Aega warna, 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 : 213-219

AEGA WARNA SP. NOV. ( FIGS 53–56 , 64 )

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

Material examined

Holotype: ♀ (non-ovig. 49 mm), Western Bass Strait , 35 km WNW of West Point, 40∞47.4¢S, 144∞17.¢E, 2.ii.1991, 99 m, coarse sand, coll. R. Gomon et al. ( NMV J1335 ).

Paratypes: ♀? (56 mm), Lakes Entrance, Vic. , 33 m, ix.1948, coll W. French ( NMV J8887 ) (apex of pleotelson rubbed away, otherwise intact) . ♀ (non-ovig. 50 mm), off Albert Park, Port Phillip Bay, Vic. , 3.ix.1964 (uropods missing and some legs broken) ( NMV J8886 ) . ♀ (non-ovig. 36 mm [one uropod malformed]), Tasmania, off coast, 1912, no other data ( Hale, 1940) ( AM E5353 ) . ♀ (non-ovig. 59 mm), off Marsden Point, Kangaroo Is., South Australia ( AM E4865 ) ( Hale, 1940).

Non-type: ♀ (or imm ♂, 25 mm), west of north-west Tasmania, 41∞02.50¢S, 143∞53.10¢E, 27.i. 1985, 518 m, coll. R. Plant on RV Soela ( NMV J27711 ). Manca (21 mm), off Freycinet, Tasmania, 41∞57.50¢S, 148∞37.90¢E, 27.vii. 1986, 400 m, on coarse shell, coll. M.F. Gomon et al. ( NMV J18389 ) .

Description

Body 2.7 times as long as greatest width, dorsal surfaces polished in appearance (finely punctate), widest at pereonite 5, lateral margins weakly ovate. Rostral point projecting anteriorly, not ventrally folded. Eyes large, medially united, anterior clear field 11% length of head, posterior clear field 40% 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 right-angled (with minute posteroventral point); 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 1.0 times as long as anterior width, dorsal surface without longitudinal carina; lateral margins weakly convex, smooth, posterior margin with elongate medial point, with 12–14 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 2.6¥ LW; flagellum with 15 articles, extending to posterior margin of eye. Antenna peduncle article 2 inferior surface with distinct longitudinal suture; article 4 1.8¥ 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, 2.2¥ LW, inferior margin with 1 plumose seta, anterodistal angle with cluster of 3 short simple setae; flagellum with 19 articles, extending to posterior of pereonite 1.

Frontal lamina flat, as wide as long, lateral margins converging posteriorly (weakly converging), anterior margin rounded, without small median point, posterior margin not abutting clypeus.

Mandible molar process absent; palp article 2 with 8 distolateral setae, palp article 3 with ~30 setae. Maxillule with 8 terminal RS. Maxilla medial lobe with 3 RS; lateral lobe with 4 RS. Maxilliped endite with 1 apical seta; palp article 2 with 4 RS (curved); article 3 with 7 recurved RS; article 4 with 5 hooked RS (3 large and 2 small; distolateral margin with 2 straight long RS); article 5 articulating with article 4, with 6 RS (3 slender, straight and 3 stout, curved).

Pereopod 1 basis 2 times as long as greatest width; ischium 0.5¥ L basis, inferior margin with 0 RS, superior distal margin with 3 RS; merus inferior margin with 4 RS, set as 2 groups (2 and 2), superior distal angle with 2 RS; carpus 0.6¥ L merus, inferior margin with 0 RS; propodus 1.5 times as long as proximal width, inferior margin with 0 RS, propodal palm with simple, without blade or process, dactylus smoothly curved, 1.6¥ L propodus. P2 ischium inferior margin with 2 RS, superior distal margin with 2 RS; merus inferior margin with 7 RS (4 and 3), set as 2 groups, superior distal margin with 2 acute RS; carpus similar in size to that of P1, inferodistal angle with 0 RS, propodus without large club-shaped distal RS. P3 similar to P2; propodus without large club-shaped distal RS. P6 similar to P7. P7 basis 2.2 times as long as greatest width, inferior margin with 7 RS (set as 1, 1, 4 and 1); ischium 0.6¥ L basis, inferior margin with 7 RS (set as 1, 1, 4 and 1), superior distal angle with 7 RS, inferior distal angle with 5 RS; merus 0.7¥ L ischium, 1.9¥ LW, inferior margin with 4 RS (set as 2 and 2), superior distal angle with 5 RS, inferior distal angle with 7 RS; carpus 0.9¥ L ischium, 3¥ LW, inferior margin with 2 RS (set as single cluster), superior distal angle with 3 RS, inferior distal angle with 6 RS; propodus 0.8¥ L ischium, 5¥ LW, inferior margin with 2 RS (set as single cluster), superior distal angle with 3 slender setae (simple and palmate), inferior distal angle with 3 RS.

