Protochondracanthus trilobatus, (Pillai, 1964)

Ju-Shey, 2000, Chondracanthid copepods parasitic on flatfishes of Kerala, India, Journal of Natural History 34 (5), pp. 709-735 : 732-734

Protochondracanthu s trilobatus ( Pillai, 1964)

(®gures 15±16)

Material examined. Two adult mm (each with attached l) from gill ®laments of Psettodes erumi : one collected on 29 July 1994 and another on 12 October 1994.

Female. Body (®gure 15A) elongated, 2.86 mm long. Head globose, but wider than long. First pediger transformed into a short neck, bearing a pair of small, tripartite processes on ventral surface where leg 1 attaches. Remaining pedigers fused into a long cylindrical trunk, bearing a pair of long, lateral processes in front (®gure 15A) and another pair of short, posterior processes at end (®gures 15A, B). Genital double somite (®gure 15B) wider than long, 104Ö 142 m m, bearing a long seta in egg sac attachment area. Abdomen (®gure 15B) wider than long, 54Ö 75 m m. Caudal ramus (®gure 15B) a spiniform process armed with three setae and a small tubercle. Egg sac not seen.

Antennule (®gure 15C) with cylindrical basal portion and a short, oOEset, distal process; armature being 11 on basal portion and ten on distal process. Antenna (®gure 15D) two-segmented; ®rst segment small and unarmed, second segment a sharp, recurved hook with a minute, medial tubercle in basal region. Labrum (®gure 15E) with a small tubercle on lateral margin. Mandible (®gure 15F) twosegmented; terminal blade with a row of 12 teeth on convex (inner) side. Maxillule (®gure 15G) tipped with a lobe and two short setae. Maxillule (®gure 15H) twosegmented; basal segment large but unarmed, distal segment bearing one small, simple seta, one large seta with hyaline tip in basal region and a row of about 25 teeth on terminal process. Maxilliped (®gure 15I) three-segmented; ®rst segment largest but unarmed, second segment with spinules in terminal and subterminal regions, and third segment drawn out into a pointed process with a subterminal setule (®gure 15J). Leg 1 (®gure 15K) located at base of tripartite, ventral process in neck region and consisting of a protopod carrying a long, outer seta, an exopod armed with six setae, and an endopod tipped with two setae. Long, lateral process in anterior region of trunk equipped with a subterminal seta and four or ®ve terminal setae (®gure 15L).

Male. Body (®gure 16A) globose, with posterior portion strongly bent forward. Genital somite and abdomen indistinguishably fused (®gure 16B). Caudal ramus (®gure 16B) a short spinulose process. Antennule (®gure 16C) ®liform, armature being 1-1-1-7. Antenna (®gure 16D) two-segmented; terminal hook short and stubby. Mandible (®gure 16E) with a row of 13 teeth on convex margin of terminal blade. Maxillule (®gure 16F) tipped with a blunt knob and 2 setae. Maxilla (®gure 16G) as in female except for fewer teeth (about ten) on terminal process. Maxilliped (®gure 16H) constructed as in female only stubbier. No traces of legs.

Remarks. Although P. trilobatus and P. alatus were often found occurring together on ¯at®shes, their appearances are quite diOEerent. The former, though smaller, can not be mistaken for the juvenile of the latter.

In the female, T. trilobatus lacks the cephalic and oral process and has shorter neck and trunk processes. These diOEerences are discernible without dissection of the specimen. There are also diOEerences in the ®ne anatomy, visible only after dissection. The present species is distinguishable from P. alatus in lacking a vermiform process on the antennule (see ®gure 2E), having fewer teeth on the mandible (12 vs. 36) and maxilla (45 vs. 60), and bearing two setae (instead of none) on the endopod of leg 1. The male of P. trilobatus also has fewer teeth on the mandible (13 vs. 25) and maxilla (10 vs. 22) than those of P. alatus . Additionally, it lacks an outer knob on the antenna (see ®gure 14E) and leg 1 is entirely missing.

The tripartite body process in the neck region of Protochondracanthus represents, perhaps, the modi®ed coxal region of leg 1. This is more apparent in P. trilobatus then in P. alatus . Due to the tremendous expansion and elongation of the middle one of these three lobes in P. alatus (see ®gure 13G), it looks more like a body process then a coxal expansion. The true identity of these lobes can only be corroborated through studies on their maturation transformation.