Encheloclarias kelioides Ng & Lim, 1993

Tan, Zhi Wan, Toh, Elysia X. P., Cai, Yixiong, Tan, Heok Hui & Yeo, Darren C. J., 2023, Discovery of Encheloclarias (Teleostei: Clariidae) from Singapore, with notes on morphology and distribution, Raffles Bulletin of Zoology 71, pp. 196-206 : 198-202

Encheloclarias kelioides Ng & Lim, 1993

( Figs. 1–4 )

Encheloclarias kelioides Ng & Lim, 1993: 30–31 ; Kottelat & Whitten, 1996: 4; Ng & Tan, 2000: 536; Ferraris, 2007: 149–150; Hărşan & Petrescu-Mag, 2008: 197 (list); Ng & Lim, 2008: 44–45; Chong et al., 2010: 2024, 2048; Chew & Zulkafli, 2012: 283 (list); Sule et al., 2016: 429, 449, Table 3 (list); Ng et al., 2017: 15; Polgar & Jaafar, 2018: 137 (list); Vythalingam et al., 2022: 165 (list).

Encheloclarias tapeinopterus (non Bleeker) – Herre & Myers, 1937: 66 (Mawai, Johor); Hora & Gupta, 1941: 40 (key); Kottelat, 1989: 15 (list); Roberts, 1989: 128 (in part; no new record)

Encheloclarias kelioides (non Ng & Lim) – Tan & Tan, 1995: 355; Kottelat & Whitten, 1996: 4; Apriadi et al., 2018: 971–972.

Material examined. ZRC 29401 , holotype, 64.8 mm SL; Peninsular Malaysia: Pahang, south of Pekan, blackwater stream across road, 69 km stone on road from Mersing to Pekan , near Kuantan ; coll. M. Kottelat & P. K. L. Ng, 9 March 1992 . --- ZRC 63056 , 2 ex., 61.2–77.8 mm SL; Singapore: Central Catchment Nature Reserve, Nee Soon Swamp Forest ; coll. E. X. P. Toh et al., 9 September 2022 . --- ZRC 63084 , 3 ex., 68.6–92.0 mm SL; Singapore: Central Catchment Nature Reserve, Nee Soon Swamp Forest ; coll. Cai Y. et al., 21 September 2022 . --- ZRC 63406 , 2 ex., 48.9–80.1 mm SL; Singapore: Central Catchment Nature Reserve, Nee Soon Swamp Forest ; coll. Cai Y. et al., 23 November 2022 . --- ZRC 63638 , 4 ex., 78.2–102.4 mm SL; Singapore: Central Catchment Nature Reserve, Nee Soon Swamp Forest ; coll. Cai Y. et al., 26 January 2023 .

Diagnosis. Body ( Figs. 2 , 3 ) slender, moderately long, body depth 6–11% SL. Vertebrae 14–16 + 40–44 = 54–60 (n = 5). Anal fin and caudal fin fused only at base, completely disjunct beyond base. Head ( Fig. 4 ) blunt, lateral edges with protuberance due to opercular muscles, proportionately short, about 15–17% SL. Pectoral fin spine with 4–8 distinct sharp serrae.

Description. Biometric data as in Table 1. Body moderately long, slender, cylindrical, gently tapering towards caudal peduncle. Dorsal profile rising gently from tip of snout to origin of dorsal fin, thereafter straight to end of caudal peduncle, except gently convex along base of adipose fin. Ventral profile of head slightly convex, thereafter almost horizontal to end of caudal peduncle. Skin smooth. Lateral line complete and midlateral in position. Vertebrae 14–16 + 40–44 = 54–60 (n = 5). Largest specimen examined is 102.4 mm SL (ZRC 63638).

Head gently depressed; predorsal profile slightly convex, ventral profile straight. Bony elements of dorsal surface of head covered with smooth, velvety skin; bones not readily visible. Front fontanelle longitudinally ovoid; located in interorbital region, with anterior tip reaching imaginary line connecting anterior orbital margins. Occipital fontanel ovoid, located at base of occipital process, slightly narrower than frontal fontanelle, posterior edge reaching imaginary line connecting bases of pectoral spines. Occipital process broad, with rounded tip. Eye ovoid, horizontal axis longest, subcutaneous, located dorsolaterally on head. Gill openings narrow, extending from dorsal-most point of pectoral-fin base to isthmus. Gill membranes free from each other, only united across isthmus, with 9 branchiostegal rays. First branchial arch with 7 gill rakers (from Ng & Lim, 1993).

Mouth subterminal, with fleshy, plicate lips. Premaxillary tooth band rectangular, length 35% HL, with villiform teeth. Vomerine tooth band subequal to premaxillary tooth band, length 32% HL, with subgranular teeth. Mandibulary tooth band 51% HL, with villiform teeth (from Ng & Lim, 1993).

Barbels in four pairs; long, slender, with thick fleshy bases. Maxillary barbel typically longest and thickest at base, length 70.1–117.1% HL. Nasal barbel longer than mandibulary and mental barbel, length 74.5–113.7% HL. Mental barbel origin close to midline, length 58.5–109.4% HL. Mandibular barbel originating posterolateral of mental barbel, longer than mental barbel, length 65.7–111.1% HL. Nostril tubes of anterior naris long, extending beyond edge of mouth when directed towards the front. Posterior naris just anterior to eye at base of nasal barbel, opening about eye diameter.

vertebrae 16–17. Caudal fin long and rounded, with 19 principal rays, anterior-most lower procurrent caudal ray longer than last few anal-fin rays.

