Aega umpara, 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 : 208-213

AEGA UMPARA SP. NOV. ( FIGS 49–52 , 64 )

Aega deshaysiana – Hale, 1940: 295 (part). Material examined

Holotype: ♀ (non-ovig. 22 mm), Shag Rock, Moreton Bay , south-eastern Queensland (c. 27∞36¢S, 153∞27¢E), vi.1988, on electric ray Hypnos monopterygium , 8 m, shot number Crust. 1204, coll. N. Coleman ( QM W2672 ).

Paratypes: ♂ (24 mm), off Byron Bay , NSW, c. 28∞37¢S, 153∞39¢E, from cloaca of a tiger shark ( Hale, 1940) ( AM E4858 ) . ♀ (non-ovig. 45 mm), 29∞05¢S, 167∞57¢E, off Norfolk Island, Tasman Sea , hapuka (probably hapuku, Polyprion oxygenios ) fish behind pectoral fin ( AM P11262) . ♀ 24 mm (dissected), east of North Solitary Island , NSW, 29∞54–57¢S, 153∞37–36¢E, 11.x. 1978, 175 m, coll. FRV Kapala ( AM P37511) .

Non-type: ♂ (31 mm), Elizabeth Reef, c. 11.xii.1987, from ‘black cod’, coll. L Smith and M. Cordell on ‘ F. Bay ’ ( AM P43986) . ♀ (non-ovig. 22 mm), vicinity of Kermadec Islands , 30.2530∞S, 178.4033∞W, 90 m, Challenger Centenary, 1.v.1974, stn K0837, coll. NIWA ( NIWA 3479 ) .

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 17% length of head, posterior clear field 48% length of head; each eye made up of ~19 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 free, not overlapped by lateral margins of pleonite 4. Pleotelson 1.1 times as long as anterior width, dorsal surface without longitudinal carina; lateral margins weakly convex (very), smooth, posterior margin with elongate medial point, with 8 RS.

Antennule peduncle articles 1 and 2 flattened, article 2 without anterodistal lobe; articles 3 and 4 0.9 times as long as combined lengths of articles 1 and 2, article 3 3.1¥ LW; flagellum with 10 articles, extending to posterior margin of eye. Antenna peduncle article 2 inferior surface without distinct longitudinal suture; article 4 1.9¥ LW, 1.2 times as long as combined lengths of articles 1–3, without deep longitudinal groove, inferior margin with 1 plumose seta, and 0 short simple setae; article 5 not markedly wider or flatter than article 4, 0.9¥ L article 4, 2¥ LW, inferior margin with 2 plumose setae, anterodistal angle with cluster of 1 short simple seta; flagellum with 17 articles, extending to middle of pereonite 2.

Frontal lamina flat, longer than greatest width, rectangular, anterior margin anteriorly truncate, with small median point, posterior margin not abutting clypeus.

Mandible molar process present, minute; palp article 2 with 3 distolateral setae, palp article 3 with 25 setae. Maxillule with 8 terminal RS (falcate). Maxilla medial lobe with 3 RS; lateral lobe with 3 RS. Maxilliped endite with 0 apical setae (may be missing); palp article 2 with 2 RS; article 3 with 7 recurved RS; article 4 with 5 hooked RS (3 large, 2 small, distolateral margin with single straight seta); article 5 partly fused to article 4, with 5 RS (2 weakly recurved, 3 straight).

Pereopod 1 basis 2 times as long as greatest width; ischium 0.5¥ L basis, inferior margin with 0 RS, superior distal margin with 0 RS (3 simple setae); merus inferior margin with 3 RS, set as 2 groups (of 1 and 2), superior distal angle with 1 RS (and 2 simple setae); carpus 0.5¥ L merus, inferior margin with 0 RS; propodus 1.3 times as long as proximal width, inferior margin with 0 RS, propodal palm with simple, without blade or process, dactylus smoothly curved (but strongly recurved), 1.5¥ L propodus. P2 ischium inferior margin with 1 RS, superior distal margin with 1 RS; merus inferior margin with 5 RS (set as 3 and 2), set as 2 groups, superior distal margin with 2 acute RS; carpus similar in size to that of P1, inferodistal angle with 1 RS (minute), propodus without large club-shaped distal RS. P3 similar to P2; propodus without large club-shaped distal RS. P6 similar to P7 (slightly more robust with slightly fewer and more robust RS). P7 basis 3.5 times as long as greatest width, inferior margin with 6–8 palmate setae (all broken off); ischium 0.5¥ L basis, inferior margin with 6 RS (set as 1, 3, 1 and 1), superior distal angle with 5 RS, inferior distal angle with 6 RS; merus 0.7¥ L ischium, 1.8¥ LW, inferior margin with 5 RS (set as 2 and 3), superior distal angle with 6 RS, inferior distal angle with 6 RS; carpus 0.9¥ L ischium, 3.3¥ LW, inferior margin with 2 RS (single cluster), superior distal angle with 4 RS, inferior distal angle with 7 RS; propodus 0.7¥ L ischium, 4.2¥ LW, inferior margin with 2 RS, superior distal angle with 2 slender setae (palmate), inferior distal angle with 2 RS.

Pleopod 1 exopod 1.7¥ LW, distally narrowly rounded, medial margin weakly oblique, lateral margin distally concave (weakly), medial margin strongly convex, with PMS from base; distally subtruncate, lateral margin strongly concave, with PMS from distal one-third, medial margin with PMS from distal half; peduncle 1.9¥ WL, medial margin with 10 coupling hooks. Exopods of pleopods 1–5 each with distolateral margin not deeply serrate; endopods of pleopods 3–5 each with mediodistal point; pleopods 2–5 peduncle distolateral margin without prominent acute RS.

