Leongathus alannah, Taylor, 2006

Taylor, Joanne, 2006, A new species of Leongathus from the Tasman Sea collected during the 2003 NORFANZ Expedition (Crustacea: Amphipoda: Phoxocephalidae), Memoirs of Museum Victoria 63 (2), pp. 207-213 : 208-213

Leongathus alannah sp. nov

Figures 1–4

Material examined. Holotype: Australia, Tasman Sea , West Norfolk Ridge, Wanganella Bank (32°36.29'S, 167°43.59'E), 707 m, beam trawl, P.B. Berents, 29 May 2003 (stn TAN0308/107), AM P68013 (female, tl. 20 mm).

Paratypes: Type locality, AM P73354 (1 female, tl. 16 mm). Australia, TasmanSea ,NorthNorfolkRidge,(28°51.13'S, 167°42.32'E), 812 m, beam trawl, D.J. Bray, 15 May 2003 (stn TAN0308/029) NMV J53346 (2 females, tl. 13–14 mm). Tasman Sea, North Norfolk Ridge, (32°36.18'S, 167°47.26'E), 1029 m, beam trawl, P.B. Berents, 29 May 2003 (stn TAN0308/111), AM P66426 (female, tl. 18 mm) .

Description. Female. Eyes present. Rostrum unconstricted, exceeding apex of peduncular article 1 on antenna 1. Antenna 1 peduncular article 1 about 1.5 times as long as wide, about 2.1 times as wide as peduncular article 2, ventral margin with 4 setae, dorsal apex with 3 setae; peduncular article 2 about 0.5 times as long as peduncular article 1, with 13 ventral and 3 apical setae; primary flagellum with 16 articles, about 0.8 times as long as peduncle; accessory flagellum with 12 articles. Antenna 2 not ensiform, peduncular article 4 with 11 robust setae in 1 apical row, dorsal margin with 2 notches each bearing 1 robust seta and simple setae, ventral margin with 19 long setae, 3 long ventrodistal robust seta; peduncular article 5 about 0.8 times as long as peduncular article 4, with 7 facial robust seta, dorsal margin with 4 setae, ventral margin with 15 long setae; flagellum 1.1 times as long as peduncular articles 4–5 combined, with 16 articles. Mandible, molar partly trituritive, bearing 13 large teeth; right incisor with 3 teeth; left incisor with 3 humps in 2 branches; right lacinia mobilis bifid, distal branch shorter than proximal, flabellate, denticulate, proximal branch simple; left lacinia mobilis with 5 teeth; right raker 10; left rakers 11; molars composed of elongate lamina in form of cone bearing 14 cusps and 2 short plusetae weakly disjunct, molars covered with fine setae; palp article 1 short, article 2 with 10 medium inner apical setae, 6 outer setae and 4 facial setae, article 3 about 1.1 times as long as article 2, apex oblique with 19 robust-slender setae, with 6 basofacial setae. Maxilla 1 inner plate bearing 2 long apical pluseta, 3 apicolateral much shorter seta; palp article 2 with 18 marginal robust setae. Maxilla 2 plates extending equally, outer slightly broader than inner, setation of inner and outer plate as illustrated. Maxilliped inner plates with 2 large thick apical robust setae, 6 apicofacial setae; outer plate large with 12 medial and apical robust setae, 13 apical and lateral setae; palp article 1 lacking apicolateral setae, article 2 with 3 apicolateral setae, medial margin of article 2 strongly setose, article 3 protuberant, with 12 facial setae, 5 lateral setae, nail of article 4 obsolescent, with 2 accessory setules. Coxa 1 slightly expanded distally; main ventral setae of coxae 1–4=21–25–18–43, posteriormost seta of coxae 1–3 shortened; anterior and posterior margins of coxa 4 divergent, posterodorsal corner rounded, posterodorsal margin short, width-length ratio of coxa 4 almost = 5:6. Long posterior setae on basis of gnathopods 1–2 and pereopods 3–4 =17–19–21–16, short posteriors = 2–0–3–2, long anteriors = 12–20–12–6, short anteriors = 1–0–2–0.

