "like Orchestia , except that female gnathopod 1 is simple, instead of subchelate. Pereopod 2 [actually pereopod 4] usually has the inner margin of the finger more sharply constricted than in allied genera" is brief and difficult to apply in a modern concept when compared to other genera ( Hurley, 1956). Considering these points, Morino & Miyamoto (1988) and later on Miyamoto & Morino (1999) redefined Talorchestia , including the type species T. gracilis Dana, 1852 , and other three species of the tropical Pacific spinipalma ­complex. “ Talorchestia ” tucurauna differs from this new definition of Talorchestia by palm of male gnathopod 1 being longer than dactylus, female gnathopod 2 without constriction on the distal end of carpus, and uropod 1 outer ramus has robust setae. Thus, T. tucurauna is part of the Talorchestia s.l complex, which has not been fully revised yet. Bellan­Santini & Ruffo (1991) had the same problem with the new species “ Talorchestia ” ungolinii described from the Mediterranean Sea. Later on, Tafani et al. (2004) proposed a revision based on mitochondrial DNA on the Mediterranean Talorchestia s.l species. Based on this analysis, a preliminary diagnosis of two new genera were proposed by Ruffo in Tafani et al. (2004), but none of these would comprise the Brazilian species. A currently study with Australian coastal talitrids with a further revision within the Talorchestia s.l complex is being prepared (Serejo in prep.).

Figures

FIGURE 12. “ Talorchestia ” tucurauna (Müller, 1864), male, 9.2 mm, MNRJ 18739. A, pereopod 5; B, pereopod 6; C, pereopod 7; D, uropod 1; E, uropod 2; F, uropod 3; G, telson. Scale bars: A – E, 0.5 mm; F – G, 0.2 mm.

FIGURE 13. “ Talorchestia ” tucurauna (Müller, 1864), female, 9.5 mm, MNRJ 18739. A, head; B, gnathopod 1; C, gnathopod 2; D – G, oostegites 2 – 5 respectively. H, female gnathopod 1; I, male gnathopod 2 (H, I, from Müller, 1869). Scale bars: A, D – G, 0.5 mm; B, 0.2 mm; C, 0.3 mm.