Aega kixalles, Bruce, 2004

Bruce, Niel L., 2004, Reassessment of the isopod crustacean Aega deshaysiana (Milne Edwards, 1840) (Cymothoida: Aegidae): a worldwide complex of 21 species, Zoological Journal of the Linnean Society 142 (2), pp. 135-232 : 181-187

AEGA KIXALLES SP. NOV. ( FIGS 29–32 , 63 )

Material examined

Holotype: ♀ (non-ovig. 48 mm), New Caledonia, 18∞52.8¢S, 163∞21.7¢E, 19.ix.1985, Stn 0194, 545 m, coll. MUSORSTOM IV ( MNHN Is.5790).

Paratypes: ♀ (non-ovig. 38, dissected), same data as holotype ( MNHN Is.5791) . ♀ (non-ovig. 44 mm), New Caledonia, Loyalty Islands, 21∞05.25¢S, 167∞32.201¢E, 21.ii.1989, Stn CP 466, 540 m, coll. MUSORSTOM VI ( MNHN Is.5789) .

Description

Body 2.4 times as long as greatest width, dorsal surfaces smooth (finely punctate), widest at pereonite 5, lateral margins weakly ovate. Rostral point projecting anteriorly, not ventrally folded. Eyes large, medially united, anterior clear field 20% length of head, posterior clear field 43% length of head; each eye made up of ~23 transverse rows of ommatidia, each row with ~9 ommatidia; eye colour dark brown. Pereonite 1 and coxae 2–3 each with posteroventral angle rounded; coxae 5–7 with entire oblique carina. Pleon with pleonite 1 visible in dorsal view; pleonite 4 with posterolateral margins extending clearly beyond posterior margin of pleonite 5; pleonite 5 with posterolateral angles overlapped by lateral margins of pleonite 4. Pleotelson 1.1 times as long as anterior width, dorsal surface without longitudinal carina; lateral margins sinuate, smooth, posterior margin with elongate medial point, with 16 RS.

Antennule peduncle articles 1 and 2 flattened, article 2 without anterodistal lobe; articles 3 and 4 0.6 times as long as combined lengths of articles 1 and 2, article 3 3.0¥ LW; flagellum with 10 articles, extending to posterior margin of eye. Antenna peduncle article 2 inferior surface without distinct longitudinal suture; article 4 2.3¥ LW, 1.4 times as long as combined lengths of articles 1–3, without deep longitudinal groove, inferior margin with 1 plumose seta and no short simple setae; article 5 not markedly wider or flatter than article 4, 0.9¥ L article 4, 2.5¥ LW, inferior margin with 2 plumose setae, anterodistal angle with cluster of 4 short simple setae; flagellum with 18 articles, extending to middle of pereonite 2.

Frontal lamina flat, longer than greatest width, oval, anterior margin rounded, without small median point, posterior margin not abutting clypeus.

Mandible molar process absent; palp article 2 with 7 distolateral setae (3 long), palp article 3 with 26 setae. Maxillule with 8 terminal RS (large, falcate). Maxilla medial lobe with 3 RS (2 hooked, 1 straight); lateral lobe with 4 RS (hooked). Maxilliped endite with 2 apical setae (minute); palp article 2 with 3 RS (acute); article 3 with 7 recurved RS (3 large hooked, 2 small hooked and 2 simple); article 4 with 6 hooked RS (3 large and 3 small); article 5 wholly fused to article 4, with 5 RS (2 hooked, 3 straight).

Pereopod 1 basis 2.3 times as long as greatest width; ischium 0.4¥ L basis, inferior margin with 0 RS, superior distal margin with 1 RS (and 1 slender seta); merus inferior margin with 4 RS, set as single row, superior distal angle with 2 RS; carpus 0.5¥ L merus, inferior margin with 0 RS; propodus 1.2 times as long as proximal width, inferior margin with 0 RS, propodal palm with large distal lobe (distally subtruncate, narrower than propodus inferior margin), dactylus smoothly curved, 1.7¥ L propodus. P2 ischium inferior margin with 1 RS, superior distal margin with 2 RS; merus inferior margin with 7 RS, set as single row, superior distal margin with 2 acute RS; carpus longer than that of P1, with inferodistal lobe, inferodistal angle with 1 RS, propodus without large club-shaped distal RS. P3 similar to P2 (but ischium with 2 RS at inferodistal angle, merus inferior margin with 8 RS); propodus without large club-shaped distal RS. P6 similar to P7 (but larger, inferior margins with more and larger RS). P7 basis 3.2 times as long as greatest width, inferior margin with 9 palmate setae; ischium 0.6¥ L basis, inferior margin with 6 RS (set 1, 3 and 2), superior distal angle with 3 RS, inferior distal angle with 5 RS; merus 0.9¥ L ischium, 2.4¥ LW, inferior margin with 6 RS (as 2 loose groups of 3 and 3), superior distal angle with 8 RS, inferior distal angle with 7 RS; carpus as long as ischium, 3.5¥ LW, inferior margin with 5 RS (set as 2 and 3), superior distal angle with 5 RS, inferior distal angle with 6 RS; propodus 0.8¥ L ischium, 5.4¥ LW, inferior margin with 4 RS (set as 2 and 2), superior distal angle with 5 slender setae (4 simple, 1 palmate, plus 1 RS), inferior distal angle with 4 RS.