Gnathopod 1 carpus free, gnathopod 2 enlarged, carpus cryptic. Width ratios of carpus-propodus on gnathopods 1–2 = 9:11 and 8:19, length ratios = 17:23 and 1:5; palmar humps ordinary, palms oblique. Pereopods 3–4 similar, facial setae on merus = 9 and 9, on carpus = 10 and 10; main spine of carpus extending to M. 77 and M. 95, carpus lacking proximoposterior robust setae; robust setae formula of propodus = 8+4 and 9+9; acclivity on inner margin of dactyls of pereopods 3–4 weak, obsolescent, emergent setule short, midfacial pluseta ordinary. Coxae 5–7 posteroventral setae formula = 23–13–21; merus-carpus of pereopod 5 medium of pereopod 6 narrow, facial robust setae rows sparse, facial ridge formula on basis of pereopods 5–7 = 0–1–1, anterior ridge of pereopod 7 long; width ratios of basis, merus, carpus, propodus of pereopod 5 = 2:2:2:1, of pereopod 6 = 19:10:8:4, of pereopod 7 = 35:12:11:5, length ratios of pereopod 5 = 15:6:6:8, of pereopod 6 = 18:22:19:22, of pereopod 7 = 37:14:14:5; basis of pereopod 7 barely exceeding apex of merus, with row of 9 facial setae along facial ridge, with ventral setae. Pleopods 1–3 with 2 coupling hooks; articles on outer rami = 24–22–24; articles on inner rami = 16–17–17.

Epimeron 1 posteroventral corner rounded, anteroventral margin with 26 medium setae, posterior margin with 12 setae; epimeron 2 posteroventral corner rounded, with 3 rows of 5–7 anteroventral setae, posterior margin with 12 setae; epimeron 3 posteroventral corner rounded, ventral margin with 6 setae, posterior margin with 18 setae. Urosomite 1 naked; urosomite 3 without dorsal hook. Uropods 1–2 rami with distinct apical nails, uropod 1 outer ramus with 3 dorsal robust setae, inner without robust setae, uropod 2 outer and inner rami with 1 dorsomedial robust seta; uropod 1 peduncle with 11 apicolateral robust setae, with 3 sets of 1–3 basofacial slender setae, without apical enlarged robust seta; uropod 2 peduncle with 9 dorsal robust setae and 5 slender setae; apicolateral corners of peduncles on uropods 1–2 without comb. Uropod 3 unreduced, outer ramus longer than peduncle. Uropod 3 peduncle with 5 ventral robust setae, dorsally with 1 lateral robust seta; rami feminine, inner extending to M. 80 on article 1 of outer ramus, apex with 1 setae, medial margin with 4 slender setae, lateral margin naked, article 2 of outer ramus very short, 0.05, bearing 2 long setae, apicomedial margin of article 1 with 4 slender setae, lateral margin with 4 acclivities, robust setal formula = 1–2–2–2, slender setae formula = 1–0–0–0. Telson length-width ratio = 17:19, almost fully cleft, each apex wide, rounded, lateral acclivity broad, shallow, bearing 3 robust setae, midlateral setules diverse.

Adult male. Unknown.

Distribution. Australia, Tasman Sea, Norfolk Ridge; 707–812 m depth.

Etymology. Named for my daughter Alannah Taylor with whom I was pregnant whilst preparing illustrations.

Remarks. The following variations from the holotype were observed in the paratypes. The main ventral setae of coxae 1–4 = (20–21)–(21–25)–(18–22)–(42–46). Uropod 1 outer ramus with 3–5 dorsal robust setae, inner ramus 0–3 dorsal robust setae. Uropod 2 outer ramus with 1–6 dorsal robust setae, inner ramus with 1 or without dorsal robust setae.

Figures

Figure 1. Leongathus alannah sp. nov., female, holotype, tl. 20.0 mm.

Figure 2. Leongathus alannah sp. nov., female, holotype, tl. 20.0 mm.

Figure 3. Leongathus alannah sp. nov., female, holotype, tl. 20.0 mm.

Figure 4. Leongathus alannah sp. nov., female, holotype, tl. 20.0 mm.