Hippomedon hurleyi, 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 : 16-20

Hippomedon hurleyi sp. nov.

( Figures 11–13 )

Type material. Holotype, non-ovigerous female, 8 mm, NIWA 48676 , Kaikoura Canyon, 42º31.62’S, 173º37.32’E, 1029 m ( TAN0616 /107), collected by van Veen Grab. Paratypes: 1 female, 9 mm (with deformed palp on right maxilliped), NIWA 48584 , Kaikoura canyon, New Zealand, 42º30.98’S, 173º37.6’E, 1028 m ( TAN0616 /109), collected by van Veen Grab ; 2 females, 6–7.5 mm, NIWA 28274 , Kaikoura Canyon , 42º31.39’S, 173º37.14’E, 1014 m ( TAN0616 /108), collected by van Veen Grab.

Etymology. Named after D.E. Hurley, the New Zealand taxonomist in recognition of his great contribution to the knowledge of the New Zealand amphipod fanua.

Diagnosis. Eyes present, imperfectly developed. Lateral cephalic lobes acute. Antenna 1 subequal to antenna 2, callynophore absent. Mandible molar columnar, strongly triturative, palp attached distally. Maxilla 1 outer plate with setal-teeth in a modified 6/5 arrangement. Gnathopod 1 subchelate; palm acute, slightly convex; dactylus fitting palm. Gnathopod 2 carpus about 1.5 × propodus length, without posterodistal lobe. Pereopod 7 basis posterodistal margin slightly excavate, not produced distally. Epimeron 1 anterodistal corner producing small up-turned spine. Uropod 2 peduncle not producing flange.

Description of female holotype. Antenna 1 subequal to antenna 2; flagellum 17-articulate, article 1 slightly longer than article 2, callynophore absent; accessory flagellum 3-articulate. Antenna 2 less than 40% of body length; flagellum 17-articulate. Calceoli absent. Eyes imperfectly developed, barely visible in alcohol. Lateral cephalic lobes acute. Epistome and upper lip seperate. Mandible incisor smooth; lacinia mobilis present on left mandible only; molar columnar and strongly triturative; palp attached distally. Maxilla 1 outer plate with setal-teeth in a modified 6/5 arrangement; palp present. Maxilla 2 inner plate without oblique setal row. Maxilliped palp 4-articulate, article 4 well developed, with unguis; outer plate large, reaching beyond halfway of palp article 3, with strong, well-developed apical robust setae; inner plate well developed, greater than half the length of outer plate.

Coxae 1–3 posterodistal corner with slight notch with inserted seta. Gnathopod 1 subchelate; coxa 1 large, about as long as coxa 2, subrectangular, with straight anterior margin; ischium moderately elongate, about 1.5 × as long as broad; carpus long, very slightly longer than propodus; propodus margins subparallel, palm acute, slightly convex and minutely denticulate, defined by robust setae at posterodistal corner; dactylus fitting palm, without accessory tooth. Gnathopod 2 minutely subchelate; carpus about 1.5 × propodus length. Pereopod 3 merus weakly expanded anterodistally and subequal in length to carpus; carpus slender, subequal in length to propodus; propodus slender, without blunt, locking robust setae at posterodistal corner. Pereopod 4 coxa with moderately-developed posterodistal lobe; merus weakly expanded anterodistally and slightly longer than carpus; carpus slender, slightly shorter than propodus; propodus slender, without blunt, locking robust setae at posterodistal corner. Coxa 5 equilobate; pereopod 5 basis slightly longer than broad, slightly crenate posteriorly; merus moderately expanded posterodistally; carpus broad, robust, slightly shorter than propodus. Pereopod 6 basis slender, distinctly longer than broad, posterior margin slightly crenate; merus barely expanded posteriorly; carpus slender, subequal in length to propodus. Pereopod 7 basis longer than broad, crenate posteriorly, slightly producing posterodistal lobe, not reaching merus; merus not expanded. Gills from gnathopod 2 to pereopod 7.

Epimeron 1 anterodistal corner quadrate. Epimeron 2 posterodistal corner quadrate. Epimeron 3 posterodistal corner produced, forming a large upturned spine. Urosomite 1 with slight dorsal depression. Uropod 1 peduncle slightly longer than rami; rami subequal. Uropod 2 peduncle subequal in length to rami, not producing flange; rami subequal, inner ramus without marginal constriction. Uropod 3 peduncle distinctly shorter than rami; outer ramus much longer than inner ramus, outer ramus 2-articulate, article 2 about 33% the length of article 1, inner ramus not extending past article 1 of outer ramus. Telson distinctly longer than broad, deeply cleft.

Length. 9 mm.

Distribution. New Zealand: Kaikoura canyon; 1014–1029 m.

Ecology. Associated with marine canyon sediments.

Remarks. Unlike other hippomedontines, H. hurleyi sp. nov. appears not to possess a callynophore and is thus unusual in this regard. Otherwise, it is most similar to H. tasmanicus Barnard, 1961 , differing in the presence of eyes; the relative length of antenna 1, which is much shorter than antenna 2 in H. tasmanicus but subequal to antenna 2 in this species; the shape of epimeron 3, which is more strongly produced in H. hurleyi ; and the relative length of the inner ramus of uropod 3, which does not reach to article 2 of the outer ramus in H. hurleyi , but reaches beyond it in H. tasmanicus , article 2 of the outer ramus also being much shorter in the latter species.

Figures

FIGURE 11. Hippomedon hurleyi sp. nov., holotype, female, 8 mm, NIWA 48676: A, habitus; B, antenna 1; C, antenna 2; D, left mandible; E, right maxilliped; F, maxilla 1; G, maxilla 2. Scale bars: a = 1 mm (fig 11A); b = 0.4 mm (figs 11B– C); c = 0.2 mm (figs 11D–G).

FIGURE 12. Hippomedon hurleyi sp. nov., holotype, female, 8 mm, NIWA 48676: A, gnathopod 1; B, gnathopod 2; C, pereopod 3; D, pereopod 4. Scale bar = 0.4 mm.

FIGURE 13. Hippomedon hurleyi sp. nov., holotype, female, 8 mm, NIWA 48676: A, pereopod 5; B, pereopod 6; C, pereopod 7; D, telson; E, uropod 3; F, uropod 2; G, uropod 1. Scale bars: a = 0.4 mm (figs 13A–C); b = 0.4 mm (figs 13D–G).