New species of Acanthochondria Oakley, 1930 and Chondracanthus Delaroche, 1811 (Copepoda: Cyclopoida: Chondracanthidae) parasitizing marine fishes from Indian waters

This paper describes two new species of parasitic copepods of the family Chondracanthidae H. Milne Edwards, 1840. Acanthochondria krishnai sp. n. is described from Dollfus’ stargrazer, Uranoscopus guttatus Cuvier, collected from Muttom and Colachel, Tamil Nadu, and Chondracanthus kabatai sp. n. from Silvery john dory, Zenopsis conchifer Lowe, collected from Neendakara, Quilon, Kerala, both along the southwest coast of India. Both the species are described and illustrated based on the fresh female and male specimens collected from India. Both the species are the first Indian representative of the respective genera. The checklist of Indian species of the family Chondracanthidae is also presented.


MaTerials and MeThods
Fresh specimens of chondracanthids were collected from three fish landing centers on the southwest coast of India, namely Muttom and Colachel (Kanyakumari district, Tamil Nadu coast) (8°07'48.00"N 77°19'12.00"E) and Neendakara (08°30.0'N 76°53.30'E), Quilon district, Kerala coast. The chondracanthids were collected from the host fish, fixed in 5% formaldehyde, preserved in 75% ethanol (after Aneesh et al., 2018) and subjected to identification. Methods for dissection, mounting, and drawings of appendages were according to the techniques described in Aneesh et al. (2018). Drawings were digital inked using Adobe Illustrator and WACOM CTL-472/K0-c drawing pad. The specimens were microphotographed using multifocusing dissection microscope Leica-M205A and image capturing software (Leica Application Suit). Morphological details of the parasite were also examined using a scanning electron microscope (Zeiss EVO 18 SEM). Fish taxonomy and host nomenclature were performed according to FishBase (Froese and Pauly, 2020). The types and voucher specimens are deposited in the Western Ghat Field Research Centre of Zoological Survey of India, Kozhikode (ZSI/WGRC).

