Leucon (Leucon) echinolophotos Gerken, 2016, n. sp.

Leucon (Leucon) echinolophotos n. sp.

(Figs 19–21)

Material examined. Holotype— ovigerous female, MV J62349, 65°56’24”S, 50°52’06”E, 386–400 m, 15 Nov 1985, M.D. Norman. Paratypes— ovigerous female (dissected), MV J62360, 65°56’24”S, 50°52’06”E, 386–400 m, 15 Nov 1985, M.D. Norman; subadult male (dissected) MV J68461, 65°56’24”S, 50°52’06”E. 386–400 m, 15 Nov 1985, M.D. Norman. Non-type material— 1 subadult female, MV J68460, 65°56’24”S, 50°52’06”E. 386– 400 m, 15 Nov 1985, M.D. Norman.

Diagnosis. Female and subadult male. Carapace dorsal margin with few strong serrations posteriorly, separated by short smooth area from strong serrations that continue to anterior border of frontal lobe, with few small setae dorsally. Pseudorostrum extending 0.15 times carapace length anterior of frontal lobe, blunt, with setae. Antennal notch deeply excavate, anteroventral corner acutely produced, with small teeth dorsal to and large teeth ventral to anteroventral corner. Pereopod 1 broken off. Adult male. Unknown.

Etymology. The species is named echinolophotos from the Greek meaning spine crested, in reference to the strong serrations on the dorsal crest.

Description. Ovigerous female holotype 6.5 mm, ovigerous female paratype 6.3 mm. Body (Figs 19 A–B). Carapace subequal to pereon, with strong serrations on dorsal margin only, with few posterior serrations separated by a smooth area from serrations that continue to anterior border of frontal lobe, serrations interspersed with short setae; antennal notch deeply excavate, anteroventral corner acutely produced, with small teeth dorsal of corner, larger teeth ventral of corner; eyelobe absent; pseudorostrum short, extending 0.15 times carapace length anterior of frontal lobe, blunt, with moderately long setae. Pleon 0.5 times total body length; pleonite 6 with 2 long setae terminally.

Antennule (Fig. 20 A) article 1 shortest, with few simple setae; article 2 longest, with simple setae; article 3 longer than article 1, with simple setae. Main flagellum of 3 articles, with 2 aesthetascs; accessory flagellum of 1 article, much less than half length of article 1 main flagellum, with simple setae.

Antenna (Fig. 20 A) of 4 articles; article 1 stout, with 2 pappose setae; articles 2–3 slender, unarmed; article 4 slender, with small simple setae.

Mandible (Fig. 20 B) truncate, lacinia mobilis with 2 cusps, with 2 very short setae medially.

Maxillule (Fig. 20 C) with 2 endites; palp with 1 seta.

Maxilla (Fig. 20 D) with 3 endites; broad endite medial row of setae pappose; narrow endites with plumose setae.

Maxilliped 1 (Fig. 20 E) basis with plumose seta, lobe with 1 microserrate, hook and simple setae; carpus with simple setae, no beak-like setae.

Maxilliped 2 (Fig. 20 F) basis with 2 short plumose setae; merus with short plumose seta; medial setae on carpus and propodus simple.

Maxilliped 3 (Fig. 20 G) 100:7:20:31:20:20; basis with plumose setae, distolateral corner with 2 stout and 2 slender plumose setae; ischium unarmed.

Pereopod 1–4 broken, not examined.

Pereopod 5 (Fig. 20 H) 100:14:21:28:24:7; basis with simple and plumose setae; ischium simple seta; merus with simple and plumose setae; carpus with simple and annulate setae; propodus with annulate seta; dactylus minute, with simple seta.

Uropods (Fig. 20 I) peduncles 1.5–1.6 times length of pleonite 6, with 4 long and 6–7 short microserrate setae; endopod biarticulate, article 1 2.0 times length of article 2, with 6–8 microserrate setae medially, article 2 with 5–6 microserrate setae medially, microserrate seta terminally; exopod 1.3 times length of endopod, with 6 plumose and 6–7 simple setae laterally, 3 simple setae terminally.

S ubadult male paratype 5.2 mm. Body (Fig. 19 C). Carapace subequal to pereon, with stronger serrations in same pattern as in female; pseudorostrum extending 0.2 times carapace length anterior of frontal lobe. Pleon 0.5 times total body length.

Antennule (Fig. 21 A) article 1 equal to article 2 length, with simple setae; article 2 with simple setae; article 3 with simple setae. Main flagellum of 3 articles, with simple setae and 2 aesthetascs; accessory flagellum of 1 article, minute, much less than half main flagellum article 1 length, with simple setae.

Antenna (Fig. 21 B) not yet developed, peduncle with few plumose setae.

Maxilliped 3 (Fig. 21 C) 100:9:17:26:21:17; basis with plumose setae, distolateral corner with 2 stout and 1 slender plumose setae; ischium unarmed.

Pereopod 1 broken, not examined.

Pereopod 2 (Fig. 21 D) 100:11:26:38:17:30; basis with simple and plumose setae; ischium with plumose seta; merus, carpus with simple and plumose setae; propodus with simple seta; dactylus with simple setae.

Pereopod 3 (Fig. 21 E) 100:6:9:13:9:4; basis, ischium, merus with plumose setae; carpus with plumose and annulate setae; propodus with annulate seta; dactylus with simple setae.

Pereopod 4 (Fig. 21 F) 100:11:17:20:14:6; basis with plumose setae; ischium unarmed; merus with simple seta; carpus with simple and annulate setae; propodus with annulate seta; dactylus with simple seta.

Pereopod 5 (Fig. 21 G) 100:21:21:37:21:5; basis with simple setae; ischium with plumose seta; merus with simple seta; carpus with plumose and annulate setae; propodus with annulate seta; dactylus with simple seta.

Uropods (Fig. 21 H) peduncles 1.1 times pleonite 6 length, with 3–4 long and 4–5 short microserrate setae; endopod biarticulate, article 1 1.8 times article 2 length, with 4–5 microserrate setae medially, article 2 with 3–4 microserrate setae medially, 3 simple setae terminally; exopod 1.2 times length of endopod, with 4 simple, 6–7 plumose setae marginally and 3 annulate setae terminally.

Distribution. Off Enderby Land, Antarctica, 386– 400 m.

Remarks. This species is easily identifiable by the combination of a pair of large setae terminally on pereonite 6 and a lack of lateral ridges on the carapace. The only Antarctic species of Leucon (Leucon) with similar terminal setae is L. adelae Petrescu, 1991, which has a distinct lateral ridge on the carapace ending in a tooth, while in L. echinolophotos the carapace does not have a lateral ridge.