Zoosyst. Evol. 100 (1) 2024, 119-128 | DOI 10.3897/zse.100.116611 gee BERLIN Two new species of the congrid eel genus Ariosoma (Anguilliformes, Congridae, Bathymyrinae) from Indian waters Paramasivam Kodeeswaran!*, Ayyathurai Kathirvelpandian', Dipanjan Ray*, Anil Mohapatra’, Thipramalai Thangappan Ajith Kumar‘, Chelladurai Raghunathan*, Uttam Kumar Sarkar? ICAR-National Bureau of Fish Genetic Resources, Lucknow, Uttar Pradesh 226 002, India Faculty of Fisheries Science, Kerala University of Fisheries and Ocean Studies, Kochi 682 506, India Bajkul Milani Mahavidyalaya, Kismat Bajkul, Purba Medinipur, West Bengal 721 655, India Estuarine Biology Regional Centre, Zoological Survey of India, Gopalpur-on-Sea, Ganjam, Odisha 761 002, India Zoological Survey of India, New Alipore, Kolkata 700 053, India oF WN FP https://zoobank. org/FD307F 80-4B3E-41E1-9283-E5C93C17C399 Corresponding author: Thipramalai Thangappan Ajith Kumar (ttajith8 7@gmail.com) Academic editor: Nalani Schnell # Received 30 November 2023 Accepted 10 January 2024 Published 26 January 2024 Abstract Two new species have been described from Indian waters, based on the materials collected from Kochi coast, Arabian Sea, Gulf of Mannar and West Bengal coast along the Bay of Bengal. Ariosoma gracile sp. nov. is described, based on five specimens collected from the landings at Kalamukku Fishing Harbour, Arabian Sea. The new species is characterised by longer tail, 55.3-58.7% TL; dorsal-fin origin above pectoral-fin base; no dark or whitish bands on dorsal surface of head, ventral extremities of lower jaw and mid-portion with minute dark pigmentation patch; anus positioned well before the middle of total length; SO canal with 4 pores; 0 or 3 pores on ST canal; pre-dorsal vertebrae 9; pre-anal vertebrae 49-54; total vertebrae 140-142. Ariosoma gracile sp. nov. is closely related to Ariosoma dolichopterum and Ariosoma emmae by sharing similar morphometrics and pre-anal vertebral counts. However, it differs by having more total pores (132-135 vs. 121-129 in A. dolichopterum, 123-126 in A. emmae); fewer pre-anal pores (43-46 vs. 47-51 in A. dolichopterum, 50-53 in A. emmae);, more pre-dorsal pores (9 vs. 5—9 in A. dolichopterum, 4-6 in A. emmae). Another new species, Ariosoma kannani sp. nov. is described on the basis of two specimens (157-171 mm TL) from Gulf of Mannar and one specimen (201 mm TL) collected from Shankarpur Fish Landing Centre, West Bengal. This species 1s similar to Ariosoma megalops, but readily differs by having smaller eyes, smaller interorbital distance and exhibits 10.8% genetic divergence from A. megalops from the Taiwan waters. Key Words Arabian Sea, Bathymyrinae, Bay of Bengal, new eel, systematics Introduction The congrid eel genus, Ariosoma Swainson, 1838, in- cludes 38 valid species (Fricke et al. 2023). The genus Ariosoma along Indian waters was known only by two species till 2021 (Roy et al. 2021). Then, extensive sam- pling efforts and integrative taxonomic approaches result- ed in the description and documentation of an addition- al six species from the Indian waters (Roy et al. 2021; Kodeeswaran et al. 2021, 2022a, 2022b, 2023; Ray et al. 2022) and also Kodeeswaran et al. (2021) mentioned the existence of a few more undescribed species along the Indian waters. Following sampling along the southern coasts of India, several specimens of an unknown congrid eel were encountered as trawl by-catch, with one uniden- tified specimen also being collected from the northern part of the Bay of Bengal. Subsequent comparison with existing species from Indian waters suggested that the presently collected specimens were undescribed. Here, we describe two new species of Ariosoma from Indian Copyright Kodeeswaran, P. et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. 120 waters, based on the meristic and morphometric details with the support of molecular analyses. Materials and methods Sampling, morphometric and meristic analyses Eel samples were collected from different landing centres along the India coast viz. Kalamukku Fishing Harbour (9°59'N, 76°14'E), off Kerala coast, west coast of India, Arabian Sea and Rameshwaram Fish Landing Centre (9°16'N, 79°18'E), Tamil Nadu, Gulf of Mannar, east coast of India, Bay of Bengal and Shankarpur Fish Land- ing Centre, West Bengal, Bay of Bengal, India. Fresh photographs were taken with a Canon 80D Digital Sin- gle-Lens Reflex camera (EF-S 18—135mm f/3.5-f/5.6 IS USM Kit Lens) and a small portion of muscle and pecto- ral fin-clips were incised and preserved in 99.9% ethanol for phylogenetic analyses. Collected specimens were pre- served in 10% formaldehyde for taxonomical studies and deposited in the National Fish Museum and Repository of the ICAR-—National Bureau of Fish Genetic Resources (NBFGR), Lucknow, India and Estuarine Biology Re- gional Centre (EBRC), Zoological Survey of India, Go- palpur-on-Sea, Odisha, India. Morphometric measuring and meristic counting fol- low Smith and Kanazawa (1977) and Smith (1989) using a Digimatic caliper with accuracy to 0.1 mm. Vertebral counting follow Bohlke (1982) with the help of digital ra- diographs. Head pores abbreviations are: IO, infraorbital; POM, pre-opercular-mandibular; SO, supraorbital; ST, supratemporal. Details of the comparative material are listed in