Tryphosella moana, 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 : 20-25

Tryphosella moana sp. nov.

( Figures 14 –16 )

Type material. Holotype male, 4.5 mm, NIWA 50651 ; allotype non-ovigerous female, 6 mm, NIWA 48585 ; paratype, female, 5 mm, NIWA 32818 ; all from Rumble V submarine volcano, Kermadec Arc, 36º08.4’S, 178º11.78’E, 414 m ( KOK0506 /21), collected by Pisces 5 submersible with suction sample of crust and small orange seastar.

Etymology. The specific name ‘moana’ is a Polynesian word, meaning ‘the sea’.

Diagnosis. Mandible molar columnar and triturative; palp attached centrally. Maxilla 1 with setal-teeth in a modified 6/5 arrangement. Maxilliped outer plate with row of strong robust setae along apical and inner margin. Gnathopod 1 subchelate; coxa 1 slightly shorter than coxa 2 and tapering posterodistally. Epimeron 1 anterodistal corner obtuse. Epimeron 3 posterodistal corner producing small spine.

Description of male holotype. Antenna 1 shorter than antenna 2; primary flagellum 11-articulate; article 1 distinctly elongate with 2-field callynophore; accessory flagellum 4-articulate. Antenna 2 less than 40% of body length, flagellum 15-articulate. Calceoli present on both antennae. Eyes apparently absent. Lateral cephalic lobes subacute, apically rounded. Mouthparts forming a quadrate bundle. Epistome and upper lip separate, epistome produced slightly in front of upper lip. Mandible incisor smooth; lacinia mobilis present on left mandible only; setal row present; molar well developed, columnar, triturative; palp attached centrally. Maxilla 1 outer plate with setal-teeth in a modified 6/5 arrangement; palp present, 2-articulate. Maxilla 2 inner plate without oblique setae. Maxilliped palp 4-articulate, article 4 well developed, without unguis; outer plate large, reaching to about half length of palp article 3, with strong, well developed robust setae along apical and inner margin; inner plate well developed, greater than half the length of the outer plate.

Coxae 1–3 posterodistal corner with slight notch with inserted seta. Gnathopod 1 subchelate; coxa 1 reduced, significantly shorter than coxa 2, tapering distally; basis with sparse setal fringe; ischium short, about 1.5 × as long as broad; carpus long, of subequal length to propodus; propodus margins subparallel; palm acute, minutely denticulate and defined by robust seta at posterodistal corner; dactylus fitting palm, with accessory tooth. Gnathopod 2 minutely subchelate; carpus about 1.8x as long as propodus. Pereopod 3 merus weakly expanded anterodistally and slightly longer than carpus; carpus slender, slightly shorter than propodus; propodus slender, with 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, shorter than propodus; propodus slender, with blunt, locking robust setae at posterodistal corner. Coxa 5 equilobate; pereopod 5 basis slightly longer than broad, crenate posteriorly; merus moderately expanded posterodistally; carpus subequal in length to merus; propodus slender, about 1.5 × as long as carpus; dactylus less than half propodus length. Pereopod 6 basis distinctly longer than broad, posterior margin almost straight, slightly crenate, producing slight posterodistal lobe, not reaching merus. Pereopod 7 basis distinctly longer than broad, crenate posteriorly, posterodistally produced, not reaching merus; merus barely expanded posteriorly. Gills on gnathopod 2 to pereopod 7.

Epimeron 1 anterodistal corner widely obtuse. Epimeron 3 posterodistal corner produced, forming a small spine. Urosomite 1 with strong dorsal depression and rounded hump. Uropod 1 peduncle subequal in length to rami, rami slightly unequal in length; uropod 2 peduncle subequal in length to rami, rami subequal in length, inner ramus without marginal constriction; uropod 3 peduncle distinctly shorter than rami, outer ramus 2– articulate, article 2 long, greater than half the length of article 1, rami distinctly unequal in length, inner ramus with 5 long setae along outer margin. Telson distinctly longer than broad, deeply cleft.

Length. 4.5 mm.

Female (sexually dimorphic character s; based on allotype female). Calceoli absent from antennae. Lateral cephalic lobes slightly more broadly rounded than in male. Gnathopod 1 basis with dense setal fringe. Uropod 3 outer ramus 2-articulate, article 2 about 0.33 × article 1, inner ramus extending slightly past article 1 of outer ramus and lacking slender setae.

Distribution. New Zealand: Rumble V submarine volcano, Kermadec Arc.

Ecology. Associated with crustal material on a hydrothermally active submarine volcano.

Remarks. Tryphosella is a common and widespread genus ranging from the tropics to the polar regions, so it is somewhat surprising that this is only the second species of the genus to be recorded from New Zealand. Tryphosella serans Lowry & Stoddart, 1983 was recorded from The Snares and Campbell Island. Tryphosella moana sp. nov. differs from T. serrans in the lack of eyes and the slightly broader lateral cephalic lobes; the outer plates of the maxillipeds, which are larger and more strongly armed with robust setae; the relatively longer article 4 of the second antenna; and the shorter telson.

Tryphosella ama Lowry & Stoddart, 1994 , described from south of the Isle of Pines, New Caledonia, is quite similar in appearance to T. moana , though, the lateral cephalic lobes are more down-turned in that species, the gnathopod 1 ischium is extremely elongate, the pereopod 5 basis is slightly excavate posteriorly, the epimeron 3 spine is lacking and the uropod 2 inner ramus is moderately constricted, unlike the unconstricted ramus of T. moana .

Tryphosella oupi Lowry & Stoddart, 1994 , described from north of the Isle of Pines, New Caledonia differs from T. moana sp. nov. in the more acute lateral cephalic lobes, the larger outer maxilliped plates, the smaller triturating surface of the mandible, the minutely chelate gnathopod 2, and the absence of a spine on the epimeron 3 posterodistal corner.

Finally, Tryphosella astrolabensis Lowry & Stoddart, 1995b and T. wongada Lowry & Stoddart, 1995b , both described from Papua New Guinea, are also very similar to T. moana sp. nov., but may be distinguished by the presence of eyes, and the elongate ischium of gnathopod 1 in those species.

Figures

FIGURE 14. Tryphosella moana sp. nov., allotype female, 6 mm, NIWA 48585: A, habitus. Holotype male, 4.5 mm, NIWA 50651: B, head and anterior pereon segments; C, antenna 1; D, antenna 2; E, maxilla1; F, maxillipeds; G, left mandible; H, right mandible. Scale bars: a = 1 mm (fig. 14A, B); b = 0.2 mm (figs 14C, D); c = 0.2 mm (figs 14E–H).

FIGURE 15. Tryphosella moana sp. nov., allotype female, 6 mm, NIWA 48585: A, gnathopod 1. Holotype, male, 4.5 mm, NIWA 50651: B, gnathopod 1; C, gnathopod 2; D, pereopod 3; E, pereopod 4. Scale bars: a = 0.2 mm (Figures 15A–C); b = 0.2 mm (Figures 15D–E).

FIGURE 16. Tryphosella moana sp. nov., holotype, male, 4.5 mm, NIWA 50651: A, pereopod 5; B, pereopod6; C, pereopod 7; D, uropod 1; E, uropod 3; F, uropod 2; G, telson. Allotype female, 6 mm, NIWA 48585: H, uropod 3. Scale bars: a = 0.2 mm (figs 16A–C); b = 0.2 mm (Figs 16D–G).