Ensayara ursus, Kilgallen, 2009

Kilgallen, Niamh M., 2009, New species of lysianassoid Amphipoda (Crustacea) associated with seamounts, marine canyons and cold seeps of New Zealand, Zootaxa 2298 (1), pp. 1-30 : 6-10

Ensayara ursus sp. nov.

( Figures 4–6 )

Type material. Holotype, sex undetermined, 3.5 mm, NIWA 50186 , from Bear’s Paw Seep, Omakere Ridge, Hikurangi Margin, 40º03.17’S, 177º49.17’E, 1102 m (SO191-3/197), collected by TV-grab.

Other material examined. 2 specimens, 2.5–3.0 mm, NIWA 48672 , Takahe Seep, Wairarapa, 41º46.34’S, 175º24.68’E, 1056 m (SO191-3/309), collected by TV-grab .

Etymology. After bear genus, Ursus , alluding to the name of the type locality, Bear’s Paw Seep; used as a noun in apposition.

Diagnosis. Antenna 1 peduncle with 3 distinct articles, article 3 short. Lateral cephalic lobes subacute and slightly downward-pointing. Eyes apparently absent. Pereopod 3 propodus largely expanded and strongly subchelate. Pereopod 7 posteroventral margin truncate.

Description of holotype. Antenna 1 subequal to antenna 2; peduncle with 3 distinct articles, article 3 short and telescoped into article 2; flagellum 6+ articulate, article 1 slightly longer than article 2; accessory flagellum 3-articulate. Antenna 2 less than 40% of body length; flagellum 6-articulate. Calceoli absent. Eyes apparently absent. Lateral cephalic lobes subacute, narrowly rounded apically and slightly downwardpointing. Epistome and upper lip fused. Mandible incisor broad, smooth; lacinia mobilis absent from both mandibles; molar a setose flap; palp attached centrally, article 3 greater than half length of article 2. Maxilla 1 outer plate with setal-teeth in a modified 6/5 arrangement; palp present, 2 articulate. Maxilliped palp 4- articulate, article 4 well developed; outer plate poorly developed, not reaching palp article 3, inner margin with 4 or 5 weak robust setae; inner plate about half the length of outer plate.

Gnathopod 1 simple; coxa 1 large, about as long as coxa 2; ischium moderately elongate, about 1.8 × as long as broad; merus short; carpus very short, distinctly shorter than propodus; propodus margins tapering; dactylus without accessory tooth. Gnathopod 2 minutely subchelate; carpus about 1.5 × longer than propodus. Pereopod 3 highly distinctive of genus; propodus largely expanded, slightly longer than broad and strongly subchelate; palm with row of strong, blunt robust setae. Coxa 4 with moderately developed posterior lobe; merus barely expanded posteriorly, subequal in length to carpus; carpus slender, very slightly shorter than propodus; propodus slender; dactylus about two-thirds propodus length. Coxa 5 produced into an anterior lobe; basis about as long as broad, merus expanded posteriorly, subequal in length to carpus; carpus short, slightly shorter than propodus; dactylus about half propodus length. Pereopod 6 basis distinctly longer than broad; merus weakly expanded posteriorly, shorter than carpus; carpus slender, shorter than propodus; dactylus about half propodus length. Pereopod 7 basis distinctly longer than broad; merus barely expanded posteriorly, slightly shorter than carpus; carpus slender, distinctly shorter than propodus; propodus slender; dactylus about half propodus length. Gills on pereonites 2–6.

Epimeron 1 anterodistal corner quadrate. Epimeron 3 posterodistal corner acute. Urosomite 1 without distinct dorsal depression. Uropod 1 peduncle longer than rami; rami subequal in length. Uropod 2 peduncle longer than rami; rami subequal in length, inner ramus without marginal constriction. Uropod 3 peduncle subequal in length to rami; outer ramus 2-articulate, slightly longer than inner ramus; inner ramus reaching just beyond article 1 of outer ramus. Telson distinctly longer than broad, entire.

Length. 3.5 mm.

Distribution. New Zealand: Omakere Ridge and Opouawe Bank, the Hikurangi Margin; 1055–1102 m.

Ecology. E. ursus has been sampled in the vicinity of the cold seeps of the Hikurangi Margin.

Remarks. Ensayara ursus sp. nov. is also quite similar to E. iara , differing from it only in the lack of eyes, and the length of article 3 of the mandibular palp, which is much shorter in that species. The new species can be easily distinguished from E. kermadecensis sp. nov. by the lack of eyes; the shape of the lateral cephalic lobes, which are subacute and downward-pointing in this species, but subquadrate in E. kermadecensis ; and the relative widths of articles of the maxillipedal palp, which are much broader in this species.

This brings the total number of described species of Ensayara to 11, with three now known from New Zealand. The genus has a worldwide distribution, including the north and south Pacific, the Caribbean Sea, the Indian Ocean, and the Mediterranean Sea. Ensayara kermadecensis and E. ursus are thus far the only species of this genus to be collected in the vicinity of a chemosynthetic habitat.

Figures

FIGURE 4. Ensayara ursus sp. nov., holotype, 3.5 mm, NIWA 50186: A, habitus; B, antenna 2; C, antenna 1; D, left maxilliped; E, left mandible; F, maxilla 1 outer plate. Scale bars: a = 1 mm (fig 4A); b = 0.1 mm (figs 4B, C); c = 0.1 mm (figs 4D–F).

FIGURE 5. Ensayara ursus sp. nov., holotype, 3.5 mm, NIWA 50186: A, gnathopod 1; B, gnathopod 2; C, pereopod 3 (with propodus twisted on slide); D, pereopod 4. Scale bar = 0.2 mm.

FIGURE 6. Ensayara ursus sp. nov., holotype, 3.5 mm, NIWA 50186: A, pereopod 5; B, pereoopd 6; C, pereopod 7; D, telson; E, uropod 3; F, uropod 2; G, uropod 1. Scale bars: a = 0.3 mm (figs 6A–C); b = 0.2 mm (figs 6D–G).