the “Comparative material examined” section. Molecular analyses The DNA isolation, PCR cycle conditions and mtDNA gene amplifications were done, based on the methods followed in Kodeeswaran et al. (2021; 2022a). The ob- tained PCR products were sent out for sequencing with outsources. Newly-generated sequences were edited and aligned manually using clustalW Multiple alignments im- plemented in BioEdit version 5.0.9 (Hall 1999) with other sequences retrieved from the public domain (GenBank). Pair-wise distance, nucleotide diversity, nucleotide com- position and transition transversion bias (R) were es- timated using the Kimura 2 parameter (K2P) model in MEGA X (Kumar et al. 2018). The Maximum Likelihood (ML) phylogenetic tree was reconstructed using I[Q- TREE software v.1.6.12 (Nguyen et al. 2015) with the best-fit model: HK Y+F+I+G4 chosen according to the BIC score: 8550.210 using ModelFinder (Kalyaanamoor- thy et al. 2017) with ultrafast bootstrap (1000 bootstrap replicates) (UFBoot) (Hoang et al. 2018) and the tree di- agram was constructed aided by the Interactive Tree Of Life v.5 (Letunic and Bork 2021). Japonoconger pror- iger (MF956462) and Uroconger lepturus (ON799405) zse.pensoft.net Kodeeswaran, P. et al.: Two new species of congrid eel from India sequences were used as outgroups for reconstructing the phylogenetic tree. Comparative materials examined Ariosoma albimaculatum. NBFGR/CONAALB, ho- lotype, (487 mm TL); paratypes (nine specimens), NBFGR/CONAALB. 1-9 (5: 305-401 mm TL), col- lected from deep-sea trawl by-catch, Colachel Fishing Harbour, off Kanyakumari, Arabian Sea. Ariosoma bengalense. F12898, holotype (304 mm TL), collected from Petua Ghat, West Bengal, India from the depth of 168 m; EBRC/ZSI/F12899, paratype (216 mm TL), data same as holotype. Ariosoma gnanadossi. ZSI F7146/2, holotype (283 mm TL), collected from the depth of 250 m, off Madras, east coast of India, Bay of Bengal. Ariosoma indicum. | NBFGR/CONAIND, _ holo- type (362 mm TL); NBFGR/CONAIND.1-—2 (2: 355-371 mm TL), EBRC/ZSI/F13597 (2: 337-438 mm TL); NBFGR/CONAIND.3-9 (7: 335-433 mm TL) tak- en with holotype, all collected from Kalamukku Fishing Harbour, Kochi, Arabian Sea. EBRC/ZSI/F13604 (7: 223-356 mm TL) non-types, collected from Digha Mo- hana, West Bengal, Bay of Bengal. Ariosoma majus. EBRC/ZSI/F 11528 (2 specimens: 246— 290 mm TL) collected from Deshpran Fishing Har- bour, West Bengal, east coast of India, Bay of Bengal. Ariosoma maurostigma. NBFGR/CONAMAUR, §ho- lotype (233 mm TL); NBFGR/CONAMAUR.1-3, paratypes, (3: 202-295 mm TL), NBFGR/CONAM- AUR.4 (1: 229 mm TL) taken with holotype. NBFGR/ CONAMAUR:5 (15: 181-292 mm TL); EBRC/ZSI/ F12905, (4: 206-273 mm TL) all collected from Kala- mukku Fishing Harbour, Kochi, Arabian Sea. Ariosoma melanospilos. NBFGR/CONAMEL, holotype (302 mm TL), Colachel Fishing Harbour, southwest coast of India, Indian Ocean. ZSI F 14502/2, para- type (296 mm TL) same collection details as holotype. EBRC/ZSI/F 14040, Colachel Fishing Harbour, south- west coast of India, Indian Ocean. Ariosoma sp. NBFGR/CONATHO, (440 mm TL), Thoo- thukudi Fishing Harbour, southeast coast of India, Bay of Bengal. Results Ariosoma gracile Kodeeswaran, Kathirvelpandian, Mohapatra, Kumar & Sarkar, sp. nov. https://zoobank.org/757F292 | -E865-4B92-B363-F7C90DB2E241 Figs la, 2a, 3, 4, Table 1 Proposed common name: Slender Conger eel Type material. Holotype. NBFGR/CONACOM, 241 mm TL, collected from deep-sea trawl by-catch, Kalamukku Fishing Harbour, off Kerala coast, Arabian Sea, 9°59'N, 76°14'E, P. Kodeeswaran, 19 February 2021. Zoosyst. Evol. 100 (1) 2024, 119-128 121 POM - 10 Dorsal fin origin behind the pectoral-fin insertion POM - 10 Figure 1. Image showing the head pores and anterior lateral-line pores. a. Ariosoma gracile sp. nov., NBFGR/CONACOM, holo- type (241 mm TL); b. Ariosoma kannani sp. nov., NBFGR/CONAKAN, holotype, (171 mm TL). Paratypes. NBFGR/CONACOM. 1-2, (2:197-199 mm TL) and EBRC/ZSI/F15709 (2: 206-221 mm TL) taken with holotype. Diagnosis. A medium-sized slender eel species of Ariosoma distinguished from all other species by the following combination of characters: position of anus well-before middle of total length, pre-anal length 43.7% (41.3-44.7%) of TL; tail longer, 55.3-58.7% TL; dorsal-fin above pectoral-fin base; no dark or whitish bands on dorsal surface of head, ventral extremities and mid-portion of lower jaw with minute dark pigmentation patch; short vomerine teeth patch with three or four rows of pointed teeth in anterior portion, intermaxillary teeth patch curved, slightly upturned at anterior end, clearly visible when mouth closed, separated from vomerine and maxillary teeth by a definite gap; SO canal with 4 pores; 0 or 3 pores on ST canal; pre-dorsal vertebrae 9 (9); pre- anal vertebrae 48 (49-54); total vertebrae 141 (140-142). Description (dimensions in mm). Morphometric and meristic data are provided in Table 1. HL 5.9 (5.5-5.7) in TL; pre-anal length 2.3 (2.2); pre-dorsal length 5.7 (5.6—5.8); trunk length 4.9 (4.1—4.6); tail length 1.7 (1.8); and depth at gill opening 18.2 (18.1—23.4). Snout length 5.1 (4.7—5.3) in HL; eye diameter 5.8 (5.4—6.4); interor- bital width 9.9 (8.5—14.9); upper jaw 3.4 (3.1-3.6); gill opening width 5.8 (5.6—9.6); interbranchial width 8.8 (8.0—-11.3); and