Ommatoleucon megalopos Gerken, 2016, n. sp.
Creators: name: Gerken, Sarah
Publisher: name: Zenodo
Year: 2016
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Cumacea
Leuconidae
Ommatoleucon
Ommatoleucon megalopos

description: Ommatoleucon megalopos n. sp.
(Fig. 22–26)
Material examined. Holotype— adult male, MV J62353, 18°40’00”S, 146°31’00”E, 9 m, 5 Dec 5 1982, G.C.B. Poore. Paratypes— preparatory female (dissected), MV J68467, 18°40’00”S, 146°31’00”E, 9 m, 5 Dec 1982, G.C.B. Poore; adult male (dissected), MV J62352, 18°37’00”S, 146°29’00”E, 9 m, 5 Dec 1982, G.C.B. Poore.
Diagnosis. Female and subadult male. Carapace without serrations, teeth or setae. Pseudorostrum extending 0.2 times carapace length anterior of frontal lobe, acute, with setae. Antennal notch oblique, anteroventral corner rounded. Eyelobe with multiple visual elements. Uropod endopod biarticulate.
Adult male. Carapace similar to female, except pseudorostrum extending 0.1 times carapace length anterior of frontal lobe. Eyelobe larger, with more and larger visual elements. Antennal flagellum extending to pleonite 6. Maxilliped 3 to pereopod 4 exopods with expanded bases.
Etymology. The name of the new species is from the Greek, megalopos, meaning large-eyed, in reference to the very large optical area with multiple lenses.
Description. Adult male holotype 2.5 mm, adult male paratype 2.3 mm. Body (Figs 22 A–C). Carapace equal to pereon length, with no elaboration, antennal notch oblique, anteroventral corner rounded; eyelobe very large, occupying anterior portion of frontal lobe, not distinct from frontal lobe; pseudorostrum blunt in lateral view of holotype, acute in dorsal view of holotype, acute in lateral view of paratype specimen that was in poorer shape than holotype, holotype with setae. Pleon 0.5 times total body length.
Antennule (Fig. 23 A) article 1 longer than articles 2 and 3 together, with simple and plumose setae; article 2 with simple setae; article 3 shortest, without setae. Main flagellum of 2 articles, with simple setae and 2 stout aesthetascs; accessory flagellum of 1 articles, subequal to entire main flagellum, with simple setae.
Antenna (Figs 23 B–C) peduncle articles 1–3 with 1 pappose seta each, articles 4–5 with rows of short setae on anterior surface; flagellum of more than 30 articles.
Maxillule (Fig. 23 D) with 2 endites; palp with 1 microserrate seta.
Maxilliped 1 (Fig. 23 E) basis with long plumose seta, lobe with 2 stout microserrate and 2 hook setae; carpus with pappose setae medially, without beak like setae.
Maxilliped 3 (Fig. 23 F) 100:10:17:24; broken off at carpus-propodus articulation; basis with pappose setae, distolateral corner with 3 plumose setae; ischium unarmed.
Pereopod 1 (Fig. 24 A) 100:17:21:30:38:17; basis with pappose, plumose and microserrate setae; ischium with plumose seta; merus with plumose setae; carpus with plumose and simple setae; propodus with plumose and simple setae; dactylus with simple setae; exopod basal article 4.0 times width of flagellum.
Pereopod 2 (Fig. 24 B) 100:2:15:18:10:19; basis with plumose and pappose setae; ischium unarmed; merus, carpus with simple and plumose setae; propodus unarmed; dactylus with simple setae; exopod basal article 4.5 times width of flagellum.
Pereopod 3 (Fig. 24 C) 100:7:9:12:11:2; basis with simple, plumose and pappose setae; ischium, merus and carpus with simple setae; propodus with annulate seta; dactylus minute, with 2 simple setae; exopod basal article 5.0 times width of flagellum.
Pereopod 4 (Fig. 24 D) 100:9:11:13:17:4; basis, ischium, merus with plumose setae; carpus with simple and annulate setae; propodus with annulate seta; dactylus small, with simple seta; exopod basal article 4.5 times width of flagellum.
Pereopod 5 (Fig. 24 E) 100:9:23:36:18:5; basis, ischium, merus with plumose setae; carpus with simple and annulate setae; propodus with annulate seta; dactylus small, with simple seta.
