Orchestia tabladoi, Myers & Lowry, 2020

Myers, Alan A. & Lowry, James K., 2020, A revision of the genus Orchestia Leach, 1814 with the reinstatement of O. inaequalipes (K. H. Barnard, 1951), the designation of a neotype for Orchestia gammarellus (Pallas 1776) and the description of three new species (Crustacea: Amphipoda: Talitridae Talitrinae), Zootaxa 4808 (2), pp. 201-250 : 241-242

Orchestia tabladoi sp. nov.

( Figs 32–33 )

Orchestia gammarella .― Escofet et al., 1978: 68.― Alonso, 1986: 68.

Types. Holotype, male, 16 mm (MACN-In 43259), Golfo de San Matías , Argentina . Paratypes 1 male, 2 females ((MACN-In 43260), same data as holotype.

Type locality. Golfo de San Matías , Argentina .

Etymology. Named after Alejandro Tablado of the Museo Argentino de Ciencias Naturale, Buenos Aires.

Description adult male (16 mm).

Head. Eyes of moderate size. Antenna 1 short, scarcely reaching beyond peduncular article 4 of antenna 2; accessory flagellum absent; primary flagellum with 5 articles. Antenna 2 peduncular article 5 1.5 × length of peduncular article 4; flagellum subequal with combined length of peduncular articles 4 and 5, with about 18 articles, final article cone shaped, with terminal cluster of imbricated setae. Labrum without epistome. Mandible left lacinia mobilis with 4 cusps. Maxilliped palp article 2 with distomedial lobe.

Pereon. Gnathopod 1 subchelate; coxa smaller than that of coxa 2; posterior margin of carpus and propodus each with lobe covered in palmate setae; carpus moderately stout, with moderately developed palmate lobe; propodus length to carpus length 1:1.4, propodus subtriangular; dactylus shorter than palm. Gnathopod 2 subchelate; basis 2 × as long as broad; merus posterior margin with 3 setae; propodus subrectangular distal width 1.4 × proximal width, palm weakly acute. Pereopods 3–7 cuspidactylate. Pereopods 3–7 dactylus nails becoming very short and blunt with matirity. Pereopod 4 dactylus thickened proximally with a notch midway along posterior margin. Pereopod 5 basis subovoid. Pereopod 7 basis posterior margin distinctly serrate; merus strongly triangular, 2.3 × as wide distally as proximally; carpus subround, almost as broad as long, carpus subequal in length with merus; propodus 1.3 × length of carpus.

Pleon. Epimeron 3 posterior margin weakly crenulate. Uropod 1 peduncle longer than rami, without distolateral robust seta; rami subequal. Uropod 2 peduncle subequal in length with rami, rami subequal; exopod with 3 marginal robust setae; endopod with 3 marginal robust setae and 3 robust setae on inner face. U3 peduncle twice as long as broad, ramus slender 4 × as long s broad, 0.6 × length of peduncle, outer margin with 3 slender setae. Telson with 6 or less relatively slender apical robust setae on each side.

Female. Gnathopod 2 basis broad, 1.9 × as long as broad, widest proximally; carpus 1.6 × length of propodus. Pereopod 7 basis flange on posterior margin only moderately produced, posterior margin distinctly serrate, merus and carpus unexpanded.

Habitat. Algae deposited in the supralittoral in the Verrucaria lichen zone.

Remarks. Orchestia tabladoi sp. nov. shares with the other southern hemisphere species O. inaequalipes and O. perezi sp.nov., a telson that has only 6 or less relatively long and slender setae per lobe (more than 7 stouter setae in northern hemisphere species). Orchestia tabladoi sp. nov. differs from O. inaequalipes in the shorter less slender carpus of the male gnathopod 1 and in the short sub-round carpus of the male pereopod 7 (sub-ovoid becoming subrectangular in O. inaequalipes ). It differs also in the shape of the male gnathopod 2 propodus that is subrectangular with a weakly acute palm in O. tabladoi sp. nov., but subovoid in O. inaequalipes with a more acute palm. It also differs from O. inaequalipes also in the shape of the female gnathopod 2 basis (proximally broad in O. tabladoi sp. nov., slender in O. inaequalipes ). Orchestia tabladoi sp. nov. differs from O. perezi sp. nov., in the shape of the carpus of the male pereopod 7 (subround and almost as broad as long in O. tabladoi sp. nov. but subovoid and 2–3 × as long as broad in O. perezi sp. nov.) and in the shape of the female pereopod 7 basis, that is subovoid with only a moderately developed but strongly serrate posterior margin in O. tabladoi sp. nov. but subrectangular with a very well developed but weakly serrate posterior margin in O. perezi sp. nov.

Distribution. Argentina: Golfo de San Matías ( Escofet et al. 1978) (this paper); Ría Deseado, La Pesquera,

Santa Cruz ( Alonso 1986).

Figures

FIGURE 32. Orchestia tabladoi sp. nov., Golfo de San Matías, Argentina.

FIGURE 33. Orchestia tabladoi sp. nov., Golfo de San Matías, Argentina.