Liobagrus geumgangensis, Kim & Yun & Park, 2023

Kim, Su-hwan, Yun, Seung-woon & Park, Jong-young, 2023, A new species of torrent catfish, Liobagrus geumgangensis (Teleostei, Siluriformes, Amblycipitidae), from Korea, ZooKeys 1180, pp. 317-332 : 317

Liobagrus geumgangensis sp. nov.

Figs 1 , 2 , 3 , 4 , 5

Type locality.

Geum River, Korea.

Type material.

Holotype. CNUC 39103, 70.7 mm SL, male, Geum River, Namyang-myeon, Cheongyang-gun, South Korea. 36°23'41.66"N, 126°48'41.30"E, collected by J.Y. Park, S.W. Yun and H.T. Kim using a scoop net, 14 March 2018 (Fig. 1 ). Paratypes. CNUC 39102, 39104-39113, 39129-39137 (20), 57.0-88.3 mm SL, same data as holotype.

Diagnosis.

Liobagrus geumgangensis can be distinguished from other species in the genus by the length of the upper and lower jaws, and the presence or absence of serrations on the posterior edge of the pectoral fin, which are representative characteristics of the genus Liobagrus . Liobagrus geumgangensis has a longer upper than lower jaw and serrations on the posterior edge of the pectoral fin. Species that share these characteristics with L. geumgangensis are as follows: L. mediadiposalis , L. somjinensis , L. hyeongsanensis , L. huaiheensis and L. pseudostyani . This new species can be distinguished by the relatively large number of serrations (5-8) on the posterior edge of the pectoral fin (vs. 4-6 in L. mediadiposalis and L. somjinensis , 2-3 in L. hyeongsanensis , L. huaiheensis and L. pseudostyani ). It can be further differentiated from L. huaiheensis and L. pseudostyani by the subtruncate caudal fin (vs. rounded). Liobagrus geumgangensis is distinguished from its geographically closest congeners L. mediadiposalis and L. somjinensis by the following combination of characteristics: the body and fins are dark yellow, and the margins of the dorsal, anal, and caudal fins are dark brown, but the outermost rim is faintly yellow (vs. broad yellowish outer margin of the fins in L. mediadiposalis and crescent-shaped band in the middle of the caudal fin in L. somjinensis ); pectoral fin rays I, 8 (vs. both I, 7); caudal fin rays 52-56 (vs. both 57-61); a relatively short occiput to dorsal-fin origin (6.9-9.8% SL vs. 10.3-13.3% in L. mediadiposalis and 9.7-13.0 in L. somjinensis ); a short pelvic-fin origin to anal-fin origin (11.9-17.3% SL vs. 15.3-20.9% in L. mediadiposalis and 13.3-18.7% in L. somjinensis ); a long dorsal-fin base (10.6-13.5% SL vs. 7.7-10.4% in L. mediadiposalis and 8.8-11.3% in L. somjinensis ); and 8-9 gill rakes (vs. 7-11 in L. mediadiposalis and 7-9 in L. somjinensis ) (Figs 1 , 2 ).

Description.

Counts and measurements, expressed as percentages of SL, are given in Table 1 . Dorsal fin II, 6 (21); origin closer to snout tip than anal-fin origin, posterior margin convex. Dorsal-fin spine equal to or a little shorter than pectoral-fin spine. Adipose fin long, well developed, reaching to or slightly exceeding anal-fin base, confluent with caudal fin, margin convex. Adipose fin depth relatively low. Pectoral fin I, 8 (21); origin anterior to vertical through posterior margin of operculum, partially covered by opercular membrane. Pectoral-fin spine slightly sharp and long, with 4 (4), 5 (8) or 6 (9) serrations on posterior edge. Pelvic fin i, 5 (21); short, located at vertical through, or occasionally slightly anterior to adipose fin; tip not connected to base of anal fin. Anal fin with 14 (1), 15 (2), 16 (9), 17 (7), or 18 (2) rays; distal margin rounded, short, origin placed slightly posterior to vertical through adipose fin origin, posterior tip of anal fin not exceeding posterior margin of adipose fin. Caudal fin subtruncately rounded with 52 (3), 54 (5), 55 (3), or 56 (10). Vertebrae with 38 (9), 39 (8), or 40 (4) post-Weberian elements. Gill rakers 8-9.