Uropod peduncle ventrolateral margin with 1 RS (and 3 short slender setae), posterior lobe about 0.6¥ 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 (weakly), with prominent excision positioned about two-thirds along ramus, proximal lateral margin with 4 RS, distal lateral margin with 5 RS, medial margin weakly convex, with 5 RS. Exopod not extending to end of endopod, 2.8 times as long as greatest width; lateral margin weakly convex, with 8 RS; medial margin sinuate, proximally concave, with 4 RS.

Male

Similar to female. Penes opening flush with surface of sternite 7; penial openings separated by 3.3% of sternal width. Pleopod 2 appendix masculina with straight margins, 0.8¥ L endopod, distally narrowly rounded.

Size

Males 24 mm, non-ovigerous females 22–45 mm; no ovigerous females present in the material examined.

Variation

Robust setae: Pleotelson with 4 + 4. Uropod (n = 8) exopod medial margin with 4 (all); lateral margin 8–10 with 8 (50%) most frequent; uropod endopod (n = 7) medial margin varies from 4 to 6, with 4 (twice), 5 (3 times), 6 (twice), the lateral margin RS with 3 + 4 (twice), 4 + 4 (3 times) and 3 + 5 (twice). There is no discernible difference between males and females, nor does the number of RS increase with the size of the specimen.

P1 setation of the merus was consistent across its range with 1 + 2 RS (all); P2 merus ranged from 5 (all); P3 merus with 5 (6¥) or 6 (twice).

Remarks

Aega umpara sp. nov. is most readily identified by the relatively narrow eyes, rectangular shape of the frontal lamina, lack of a distal lobe on the propodal palm, elongate distalmost robust setae on the merus of pereopods 1–3, pattern of robust setae on the uropodal rami and the uropodal exopod not distally exceeding the endopod.

Aega umpara is most similar to A. alazon sp. nov. with the counts for robust setae on the pereopods, uropods and pleotelson falling within the range of that species. There are several other characters that show clear differences from A. alazon , these being the shape of the frontal lamina, relative size of the robust setae on pereopod 1 merus and the setation of the uropodal exopod which in A. umpara is without plumose marginal setae on the proximal one-third. An easily observed difference is that in A. umpara the uropodal exopod apex does not extend to the apex of the uropodal endopod, in contrast to A. alazon , which has the exopod exceeding the endopod apex. The frontal lamina in A. umpara has straight lateral margins with a distinctly wide and truncate posterior margin giving a quadrate appearance; in contrast, that of A. alazon is posteriorly narrow with convex lateral margins. The merus of pereopod 1 of both species has a similar number and arrangement of robust setae (1 + 2) but the form of these setae is different in those of A. umpara , having a small proximal seta and the distal pair consisting of one small and one long robust setae; in A. alazon they are all of similar size. The four type specimens have a greater number of robust setae on the uropodal endopod medial margin (4–6) than does A. alazon , where the most frequent is 3 or 4 (67%) robust setae with no specimens having more than 5.

The specimen from Elizabeth Reef is excluded from the type series as the eyes seem to be narrowly separated. I have been unable to determine whether this is an artefact of preservation. Otherwise, the specimen is consistent in appearance with the other specimens, showing the characteristic shape of the frontal lamina and pattern of robust setae on the pereopods. The Kermadec specimen is excluded from the paratypes as it was received after the description was finalized.

Prey

Polyprion oxygenios (Schneider & Forster, 1801) , Polyprionidae ; ‘black cod’ (= Epinephilus, Epinephilidae?); Hypnos monopterygium (Shaw, 1795) , Torpedinidae ; and Galeocerdo cuvier (Péron & Lesueur, 1882) , Carcharhinidae .

Distribution

South-western Pacific: from eastern Australia at Moreton Bay, Queensland south to the Solitary Islands, and eastwards at Elizabeth Reef, Norfolk Island and the Kermadec Islands. Recorded between 8 and 175 m; the Elizabeth Reef specimen was likely taken from angling depth and A. umpara appears to be a genuine shallow-water species.

Etymology

Umpara is an Aboriginal word for stingray, in reference to the prey of the type specimen; noun in apposition.

Figures

Figure 49. Aega umpara sp. nov. A–F, J, holotype, remainder paratype AM P37511. A, dorsal view. B, lateral view. C, head, dorsal view. D, frons. E, pleotelson posterior margin, dorsal view. F, sternite 7 showing penial openings. G, antennule. H, antenna peduncle. I, antenna peduncle, articles 1–3. J, pereopod 1, distal articles.

Figure 50. Aega umpara sp. nov. Paratype AM P37511. A, mandible. B, mandible palp article 3. C, maxillule. D, maxillule apex. E, maxilla. F, maxilla, apex. G, maxilliped. H, maxilliped palp articles 2–5. I, maxilliped palp article 5.

Figure 51. Aega umpara sp. nov. Paratype AM P37511. A–E, pereopods 1, 2, 6 and 7, respectively.

Figure 52. Aega umpara sp. nov. Paratype AM P37511. A, pleopod 1. B, pleopod 2. uropod. C, uropod. D, uropod exopod, ventral view. E, uropod endopod apex. F, uropod exopod apex.

Figure 64. Distributions of: Aega musorstom sp. nov. (•), A. trulla sp. nov. (*), A. umpara sp. nov. (O) and A. warna sp. nov. (-).