pectoral fin 2.9 (2.7-3.7). Body slender, cylindrical anterior portion, followed by more laterally compressed caudal portion; tip of caudal fin stiff and blunt or conical; anus positioned well-before mid-point of total length, pre-anal length 43.7% (41.3- 44.7%) of TL; dorsal-fin origin above pectoral-fin base, above ninth lateral-line pores, confluent with caudal and anal fin. Origin of anal fin just after anus. Pectoral fin developed, with narrow base and pointed distally. Gill opening medium, slightly larger or equal to eye diameter, its upper origin reaching nearly upper half of pectoral-fin base; interbranchial width smaller than gill opening and eye diameter. Head fairly large 5.9 (5.5—5.7) in TL, snout very short, anteriorly pointed in dorsal view, its length 1.1 (1.1—1.2) times eye diameter, projecting beyond lower jaw; length of snout relatively shorter than lower jaw; fleshy por- tion of snout projecting anteriorly beyond the end of zse.pensoft.net 122 Kodeeswaran, P. et al.: Two new species of congrid eel from India Figure 2. Dentition of upper jaw. a. Ariosoma gracile sp. nov., NBFGR/CONACOM, holotype (241 mm TL); b. Ariosoma kannani sp. nov., NBFGR/CONAKAN, holotype, (171 mm TL). intermaxillary tooth patch; rictus positioned just before middle length of eye. Fairly large tubular anterior nostril at tip of snout and relatively large elliptical pore of poste- rior nostril in front of mid-eye orbit diameter. Upper and lower Jaw with slightly reduced flange. Tongue short and narrow; anterior portion free from mouth with conical or blunt tip. Lateral-line pores complete; first pore commences moderately at level of supratemporal canal and terminat- ing well before caudal-fin base; 9 (9) pre-dorsal pores; 43 (43-46) pre-anal pores and 132 (132-138) total pores. Head pores moderate, few pores rather small. SO ca- nal with 4 pores; first (ethmoidal) relatively small, on ventral side of snout tip; second pore medium-sized, in front of anterior nostril; third pore enlarged, on dorsal surface of snout just behind anterior nostril; fourth pore circular and enlarged, no pores in interorbital portion. IO canal with 8 (4+4) pores, first pore large, behind anteri- or nostril; second pore below posterior end of posterior nostril; third pore below anterior eye-orbit margin; fourth pore at above or slightly before rictus, below mid-eye; fifth pore behind rictus, at posterior margin of eye and 3 pores at infraorbital canal behind eye. POM pores 10; 7 in mandibular section, 6 before rictus and 1 behind rictus; pre-opercular section with 3 pores in a longitudinal row. Small-sized ST pores 0 or 3, (holotype and one paratype does not possess ST pores, 2 specimens with 3 pores and one specimen with 2 pores) (Fig. 3). Pre-dorsal vertebrae 9 (9); pre-anal vertebrae 48 (49— 54); total vertebrae 141 (140-142). Teeth larger, conical or pointed (no blunt teeth) (Fig. 2a). Curved intermaxillary teeth patch with three or zse.pensoft.net four transverse rows, clearly visible when mouth closed, anterior portion fairly upturned, separated from vomer- ine and maxillary teeth by a definite gap. Maxillary and mandibular teeth continuous in bands; anterior part of maxillary teeth narrow with three rows, middle portion with two rows, innermost and outermost teeth pointed or conical, followed by uniserial pointed teeth posteriorly. Mandibular teeth wider anteriorly and narrower posteri- orly. Vomerine teeth form a short patch, reaching in front of posterior nostril, three or four rows with pointed teeth in anterior portion, followed by four irregular triserial pointed teeth and two conical teeth in a series posteriorly. Colour (in fresh specimens). Body often bicolour, dark brownish to paler, upper half almost darker and pal- er ventrally; very minute dark pigmentations irregularly spread over body. Dorsal and anal fin creamy-white with thin black margin; caudal fin dull white with black upper and lower margins (Fig. 1). Head same as body, dorsal surface of head without any dark or whitish bands, ex- tremities of lower jaw under surface and mid-portion with minute dark pigmentation patch (Fig. 4b, c). Eyes bright with dark pupil, surrounded by thick pale golden-yellow- ish ring. Pectoral fin goldish-yellow (Fig. 4a). Colour in formalin slightly darker than fresh material or almost beige; pectoral fin translucent. Dark pigmentation patch remains on the ventral head. Distribution. Known from five specimens collected from trawl by-catches landings at Kalamukku Fishing Harbour, off Kerala, south-western Indian coast, Arabian Sea, western Indian Ocean. Etymology. From the Latin word, ‘gracilis - gracile’ meaning slender, which denotes the slender-bodied eel. Zoosyst. Evol. 100 (1) 2024, 119-128 123 Figure 3. Ariosoma gracile sp. nov., NBFGR/CONACOM, ho- lotype (241 mm TL) fresh colouration. Scale bar: 40 mm. Comparisons. Ariosoma gracile differs from all the congeners but shares similar morphological characters and overlapping pre-anal vertebrae counts with Ariosoma dolichopterum Karmovskaya, 2015 from the South China Sea, off Vietnam and Taiwan and Ariosoma emmae Smith & Ho, 2018 from Taiwan waters. Ariosoma gracile dif- fers from these congeners by having: 132—135 total pores (vs. 121-129 in A. dolichopterum, 123-126 in A. em- mae); 43-46 pre-anal