Eptatretus wandoensis, Song & Kim, 2020

Song, Young Sun & Kim, Jin-Koo, 2020, A new species of hagfish, Eptatretus wandoensis sp. nov. (Agnatha, Myxinidae), from the southwestern Sea of Korea, ZooKeys 926, pp. 81-94: 81

publication ID

http://dx.doi.org/10.3897/zookeys.926.48745

publication LSID

lsid:zoobank.org:pub:5E83DB40-3A11-442E-85F3-6C8DCCF487E4

persistent identifier

http://treatment.plazi.org/id/39B19787-0894-5335-8F34-03B9F3CE2DD3

treatment provided by

ZooKeys by Pensoft

scientific name

Eptatretus wandoensis
status

sp. nov.

Eptatretus wandoensis   sp. nov. Figures 1 View Figure 1 , 2 View Figure 2 , 3 View Figure 3 , 4 View Figure 4 , 5 View Figure 5 , Table 1 New English name: Five-gilled white mid-dorsal line hagfish; new Korean name: Huin-jul-wae-meok-jang-eo

Type locality.

The coast of Yeoseo-do (southwestern Sea of Korea): Yeoseo-ri, Cheongsan-myeon, Wando-gun, Jeollanam-do, Republic of Korea, 33°59'56.5"N, 126°53'57.0"E, caught by fishing traps, 60-80 m (Fig. 1 View Figure 1 ).

Holotype.

PKU 62167, 292.0 mm TL, Yeoseo-ri, Cheongsan-myeon, Wando-gun, Jeollanam-do, Republic of Korea, 33°59'56.5"N, 126°53'57.0"E, caught by fishing traps, 60-80 m, 26 Jun 2018.

Paratypes.

PKU 62169 (1 specimen), 202.0 mm TL, Yeoseo-ri, Cheongsan-myeon, Wando-gun, Jeollanam-do, Republic of Korea, 33°59'56.5"N, 126°53'57.0"E, fishing trap, 60-80 m, 12 May 2018; PKU 62171, PKU 62173, 275.0-290.0 mm TL, Yeoseo-ri, Cheongsan-myeon, Wando-gun, Jeollanam-do, Republic of Korea, 33°59'56.5"N, 126°53'57.0"E, fishing trap, 60-80 m, 26 Jun 2018.

Diagnosis.

Gill apertures, 5; eyespots, conspicuous; fused cusps, 3/2; total cusps, 40-43; 1 GP at end of dental muscle; total slime pores, 74-82 (prebranchial, 14-18; branchial, 4; trunk, 46-49; tail, 9-11); branchial length, 5.2%-6.2% of TL; pharyngocutaneous duct confluent with last gill aperture; ventral artery splitting at approximately 3-4 GP; dorsal region with dark brown body color, ventral region with white body color; white mid-dorsal line, conspicuous.

Description.

Body elongated; laterally compressed at trunk and strongly compressed at tail (Fig. 2 View Figure 2 ). Rostrum slightly blunt and round (Fig. 3A View Figure 3 ). Nasal-sinus papilla absent. Eyespots present (Fig. 3A View Figure 3 ). Pre-eyespots shorter than branchial region (4.4%-4.9% of TL). Three pairs of barbels on head: first (1.5%-1.6% of TL) and second barbels (1.6%-1.9% of TL) nearly equal in size; third barbel is longer (2.1%-2.3% of TL) and tips of third barbels extend at the mouth (Fig. 3B View Figure 3 ). Five pairs of GP and apertures; each gill aperture arranged regularly spaced in a straight line (Fig. 3C View Figure 3 ). Teeth row comb-like, consisting of two rows with tips sharp and curved rearward (Fig. 4A View Figure 4 ); in the outer row, 3 multicusps and 7-8 unicusps; in the inner row, 2 multicusps and 8-9 unicusps; total number of cusps, 40-43. Dental muscle thick and long, posterior tip of dental muscle located in first GP (Fig. 4B View Figure 4 ). Slime pores: prebranchial, 14-18; branchial, 4; trunk, 46-49; tail, 9-11; total, 74-82. Body proportions are as follows: prebranchial length, 24.4%-26.3% of TL; branchial length, 5.2%-6.2% of TL; trunk length, 54.9%-59.3% of TL; tail length, 12.8%-14.0% of TL; cutaneous duct, 7.6%-9.3% of TL; branchial duct (with ventral fin-fold), 6.9%-9.7% of TL; and branchial duct (alone), 5.6%-7.7% of TL (Table 1). Posterior-most EBD confluent with pharyngocutaneous duct on left side, forming a larger aperture (Fig. 4B View Figure 4 ). All efferent branchial ducts are equal in length. VA consists of two SBAs and one medial section, bifurcating at approximately the third or fourth GP. First through third pairs of ABAs, which cannot be regarded as branches of the VA, branch from SBAs; however, fourth and fifth ABAs on left and right branch from the medial section of the ventral artery (Fig. 4B View Figure 4 ). Ventral fin-fold weakly developed or vestigial, beginning approximately at middle of body and extending to cloaca (Fig. 3D View Figure 3 ). Caudal fin-fold weakly developed, beginning posterior cloaca and extending around tail to dorsal surface.