Pleopod 1 exopod 2.1¥ LW, distally narrowly rounded with strongly oblique medial margin, lateral margin weakly convex, medial margin strongly convex, with PMS from base; distally subtruncate, lateral margin straight, with PMS from distal half, medial margin with PMS from distal one-third; peduncle 1.2¥ WL, medial margin with 11 coupling hooks. Exopods of pleopods 1–5 each with distolateral margin not deeply serrate; endopods of pleopods 3–5 each with mediodistal point (weak, rather more proximal that in others); pleopods 2–5 peduncle distolateral margin without prominent acute RS.

Uropod peduncle ventrolateral margin with 2 RS, posterior lobe about one-half L endopod. Uropod rami not coplanar, exopod at angle of about 135∞ to endopod, rami not extending beyond pleotelson, marginal setae in single tier, apices narrowly rounded. Endopod apically not bifid, lateral margin proximally convex, with prominent excision positioned about two-thirds along ramus, proximal lateral margin with 6 RS, distal lateral margin with 5 RS, medial margin strongly convex, with 6 RS. Exopod extending beyond end of endopod, 3.3 times as long as greatest width, apically not bifid; lateral margin weakly convex, with 10 RS; medial margin sinuate, proximally concave, with 6 RS.

Male

Not known.

Size

Present material 38–44 mm.

Variation

Robust setae: only 3 specimens, so ranges only are given. All specimens have 16 (8 + 8) on the pleotelson. Uropod exopod medial margin (n = 6) with 4 or 5, 6 once, lateral margin 8–11; uropod endopod medial margin with 5–7, with 5 (4 of 6) most frequent, lateral margin with 5 + 4, 6 + 5, 6 + 6, 7 + 5 and 7 + 6.

P1–3: counts for the RS on the inferior margin of the merus: P1 with 4 (all), P2 with 6–8, with 7 (4 of 6) most frequent, P3 with 8–11, with 11 occurring once.

Remarks

The three specimens present a highly consistent appearance, with the relatively narrow and strongly produced propodal blade on pereopods 1–3 being diagnostic. The ovate frontal lamina, stout robust setae on the posterior pereopods, deeply incised uropodal endopod lateral margin, relatively elongate uropodal exopod and pleotelson posterior margin with 16 robust setae all serve to distinguish the species.

Similar species in the region include A. alazon sp. nov. which lacks the propodal blade on the anterior pereopods, has a posteriorly narrowed frontal lamina and fewer robust setae on the lateral margin of the uropodal endopod; A. musorstom sp. nov. and A. rickbruscai sp. nov. differ in having larger eyes, many long acute robust setae on the posterior pereopods, weakly indented uropodal endopod lateral margin, a much wider uropodal exopod and the pleotelson without robust setae; A. musorstom has a far wider propodal blade while A. rickbruscai lacks a propodal blade.

Prey

Not known.

Distribution

Recorded from off New Caledonia; at depths of 540 and 545 m.

Etymology

From the Greek kixalles (highway robber) alluding to the ‘bandit-mask-like’ appearance of the eyes.

Figures

Figure 29. Aega kixalles sp. nov. A–D, H, holotype, remainder female paratype, 38 mm. A, dorsal view. B, lateral view. C, head, dorsal view. D, frons. E, antennule. F, antenna peduncle. G, pleotelson posterior margin.

Figure 30. Aega kixalles sp. nov. Female paratype, 38 mm. A, mandible. B, mandible palp article 3 detail. C, maxillule. D, maxillule apex. E, maxilla apex. F, maxilla. G, maxilliped. H, maxilliped palp articles 2–5. I, maxilliped palp article 5.

Figure 31. Aega kixalles sp. nov. Female paratype, 38 mm. A–E, pereopods 1–3, 6 and 7, respectively. F, pereopod 1, palm detail.

Figure 32. Aega kixalles sp. nov. Female paratype, 38 mm. A–E, pleopods 1–5, respectively. F, uropod. G, uropod exopod, ventral view. H, uropod endopod, apex. I, uropod exopod apex.

Figure 63. Distributions of: Aega banda sp. nov. (*), A. birubi sp. nov. (•), A. hamiota sp. nov. (-), A. kixalles sp. nov. (O) and A. rickbruscai sp. nov. (Ŧ).