pores (vs. 47—51 in A. dolichopter- um, 50-53 in A. emmae); 9 pre-dorsal pores (vs. 5—9 in A. dolichopterum, 4—6 in A. emmae); more total vertebrae (140-142 vs. 129-134 in A. dolichopterum, 127-133 in A. emmae), trunk 38.5—-42.6% TL (vs. 26.6—29.8% TL in A. dolichopterum, 28.9-32.7% TL in A. emmae); short vomerine tooth patch (vs. long in A. dolichopterum and A. emmae) (Karmovskaya 2015; Smith et al. 2018). Ariosoma gracile differs from the Indian water conge- ners, such as Ariosoma gnanadossi Talwar & Mukherjee, 1977, Ariosoma melanospilos Kodeeswaran, Jayakumar, Akash, Kumar & Lal, 2021, Ariosoma albimaculatum Kodeeswaran, Dhas, Kumar & Lal, 2022 and Ariosoma sp. nov. Kodeeswaran et al. (in press) in having fewer to- tal vertebrae (140-142 vs. 161-164 in A. albimaculatum: 146 in A. gnanadossi, 144—153 in A. melanospilos, 162- 163 in Ariosoma sp. nov.); fewer total pores (132-135 vs. 145 in A. gnanadossi, 136—144 in A. melanospilos; 148-155 in Ariosoma sp. nov.). The new species shares similar vertebral counts with Ariosoma maurostigma Kodeeswaran, Mohapatra, Dhinakaran, Kumar & Lal, 2022, but readily differs from the latter by the absence of a dark spot on posterior-dorsal margins of eye orbit (vs. present in A. maurostigma); tail longer (55.3—58.7% TL vs. 47.8-54.6% TL); shorter pre-anal length (41.3- 44.7% TL vs. 44.0-48.8% SL); fewer SO pores (4 vs. 6). Further, the new species differs from Ariosoma majus Figure 4. Lateral (a); Dorsal (b); Ventral (c) view of Ariosoma grac- ile sp. nov., NBFGR/CONACOM, 241 mm TL. Scale bar: 10 mm. (Asano, 1958) in having more pre-dorsal pores (9 vs. 6-7 in A. majus), fewer pre-anal pores (43-46 vs. 50-53); fewer total pores (132-135 vs. 139-142); smaller depth at gill opening (4.3-5.5% TL vs. 6.7—7.3% TL); fewer SO pores (4 vs. 6). Further, the new species shares over- lapping vertebral counts with newly-described sympat- ric species Ariosoma indicum Kodeeswaran, Kathirvel- pandian, Acharya, Mohanty, Mohapatra, Kumar & Lal, 2022, but the new species differs from the latter in having shorter pectoral fin (26.8-36.9% HL vs. 37.5-46.7% HL in A. indicum); smaller interorbital width (6.7—11.8% HL vs. 11.8-15.7% HL); fewer SO pores (4 vs. 5); ST pores (0 vs. 3); pectoral fin grey (vs. blackish or bicoloured). The new species differs from the species viz. Ariosoma anago (Temminck & Schlegel, 1846), Ariosoma anale (Poey, 1860), Ariosoma fasciatum (Gunther, 1872), Ari- osoma meeki (Jordan & Snyder, 1900), Ariosoma how- ensis (McCulloch & Waite, 1916), Ariosoma shiroanago (Asano, 1958), Ariosoma coquettei Smith & Kanaza- wa, 1977, Ariosoma kapala (Castle, 1990), Ariosoma ophidiophthalmus Karmovskaya, 1991, Ariosoma mul- tivertebratum Karmovskaya, 2004, Ariosoma sazonovi Karmovskaya, 2004, and Ariosoma sereti Karmovskaya, 2004 and in having fewer total vertebrae (140-142 vs. 143-144 in A. anago; 146-150 in A. anale; 155-158 in A. fasciatum, 144-155 in A. meeki;, 151-161 in.A. howen- sis; 161-162 in A. shiroanago; 152-160 in A. coquettei; 147 in A. kapala,; 150-153 in A. ophidiophthalmus, zse.pensoft.net 124 Table 1. Meristic and morphometrics of Ariosoma gracile from Arabian Sea and Ariosoma kannani from the Gulf of Mannar, Bay Kodeeswaran, P. et al.: Two new species of congrid eel from India of Bengal. Ariosoma gracile sp. nov. Ariosoma kannani sp. nov. Holotype Paratypes Holotype Paratypes Total length (mm) 241 197-221 (n = 4) 173 157-201 (n = 2) %TL Head length 17.6 17.1-18.2 16.0 16.1 Depth at gill opening 5.0 4,3-5.5 6.4 5.4-6.1 Depth at anus 4.5 3.4-5.0 6.7 6.2-6.3 Width at anus 3.6 3.2-4.0 4.9 4.7-4.9 Pre-dorsal length 17.6 17.2-17.9 18.9 17.5-17.2 Pre-anal length 43.7 41.3-44.7 46.9 46.0-47.2 Trunk length 22.5 20.3-24.4 28.0 28.0-27.9 Tail length 56.3 55,3-58.7 53a 52.8-54.0 %HL Snout length 19.8 18.7-21.4 20.8 17.7-18.1 Eye diameter 17.4 15.7-18.4 21.1 20.7-20.9 Interorbital width 9.6 6.7-11.8 8.9 10.7-8.5 Upper jaw length 29.5 27.6-31.8 29.5 23.7-28.5 Gill opening width 15.4 10.4-18.0 12.8 10.0-10.8 Interbranchial width 10.4 8.8-12.5 21.25 14.4-14.1 Pectoral-fin length 32.9 26.8-36.9 37.0 29.5-37.4 Meristics Pre-dorsal vertebrae 9 9 10 10 Pre-anal vertebrae 48 49-52 45 45-48 Total vertebrae 141 140-142 116 118-116 Lateral-line pores Pre-dorsal pores 9 9 11 10 Pre-anal pores 43 43-46 45 47 Total pores 132 133-135 110 111-110 183-189 in A. multivertebratum, 146-148 in A. sazonovi:; 168-172 in A. sereti; Ariosoma gracile differs from Ari- osoma balearicum (Delaroche, 1809), Ariosoma mega- lops Fowler, 1938, Ariosoma scheelei (Stromman, 1896) and Ariosoma sokotranum Karmovskaya, 1991 in having more vertebrae (140-142 vs. 121-135 in A. balearicum; 114-118 in A. scheelei;, 136-141 in A. sokotranum). Remarks. The specimens were directly preserved in formalin; hence this could not be included in the molec- ular analyses. Ariosoma kannani Kodeeswaran, Kathirvelpandian, Ray, Kumar, Mohapatra & Sarkar, sp. nov. https://zoobank.org/AF62080E-7DF4-43A E-BFOC-D83C0440E8AA Figs 1b, 2b, 5, Table 1 Type material. Holotype. NBFGR/CONAKAN (171 mm TL), Rameshwaram Fish Landing Centre, Tamil Nadu, Gulf of Mannar, east coast of India, Bay of Bengal (9°16'N, 79°18'E), Coll. P. Kodeeswaran and A. Kathir- velpandian, 4 February 2022. Paratype. EBRC/ZSI/F15710 (157 mm TL) taken with holotype, EBRC/ZSI/F15711 (201 mm TL), Shankarpur Fish Landing Centre, West Bengal, Coll. Dipanjan Ray, 10 November, 2021. Diagnosis. A small-sized slender eel species of Ari- osoma distinguished from all other species by the zse.pensoft.net following combination of the characters: dorsal-fin origin behind pectoral-fin insertion, pre-anal length 46.0-47.2% of TL, smaller eye, 20.7—21.1% HL, smaller interorbit- al distance, 8.9-10.7% HL, no distinct bands on head, pre-opercle whitish, teeth on jaw small, pointed, inter- maxillary and vomerine teeth continuous, short vomerine tooth patch; SO canal with 6 pores; 3 pores on ST canal; pre-dorsal vertebrae 10 (10); pre-anal vertebrae 45 (45); total vertebrae 116 (118). Description. Body stout, anterior portion cylindrical, laterally compressed in tail region; caudal fin tip round- ed; anus positioned at mid-point of body, pre-anal length 46.0-47.2% of TL; dorsal-fin origin behind pectoral-fin insertion, above tenth to eleventh lateral-line pores. Pec- toral-fin developed, with a narrow base and round or blunt distally. Gill opening small, smaller than eye diameter, interbranchial width larger than gill opening and smaller than eye diameter. Head moderately large 6.0 (5.5) in TL, snout short, anteriorly pointed in dorsal view, its length 1.1 times eye diameter, projecting beyond lower jaw; snout length shorter than lower jaw; fleshy portion of snout project- ing anteriorly beyond the end of intermaxillary tooth patch; rictus positioned just behind middle length of eye. Tubular anterior nostril moderate in size at snout tip and posterior nostril relatively large elliptical pore, in front of mid-eye orbit diameter. Upper and lower jaw with reduced flange. Zoosyst. Evol. 100 (1) 2024, 119-128 125 Figure 5. Ariosoma kannani sp. nov., NBFGR/CONAKAN, holotype, (171 mm TL). a. Lateral view; b. Lateral; c. Dorsal; d. Ven- tral view of anterior portion of head. Lateral-line pores complete; first pore commences at level of supratemporal canal and terminates well before base of caudal fin; 10-11 pre-dorsal pores; 45-47 pre- anal pores and 110—111 total pores. Head pores medium or small. SO canal pores 6; first pore (ethmoidal) smaller, on snout tip; second pore medium, just before anterior nostril; third pore enlarged, on dorsal surface of snout just behind an- terior nostril; fourth pore moderate, behind posterior nostril; fifth pore smaller, at anterior interorbital space; sixth pore small at posterior interorbital space. IO ca- nal pores 8 (4+4), first pore moderate, behind anterior nostril; second pore below posterior nostril; third pore below just before orbit eye-orbit margin; fourth pore at slightly before rictus, fifth pore behind rictus and 3 pores at infraorbital canal behind eye. POM pores 10; mandibular section with 7, pre-opercular section with 3 pores in a longitudinal row. ST pores 3, 1 median pore and 1 lateral pore on each side just behind median pore (Fig. 1b). Teeth on jaws small, pointed; continuous maxillary and intermaxillary teeth; intermaxillary and vomerine teeth continuous; vomerine teeth pointed anteriorly and blunt posteriorly, reach beyond mid-maxillary teeth row (Fig. 2b). Pre-dorsal vertebrae 10, pre-anal vertebrae 45-48; total vertebrae 116-118. Colouration. Dorsal body pale brownish; ventral half above anus whitish; dorsal fin margin black; anal fin clear; pre-opercle whitish; head brownish; interorbital region black; pectoral-fin translucent; ventral surface of lower jaw whitish without any black pigmentation (Fig. 5). Distribution. Indian Ocean: Gulf of Mannar, Bay of Bengal probably widespread in the east coast of India, but rare in catch. Etymology. The species was named after the late Prof. Dr. L. Kannan, Former Director, CAS in Marine Biology, Annamalai University and Former Vice Chan- cellor, Thiruvalluvar University for his contribution in Marine Science. Comparison. Ariosoma kannani is closely related to Ariosoma megalops from China, Taiwan and Vietnam wa- ters in having the dorsal-fin origin behind the pectoral-fin insertion and similar vertebral counts, but the new spe- cies readily differs by having smaller interorbital distance (8.9-10.7% HL vs. 12.1-18.4% HL in A. megalops) and smaller mean eye diameter (20.9% HL vs. 22.8—22.9% HL) and the new species show 10.8% genetic divergence from A. megalops from the Taiwan waters. The new spe- cies shares similar vertebral counts with Ariosoma schee- lei, a widely distributed species in Indo-West Pacific, but A. kannani can be easily distinguished from A. scheelei by having fewer POM pores (10 vs. 12 in A. scheele?) (Smith et al. 2018) and shows 19.4% genetic differences. zse.pensoft.net 126 Further, A. kannani differs from all the Indian water con- geners by having fewer total vertebrae (116—118 vs. 121— 164 in others) and dorsal-fin origin behind pectoral-fin insertion (Kodeeswaran et al. 2021, 2022a, 2022b, 2023; Ray et al. 2022). Molecular analyses Out of 548 bp studied, conserved and variable sites were found to be 348 bp, 200 bp long, respectively. Amongst variable sites, parsimony informative sites constitute 190 bp, wherein a singleton with 10 bp. The nucleotide com- position was found to be A= 26.1%; T = 30%; C = 25.2%; G = 18.7. The transition and transversion bias (R) was documented using substitution patterns and rates