Ambicholestes (Austrolestes) thetis, Just, 1998

Just, Jean, 1998, Siphonoecetinae (Crustacea: Amphipoda: Ischyroceridae) 7: Australian Concholestids, Ambicholestes n. gen., with a Description of Six New Species, and a New, Restricted Diagnosis for Caribboecetes Just, 1983, Records of the Australian Museum 50 (1), pp. 27-54 : 47-49

Ambicholestes (Austrolestes) thetis n.sp.

Figs 17-19

Siphonoecetes australis Stebbing, 1910 (partim, Stebbing 1910, Plate 54C).

Material examined. HOLOTYPE: male, 4.7 mm, Bass Strait, 63 km E of North Point, Flinders Island, 39°44.8'S 148°40.6'E, 124 m, muddy sand, epibenthic sled, R. Wilson, RV "Tangaroa", 14 November 1981, Stn BSS 167, NMV J9528. PARATYPES: 25 specimens. Eastern Bass Strait, 60 km E of North Point, Flinders Island, 39°41.7'S 148°39.5'E, 115 m, muddy sand, naturalist's dredge, G.C.B. Poore, HMAS "Kimbla", 27 March 1979, Stn BSS 32, NMV J9526 (4 specimens) and J9527 (3). Eastern Bass Strait, 63 km E of North Point, Flinders Island, Tasmania, 39°44.8'S 148°40.6'E, 124 m, muddy sand, Smith-Mclntyre grab, R. Wilson, RV "Tangaroa", 14 November 1981, Stn BSS 167 G, NMV J9529 (4). Eastern Bass Strait, 63 km E of North Point, Flinders Island, Tasmania, 39°44.8'S 148°40.6'E, 124 m, fine sand, WHOI epibenthic sled, R. Wilson, RV "Tangaroa", 14 November 1981, Stn BSS 167 S, NMV J9530 (20). New South Wales, off Cape Three Point, 40-50 fms (74-92 m), "Thetis" Expedition, Stn 13, AM P2529, (1 male, one of two former syntypes of Siphonoecetes australis Stebbing, 1910 , see Just 1985: 333). New South Wales, off Cape Three Point, 40-50 fms (74-92 m), "Thetis" Expedition, January 1911, AM P31867 (re-registered from P2528) (1 male, probably a missing syntype of Siphonoecetes australis Stebbing, 1910 , see Just 1985: 333).

Diagnosis. Austrolestes without rostrum. Cephalic front margin a rounded wide triangle. Cephalon along midline as long as first lllz pereonites

Further description. Antenna 1 peduncle article 1 with 1 recurving robust seta ventrally in proximal half. Antenna 2 peduncular article 3 without robust setae; ventroapical projection of peduncular article 2 wider than long, evenly rounded, with apical row of long setae. Male antenna 1

about as long as first 61/z pereonites with up to 7 flagellar articles. Male antenna 2 as long as cephalon, pereon and pleon combined.

Coxal plates 5 and 6 with posterior lobe rounded; plate 5 without long anterior setae. Pleonal sideplates I and 2 evenly rounded.

Mandibular palp overreaching mandibular incisor by about 1/10 palp length, with distolateral and medioventral cover of microsetules, tip naked.

Pereopod 1 article 5 with 1 posterodistalrobust seta; article 6 with small posterodistal tooth. Pereopod 2 article 2 anterior margin straight, fringed with moderately long simple setae; article 6 with up to 5 posterior robust setae. Pereopods 5 and 6 article 2 anterodistally with 1 long and a few short setae.

Uropod 1 peduncle about 21/z times longer than wide, with up to 8 distal robust setae dorsolaterally; outer ramus barely 4 times longer than broad, with 15-17 lateral robust setae, single as well as double; inner ramus c. 2/5 length of outer ramus with up to 12 lateral and apical robust setae.

Urosomites 1 and 2 free. Urosomite 3 and telson fused dorsally.

Size. Largest male: 4.7 mm; largest female: 3.8 mm.

Colour. Not known.

Biology. On muddy sand.

Distribution. Eastern Australia: central New South Wales to eastern Bass Strait; 74-124 m depth.

Etymology. The specific epithet refers to HMCS "Thetis" from which the first specimens of this species were collected off Botany Bay.

Figures

Fig. 17. Ambicholestes (Austrolestes) thetis n.sp., holotype. Scale bar: 1 mm.

Fig. 18. Ambicholestes (Austrolestes) thetis n.sp., holotype. c, cephalon, dorsal and lateral view; p, pereopod (1 and 2); upl, left uropod 1, ventral view, inner ramus, enlarged; us, urosome, dorsal view.

Fig. 19. Ambicholestes (Austrolestes) thetis n.sp., holotype. 11, lower lip; md, mandible: mdp, mandibular palp, dorsolateral view; mp, maxilliped; p, pereopod (3 and 5); vp, ventral process of article 2, antenna 2.