Aega deshaysiana (Milne Edwards, 1840)

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 : 207-208

REVIEW OF AEGA DESHAYSIANA , A WORLD-WIDE SPECIES COMPLEX 207

Male

Not known.

Size

Present material 39–53 mm.

Variation

Robust setae: only 3 specimens, so ranges only are given. There are 15–17 (7 + 8, 8 + 9) on the pleotelson. Uropod exopod medial margin (n = 6) with 5 or 7, lateral margin 12–14; uropod endopod medial margin with 5, 6 once, lateral margin with 2 + 3, 2 + 4, 6 + 6, 1 + 5.

P1–3 counts for the RS on the inferior margin of the merus: P1 with 5, 4 once; P2 with 8, 7 once; and P3 had 8, 9 once.

Remarks

The three specimens, despite the difference in their size (39–53 mm) and locations (off the Great Barrier Reef and eastern Solomon Islands) present a uniform and distinctive appearance. The eyes are huge, effectively comprising the entire head in dorsal view, the coxae are bluntly rounded, the frontal lamina has a concave ventral surface, the propodal palm of pereopods 1–3 has a wide blade, the setation of the merus of pereopods 1–3 has a characteristic somewhat radiating loosely double row of RS, the wide and paddlelike uropodal exopod falls short of the endopod apex and is notably wider than most other species (2.2 times as long as greatest width, with most species ranging from 2.5 to 4.1¥ LW) except A. hamiota sp. nov .

There are several species with large eyes, but only A. musorstom sp. nov. has wide paddle-like uropods and a wide propodal blade on the anterior pereopods. A. musorstom , known only from New Caledonia, is readily distinguished by the ventrally flat, ovate frontal lamina, the merus of pereopods 2 and 3 having a single row of 12–14 robust setae, long slender setae at the superior distal angles of the merus, the uropod exopod extending posterior to the endopod and the pleotelson posterior margin lacking robust setae. Aega hamiota sp. nov. has the widest uropodal exopod of all species (1.9¥ LW) and may immediately be distinguished by the lack of a propodal blade on pereopods 1–3, long acute robust setae on the superior margins of the ischium, merus and carpus of pereopods 4–7 and the pleotelson lacking robust setae.

Hale (1940) described the specimen from Ontong Java as having been ‘recently seen’, strongly suggesting that this is not the same specimen he previously mentioned ( Hale, 1925) as coming from ‘South Sea Islands’. The identity (and locality) of that earlier record remains unknown in the absence of the specimen.

Pleopods 3-5 are not illustrated owing to the fragility and age of the nontype specimens. They show few definable species-specific characters and are of little utility in determining species identity or relationships.

Prey

Not known.

Distribution

From the Coral Sea in the general vicinity of Marion Reef, and from Ontong Java, Solomon Islands; at recorded depths of 650–752 m.

Etymology

The epithet is trulla (Latin: a spoon or skimmer), alluding to the spoon-like blade on pereopods 1–3.