Two new species of chondracanthids from India
Nauplius, 28: e2020014

Two new species of chondracanthids from India
Nauplius, 28: e2020014 Description. : Body long and slender (16-18 mm) (excluding egg strings; from anterior margin of head to distal end of posterior processes), divisible into short head, much elongated neck, stout trunk with prominent constrictions on posterior half, as long as neck, bearing a pair of posterior processes, small genito-abdomen and abdomen with the prominent process which extends to the posterior tip of caudal rami. Cephalon, small, 1.2 times longer than wide, attached to neck; posteroventral region swollen, with mouthparts. Neck greatly elongated (8-9 mm) and gradually jointed into trunk. Trunk as long as neck, postero lateral margin with pair of long processes (4-5.5 mm) directed laterally, posterolaterally, or posteriorly. Genito-abdomen (0.45-0.5 mm, long; total length including the median projection, the abdomen), funnel-shaped, longer than wide, basally wider (0.28-0.30 mm wide), with median projection (the abdomen) (0.25-0.28 mm long and 0.06 mm wide) gradually narrowing posteriorly, with curved apex. Genital complex with pair of setules in midventral region bearing egg strings.
Aneesh et al. 8 Two new species of chondracanthids from India Nauplius, 28: e2020014 Egg strings cylindrical, not coiled and longer than trunk; eggs multiseriate. Number of eggs per string ranged from 170 to 240, dependent on length of the string. Genital complex carrying pair of conical rami with numerous spinules on terminal portion.
Antennule cylindrical and fleshy, without division, basally swollen, and distally slender with few terminal setae. Antenna, usual form with heavily sclerotized and unarmed basal segment and strongly curved, pointed terminal claw. Mandible with many teeth (55-60) on convex side and 40-44 teeth on concave side. Maxillule with spinulose inner-terminal surface; distal margin with 2 unequal setae. Two-segmented maxilla; first segment greatly broad and unarmed; terminal segment with more or less equal robust seta in basal region, and the outer margin claw-like, armed with row of 28-32 denticles. Maxilliped 3-segmented; first segment stout, largest, unarmed; second segment with two patches of denticles on medial surface and protruded medio-distal corner, partially overlapping base of the distal segment; terminal segment ending in curved claw-like structure with small, sub-terminal hooklet on inner surface. Legs biramous, protopod with one seta, leg 1 (0.25 mm); both rami bearing spinules/pectinate scales on terminal portion. Leg 2 (0.4 mm) much longer than (1.8 times) leg 1.
Antennule elongated, with armature formula 2, 1, 2, 2, and 8-9. Antenna, solid, robust and strongly curved, sharp claw; with seta on dorso-lateral surface. Mandible with 16-18 teeth on convex side and 12-14 teeth on concave side. Maxillule with 2 setae, more or less similar to female. Maxilla without teeth on terminal process. Maxilliped article 2 with few denticles. Legs bilobate, leg 1 larger than leg 2; with few long lateral setae, larger in leg 1; endopods reduced to lobes.  Description. : Body 4.8-8.0 mm length (without egg strings, from anterior margin of head to distal end of longest posterior processes on trunk), unsegmented, divisible into head, short neck, stout trunk and genito-abdomen. Cephalon having cephalosome, as long as wide, with two pairs of elongated and fusiform, pedunculate ventro-lateral processes, the second process about 1.8-2 times longer than process 1. Cephalon dorsally bearing medial longitudinal sclerotized bar. Neck, short and narrow Two new species of chondracanthids from India Nauplius, 28: e2020014 without processes. Trunk much broader, armed with elongated, narrow, fusiform processes; three pairs of anterior, three pairs of posterior and single posteriomedian. Anterior processes including (1) pair of dorsal (1.0-1.2 mm long), horn-like, on either side close to the lateral margin, directed forward; (2) pair of long (2.1-2.4 mm long), laterally directed, from the lateral margin; and (3) pair of much longer, bifurcate (outer one (3.1-3.2 mm long), inner one much longer (4.2-4.4 mm long)), from the ventral side near to either side of second pair of legs. Posterior processes including (1) pair of ventro-lateral, from the corner (3.5-3.7 mm long); (2) pair at posterior corner, much longer, trifurcate (outer one (3.3-3.4 mm long), middle (3.5-3.6 mm long), and inner (3.9-4.2 mm long)); (3) single, median processes (3.8-4.1 mm long) (much reduced in two specimens ( Fig. 9 c)) on dorsal side, apparently intersect the lateral processes; (4) a paired, long process on ventral surface (3.5-3.6 mm long), close to either side of median line, just above genito-abdomen. Genito-abdomen (0.25-0.3 mm, long; 0.2 mm wide) globular, longer than wide. Genital complex with pair of setules in midventral region bearing egg strings. Abdomen 2 times wider than long (0.16 mm wide, 0.08 mm long). Caudal ramus conical, directed ventrally and armed with two ventral setae, one dorsal seta and apical conical spinulose papilla.
Egg strings cylindrical, yellow colored, irregularly coiled and extremely longer than trunk; eggs multiseriate. Number of eggs per string ranged from 370 to 440, depending on length of the string.

Two new species of chondracanthids from India
Nauplius, 28: e2020014

Two new species of chondracanthids from India
Nauplius, 28: e2020014
Color: White after fixation, with yellow egg sac.

Host: Zenopsis conchifer Lowe.
Distribution: Known only from the type locality at Neendakara, Southwest coast, India.

Site of attachment:
Attached to the floor of the buccal cavity, over the gill.
Etymology: This species is named in honor of recently deceased Prof. Zbigniew Kabata, one of the pioneer researchers on parasitic copepods of fish and world-renowned fish parasitologist.

Two new species of chondracanthids from India
Nauplius, 28: e2020014

disCussion
The family Chondracanthidae H. Milne Edwards, 1840, can be recognized by the following combination of characters: body segmentation largely concealed, cephalon, with or without processes, not fused with any of the trunk segments; neck formed from first two pedigerous segments, trunk with or without processes; genital segment and abdomen fused; antennule fleshy and the antenna is strongly prehensile; two pairs of highly modified, fleshy and bi-or trilobate legs; dwarf male attached to the genito-abdomen of female (Ho, 1970;Kabata, 1979;Pillai, 1985;Ho and Kim, 1995;Cantatore and Timi, 2010). Ho (1970) revised the family by excluding 12 old genera and also provided the key to the remaining 30 valid genera. Later, another 12 new genera have been erected by various authors and a revised key for 42 genera has been provided by Ho (1994), two among them later became synonyms. After Ho (1994), another eight new genera (viz., Argentinochondria Etchegoin, Timi and Sardella, 2003, Bactrochondria Ho, Kim and Kumar, 2000, Bereacanthus Huys, 2009, Bobkabata Hogans and Benz, 1990, Brasilochondria Thatcher and Pereira Júnior, 2004, Parapercicola Ho, Liu and Lin, 2011, Pseudolernentoma Luque and Alves, 2003, Ttetaloia Uyeno and Nagasawa, 2012 were erected and three older genera (viz., Immanthe Leigh-Sharpe, 1934, Lernaeosolea Wilson 1944, Pharodes Wilson C.B., 1935 were restored. Now the family Chondracanthidae includes 51 valid genera, among them only four genera were previously known from India. With the current description of two new species, the genera Acanthochondria Oakley, 1930 andChondracanthus Delaroche, 1811 are also represented in fishes of the Indian coastline. The list of current species of Chondracanthidae, its host fishes and distribution records are presented in Tab. 1.