Coloration when fresh: Body uniformly dark brown or purplish dorsally and white ventrally; white mid-dorsal line conspicuous, beginning from the upper region of the first prebranchial slime pore to around the tail. Eyespots conspicuous; whole barbels (rarely the tip) pale, and pale around mouth. Each gill aperture and pharyngocutaneous duct aperture with white margin; most slime pores blackish (except for tail region), tail slime pores same as surrounding color. White around cloaca; ventral fin-fold with a white line along the ventral midline; posterior margin of caudal fin pale (Fig. 2 View Figure 2 ).

Coloration when preserved: Body brown to dark brown dorsally and murky white ventrally (more conspicuous than fresh specimen). Eyespots conspicuous; all slime pores surrounded by conspicuous white ring. Each gill aperture and pharyngocutaneous duct aperture conspicuous; ventral fin-fold pale; white mid-dorsal line inconspicuous.

Distribution.

Southwestern Sea of Korea.

Biology.

Attains a maximum TL of 292.0 mm (fresh specimen); this specimen is female, without mature eggs in the body cavity. A female specimen of 290.0 mm TL carries approximately 20 developing eggs, which have no terminal anchor filaments or hooks; each egg approximately 4-7 mm in diameter and 10-12 mm in length.

Etymology.

The specific name, wandoensis   , refers to the type locality, in Korea.

Morphological comparisons

Eptatretus wandoensis   sp. nov. is most similar to Eptatetus burgeri   (Girard, 1855) and Eptatretus minor   Fernholm & Hubbs, 1981 due to the presence of a light mid-dorsal line, gill apertures regularly spaced in a straight line, and EBDs of equal length. These three species differ from each other in the number of gill apertures (5 for E. wandoensis   , compared to 6 for E. burgeri   and E. minor   ), body color (dark brown or purplish dorsally and white ventrally for E. wandoensis   , compared to brown for E. burgeri   and gray/brown pale for E. minor   ), prebranchial slime pores (14-18 for E. wandoensis   , compared to 18-23 for E. burgeri   ), total slime pores (74-82 for E. wandoensis   , compared to 81-92 for E. burgeri   ), ventral fin-fold (weakly developed for E. wandoensis   , compared to well developed for E. burgeri   ), multicusps (3/2 for E. wandoensis   , compared to 3/3 for E. minor   ), total cusps (40-43 for E. wandoensis   , compared to 46-52 for E. minor   ) (Table 1), nasal-sinus papillae (absent for E. wandoensis   , compared to paired for E. minor   ), and eyespots (present for E. wandoensis   , compared to absent for E. minor   ). Eptatretus wandoensis   sp. nov. can be distinguished from Eptatretus cheni   (Shen & Tao, 1975), Eptatretus nelsoni   (Kuo, Huang & Mok, 1994), and Eptatretus yangi   (Teng, 1958) by the presence of regularly spaced gill apertures in a linear (vs. irregular and crowded for E. cheni   , E. nelsoni   , and E. yangi   ) arrangement; equal length of all EBDs (vs. length of first efferent branchial duct notably longer than that of the most posterior efferent branchial duct); 40-43 total cusps (vs. 50-53 for E. cheni   ; 32-40 for E. nelsoni   and E. yangi   ); 4 branchial slime pores (vs. no branchial slime pores); prebranchial length, 24.4%-26.3% of TL (vs. more than 29.0% of TL); branchial length, 5.2%-5.9% of TL (vs. less than 3.4% of TL); trunk length, 54.9-59.3% of TL (vs. less than 54.9%); eyespots conspicuous (vs. inconspicuous), and dorsal dark brown and ventral white body color (vs. brownish-grey). In comparison to Eptatretus   species occurring in Korean and Japanese waters, this new species is well distinguished from the three most common hagfishes, Eptatretus atami   (Dean, 1904), Eptatretus walkeri   (McMillan & Wisner, 2004), and Eptatretus okinoseanus   (Dean, 1904) based on the difference of gill apertures (5 in E. wandoensis   sp. nov. vs. 6 in E. atami   and E. walkeri   vs. 8 in E. okinoseanus   ), branchial slime pores (4, 0-1, 0, and 6-8), and a white mid-dorsal line (present, absent, absent, and absent) (Table 2).

Genetic comparisons

Differences among mtDNA sequences obtained from the holotype and paratypes of Eptatretus wandoensis   sp. nov. were consistent with species-level divergences in other hagfish species ( Fernholm et al. 2013). The phylogenetic relationships of myxinid species, inferred from neighbor-joining trees, showed large genetic distances between similar hagfish species using mtDNA 16S rRNA (477 bp) and cytochrome c oxidase subunit I (COI) (466 bp) sequences. Eptatretus wandoensis   sp. nov. is separated from other congeneric species by high genetic divergences of 0.9%-7.5% in 16S rRNA sequences and 4.9%-13.9% in COI sequences (Fig. 5 View Figure 5 ). The respective genetic distances between this species and E. burgeri   and E. minor   were 0.9% and 4.5% in 16S rRNA sequences and 8.5% and 13.9% in COI sequences. In addition, phylogenetic analysis of 16S rRNA sequences showed that E. wandoensis   sp. nov. is well separated from other five-gilled hagfishes ( E. cheni   , E. nelsoni   , and E. yangi   ), with genetic differences of 7.5%, 1.4%, and 1.6%, respectively. Eptatretus cheni   is located at a basal position of hagfishes and well nested in the Eptatretus   clade.

Kingdom

Animalia

Phylum

Chordata

Class

Myxini

Order

Myxiniformes

Family

Myxinidae

Genus

Eptatretus