were ascertained using the Kimura 2 Parameter model. The ob- tained R value of 7.48, clearly indicate the sequences of the species used for analyses are delineated in a proper manner. The R value supports the findings of genetic di- vergence values and phylogenetic tree analyses. The Maximum Likelihood tree (Fig. 6), obtained us- ing the sequences generated for the new species Arioso- ma kannani along with other sister species, confirms the species identification as the new species forms a separate Tree scale: 0.1 Kodeeswaran, P. et al.: Two new species of congrid eel from India cluster and 1s closely related to the sequences of Arioso- ma megalops from the Taiwan waters with 10.8% genetic divergence. Further, the new species A. kannani exhibits 16.3% distance with the sequences of Ariosoma kapala, 17.6% with A. bowersi, 18.9% with A. shiroanago, 19.2% with A. balearicum and 19.3% with A. anago. Discussion At present, 40 species of the genus Ariosoma were de- scribed (Fricke et al. 2023 and this study), with at least 74% (31 species) of all species of this genus being de- scribed or identified from the Indo-West Pacific, seven species distributed along the Atlantic Ocean and two from the eastern Pacific Ocean (Smith and Kanazawa 1977; Karmovskaya 1991, 2004, 2015, 2018; Shen 1998; Smith et al. 2018; Roy et al. 2021; Kodeeswaran et al. 2021, 2022a, 2022b, 2023; Fricke et al. 2023) and doubt- lessly there will be many undescribed species to be dis- covered. Very few species of the genus Ariosoma exhibit an endemic distributional range like a specific locality or around several islands, for example, Ariosoma baucho- tae Karrer, 1983 collected around western Madagascar (Smith 1989; Fricke et al. 2018); Ariosoma emmae Smith Sa SS ae a aes a ee ae MG816647 Ariosoma bowersi sie Nash a eh a ca eee set Sa ca cr al GU702529 Ariosoma sp. so ticinetiacibeincnasiadietieatata tidied atieadien teeter ied KM538201 Ariosoma balearicum 98 97 tN is ae te weg ewe chor eter, eri w erie ke oe el Were A as Lr Pe ete Oey eMart ee etree 100 a Pann "oe 69 100 -- 100 ale MG702269 Ariosoma sp. HM902638 Ariosoma kapala KP267573 Ariosoma anago MG/702271 Ariosoma shiroanago JQ431460 Ariosoma scheelei MK657774 Ariosoma scheelei MH496115 Ariosoma megalops MH496114 Ariosoma megalops OR189206 Ariosoma kannani sp. nov. OR189205 Ariosoma kannani sp. nov. MT323704 Ariosoma selenops OM509709 Ariosoma indicum OM509710 Ariosoma indicum MW043016 Ariosoma melanospilus MW043015 Ariosoma melanospilus OK480045 Ariosoma sp. OK480044 Ariosoma sp. MZ570443 Ariosoma maurostigma MZ570445 Ariosoma maurostigma MZ570444 Ariosoma maurostigma OM275351 Ariosoma albimaculatum OM275350 Ariosoma albimaculatum OM275349 Ariosoma albimaculatum MF539661 Ariosoma meeki MG856723 Ariosoma anale MG856646 Ariosoma anale MT323658 Ariosoma anale ON799405 Uroconger lepturus (Outgroup) MF956462 Japonoconger proriger (Outgroup) Figure 6. Maximum Likelihood phylogeny tree of the genus Ariosoma from analysis of cytochrome c oxidase subunit I gene, including new species, Ariosoma kannani collected from the south Indian coast, based on the IQ-Tree. The ML tree was plotted with the HK Y+F+I+G4 model using ModelFinder (Kalyaanamoorthy et al. 2017). Each node is labelled with a GenBank accession number and support values (bootstrap probability) are indicated along branches. zse.pensoft.net Zoosyst. Evol. 100 (1) 2024, 119-128 & Ho, 2018, known only from Taiwan (Smith et al. 2018); Ariosoma hemiaspidus (Wade, 1946), described from the Gulf of California, Mexico (McCosker and Rosenblatt 2010); Ariosoma mellissii (Gunther, 1870), endemic to Saint Helena, southern-central Atlantic (Smith 2016); Ariosoma multivertebratum Karmovskaya, 2004, known only from Marquesas Islands (Karmovskaya 2004; Del- rieu-Trottin et al. 2015); Ariosoma sereti Karmovskaya, 2004, described only from Hiva Oa Island, Marquesas Islands (Karmovskaya 2004); and Ariosoma sazonovi Karmovskaya, 2004, collected and described only from the Philippines (Karmovskaya 2004); these species were known and described only from holotypes or with very few paratypes. Amongst the ten species from Indian wa- ters, A. majus was recorded by Roy et al. (2021) along the east coast of India in the Bay of Bengal showing that A. majus was widely distributed in the Indo-Pacific. The new species, Ariosoma kannani was collected from two different localities from the Bay of Bengal, which might indicate a wider distributional range, but it is rare in land- ings. Further, A. indicum shows a continuous distribution along the coast of the Arabian Sea and Bay of Bengal. The species, A. albimaculatum and A. melanospilos were previously known only from type locality, but the first au- thor found plenty of specimens in deep-sea trawl landings at Kollam coast, Arabian Sea. The phylogenetic analyses of this study was based on only one marker due to availability of comparative se- quences in public domain. Phylogenetic analyses for most of the species of the genus Ariosoma was meagre, hence vast sampling is needed to fulfil the complete genomics of these congrid eel groups. Furthermore, most eels do not possess economic value and are landed mostly as by- catch and sampling on this group was very rare in Indian waters (Kodeeswaran et al. 2021), but extensive sam- pling