Pectoral fin broad, abruptly and sharply pointed at tip, with I,8 rays. Anterior margin of spine smooth, posterior margin with 4–8 inward directed serrations (n = 6). Pectoral-fin margin weakly convex anteriorly, gently convex posteriorly. Pelvic-fin origin at vertical through base of fifth dorsal-fin ray, pterygiophore insertion at vertebrae 13–14, with i,6 rays and convex margin; tip of fin reaching base of second anal-fin ray. Anus and urogenital openings located at vertical through middle of pelvic fin and anal-fin origin.

Live colouration. Dorsal surface of head, body and base of dorsal and caudal fin uniform brown, fading to a slightly paler colour on venter; adipose fin colouration similar to that of body, brown with hyaline margin; rays of all other fins dusky, with hyaline inter-radial membranes ( Fig. 5 ). Barbels dirty white distally, fading to light brown proximally. Pectoral-fin spines very light brown dorsally, light grey ventrally ( Fig. 5 ).

Comparative notes. Similar-sized specimens collected from Nee Soon Swamp Forest, Singapore, agree well in their characters with those of the holotype ( ZRC 29401 ) and paratype ( CAS-SU 32004 ) of Encheloclarias kelioides ( Table 1). The specimens from Singapore are therefore regarded as conspecifics. The species can be distinguished from all other congeners by its habitus, fin morphology and vertebral count .

Dorsal fin with moderately short base, spanning middle onethird of body; with 23–26 (mode 25) rays covered by thick layer of skin, without spine; pterygiophore insertion (origin) at vertebrae 9–10. Dorsal-fin margin approximately straight, parallel to dorsal edge of body. Adipose fin with gently convex dorsal margin; anterior point of origin contacting base of last dorsal-fin ray; gently curving posteriorly to fuse broadly with upper procurrent caudal fin rays. Anal-fin base long, with 47–52 (mode 47) rays, covered by thick layer of skin; margin straight, parallel to ventral edge of body, not confluent with caudal fin base. Anal-fin origin at vertical through tenth dorsal-fin ray, pteryogiophore insertion at Encheloclarias kelioides can be immediately distinguished from E. tapeinopterus and E. velatus in the posteriormost part of the anal-fin and the ventral anteriormost part of the caudal-fin being fused only at the base, while remaining separated beyond the base ( Figs. 3 , 4 ) (vs. anal fin confluent with caudal fin along entire height of fins, cf. Ng & Lim, 1993: fig. 3; Ng & Tan, 2000: fig. 1); and from E. curtisoma by its proportionately longer, more shallow body: body depth 6–11% SL ( Figs. 3 , 4 ) (vs. proportionately shorter, stouter body: body depth 10.5–13.8% SL, cf. Ng & Lim, 1993: fig. 11). Encheloclarias kelioides can be distinguished from E. prolatus and E. baculum by its fewer vertebrae, and fewer dorsal and anal-fin rays (54–60, 23–26, 47–53, respectively, vs. 65–67, 26–29 and 54–65, respectively); and from E. medialis by the proportionately shorter head, 15–17% SL, with distinct lateral protuberance due to opercular muscle when viewed dorsally and ventrally ( Figs. 2–4 ) (vs. relatively more rounded head shape without lateral protuberance when viewed dorsally, ventrally and proportionately longer head, 19.2% SL, cf. Ng, 2012a: fig. 3) and more numerous and distinct serrations on the posterior margin of the pectoral spine, 4–8 distinct sharp serrae (vs. 2 indistinct serrae on pectoral spine).

Within Singapore, Encheloclarias kelioides differs from all other clariid catfishes known, viz., Clarias batrachus , C. leiacanthus , C. nieuhofii and C. gariepinus (non-native), by its comparatively small adult size, SL up to 102.4 mm recorded (vs. relatively larger size, SL up to 1700 mm for C. gariepinus ); and short dorsal fin, which does not reach the caudal fin combined with the presence of a very low adipose fin (vs. long dorsal fin reaching caudal fin, and absence of adipose fin).

Taxonomic significance. Encheloclarias kelioides was originally described from two specimens (the holotype and a paratype: Ng & Lim, 1993), with no other specimens known to have been collected since. The two type specimens are similar in length, measuring 64.8 mm and 63.3 mm SL, respectively. The fresh specimens collected from Singapore in the present study range between 48.9–102.4 mm SL, providing new understanding with regard to the size and ontogenic variation of this species (e.g., the pectoral-fin spine serrae count). Irrespective of the size range, the meristic and morphometric data reported in the original description ( Ng & Lim, 1993) still hold true, further supporting the validity of this species and its distinctiveness from other closely related and distributed species.

Distribution. Pahang, Johor, eastern Peninsular Malaysia and Nee Soon Swamp Forest, Singapore; and possibly central Sumatra (fide Ng & Tan, 2000).

Figures

Fig. 1. Top two; Encheloclarias kelioides - ZRC 63056, 77.8 mm SL, Singapore. Bottom two; Heterobrachus longifilis - ZRC 38289, 119.4 mm SL, Africa. Composite images of lateral views of preserved fish and X-ray images. Specimens not to scale (THH).

Fig. 2. Encheloclarias kelioides, composite of dorsal, lateral and ventral views of freshly preserved fish - ZRC 63056, 77.8 mm SL, Singapore (THH).

Fig. 3. Encheloclarias kelioides, composite (laterally inverted) of dorsal, lateral and ventral views of freshly preserved fish - ZRC 63056, 61.2 mm SL, Singapore (THH).

Fig. 4. Encheloclarias kelioides, composite of dorsal, lateral and ventral close-up views of head - ZRC 63056, 77.8 mm SL, Singapore (THH).

Fig. 5. Encheloclarias kelioides, composite of dorsal and lateral (laterally inverted) views of live fish - ZRC 63056, 77.8 mm SL, Singapore (THH).