Pleopod 1 (Fig. 24 F) basal article with plumose seta; rami with plumo-annulate setae.
Pleopod 2 (Fig. 24 G) basal article unarmed; rami with plumo-annulate setae.
Uropods (Fig. 24 H) peduncles 1.1 times length of pleonite 6, with 7 long microserrate setae; endopod biarticulate, article 1 2.0 times length of article 2, with 9 microserrate setae medially, article 2 with 4 microserrate setae medially, 2 microserrate setae terminally; exopod 0.9 times length of endopod, with 3 short and 3 long microserrate setae marginally, with 3 long microserrate setae terminally.
Preparatory female paratype 2.3 mm. Body (Fig. 22 D). Carapace subequal to pereon, with no elaboration, antennal notch oblique, anteroventral corner rounded; eyelobe large, with visual elements; pseudorostrum acute in lateral view, with few setae. Pleon 0.5 times total body length.
Antennule (Fig. 25 A) article 1 longer than articles 2 and 3 together, with 1 complex pedunculate seta; article 2 with plumose setae; article 3 shortest, with plumose seta. Main flagellum of 3 articles, with simple setae and setae with single setule, no aesthetascs; accessory flagellum of 2 articles, equal to main flagellum length, with simple setae.
Antenna (Fig. 25 B) of 4 articles; articles 1–2 with 1 pappose seta each; article 4 with pedunculate setae terminally.
Mandible (Fig. 25 C) truncate, lacinia mobilis beak like, with 3 cusps on upper portion, no setae medially. Maxilla (Fig. 25 D) with 3 endites; broad endite medial row of setae pappose; narrow endites with long simple setae.
Maxilliped 1s (Fig. 25 E) basis with few pappose setae medially; carpus with simple setae medially, no beak like setae; distal plumose setae on carpus and propodus are short.
Maxilliped 2 (Fig. 25 F) basis quite short, with plumose seta.
Maxilliped 3 (Fig. 25 G) 100:2:21:30:25:14; basis with pappose setae, distolateral corner with 5 plumose setae; ischium unarmed.
Pereopod 1 (Fig. 25 H) 100:9:36:46:54:26; stout; basis with plumose setae; ischium, merus with simple setae; carpus, propodus with simple and plumose setae; dactylus with simple setae.
Pereopod 2 (Fig. 26 A) 100:0:27:27:16:33; basis with plumose setae; ischium absent or not visible; merus, carpus with simple and plumose setae; propodus unarmed; dactylus with simple setae.
Pereopod 3 (Fig. 26 B) 100:12:16:21:16:2; basis with plumose setae; ischium with simple and plumose setae; merus with plumose seta; carpus with simple and annulate setae; propodus with annulate seta; dactylus minute, with 2 simple setae.
Pereopod 4 (Fig. 26 C) 100:10:20:25:20:3; basis with plumose setae; ischium with simple seta; merus with simple and plumose setae; carpus, propodus with simple and annulate setae; dactylus minute, with 3 simple setae.
Pereopod 5 (Fig. 26 D) 100:13:29:33:25:4; basis, ischium, merus with simple setae; carpus with annulate seta; propodus with simple and annulate setae; dactylus minute, with 2 simple setae.
Uropods (Fig. 26 E) peduncles 1.5 times length of pleonite 6, with 3 or 5 short and 1 long setae with single setule; endopod biarticulate, article 1 1.7 times length of article 2, with 6 microserrate setae with long setule medially, article 2 with 4 microserrate setae with long setule medially, long plumose seta terminally; exopod subequal to length of endopod, with 3 simple, 2 microserrate, 5 plumose setae marginally, plumose seta terminally.
Distribution. Orpheus Island, Fantome Island, Queensland, 1.5– 9 m.
Remarks. There are only two species known in the genus Ommatoleucon, and they can be easily differentiated by the uropod endopod, which is biarticulate in O. megalopos and uniarticulate in O. ocularis. Ommatoleucon ocularis is known from South Australia (Hale 1945) and Tasmania (Mühlenhardt-Siegel 2003), and O. megalopos is only known from Queensland.
description: Published as part of Gerken, Sarah, 2016, Leuconidae (Crustacea: Cumacea) from the collections of the Museum Victoria, Australia, pp. 251-292 in Zootaxa 4067 (3) on pages 285-291, DOI: 10.11646/zootaxa.4067.3.1, http://zenodo.org/record/263497