Pleopodias nielbrucei, Hadfield, Kerry A. & Smit, Nico J., 2017

Hadfield, Kerry A. & Smit, Nico J., 2017, Revision of the fish parasitic genus Pleopodias Richardson, 1910 (Isopoda, Cymothoidae), with the description of a new species and key to the genus, ZooKeys 667, pp. 21-37 : 26

Pleopodias nielbrucei sp. n.

Material examined.

Holotype. Female (30mm TL; 9mm W), RV Africana Cruise 060 (34°46.6'S 18°02.5'E), Station A7033-060-14-03M, South Africa, 14 March 1988, 702m depth (SAMC A088881). Paratype. Male (20mm TL; 5 mm W), same info as holotype (SAMC A43478).

Description.

Female holotype. Length 30 mm, width 9 mm.

Body narrow, 3.3 times as long as greatest width, dorsal surfaces smooth and polished in appearance, widest at pereonite 5, most narrow at pereonite 1, lateral margins subparallel. Cephalon 0.7 times longer than wide, visible from dorsal view, subtriangular. Frontal margin thickened, ventrally folded and truncate. Eyes oval with distinct margins, one eye almost 0.5 times width of cephalon; 0.6 times length of cephalon. Pereonite 1 smooth, anterior border slightly indented, anterolateral angle narrowly rounded, extend to one third of the eye. Posterior margins of pereonites smooth and slightly curved laterally. Coxae 2-3 wide, with posteroventral angles rounded; 4-7 small and narrow, not extending past pereonite margin. Pereonites 1-5 increasing in length and width; 6-7 decreasing in length and width. Pleonites posterior margin smooth, mostly concave. Pleonite 1 widest, visible in dorsal view. Pleonite 2 not overlapped by pereonite 7; posterolateral angles of pleonite 2 narrowly rounded. Pleonites 3-5 similar in form to pleonite 2; pleonite 5 not overlapped by lateral margins of pleonite 4, posterior margin produced medially. Pleotelson 1.2 times as long as anterior width, dorsal surface slightly depressed, lateral margins straight, posterior margin subtruncate.

Antennula thinner and shorter than antenna, bases widely separated, consisting of 8 articles; peduncle articles 1 and 2 distinct and articulated; extending to anterior of pereonite 1. Antenna consisting of 11 articles, extending to middle of pereonite 2. Pereopod 1 basis 1.4 times as long as greatest width; ischium 0.7 times as long as basis; merus with simple setae, proximal margin without bulbous protrusion; carpus with rounded proximal margin; propodus 1.5 times as long as wide; dactylus moderately slender, 1.7 times as long as propodus, 3.3 times as long as basal width. Pereopod 2 propodus 1.4 times as long as wide; merus with simple setae; dactylus 1.7 times as long as propodus. Pereopod 6 basis twice as long as greatest width, ischium 0.6 times as long as basis, propodus 1.7 times as long as wide, dactylus 1.8 times as long as propodus. Pereopod 7 longer than other pereopods, basis 2.3 times as long as greatest width; ischium 0.8 times as long as basis, without protrusions; merus proximal margin without bulbous protrusion, 1.2 times as long as wide, 0.6 times as long as ischium; carpus with numerous acute robust setae, 1.4 times as long as wide, 0.5 times as long as ischium, without bulbous protrusion; propodus with numerous acute robust setae, 2.8 times as long as wide, as long as ischium; dactylus slender, as long as propodus, 3.5 times as long as basal width. Uropod longer than the pleotelson, peduncle 0.4 times longer than rami, peduncle lateral margin without setae. Endopod apically slightly pointed, 5 times as long as greatest width, terminating without setae. Exopod extending beyond posterior of endopod, apically narrowly rounded, terminating without setae.

Male paratype. Length 20 mm, width 5 mm.

Male similar to female but smaller. Body rectangular, body 3.5 times as long as wide. Antennula bases separated, consisting of 8 articles, extending to posterior margin of cephalon. Antenna consisting of 12 articles, extending to middle of pereonite 2. Eyes slightly separated, one eye almost 0.5 times width of cephalon; 0.7 times length of cephalon.

Etymology.

Named in honour of Dr Niel Bruce, in recognition of his significant contribution to the taxonomy of isopods, specifically that of fish parasitic cymothoids.

Distribution.

Off the coast of Cape Town, South Africa.

Hosts.

Not known.

Remarks.

Pleopodias nielbrucei sp. n. can be identified by the narrow body, large eyes covering majority of the cephalon (almost in contact), antennula bases wide apart, antenna extending to middle of pereonite 2, subtruncate pleotelson, pereopod 7 with numerous acute robust setae on the propodus as well as the carpus, and the uropodal exopod longer than the endopod.

This is the first named Pleopodias species from the southern hemisphere (not including the unknown Pleopodias sp. mentioned below). It differs from the other three known species in having larger eyes and a more elongate body, as well as a shorter and more quadrate pleotelson and antennula bases which are further apart than the other species. Pleopodias nielbrucei sp. n. also has a less graduated pleon (the pleonites do not decrease in width from pleonite 1 to 5 as prominently as P. diaphus and P. elongatus ).