Two new species of chondracanthids from India
Nauplius, 28: e2020014

Two new species of chondracanthids from India
Nauplius, 28: e2020014 Acanthochondria krishnai sp. n.: most species of Acanthochondria possess a short neck (Kabata, 1979;Ho and Kim, 1995;Cantatore and Timi, 2010). By having a very long neck (at least 12-14 times longer than wide) the female of A. krishnai sp. n. can be distinguished from most of its congeners. Only three species described earlier, such as A. helicoleni Cantatore and Timi, 2010, A. uranoscopi Ho and Kim, 1995and A. diastema Kabata, 1965 exhibit these characteristics. The new species is well distinguished from most of its congeners by: a much elongated body, presence of a pair of long distal process on trunk, funnel shaped genito-abdomen complex. The new species differs from A. helicoleni and A. diastema in having (1) the neck indistinguishably fused into the trunk; (2) presence of a pair of long, slender postero-lateral processes; (3) presence of much longer legs. Acanthochondria krishnai sp. n. is very close to A. uranoscopi by the presence of a pair of long, slender postero-lateral processes and the elongated neck and trunk. But the new species is very distinct from A. uranoscopi in: the shape of genitoabdomen, it is longer than wide and funnel shaped;  Tang et al. (2007), and its amendment by Gomez et al. (2018), the divergence within the genus is mainly based on certain key characters of the female, which includes: presence or absence and the number of cephalic processes; presence or absence of dorsal/ lateral/ventral outgrowths or processes on the trunk; relative length of processes; legs 1 and 2, unilobate/ bilobate/trilobate condition of legs 1 and 2 (Kabata, 1979;Boxshall and Halsey, 2004;Tang et al., 2007;Gomez et al., 2018). The new species C. kabatai can be separated from most of its congeners by having: the cephalon with two pairs of lateral processes; legs 1 and 2 bilobate; the trunk region with a pair of dorsal, horn-like processes, on either side close to the lateral margin; bearing more than two pairs of lateral processes; the abdomen not extended posteriorly. Braicovich et al. (2013) suggested that the close resemblance of C. distortus (collected from Zeus faber Linnaeus and Zenopsis nebulosa (Temminck and Schlegel) and C. hoi (from Z. conchifer) may be due to the phylogenetic relatedness of host fishes, i.e., zeids. Corroborating this observation, the present new species is also collected from a zeid fish, Z. conchifer. Chondracanthus kabatai n. sp. is closely related to C. distortus and C. hoi by having the two pairs of cephalic processes. Nevertheless, the new species C. kabatai can be differentiated from both C. distortus and C. hoi in having a pair of dorsal, long, horn-like processes (0.5 times as long as lateral processes), on either side close to the lateral margin on trunk (vs dorsal processes absent in C. hoi and short and bluntly rounded in C. distortus); the cephalic process, much elongated and the posterior process is almost twice as long as anterior one (vs processes are blunt, pedunculate in C. hoi and shorter and process 2 is sub-equal in length to process 1 in C. distortus); anterio-lateral processes twice as long as dorsal processes (vs absent in C. hoi and smaller in C. distortus); abdominal processes are invariably much elongated (both smaller as well as larger specimens [4.8 mm-8 mm]) (vs stout, robust and shorter in both C. distortus and C. hoi); egg strings, narrow, cylindrical, irregularly coiled and extremely longer than trunk (vs broad, comparatively shorter in C. hoi and uncoiled, broad and short in C. distortus).
aCKnowledgeMenTs PTA thankfully acknowledges the Dr. D.S. Kothari Post-Doctoral Fellowship (No.F.4-2/2006 (BSR)/ BL/16-17/0401; dated: 28 August 2017) awarded by University Grants Commission. We extend our sincere thanks to Dr. Uyeno Daisuke, for his valuable suggestions/discussions on the species identity during the later stage of the manuscript revision. Further, we gratefully acknowledge the effort made by the two anonymous reviewers for their critical reviewing of the manuscript and making valuable suggestions for the improvement of the manuscript. Redescription of Lernaeenicus stromatei Gnanamuthu, 1953