Antennuloniscus latoperculus, Brökeland, Wiebke, 2006

Brökeland, Wiebke, 2006, Three species of the isopod crustacean genus Antennuloniscus Menzies, 1962 (Asellota: Haploniscidae) from the Southern Ocean, Zootaxa 1115, pp. 1-29 : 22-28

Antennuloniscus latoperculus n. sp. ( Figs 1 C, 14–17)

Material

Holotype: Ψ, 1.6 mm; station 134­3, 65°19.20–19.05’S 48°03.77–02.92’W, 4069 m; ZMH K­ 40727.

Paratypes: same locality as holotype: 1 female, 1.7 mm, ZMH K­ 40728. Station 131­3, 65°19.83–19.99’S 51°31.61–31.23’W, 3053 m: 4 ΨΨ 1.3–1.8 mm; 1 ovigerous Ψ, 1.4 mm; ZMH K­ 40729.

Diagnosis

Body almost oblong, length 2.6 width, all pereonites with similar width. Head width 1.6 length, frontal margin slightly concave with medial rostral process. Broad, tapering, rostral process bent ventrally, with rounded apex. Pleotelson in females anterior margin width 1.7 posterior margin¸ posterolateral processes slender, acute, not reaching terminal margin. Antennula with 3 flagellar articles in females. Antenna peduncular article 3 with relatively large dorsal tooth, longitudinal groove distinct, flagellum almost as long as articles 5 and 6, with 8 articles. Carpus of pereopods 1–3 with long simple setae ventrally, shorter on pereopods 4–7. Pleopod 2 of the female oval, wider than long.

Description of paratype female

Body ( Fig. 14 ): Margins of pereonites smooth; suture between pereonite 7 and pleotelson not distinct ventrally. Pleotelson 0.3 times as long as body, tapering slightly distally, lateral margins slightly convex, weakly serrated, with 3 setae each; terminal margin convex; posterolateral processes slender, acute, not reaching terminal margin; dorsal surface with 2 indistinct short longitudinal keels, ventral surface with cuticular suture line surrounding the branchial chamber. Cuticle of body, pleopods 1 and 2, maxillipedal epipod and peduncular articles of antenna with numerous small round depressions.

Antennula ( Fig. 15 ) length 0.2 body length, article 1 broadest, length 1.5 width, article 2 slightly shorter, width 0.4 article 1 width, both articles with several broom setae; article 3 length 0.4 article 2 length, with simple seta; flagellum with 3 articles; article 1 shortest, with 2 broom setae; article 3 length 1.6 article 2 length, article 3 more than twice as long as article 1, with 2 apical aesthetascs, 3 simple setae and 1 short broom seta.

Antenna ( Fig. 15 ) length 0.4 body length, article 1 minute, concealed by article 2, article 2 about as long as wide, article 3 length 1.8 width, 1.4 article 2 length, large dorsal tooth acute, article 4 length 0.5 article 3 length, fused articles 5 and 6 (not including apical tooth) length 1.3 article 3 length, with numerous simple setae, at least 1 broom seta and long apical tooth; flagellum slightly shorter than fused articles 5 and 6, with 8 articles of decreasing width, each with several simple setae.

Mandible ( Fig. 15 ) incisor with 5 blunt teeth, left mandible lacinia mobilis with 5 teeth, right mandible with serrated spine, lacinia mobilis absent, spine row comprising 2 serrated and 3 simple spines; molar tooth row with 8 teeth and 4 setulated setae proximally, cuticular ledge tapering off forming a single blunt tooth, right mandible with row of 6 indistinct accessory teeth proximally of cuticular ledge; palp article 2 with 1 long and 1 short serrated spine­like setae proximally of insertion of article 3, article 3 with 6 serrated spine­like setae of increasing length, distal seta about 10 times as long as proximal seta.

Maxillula ( Fig. 16 ) outer lobe with 10 simple and 3 serrated spine­like setae and several simple setae on lateral and medial margin; inner lobe apically with 2 short spinelike setae and several simple setae.

Maxilla ( Fig. 16 ) outer lobe with 2 long and 1 short simple spine­like setae apically and rows of simple setae on lateral margin; medial lobe with 2 long simple spine­like setae and 1 shorter serrated spine­like seta apically and 3 spine­like setae on medial margin; inner lobe with 2 apical serrated spine­like setae, 3 stout apical simple setae and numerous simple setae on surface and margins.

