Strophidon tetraporus Huang et Liao, 2020

Sohn, Min-Soo, Kwun, Hyuck-Joon & Kim, Jin-Koo, 2025, First record of the four-pore slender giant moray, Strophidon tetraporus (Actinopterygii, Anguilliformes, Muraenidae), from Sinan, Korea, Acta Ichthyologica et Piscatoria 55, pp. 413-417 : 413-417

Strophidon tetraporus Huang et Liao, 2020

English common name: four-pore slender giant moray Korean common name: 네눈가는곰치 Fig. 2

Material examined.

MABIK PI 00060540 , 1 specimen, 2318 mm TL, St. 210-6, Heuksan-myeon , Sinan-gun, Jeollanam-do, Korea ( 34°15′00″N, 125°24′60″E) .

Description.

Meristic and morphometric characters summarized in Table 1 . Total vertebrae 195, including 8 predorsal and 79 preanal vertebrae. Dorsal fin consisting of 498 rays; anal fin consisting of 339 rays; both fins continuous with caudal fin. Body extremely elongate and cylindrical along anterior half, becoming slightly compressed from behind anus to tail tip. Body depth ( BD) 22.4 in TL; at gill opening 26.5 in TL; at anus 26.5 in TL. Anus situated slightly anterior to midbody, preanal length 2.3 in TL. Head moderately long, 9.8 in TL, with gently convex dorsal profile. Snout blunt and short, 3.0 in HL. Eye small, diameter 23.8 in HL, located in anterior half of upper jaw cleft. Interorbital space broad, 11.3 in HL. Mouth large and terminal, upper and lower jaws nearly equal in length (2.9 and 3.0 in HL, respectively). Both jaws bearing biserial teeth, inner row with larger conical teeth, outer row with smaller pointed teeth. Anterior nostril tubular, positioned at tip of snout, directed forward. Posterior nostril forming small pore above anterior margin of eye, opening posteriorly. Cephalic sensory-pore pattern including three supraorbital pores, four infraorbital pores (including distinct posterior fourth pore), and six preoperculo-mandibular pores. Four branchial pores situated dorsally above gill opening (Fig. 3 ). Gill opening slightly posterior to origin of dorsal fin. Skin from head to gill opening slightly wrinkled, becoming smooth along remainder of body. Dorsal fin originating above first branchial pore; anal fin beginning immediately behind anus.

Coloration in preservation.

Dorsal surface of body uniformly dark brown, becoming lighter brown on ventral side behind gill openings. lower jaw pale brown. region anterior to gill opening appeared slightly darker owing to presence of folds. fin membranes generally similar in color to adjacent dorsal body surface and gradually becoming darker toward distal margins.

Distribution.

Korea (Present study), Taiwan (Type locality), Philippines, Vietnam, Indonesia ( Huang et al. 2020), and Japan ( Koreeda and Motomura 2025)

Molecular analysis.

Molecular analysis of the Korean specimen of S. tetraporus was conducted based on a 652 bp fragment of the COI gene (Fig. 4 ). The sequence was compared with reference sequences obtained from the holotype and paratypes of S. tetraporus , as well as specimens from previously reported localities, including Taiwan, Philippines, and Vietnam. The Korean specimens clustered consistently with these conspecific individuals in a monophyletic clade corresponding to S. tetraporus . Pairwise genetic distances calculated using the Kimura 2 - parameter ( K 2 P) model showed a divergence of only 0.02–0.03 percentage points (PP) between the Korean specimen and the holotype and paratype sequences, indicating extremely low intraspecific variation. This level of genetic similarity strongly supports the assignment of the Korean specimen to S. tetraporus . In contrast, the Korean specimen exhibited substantial genetic divergence from the other recognized species within the genus. K 2 P distances ranging from 11.2 to 11.6 percentage points when compared to Strophidon ui Tanaka, 1918, with 11.4–11.6 PP against S. sathete , with 12.5–12.7 PP relative to S. dorsalis , clearly supporting interspecific separation. The mean interspecific K 2 P distance among species of Strophidon was 11 PP. Thus, the COI sequence data provided molecular evidence supporting the morphological identification of the Korean specimen as S. tetraporus and confirmed its placement within the current phylogenetic framework of the genus.

Figures

Figure 2. Preserved specimen of Strophidon tetraporus (MABIK PI 00060540, 2318 mm TL) collected from Heuksan-do Island, Korea.

Figure 3. Cephalic sensory pore pattern of Strophidon tetraporus (MABIK PI 00060540): AN: anterior nostril; PN: posterior nostril; IO: infraorbital; LL: branchial; POM: preoperculo- mandibular; SO: supraorbital.

Figure 4. Neighbor-joining tree based on mitochondrial COI sequences of Strophidon species. Numbers at each node indicate bootstrap support values (1000 replicates). The Korean specimen is marked in bold. Gymnothorax prionodon is selected as the outgroup.