Atlantorchestoidea brasiliensis ( Dana, 1853 )

Serejo, Cristiana S., 2004, Talitridae (Amphipoda, Gammaridea) from the Brazilian coastline, Zootaxa 646, pp. 1-29 : 9-14

Atlantorchestoidea brasiliensis ( Dana, 1853) ( Figs. 4–6 )

Orchestia (Talitrus) brasiliensis Dana, 1853: 857 , pl. 57, fig. 2a–g.

Orchestoidea Brasiliensis — Bate, 1862: 13, pl 2, fig. 4.

Orchestoidea brasiliensis — Stebbing, 1906a: 529; Schellenberg, 1938: 209, fig 3; Oliveira, 1953: 335, figs. 13–14.

" Orchestoidea " brasiliensis — Bousfield, 1982: 24; 44.

Pseudorchestoidea brasiliensis — Cardoso & Veloso, 1996: 111; Gomez & Defeo, 1999: 209; Cardoso, 2002, 167.

Material examined. Rio Grande do Norte — Between Barreira d'água beach and Roxa beach, Natal, RN, 1 female, 27/I/1964, MNRJ 10921. Rio de Janeiro ­ Itaúna beach, Saquarema, RJ, 53 females and 12 males, C. Serejo & P.S. Young col., 02/IV/1999, MNRJ 18736; Grande beach, Arraial do Cabo, RJ, 4 males and 4 females, 102/ VII/1993, MNRJ 9791; Conchas beach, Cabo Frio, RJ, 6 males, 10 females, W. Zwink & L.F. Reis col., IV/ 1985, MNRJ 9747; Prainha beach, RJ, 1 male and 7 females, 09/X/1992, MNRJ 14451; Urca Beach, Guanabara Bay, RJ, 4 males and 13 females, M. S. Leite col., X/1990, MNRJ 9796; Parnaioca beach, Ilha Grande, Angra dos Reis, RJ, 12 males and 8 females, A. Rezende col., 3/VIII/2002, MNRJ 18738. São Paulo — São Sebastião, SP, 2 males, 21/VI/ 1960, MNRJ 9789. Santa Catarina — Campeche beach, Florianópolis, SC, 45 males and 4 females, P.S. Young & C. Serejo col., 14/II/1999, MNRJ 18737; Itacoarinha beach, SC, 1 male and 2 females, N. Magalhães col., 23/II/2002, MNRJ 18450.

Diagnosis. as given for the genus.

Description. Male, 11.9 mm. Eyes large. Antenna 1 reaching half way of article 4 of antenna 2, flagellum with 3 articles. Male antenna 2 not incrassate, peduncle article 4 about half length of article 5, flagellum with about 17 articles ( Fig. 4 A). Mandible with left lacinia mobilis 4­dentate ( Fig. 4 B), right lacinia with two minutely dentate plates. 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 3­articulate, article 2 with setose medio­distal inner lobe ( Fig. 4 C).

Gnathopod 1 ( Fig. 4 D) simple and setose, carpus and propodus lacking posterior lobe. Gnathopod 2 ( Fig. 4 E) robust and sexually dimorphic, palm straight and oblique, bearing robust setae. Coxa 2–4 ( Fig. 4 E–G) deeper than wide with distinct posterior process. Pereopods 3–7 cuspidactylate, cusps elongate. Pereopod 4 shorter than pereopod 3, dactylus slightly crenellated ( Fig. 4 G). Pereopod 5 ( Fig. 5 A) much shorter than pereopods 6–7, reaching half way of merus of pereopod 6; anterior margin of carpus with 3–4 long truncated robust setae, dactylus robust and short, distinct of that of pereopods 6–7. Posterior lobe of coxa 6 rounded and very long. Pereopod 6 a little shorter than pereopod 7 ( Fig. 5 B, C). Pleopod 1–3 reduced, uniramous, each ramus 1­articulate ( Fig. 5 D–F). Peduncle of pleopod 1 about 2.5 times longer than ramus, ramus with marginal and distal robust setae. Peduncle of pleopod 2 about 3.3 times longer than ramus. Peduncle of pleopod 3 robust, about 3.2 times longer than ramus, ramus with a single distal setae. Uropod 1 ( Fig. 5 G), rami with 3 marginal and 4 robust distal setae. Uropod 2 ( Fig. 5 H), outer ramus shorter than inner ramus, rami bearing robust setae. Uropod 3 ( Fig. 5 I), peduncle with one distal seta, ramus about 1.7 times the peduncle, with 4 marginal and 2 distal robust setae. Telson ( Fig. 5 J) wider than long, distally rounded, each side with 2 marginal robust setae.

