Heterochondria similis (Yu & Wu, 1932)

Ju-Shey, 2000, Chondracanthid copepods parasitic on flatfishes of Kerala, India, Journal of Natural History 34 (5), pp. 709-735 : 726-728

Heterochondria similis (YuÈ and Wu, 1932)

(®gure 11)

Material examined. Eleven adult mm (eight with attached l) from gill ®laments of Crossorhombus azureus (Alcock) : four collected on 11 March 1994, four on 20 July 1994 and three on 29 April 1994.

Female. Body (®gure 11A) elongated, with pinball-shaped trunk and measuring 4.98±6.89 mm long. Head longer than wide, 1.20Ö 1.09 mm (not including ināted antennule), with lateral protrusion in front and large, swollen, oral region in rear. Neck region (®rst pediger) not marked oOE from trunk. Trunk region posterior to second pediger enlarged laterally (1.87 mm) and becoming wider than head. Both genital double somite and abdomen (®gure 11B) distinctly wider than long. Caudal ramus (®gure 11C) a spiniform, pointed process bearing three setae. Egg sac about as long as body .

Antennule (®gure 11D) ¯eshy, sausage-shaped, and tipped with seven setae. Antenna broken in all specimens examined. Labrum (®gure 11E) with smooth posterior margin. Terminal blade of mandible (®gure 11F) with a row of 45 teeth on convex (inner) side and a row of 15 teeth on concave (outer) side. Paragnath (®gure 11G) a small, spinulose lobe. Maxillule (®gure 11E) tipped with two setae. Second segment of maxilla (®gure 11H) bearing in basal region a small, simple seta and one large seta with hyaline tip, and a row of about 20 teeth on terminal process. Maxilliped (®gure 11I) three-segmented; ®rst segment largest but unarmed; second segment with a large, basal swelling and a spinulose distal lobe; and third segment (®gure 11J) a short, stout claw. Leg 1 (®gure 11K) and leg 2 (®gure 11L) alike and about equal in size; appearing as a large, blunt process covered with ®ne spinules and armed with a long outer seta and a small terminal seta.

Male. Body (®gure 11M) 642 m m long, with swollen cephalosome and cylindrical metasome and urosome. Details of body parts as in H. pillaii . Antennule reduced to a simple seta as in Acanthochondria zebriae . Antenna and mouth parts as in H. pillaii . Leg 1 reduced to a spiniform seta (see ®gure 11M) and leg 2 missing.

Remarks. This is the ®rst record of H. similis since its discovery at Hainan (in the South China Sea) more than half a century ago by YuÈ and Wu (1932). Of the 21 species of ¯at®shes examined in our survey, H. similis was found parasitic only on the bluespotted ¯ounder ( Crossorhombus azureus ) and it is also the only host from its type locality. Therefore, it is very likely that H. similis is host speci®c to C. azureus .

In their original description of the present species, the maxilliped of H. similis was stated and illustrated to be`of two joints’ and the`terminal joint’ was`much smaller and divided at tip into two equal lobes.’ Apparently, YuÈ and Wu (1932) observed the maxilliped in a view as shown here in ®gure 11I and did not examine it in a view shown here in ®gure 11J. Thus, they stated that the terminal claw was`not seen in the ventral lobe.’

The most outstanding characteristic of the present species is in the general appearance of the body. It is the only species of Heterochondria without a long head and cylindrical trunk. As noted above in the description, it has a pinball-shaped body. Another remarkable distinction is in the shape of the antennule. Its terminal, setae-bearing portion is large, not constricted into a small process protruding at the tip of the tremendously enlarged, basal portion.