Mouth terminal; lips thickened and papillate, premaxillary and mandibular toothpads curved, teeth small and ciliform or setiform, with upper jaw slightly longer than lower jaw. Four pairs of barbels; maxillary barbel longest, reaching to base of pectoral-fin spine; nasal barbel short, not reaching to posterior margin of preoperculum; outer mental barbel long, reaching to posterior edge of pectoral-fin base; inner-mental barbel shortest among four pairs of barbels, about half length of outer mental barbel, reaching to gill membrane. Body compressed and round, head depressed and caudal peduncle strongly compressed; dorsal and ventral profiles straight. Predorsal profile slightly sloping ventrally from dorsal fin to occiput. Eye smaller, dorsolateral, subcutaneous, ovoid. Snout rounded in dorsal view. Anterior nostril tubular, rim with a fleshy flap forming a short tube; posterior nostril porelike, rim posteriorly confluent with base of nasal barbel. Gill membranes narrowly joined at isthmus. Lateral line absent or vestigial.

Coloration.

See Fig. 1 for general appearance. In life (Fig. 1 ): body generally brownish yellow, fading to light yellow on ventral surface, without any distinct markings. All barbels pale gray. All fins with similar color to body, without deep yellow outer margins.

Sexual dimorphism.

The adductor mandibulae in males is somewhat swollen during the spawning season, from late April to June.

Etymology.

Named after the Geum River (Geumgang in Korean), the type locality. We propose the Korean name Geumgang-Jagasari for this species.

Distribution.

Liobagrus geumgangensis sp. nov. is restricted to some rivers flowing to the west coast of South Korea: Geum River and upper stream of Mangyeong River (Fig. 5 ).

Biology and habitat.

Liobagrus geumgangensis is nocturnal and benthic. They inhabit the bottom stratum of large and small stone or pebble substratum in shallow waters, about 0.3-0.6 m deep, with running waters with moderately fast currents. The spawning season is from late April to June. The adult females reach up to 99.8 mm SL and lay eggs 2.5-3.0 mm (2.8 ± 0.1) in diameter. The adult males guard their fertilized egg. They feed mostly on aquatic insect larvae such as those of the Trichoptera , Ephemeroptera and Diptera .

Figures

Figure 1. Liobagrus geumgangensis sp. nov. holotype (CNUC 39103), 70.7 mm SL, male, Geum River, Namyang-myeon, Cheongyang-gun, South Korea; lateral (A), dorsal (B) and ventral (C) views.

Figure 2. Comparison of pectoral-fin spines and rays of Liobagrus geumgangensis (A) and its congener L. mediadiposalis (B) A CNUC 38919, 87.8 mm SL, Geum River, Cheongyang-gun, South Korea B CNUC 38930, 77.5 mm SL, Nakdong River, Sancheong-gun, South Korea.

Figure 3. Phylogenetic tree using maximum likelihood (ML) method based on mitochondrial cytochrome b gene sequences of Siluriformes species including L. geumgangensis. Bootstrap support values based on 1000 replicates are displayed on each node as> 50. The blue color of the branches indicates L. geumgangensis.

Figure 4. Liobagrus mediadiposalis (A), CNUC 39153, 97.0 mm SL; male, Nakdong River, Sancheong-gun, South Korea and L. somjinensis (B), CNUC 39170, 99.4 mm SL, male, Somjin River, Namwon-si, South Korea.

Figure 5. South Korea, showing distributions of Liobagrus geumgangensis (1 - 7), L. somjinensis, L. hyeongsanensis, and L. mediadiposalis. Dark green line: Baekdudaegan mountain range, showing three biogeographical ranges of ichthyofaunal endemism on the Korean Peninsula (modified from Kim 1997).