Strophidon dorsalis (Seale, 1917)

Cabebe-Barnuevo, Roxanne A., Obar, El Andro A., Penuela, Dianne Frances A., Motomura, Hiroyuki, Babaran, Ricardo P. & Malay, Maria Celia D., 2023, Two new records of moray eels representing genera Gymnothorax and Strophidon (Actinopterygii: Anguilliformes: Muraenidae) from the Philippines, Acta Ichthyologica et Piscatoria 53, pp. 217-226 : 217

Strophidon dorsalis (Seale, 1917)

English common name: three-pore moray (Fig. 4

Material examined.

UPVMI-03151, 777 mm TL, off Batan , Aklan Province, Panay Island, Philippines, bottom set gillnet, 31 May 2021, Sunshine Sucgang leg.

Morphological diagnosis and description.

Body elongated and cylindrical, becoming compressed behind anus towards tail area. Head moderately long with wrinkled skin. Eyes moderate in size, and situated closer to snout (11% of HL) than rear of lower jaw (18% of HL, see Table 1 ). Mouth large; snout short and blunt; anterior nostril located at snout tip, short and tubular; posterior nostril located above anterior margin of eye, large and circular; upper jaw slightly more pronounced relative to lower jaw; teeth on both jaws sharply pointed. Dorsal-fin base very long; origin anterior to gill opening. Anal-fin base shorter; origin just behind anus. Caudal fin slightly damaged but still visibly connected with dorsal and anal fins. Pectoral and pelvic fins absent. Gill opening moderately large and elongated; located on lower portion of body. Anus moderate in size, circular, and positioned anterior to midpoint of body. Supraorbital pores 3: first pore located on snout tip, small and circular; second pore located above anterior nostril; third located above first infraorbital pore, largest in size and somewhat elongated circular pore. Infraorbital pores 4, located along upper jaw; first pore located below base of anterior nostril; second pore between anterior nostril and anterior margin of eye; third pore below ventral margin of eye; fourth pore located beyond posterior margin of eye. Preoperculo-mandibular pores 6, located along lower jaw; all pores positioned anterior to rictus. Branchial pores 2, located along postero-dorsal head anterior to gill opening. Teeth on both jaws pointed; intermaxillary teeth 6; median intermaxillary teeth 3; inner maxillary teeth 5; vomerine teeth 4; inner dentary teeth 4.

Fresh coloration.

Body brown becoming dark towards caudal area; margins of dorsal and anal fins dark brown; caudal fins dark brown to black.

Color of preserved specimen.

Body uniformly dark brown; fins dark brown to black.

Distribution.

Tropical to subtropical Indo-West Pacific Ocean. Specific reports are summarized in Table 2 .

DNA Barcode.

A 568 bp COI sequence fragment was submitted to GenBank under accession number OR214977.

Remarks.

Strophidon dorsalis was originally placed in the genus Gymnothorax by Seale (1917) based on collections from Hong Kong. However, Loh et al. (2015) suggested that Gymnothorax dorsalis belongs to the genus Strophidon based on molecular data and similarities in some morphological features. Following the work of Loh et al. (2015), S. dorsalis was reported from Taiwan ( Ho et al. 2015; Huang et al. 2020), Vietnam ( Loh et al. 2015; Huang et al. 2020), India ( Mohapatra et al. 2016, 2021), and Korea ( Kang et al. 2020). Based on the report of Böhlke (1997), this species can be found in depths down to 110 m. The largest recorded specimen, measuring 1262 mm TL, collected from Vietnam was reported by Huang et al. (2020). Randall and Lim (2000) included Gymnothorax dorsalis on their list of fishes from the South China Sea which covers Taiwan, the Philippines, and Borneo. However, it was not specified whether the specimen was collected in Philippine waters. As a result, this study confirms the presence of the species in the Philippine waters. Table 2 provides a list of all published geographic records of the species while Table 3 includes other species within the genus Strophidon reported in the country.

This species can be distinguished from its congeners based on the following combination of characters: body uniformly brown, anus located anterior to the midpoint of the body, 3-4 infraorbital pores, 2-7 inner maxillary teeth, 3-5 inner dentary teeth, 62-73 pre-anal vertebrae, and 155-174 total vertebrae ( Böhlke and Smith 2002; Huang et al. 2020). Strophidon dorsalis and S. sathete (Hamilton, 1822) are considered sister species ( Loh et al. 2015). Based on the summarized morphological comparisons of the species under the genus Strophidon given by Huang et al. (2020), they have overlapping meristic counts which include infraorbital pores (both 3-4), supraorbital (both 3), preoperculo-mandibular (5-7 vs. 6-7), branchial pores (2-6 vs. 2-7), and pre-anal vertebrae (62-73 vs. 73-82). Moreover, these two species have unpatterned body coloration, short snouts, and an anus located before body mid-length. However, S. dorsalis can further be distinguished from S. sathete based on the number of teeth on the inner maxillary (2-7 vs. 10-15), teeth on the inner dentary (3-5 vs. 6-11), and total vertebrae (155-174 vs. 187-213). The specimen used in the study was initially identified as S. dorsalis based on the number of infraorbital pores (4) and fewer teeth on the lower jaw, and this was supported by the generated COI sequence.

Figures

Figure 4. Strophidon dorsalis, UPVMI- 03151, 777 mm TL, off Batan, Aklan, Philippines.