Maxilliped ( Fig. 16 ) endite apical margin with 2 small fan setae and 1 short spine­like setae, ventral surface with numerous simple setae, separated apical medial margin dorsally with 1 small and 1 large serrated spine­like seta and row of simple setae, medial margin with 3 retinaculae; epipod slightly longer than endite.

Pereopods ( Fig. 17 ): Basis of pereopods 1–3 and 7 with 1, of pereopods 4–6 with 2 simple setae ventrally; dorsally with 1 simple seta, pereopods 2–4 with 1, pereopods 5 and 6 with 2 broom setae. Ischium with 1 short simple seta on pereopods 1–4 and 1–2 long simple setae ventrally on pereopods 5–7. Merus with 4 apical setae. Carpus with ventral comb­like scale rows slightly reduced on pereopods 5–7; carpus of pereopod 1 with 3 long simple setae ventrally, of pereopods 2–4 with 2 simple setae of decreasing length, carpus of pereopods 5–7 with 2 stout and 1 simple seta ventrally; pereopod 7 with dorsal stout flagellate seta; apical comb on carpus of pereopod 1 small and setose, apical combs on pereopods 2–7 comprised of 1 small and 1 large spinose comb, largest on pereopods 4–6. Propodus with ventral row of comb­like scales and 3 simple setae ventrally (some broken off in illustrated specimen). Dactylus with 3 lateral setae on pereopods 1–4 and 1–2 lateral setae on pereopods 5–7; accessory tooth acute.

Pleopods ( Figs 14 , 16 ): Operculum oval, width 1.3 length, margins with several simple setae. Pleopod 3 endopod length 1.3 width, with rounded distal and lateral margin; exopod almost triangular, length 1.2 width, 0.4 endopod length, width 0.5 endopod width, lateral margin rounded, with 3 simple setae and fringe of fine bristles. Pleopod 4 endopod length 1.7 width; exopod length 1.5 width, 0.4 endopod length, width 0.4 endopod width, lateral margin rounded with fringe of long bristles. Pleopod 5 almost as wide as long.

Uropods ( Fig. 14 ) short, stout, not reaching terminal margin.

Remarks

This species is unique in possessing an operculum which is wider than long and, corresponding to this, pleopods 3–5 tend to be rather short and broad. A. latoperculus also has an unusually large tooth on article 3 of the antennula compared to that of the other species of the genus, although in other genera, like Chauliodoniscus , this tooth might be much larger. Only three species within Antennuloniscus possess a distinct rostrum: A. armatus , A. dilatatus , and A. diversus . While it is acute in A. armatus and A. diversus , only A. dilatatus has a rostrum similar to that of the new species. All three species can easily be distinguished from A. latoperculus by the shape of the pleotelson, which is rounded, with distinctly produced but small posterolateral projections in the new species.

Figures

FIGURE 1. Fronteroventral view of head: A, Antennuloniscus ornatus Menzies, 1962, ɗ, K­ 40723, 2.1 mm; B, Antennuloniscus armatus Menzies, 1962, ɗ, K­ 40725, 2.2 mm; C, Antennuloniscus latoperculus n. sp., Ψ, holotype, K­ 40727, 1.6 mm.

FIGURE 14. Antennuloniscus latoperculus n. sp., paratype ΨΨ, 1.8 mm: A, dorsal view; B, anterior part of body, dorsal view; C, prolonged clypeus with labrum, ventral view; D, lateral view; E, posterior part of body, dorsal view; F, posterior part of body, ventral view; paratype Ψ, 1.7 mm: G, pleopod 3; H, pleopod 5; I pleopod 4.

FIGURE 15. Antennuloniscus latoperculus n. sp., paratype Ψ, K­ 40729, 1.8 mm: A, antenna; B, antenna, article 3, dorsal tooth, lateral view; C, antennula; D, left mandible; E, right mandible.

FIGURE 16. Antennuloniscus latoperculus n. sp., paratype Ψ, K­ 40729, 1.8 mm: A, maxillula; B, maxilla; C, right maxilliped, ventral view; D, detail of left maxilliped, dorsal view; E, pleopod 2.

FIGURE 17. Antennuloniscus latoperculus n. sp., paratype Ψ, K­ 40729, 1.8 mm: A, pereopod 1; B, pereopod 2; C, pereopod 3; D, pereopod 4; E, pereopod 5; F, pereopod 6; G, pereopod 7.