Heterochondria pillaii Ho, 1970

Ju-Shey, 2000, Chondracanthid copepods parasitic on flatfishes of Kerala, India, Journal of Natural History 34 (5), pp. 709-735 : 720-723

Heterochondria pillaii Ho, 1970

(®gures 7±8)

Material examined. Thirty four adult mm (each with attached l) found on gill ®laments of their hosts: 25 from Pseudorhombus triocellatus (Bloch) (12 collected on 29 July 1994, two on 12 October 1994 and 11 on 29 April 1995), four from P. elevatus Obilby collected on 12 October 1994, two from P. arsius (Hamilton) collected on 29 April 1995, one from P. javanicus (Bleeker) collected on 12 October 1994, one from Cynoglossus dubius (Regan) collected on 14 February 1994 and one from C. lida collected on 26 December 1994.

Female. Body (®gure 7A) elongated, cylindrical and measuring 2.52±5.71 mm long. Head (®gure 7B) longer than wide, 910Ö 482 m m (not including ināted antennule), with two lateral protrusions in front and one similar but smaller protrusion in rear. Neck region (®rst pediger) not marked oOE from trunk. Genital double somite (®gure 7C) wider than long and bearing a lateral seta in egg sac attachment area. Abdomen (®gure 7C) distinctly longer than wide. Caudal ramus (®gure 7C) a spiniform, pointed process bearing three setae and a medial knob. Egg sac lengths variable, ranging from less than one-half of to more than twice body length.

Antennule (®gure 7D) ¯eshy, ināted, with a subterminal, posteroventra l protrusion; armature being 1-1-8 (®gure 7E, from proximal to distal). Antenna (®gure 7F) two-segmented; proximal segment small, bearing a sclerotized process at base of terminal segment, which is a slender claw with corrugated surface in the distal third. Labrum (®gure 7G) with denticles on posterior margin. Mandible (®gure 7H) twosegmented; terminal blade with a row of 22 to 26 teeth on convex (inner) side and two rows of about 25 teeth on concave (outer) side. Maxillule (®gure 7I) a small ¯eshy lobe tipped with two short setae and a patch of spinules. Maxilla (®gure 7J) two-segmented; ®rst segment large but unarmed, second segment bearing in basal region one small, simple seta and one large seta with hyaline tip, and a row of about 30 teeth on terminal process. Maxilliped (®gure 7K) three-segmented; ®rst segment largest but unarmed, second segment expanded distally and bearing two rows of spines with terminal claw bending between them. Leg 1 (®gure 8A) larger than leg 2 (®gure 8B); both legs constructed on same plan with a long outer seta, a patch of spinules on distal surface, a small terminal seta, and a small nipple-like bud on medial surface.

Male. Body (®gure 8C) 292 m m long, with swollen cephalosome and cylindrical metasome and urosome. Genital somite with usual ventrolateral ridges and indistinguishably fused with abdomen (®gure 8D). Caudal ramus as in female but naked. Antennule (®gure 8E) reduced to a small rod tipped with few setae. Antenna (®gure 8F) two-segmented; terminal segment a short, stout claw. Labrum (®gure 8G) roughly as in female. Mandible (®gure 8H) with fewer teeth on terminal blade, 15 on convex side and six on concave side. Paragnath (®gure 8I) a small, spinulose lobe. Maxillule (®gure 8J) as in female but lacking spinules. Maxilla (®gure 8K) with seven teeth on terminal process. Maxilliped (®gure 8L) generally as female except terminal teeth on second segment occurring in two patches rather than in two rows. Leg 1 (®gure 8C) reduced to a simple spiniform seta as in Acanthochondria zebriae (see ®gure 2J). Leg 2 absent.

Remarks. The most characteristic feature of H. pillaii is the possession of a nipple-like bud on the medial surface of leg 1 in the female (see ®gure 8A) and a small, rod-like antennule in the male (®gure 8E). Both of them are rather unusual for the species of Heterochondria . If the nipple-like bud on the female leg 1 was considered to represent the modi®ed, reduced endopod, then H. pillaii could have been placed in Bactrochondria . However, the structure of leg 2 in the female of H. pillaii will de®nitely preclude such consideration.

H. pillaii is the most common chondracanthid copepod parasitic on the six species of ¯at®shes in Kerala ( table 1). Thus, it is not surprising to see it being reported on Pseudorhombus arsius (Hamilton) from the Persian Gulf by Ho and Sey (1996) .