Pleopod 1 exopod 1.9¥ LW, distally narrowly rounded with strongly oblique medial margin, lateral margin straight, medial margin strongly convex, with PMS from base; endopod 2¥ LW, distally subtruncate, lateral margin strongly concave, with PMS from on distal margin only, 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 2 RS (and 1 slender seta), 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 broadly rounded (endopod, exopod narrowly truncate). Endopod apically not bifid, lateral margin proximally convex, distally straight, with prominent excision positioned about two-thirds along ramus, proximal lateral margin with 9 RS, distal lateral margin with 5 RS, medial margin strongly convex, with 6 RS. Exopod extending beyond end of endopod (slightly), 2.9 times as long as greatest width, apically not bifid; lateral margin straight, with 9 RS; medial margin distally concave (proximally weakly sinuate), with 5 RS.

Male

Not known.

Size

Females 36–59 mm (mean = 50.0 mm); no ovigerous females present in the material examined; manca 21 mm.

Variation

Robust setae: all specimens had some degree of damage to the uropod and pleotelson apices, therefore only the ranges for RS are given. Pleotelson with 12–14 (6 + 6 and 7 + 7). Uropod exopod medial margin with 5, once with 6, lateral margin 9–12; uropod endopod medial margin varied from 5 to 7, with 6 most frequent (6 of 8), lateral margin RS variable with the proximal RS at 5–9, distal RS 4–7 with 8 proximal most frequent (4 of 8) and 5 distal most frequent (5 of 8).

Pereopod RS are highly consistent with the merus of P1, usually asymmetric with 1 + 2 and 2 + 2, P2 merus with 4 + 3 (100%) and P3 merus with 4 + 3 (70%) or 5 + 3 (30%).

Remarks

This large isopod can be immediately distinguished from other similar species by the ‘heavily spined’ uropodal rami with the uropodal endopod lateral margin with a total of 11–16 large robust setae, ovate frontal lamina with a thick posterior stem, and by the characteristic pattern of setation of the anterior pereopods. Additionally, the robust setae on the uropod endopod are noticeably stout. The maxilliped and maxillule are furnished with larger robust setae than many other similar species, presumably a reflection of differences in the targeted prey.

Only pleopods 1 and 2 of the holotype have been examined in detail as these were either damaged or brittle in all specimens. Pleopods 3–5 were examined in situ, and appear similar to those of other similar species.

Two small specimens are excluded from the type series though they generally agree well with the pattern and range of robust setae of the anterior pereopods and the uropods shown by the adults, as well as having the characteristic frontal lamina shape. There are minor differences in the number of robust setae on the uropods and the distribution pattern and number of robust setae on the pereopods. The propodi of pereopods 1–3 of the manca ( NMV J18389 ) are more slen- der than those figured for the adult, and it is also from markedly deeper water than the other specimens, so the identification of this specimen as A. warna is regarded as tentative .

Prey

No records.

Distribution

Tasmania and Bass Strait, westwards to Victoria and South Australia. Most specimens lack precise locality or capture data; at depths of 33 and 99 m, one manca from 400 m and one immature specimen from 518 m.

Etymology

Warna is an Aboriginal word for the sea; noun in apposition.

Figures

Figure 53. Aega warna sp. nov. All figs holotype, except H (AM E5353). A, dorsal view. B, lateral view. C, head, dorsal view. D, frons and pereopod 1. E, antennule. F, antenna. G, antenna peduncle, articles 1–3. H, pleotelson posterior margin, dorsal view.

Figure 54. Aega warna sp. nov. Holotype: A, mandible. B, mandible palp article 3. C, maxillule apex. D, maxillule. E, maxilliped. F, maxilliped palp articles 2–5. G, maxilla. H, maxilliped palp article 5.

Figure 55. Aega warna sp. nov. Holotype: A–E, pereopods 1–3, 6 and 7, respectively. F, pereopod 2, ischium mesial face. G, pereopod 2 propodus and dactylus, perpendicular view.

Figure 56. Aega warna sp. nov. A–D holotype, E and F, AM E4865. A, pleopod 1. B, pleopod 2. 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. (-).