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

Ho, Ju-Shey, Kim, Il-Hoi & Kumar, A. Biju, 2000, Chondracanthid copepods parasitic on flatfishes of Kerala, India, Journal of Natural History 34 (5), pp. 709-735 : 723-726

Heterochondria petila sp. nov.

( figures 9-10 )

Material examined. One hundred and thirty-six adult ♀♀ (each with attached ♂) found on gill fi laments of their hosts: 124 from Pseudorhombus arsius (four collected on 11 March 1994, five on 20 July 1994, 12 on 12 October 1994, 23 on 26 December 1994, 90 on 29 April 1995), nine from P. javanicus (five 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 ( figure 9A ) elongated and cylindrical, measuring 2.85-3.73 mm. Head ( figure 9B ) longer than wide, 610✕ 360 μ m (not including inflated antennule), with round, lateral protrusion in front and rear; in lateral view posterior (oral) region thicker than anterior (antennal) region ( figure 9C ). Neck region (first pediger) distinct. Trunk slightly wider in posterior region. Genital double somite ( figure 9D ) wider than long, carrying egg sacs on its ventral surface ( figure 9E ). Abdomen ( figures 9D, E ) globose. Caudal ramus ( figures 9D, E ) a spiniform, pointed process bearing three setae and a small, medial lobe. Egg sac ( figure 9A ) about as long as trunk.

Antennule ( figure 9F ) fl eshy, with greatly inflated basal portion; armature being 1-1-1-2-8. Antenna ( figure 9G ) two-segmented; proximal segment small, with a round, distal protrusion; terminal segment a slender, uncinate hook bearing fi ne annuli in distal portion. Labrum ( figure 9H ) with denticles on posterior margin. Mandible ( figure 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 ( figure 10B ) a small lobe with spinules on distal surface. Maxillule ( figure 10C ) a spinulose lobe tipped with two small setae. Maxilla ( figure 10D ) two-segmented; first 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 ( figure 7K ) three-segmented; first segment largest but unarmed, second segment expanded distally and bearing two groups of spines with terminal claw bending between them. Leg 1 ( figure 10F ) a large, fl 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 five short setae on distal portion, of which the middle three are on a small knob. Leg 2 ( figure 10G ) small, less then one-half of leg 1, armed with a regular long, outer seta and two small, distal setae.

Male. Body ( figure 10H ) 288 μ m long, with swollen cephalosome and cylindrical metasome and urosome. Genital somite with usual ventrolateral ridges but indistinguishably fused with abdomen ( figure 10I ). Caudal ramus as in female but armed with only a small, basal knob on ventral surface. Antennule absent. Antenna ( figure 10J ) two-segmented; terminal segment a short, stout claw. Labrum ( figure 10K ) with smooth posterior margin. Mandible ( figure 10L ) with fewer teeth on terminal blade, 18 on convex side and three on concave side. Maxillule ( figure 10M ) tipped with a knob and two setae. Maxilla ( figure 10N ) with only three teeth on terminal process. Maxilliped ( figure 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 figure 10H ) and leg 2 missing.

Etymology. The speci fi 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 five species occurring in Asia are parasitic only on flatfishes, whereas the other two occurring elsewhere are not. Heterochondria atypica Ho, 1972 from California is found on wrasses ( Labridae ) and H. crassicornis (KrØyer, 1835) from the Gulf of Mexico and Caribbean Sea, on wrasses and damsel fishes ( Pomacentridae ) ( Ho, 1972). Furthermore, while those five species from flatfishes have a long head and trunk, those on other fishes differ in having a square head and short trunk.

Heterochondria longicephalus (Yü 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 figure 9C ); (3) more teeth on the mandible and maxilla; and (4) no antennule in the male.

Figures

FIG. 9. Heterochondria petila sp. nov. Female: (A) habitus of adult, dorsal; (B) head and neck region, dorsal; (C) same, lateral; (D) genito-abdomen, dorsal; (E) same, ventral; (F) antennule; (G) antenna; (H) labrum. Scale bars: 0.5 mm in (A); 0.2 mm in (B, C); 0.1 mm in (D, E, G); 0.05mm in (F, H).

FIG. 10. Heterochondria petila sp. nov. Female: (A) mandible; (B) paragnath; (C) maxillule; (D) maxilla; (E) maxilliped; (F) leg 1; (G) leg 2. Male: (H) habitus of adult, lateral; (I) genito-abdomen, ventral; (J) antenna; (K) labrum; (L) mandible; (M) maxillule; (N) maxilla; (O) maxilliped. Scale bars: 0.02mm in (A-E, I, K, O); 0.1 mm in (F-H); 0.01mm in (J, L-N).

FIG. 7. Heterochondria pillai Ho. Female: (A) habitus of adult, dorsal; (B) head, dorsal; (C) genito-abdomen, ventral; (D) antennule; (E) terminal part of antennule; (F) antenna; (G) labrum; (H) mandible; (I) maxillule; (J) maxilla; (K) maxilliped. Scale bars: 0.5 mm in (A); 0.2 mm in (B); 0.1 mm in (C, F); 0.05mm in (D, G, K); 0.02mm in (E, H-J).