Female, 11.8 mm. Antenna 2 as in males, although flagellum has 13–14 articles. Gnathopod 1 simple ( Fig. 6 A). Gnathopod 2 ( Fig. 6 B) mitten shaped, basis not enlarged. Oostegites 2–5 oval and broad ( Fig. 6 C–F).

Type locality. Rio de Janeiro harbor.

Distribution. Brazil: Rio Grande do Norte.

Ecology. Commonly found in the supra­littoral of exposed beaches on the wrack or usually hidden under the sand at daytime. Ovigerous females and juveniles are found thoughout the year, indicating a continuous reproductive cycle for this species ( Cardoso & Veloso, 1996).

Remarks. Atlantorchestoidea brasiliensis is one of the endemic species of sandhoppers found on the Brazilian coastline. It was originally described by Dana (1853) from the Rio de Janeiro harbor, who illustrated the unmodified dactylus of pereopod 5 and did not mentioned the modifications on pleopods 1–3. Later, Schellenberg (1938) redescribed this species with material from Recife, Pernambuco. This author not only depicted the modified pereopod 5 with blunt anterior setae on carpus and robust dactylus and reduced pleopods 1–3, but also pointed these characters as important modifications for the habit of digging in sand. Actually, the highly reduced pleopods 1–3 of A. brasiliensis with the loss of the swimming and respiratory current functions of these appendages indicate the adaptation of this species to a semi­terrestrial life style. A trend toward reduction of pleopods is well documented for landhoppers ( Friend & Richardson, 1986), although it is not commonly observed in sandhoppers. Oliveira (1953) also redescribed this species with material from Cabo Frio, Maricá, and Marambaia, all from Rio de Janeiro state, but still did not mention some important taxonomic details of A. brasiliensis . The material observed agrees with previous descriptions.

Since Bate (1862), this species has been allocated in Orchestoidea . Some years ago, material of A. brasiliensis was sent by Dr. Yoko Wakabara (Universidade de São Paulo) to Dr. Bousfield (Canadian Museum of Nature) for identification. He identified this species as Pseudorchestoidea brasiliensis , a name that has been used in some recent ecological works ( Cardoso & Veloso, 1996; Gomez & Defeo, 1999; Cardoso, 2002). Different from his identification, Bousfield (1982: 45) has stated previously that " Orchestoidea " brasiliensis should be placed in a monotypic genus because of its distinctive pereopod 5, structures of gills, pleopods and uropods. However, no formal change was made in the literature, and this species definitely does not belong to Pseudorchestoidea . Taking this into account, a new genus is proposed herein for this species as discussed above.

Figures

FIGURE 4. Atlantorchestoidea brasiliensis (Dana, 1853), male, 11.9 mm, MNRJ 18736. A, head, B, left mandible; C, maxilliped; D, gnathopod 1; E, gnathopod 2; F, pereopod 3; G, pereopod 4; H, dactylus of pereopod 4. Scale bars: A, 1 mm; B – C, 0.2 mm; D – G, 0.5 mm; H, 0.1 mm.

FIGURE 5. Atlantorchestoidea brasiliensis (Dana, 1853), male, 11.9 mm, MNRJ 18736. A, pereopod 5; B, pereopod 6; C, pereopod 7; D, pleopod 1; E, pleopod 2; F, pleopod 3; G, uropod 1; H, uropod 2; I, uropod 3; J, telson. Scale bars: A, 0.5 mm; B – C, 1 mm; D – J, 0.2 mm.

FIGURE 6. Atlantorchestoidea brasiliensis (Dana, 1853), female, 11.8 mm, MNRJ 18736. A, gnathopod 1; B, gnathopod 2; C – F, oostegites 2 – 5 respectively. Scale bars: A – F, 0.5 mm.