Thrombasia umina, Kilgallen & Lowry, 2014

Kilgallen, N. M. & Lowry, J. K., 2014, The Tryphosa group (Crustacea: Amphipoda: Lysianassoidea: Lysianassidae: Tryphosinae), Zootaxa 3768 (5), pp. 501-545 : 534-536

Thrombasia umina sp. nov.

( Figs 21 , 22 )

Types. Holotype, female, 8.6 mm, AM P.69048, east of Broken Bay , New South Wales, Australia (33°37.2’S 152°04.2’E to 33°39.0’S 152°01.8’E), 896–923 m, dredge, 10 December 1980, R. T. Springthorpe, FRV Kapala stn K80-20-09 . Paratypes: 2 specimens, 9.0– 9.5 mm, AM P.69049, same collection details as holotype ; 5 specimens, 6.0– 9.7 mm, AM P.69050, from east of Broken Bay , New South Wales, Australia (33°30.0’S 152°12.0’E to 33°33.0’S 152°09.0’E), 1053–1066 m, beam trawl, 12 February 1986, R. T. Springthorpe, FRV Kapala stn K86-01- 10 .

Additional material examined: 3 specimens, AM P.51385, from east of Fortescue Bay , Tasmania, Australia (43°08.96’S 148°15.36’E), 1000 m, baited trap, 8 April 1994 – 9 April 1994, J.K. Lowry & K. Dempsey, MV Martrudan stn TAS-422 ; 31 specimens, AM P.57989, from east of Fortescue Bay , Tasmania, Australia (43°08.96’S 148°15.36’E), 1000 m, baited trap, 8 April 1994 – 9 April 1994, J.K. Lowry & K. Dempsey, MV Martrudan stn TAS-423 .

Type Locality. East of Broken Bay , New South Wales, Australia (33°37.2’S 152°04.2’E to 33°39.0’S 152°01.8’E), 896–923 m.

Etymology. Named for Umina Beach in Broken Bay, near the type locality; used as a noun in apposition.

Description. Based on holotype, female, 8.6 mm, AM P.69048. Head lateral cephalic lobe subtriangular, apically subacute. Antenna 1 accessory flagellum forming cap partially covering callynophore; primary flagellum with strong 2-field callynophore, robust setae absent from proximal articles; calceoli absent. Antenna 2 peduncular articles 3 to 5 not enlarged; flagellum short, calceoli absent. Labrum, epistome and upper lip separate; epistome less produced than upper lip, narrowly rounded and concave; upper lip produced, strongly rounded apically. Mandible molar columnar, with oval fully triturating surface. Maxilla 1 outer plate setal-tooth 7 present, cuspidate distally; palp distal margin with apical robust setae. Maxilliped outer plate with one slender and one broad apical robust setae.

Pereonites 1–7 dorsally smooth. Gnathopod 1 subchelate; coxa reduced, significantly shorter than coxa 2, tapering distally; carpus without posterior lobe; propodus small, margins subparallel, sparsely setose along posterior margin, palm moderately acute, entire, straight. Pereopod 5 basis longer than broad, not posteroproximally excavate, posterior margin not serrate. Pereopod 7 basis posterodistally produced less than halfway along merus.

Pleonite 3 without mid-dorsal carina, not produced dorsodistally. Epimeron 3 posterior margin smooth, posteroventral corner forming broad spine. Urosomite 1 not projecting over urosomite 2, dorsally straight. Uropod 2 inner ramus with constriction. Uropod 3 stout; inner and outer rami well developed, without plumose setae, outer ramus article 2 short. Telson moderately cleft, with 2 dorsal robust setae and 1 apical robust setae on each lobe.

Sexually dimorphic characters. Based on paratype, male, AM P.69050. Antenna 2 peduncle article 3 enlarged, article 4 slightly enlarged, articles 4–5 with weak brush setae on anterior margin, flagellum long, calceoli absent. Uropod 3 rami without plumose setae.

Habitat. None recorded.

Feeding strategy. Scavenger (from baited trap) (this study).

Depth range. 896–1066 m (this study).

Remarks. The only male of this species available for study does not have calceoli on either antenna and does not appear to have plumose setae on the rami of uropod 3. However, it may still be an immature specimen that has not yet developed these characters.

Thrombasia umina shares a type locality and partial distribution with T. evalina , and is morphologically similar to that species. However, T. umina has an upturned spine on the posteroventral corner of epimeron 3, which is lacking in T. evalina . Two other species of Thrombasia have a spine on epimeron 3, T. grabenis and T. tracalero . Both of those species have a longer gnathopod 1 coxa that is more weakly tapered and so are quite distinct from the T. umina .

Distribution. Tasman Sea. East coast of Australia from Broken Bay, New South Wales to Fortescue Bay, Tasmania (this study).

Figures

FIGURE 21. Thrombasia umina sp. nov., holotype, female, 8.6 mm, AM P.69048, from east of Broken Bay, New South Wales, Australia. Scale bars: 0.1 mm.

FIGURE 22. Thrombasia umina sp. nov., holotype, female, 8.6 mm, AM P.69048, from east of Broken Bay, New South Wales, Australia. Scale bars: 0.1 mm.