is a prerequisite to understand the complete aspects of this conger eel group’s biodiversity along the Indian coast. In addition, species in the genus Ariosoma dwell in unusual habitats like continental slopes and underwa- ter seamounts (Shen 1998; Karmovskaya 2018) making them rare in landings. Based on our analyses and results, it suggests that future surveys (sampling and collections) will be extended along the entire coast of India including the islands and may reveal many new species which addi- tionally afford detailed insights into the diversity, ecology and evolution of the Ariosoma species. Authors contribution PK collected, identified, examined the specimens and prepared the manuscript. PK and AK performed molec- ular analyses and revised the manuscript. AM identified, examined the specimens and revised the manuscript. DR collected and identified specimens from West Bengal. TTA and CR revised the manuscript. UKS provided com- prehensive guidance and supported the work. All authors read and approved the final version of the manuscript. 127 Acknowledgements The authors acknowledge the Director, ICAR-—Na- tional Bureau of Fish Genetic Resources (NBFGR), Lucknow, for providing support and encouragement through the Institutional exploration project. AM and CR thank Dr. Dhriti Banerjee, Director, Zoolog- ical Survey of India for providing essential working facilities. References Asano H (1958) Studies on the conger eels of Japan. I. Description of two new subspecies referable to the genus A//oconger. Zoological Magazine Tokyo 67: 191-196. Bohlke EB (1982) Vertebral formulae for type specimens of eels (Pisces: Anguilliformes). Proceedings of the Academy of Natural Sciences of Philadelphia, 31-49. Castle PHJ (1990) Two new species of the previously monotypic con- grid eel genera Poeciloconger and Macrocephenchelys from east- ern Australia. Records of the Australian Museum 42(2): 119-126. https://doi.org/10.3853/j.0067-1975.42.1990.109 Delaroche FE (1809) Suite du mémoire sur les espéces de poissons observées a Ivica. Observations sur quelques-uns des poissons in- diqués dans le précédent tableau et descriptions des especes nou- velles ou peu connues. Annales du Muséum d’ Histoire Naturelle, Paris 13: 313-361. [pls. 20-25] Delrieu-Trottin E, Williams JT, Bacchet P, Kulbicki M, Mourier J, Galz- in R, de Loma TL, Mou-Tham G, Siu G, Planes S (2015) Shore fishes of the Marquesas Islands, an updated checklist with new re- cords and new percentage of endemic species. Check List 11(5): 1758-1758. https://doi.org/10.15560/11.5.1758 Fowler HW (1938) Studies of Hong Kong fishes. No. 3. Hong Kong Naturalist 6: 1-52. Fricke R, Mahafina J, Behivoke F, Jaonalison H, Léopold M, Ponton D (2018) Annotated checklist of the fishes of Madagascar, southwest- em Indian Ocean, with 158 new records. FishTaxa : Journal of Fish Taxonomy 3(1): 1-432. Fricke R, Eschmeyer WN, Fong JD (2023) Species by Family/Subfam- ily. Eschmeyer’s Catalog of Fishes. http://researcharchive.calacade- my.org/research/ichthyology/catalog/SpeciesByFamily.asp [Online Version, Updated 19 August 2023] Gunther A (1870) Catalogue of the Physostomi, containing the families Gymnotidae, Symbranchidae, Muraenidae, Pegasidae, and of the Lophobranchii, Plectognathi, Dipnoi, Ganoidei, Chondropterygii, Cyclostomata, Leptocardii, in the British Museum. Catalogue of the fishes in the British Museum 8: 1-549. Gunther A (1872) Report on several collections of fishes recently obtained for the British Museum. Proceedings of the Zoological Society of London 3: 652-675. [pls. 53-70] Hall TA (1999) BioEdit: A user-friendly biological sequence alignment editor and analysis program for Windows 95/98/NT. Nucleic Acids Symposium Series 41: 95-98. Hoang DT, Chernomor O, Von Haeseler A, Minh BQ, Vinh LS (2018) UFBootz2: Improving the ultrafast bootstrap approximation. Molec- ular Biology and Evolution 35(2): 518-522. https://doi.org/10.1093/ molbev/msx281 zse.pensoft.net 128 Jordan DS, Snyder JO (1900) A list of fishes collected in Japan by Keinosuke Otaki, and by the United States steamer Albatross, with descriptions of fourteen new species. Proceedings of the United States National Museum 23(213): 335-380. https://doi.org/10.5479/ $1.00963801.23-1213.335 Kalyaanamoorthy S, Minh BQ, Wong TK, Von Haeseler A, Jermiin LS (2017) ModelFinder: Fast model selection for accurate phylogenetic estimates. Nature Methods 14(6): 587-589. https://doi.org/10.1038/ nmeth.4285 Karmovskaya ES (1991) New species of conger eel (Congridae) from the western Indian Ocean. Voprosy Ikhtiologii 3: 891-897. [In Rus- sian. English translation in Journal of Ichthyology 32:1-8.] Karmovskaya ES (2004) Benthopelagic bathyal conger eels of families Congridae and Nettastomatidae from the western tropical Pacific, with descriptions of ten new species. Journal of Ichthyology 44(sup- pl. 1): S1-S32. Karmovskaya ES (2015) New species of the genus Ariosoma, A. dol- ichopterum (Bathymyrinae), from the waters of Central Vietnam. Journal of Ichthyology 55(6): 906-910. https://doi.org/10.1134/ S0032945215060077 Karmovskaya ES (2018) On the species composition of eels of the ge- nus Ariosoma (Anguilliformes: Congridae) from NhaTrang and Van Phong Bays (South China Sea, Central Vietnam). Journal of Ichthy- ology 58(4): 