Heterochondria petila, Ho, Kim I.H. & Kumar, 2000

Ju-Shey, 2000, Chondracanthid copepods parasitic on flatfishes of Kerala, India, Journal of Natural History 34 (5), pp. 709-735 : 723-726

Heterochondria petila sp. nov.

(®gures 9±10)

Material examined. One hundred and thirty-six adult mm (each with attached l) found on gill ®laments of their hosts: 124 from Pseudorhombus arsius (four collected on 11 March 1994, ®ve on 20 July 1994, 12 on 12 October 1994, 23 on 26 December 1994, 90 on 29 April 1995), nine from P. javanicus (®ve collected on 12 October 1995 and four on 25 December 1995) and three from P. triocellatus collected on 12 October 1994. Holotype ( USNM 285486) and 30 paratypes ( USNM 285486) have been deposited in the US National Museum of Natural History, Smithsonian Institution, Washington, DC and the remaining paratypes and other specimens in the author’ s (IHK) collection.

Female. Body (®gure 9A) elongated and cylindrical, measuring 2.85±3.73 mm. Head (®gure 9B) longer than wide, 610Ö 360 m m (not including ināted antennule), with round, lateral protrusion in front and rear; in lateral view posterior (oral) region thicker than anterior (antennal) region (®gure 9C). Neck region (®rst pediger) distinct. Trunk slightly wider in posterior region. Genital double somite (®gure 9D) wider than long, carrying egg sacs on its ventral surface (®gure 9E). Abdomen (®gures 9D, E) globose. Caudal ramus (®gures 9D, E) a spiniform, pointed process bearing three setae and a small, medial lobe. Egg sac (®gure 9A) about as long as trunk.

Antennule (®gure 9F) ¯eshy, with greatly ināted basal portion; armature being 1-1-1-2-8. Antenna (®gure 9G) two-segmented; proximal segment small, with a round, distal protrusion; terminal segment a slender, uncinate hook bearing ®ne annuli in distal portion. Labrum (®gure 9H) with denticles on posterior margin. Mandible (®gure 10A) two-segmented; terminal blade with a row of about 80 teeth on convex (inner) side and two rows of about 40 teeth on concave (outer) side. Paragnath (®gure 10B) a small lobe with spinules on distal surface. Maxillule (®gure 10C) a spinulose lobe tipped with two small setae. Maxilla (®gure 10D) twosegmented; ®rst segment larger but unarmed, second segment bearing in basal region one small, simple seta and a large seta with hyaline tip, and a row of more than 30 teeth on terminal process. Maxilliped (®gure 7K) three-segmented; ®rst segment largest but unarmed, second segment expanded distally and bearing two groups of spines with terminal claw bending between them. Leg 1 (®gure 10F) a large, ¯eshy process bearing a small medial, basal protrusion; outer surface with a regular, long seta and inner surface with two small setae near basal protrusion and ®ve short setae on distal portion, of which the middle three are on a small knob. Leg 2 (®gure 10G) small, less then one-half of leg 1, armed with a regular long, outer seta and two small, distal setae.

Male. Body (®gure 10H) 288 m m long, with swollen cephalosome and cylindrical metasome and urosome. Genital somite with usual ventrolateral ridges but indistinguishably fused with abdomen (®gure 10I). Caudal ramus as in female but armed with only a small, basal knob on ventral surface. Antennule absent. Antenna (®gure 10J) two-segmented; terminal segment a short, stout claw. Labrum (®gure 10K) with smooth posterior margin. Mandible (®gure 10L) with fewer teeth on terminal blade, 18 on convex side and three on concave side. Maxillule (®gure 10M) tipped with a knob and two setae. Maxilla (®gure 10N) with only three teeth on terminal process. Maxilliped (®gure 10O) generally as female except terminal teeth on second segment occurring in one patch and distal claw (third segment) with a subterminal hooklet. Leg 1 represented by two minute setae (see ®gure 10H) and leg 2 missing.

Etymology. The speci®c name petila is Latin (= thin, slender), it refers to the reduction of leg 2 relative to leg 1.

Remarks. Currently, seven species of Heterochondria are known, including the present new species. It is interesting to note that the ®ve species occurring in Asia are parasitic only on ¯at®shes, whereas the other two occurring elsewhere are not. Heterochondria atypica Ho, 1972 from California is found on wrasses ( Labridae ) and H. crassicornis (Krùyer, 1835) from the Gulf of Mexico and Caribbean Sea, on wrasses and damsel®shes ( Pomacentridae ) ( Ho, 1972). Furthermore, while those ®ve species from ¯at®shes have a long head and trunk, those on other ®shes diOEer in having a square head and short trunk.

Heterochondria longicephalus (YuÈ and Wu, 1932) and H. longa Tripathi, 1959 were not adequately treated in their original description and have not been recorded again since their discovery. Thus, no comparison can be made with them. Both of them were taken from Pseudorhombus arsius , H. longicephalus from Amoi, China, and H. longa from Madras, India.

Heterochondria petila can be distinguished from H. pillaii and H. similis by having: (1) a median ratio (length/width) for trunk (6.98 vs. 11 in pillaii and 3.58 in similis ); (2) two pairs of unequal legs with leg 2 distinctly smaller than leg 1 (see ®gure 9C); (3) more teeth on the mandible and maxilla; and (4) no antennule in the male.