455-472. https://doi.org/10.1134/S00329452 18040070 Karrer C (1983) Anguilliformes du Canal de Mozambique (Pisces, Te- leostei). Faune Tropicale (23): 1-116. Kodeeswaran P, Jayakumar TKT, Akash S, Kumar TTA, Lal KK (2021) A new species of Congrid eel, Ariosoma melanospilos sp. nov., from Indian waters with taxonomic description of A. dolichopterum (Con- gridae: Bathymyrinae). Marine Biodiversity 51(3): 47. https://doi. org/10.1007/s12526-021-01187-8 Kodeeswaran P, Mohapatra A, Dhinakaran A, Ajith Kumar TTP, Lal KK (2022a) A new species of the congrid eel genus Ariosoma (Anguilliformes: Congridae) from the Southwest coast of India. Journal of Fish Biology 100(3): 775—782. https://doi.org/10.1111/ jfb.14994 Kodeeswaran P, Kathirvelpandian A, Acharya S, Mohanty SR, Mohapa- tra A, Ajith Kumar TTP, Lal KK (2022b) Ariosoma indicum sp. nov., a new species of congrid eel (Anguilliformes: Congridae: Bathy- myrinae) from the Indian waters. Journal of Fish Biology 100(6): 1447-1454. https://doi.org/10.1111/jfb.15055 Kodeeswaran P, Dhas D, Ajith Kumar TTP, Lal KK (2023) Description of a new congrid eel, Ariosoma albimaculata sp. nov. (Anguilli- formes: Congridae), from the southwest coast of India, Arabian Sea. Ichthyological Research 70(2): 233-242. https://doi.org/10.1007/ $10228-022-00882-1 Kodeeswaran P, Kathirvelpandian A, Mohapatra A, Ajith Kumar TTP (in press) A new species of the congrid eel genus Ariosoma (Tele- oste1: Anguilliformes: Congridae) from the Southeast coast of India. Bay of Bengal. Kumar S, Stecher G, Li M, Knyaz C, Tamura K (2018) MEGA X: Mo- lecular Evolutionary Genetics Analysis across computing platforms. Molecular Biology and Evolution 35(6): 1547-1549. https://doi. org/10.1093/molbev/msy096 Letunic I, Bork P (2021) Interactive Tree Of Life (i1TOL) v5: An on- line tool for phylogenetic tree display and annotation. Nucleic Ac- ids Research 49(W1): W293—W296. https://doi.org/10.1093/nar/ gkab301 zse.pensoft.net Kodeeswaran, P. et al.: Two new species of congrid eel from India McCosker JE, Rosenblatt RH (2010) The fishes of the Galapagos Ar- chipelago: An update. Proceedings of the California Academy of Sciences 61(2): 167-195. McCulloch AR, Waite ER (1916) Additions to the fish fauna of Lord Howe Island No. 5. Transactions of the Royal Society of South Aus- tralia 40: 437-451. Neguyen LT, Schmidt HA, Von Haeseler A, Minh BQ (2015) IQ-TREE: A fast and effective stochastic algorithm for estimating maxi- mum-likelihood phylogenies. Molecular Biology and Evolution 32(1): 268-274. https://doi.org/10.1093/molbev/msu300 Poey F (1860) Memorias sobra la historia natural de la Isla de Cuba, acompafiadas de sumarios Latinos y extractos en Francés. Tomo 2. La Habana 2: 97-336. https://doi.org/10.5962/bhi.title.2485 Ray D, Acharya S, Khatua T, Roy D, Mohapatra A, Mishra SS (2022) A new species of conger eel, Ariosoma (Congridae: Bathymyri- nae), from the Bay of Bengal, India. Zootaxa 5165(1): 133-143. https://doi.org/10.11646/zootaxa.5165.1.8 Roy D, Khatua T, Ray D, Mohapatra A (2021) First Report of Conger Eel (Anguilliformes: Congridae) Ariosoma majus (Asano, 1958) From Indian Ocean. Thalassas. Thalassas 37(1): 93-96. https://doi. org/10.1007/s41208-020-00284-y Shen SC (1998) A review of congrid eels of the genus Ariosoma from Taiwan, with description of a new species. Zoological Studies-Tai- pei 37: 7-12. Smith DG (1989) Family Congridae. In: Bohlke EB (Ed.) Fishes of the Western North Atlantic, Pt 9, 1. Memoir Sears Foundation for Ma- rine Research, New Haven, 460-567. Smith DG (2016) Miscellaneous groups (Pp. 1590-1613, 1643-1653, 1667-1714). In: Carpenter, De Angelis (Eds) The living marine re- sources of the Eastern Central Atlantic. Volume 3. Bony fishes part 1 (Elopiformes to Scorpaeniformes). FAO Species Identification Guide for Fishery Purposes, Rome, FAO. v. 3. i-x1v + 1511-2350. Smith DG, Kanazawa RH (1977) Eight new species and a new genus of congrid eels from the western north Atlantic with redescriptions of Ariosoma analis, Hildebrandia guppyi, and Rhechias vicinalis. Bulletin of Marine Science 27: 530-543. Smith DG, Ho HC, Huang JF, Chang YH (2018) The congrid eel ge- nus Ariosoma in Taiwan (Anguilliformes: Congridae), with de- scription of a new species. Zootaxa 4454(1): 84-106. https://doi. org/10.11646/zootaxa.4454.1.10 Stromman PH (1896) Leptocephalids in the University Zoological Museum at Upsala. Almqvist & Wiksell, Uppsala. 1-53. [pls. 1-5] https://do1.org/10.5962/bhI title.56320 Swainson W (1838) On the natural history and classification of fishes, amphibians, & reptiles, or monocardian animals. Vol. 1. A. Spottis- woode, London, 368 pp. https://doi.org/10.5962/bhl title.62140 Talwar PK, Mukherjee P (1977) A note on a new bathypelagic eel, Ariosoma gnanadossi, from the Bay of Bengal. The Indian Journal of Animal Sciences 47: 432-434. Temminck CJ, Schlegel H (1846) Pisces, in Fauna Japonica, Sive Descriptio Animalium Quae in Itinere per Japoniam Suscepto Annis 1823-30 Colle-git, Notis Observationibus et Adumbrationibus Illustravit P.F. de Siebold. Fauna Japonica, Sive Descriptio Animalium Quae in Itinere per Japoniam, Batavia: Lugduni Batavorum, 1846, parts 10-14, 173-269. Wade CB (1946) Two new genera and five new species of apodal fishes from the eastern Pacific. Allan Hancock Pacific Expeditions 9(7): 181-213.