Research Article |
Corresponding author: Jin-Koo Kim ( taengko@hanmail.net ) Academic editor: Maria Elina Bichuette
© 2020 Young Sun Song, Jin-Koo Kim.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Song YS, Kim J-K (2020) A new species of hagfish, Eptatretus wandoensis sp. nov. (Agnatha, Myxinidae), from the southwestern Sea of Korea. ZooKeys 926: 81-94. https://doi.org/10.3897/zookeys.926.48745
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Four specimens of the five-gilled white mid-dorsal line hagfish, Eptatretus wandoensis sp. nov. were recently collected from the southwestern Sea of Korea (Wando). This new species has five pairs of gill apertures, 14–18 prebranchial slime pores, 4 branchial slime pores, a dark brown back with a white mid-dorsal line and a white belly. These hagfish are similar to Eptatretus burgeri and Eptatretus minor in having a white mid-dorsal line, but can be readily distinguished by the numbers of gill apertures (5 vs. 6–7), gill pouches (5 vs. 6), and prebranchial slime pores (14–18 vs. > 18), as well as the body color (dark brown back vs. gray or brown pale). In terms of genetic differences, Eptatretus wandoensis could be clearly distinguished from E. burgeri (0.9% in 16S rRNA and 8.5% in cytochrome c oxidase subunit I sequences) and E. minor (4.5% and 13.9%).
mitochondrial DNA, morphology, myxinid, Myxiniformes, Northwest Pacific, taxonomy
Myxinidae (hagfishes) are currently classified into six genera and 81 species worldwide (
We obtained four specimens (202.0–292.0 mm total length) from Yeoseo-ri, Wando-gun in Korean waters in 2018, caught by fishing trapping and bought to the fish markets (Fig.
To compare molecular characters, total genomic DNA was extracted from the muscle tissues using 10% Chelex 100 resin (Bio-Rad, Hercules, CA) and PCR was then performed for mitochondrial DNA 16S ribosomal RNA (16S rRNA) and cytochrome c oxidase subunit I (COI), using an MJ Mini Thermal Cycler PTC-1148 (Bio-Rad) in mixtures consisting 1 μL of genomic DNA, 2 μL of 10× PCR buffer, 1.6 μL of 2.5 mM dNTPs, 0.5 μL of each primer, 0.1 μL of TaKaRa EX-Taq polymerase (TaKaRa Bio Inc., Kyoto, Japan), and distilled water to bring the final volume to 20 μL. PCR products were amplified using universal primers: VF2-F (5’-TCA ACC AAC CAC AAA GAC ATT GGC AC-3’) and FishR2-R (5’-ACT TCA GGG TGA CCG AAG AAT CAG AA-3’) designed by
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.
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.
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.
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.
Morphometric and meristic measurements of Eptatretus wandoensis sp. nov., and congeneric species with five gill apertures (E. cheni, E. nelsoni and E. yangi) and white mid-dorsal line (E. burgeri and E. minor).
Eptatretus wandoensis sp. nov. | E. cheni* | E. nelsoni* | E. yangi* | E. burgeri* | E. minor** | ||
---|---|---|---|---|---|---|---|
Holotype | Paratypes (3) | ||||||
Gill aperture (GA) | 5 | 5 | 5 | 5 | 5 | 6–7 | 6 |
Gill pouch (GP) | 5 | 5 | 5 | 5 | 5 | 6 | 6 |
NSP | absent | absent | absent | absent | absent | absent | paired |
Cusps | |||||||
MUC (multi) | 3/2 | 3/2 | 3/3 | 3/2 | 3/2 | 3/2 | 3/3 |
AUC (outer) | 7 | 7–8 | 9–11 | 5–8 | 5–8 | 6–8 | 8–11 |
PUC (inner) | 8 | 8–9 | 9–10 | 5–8 | 6–9 | 7–9 | 8–10 |
Total Cusps | 42 | 40–43 | 50–53 | 32–40 | 32–40 | 35–42 | 46–54 |
Slime pores | |||||||
Prebranchial | 14 | 15–18 | 24–27 | 13–20 | 16–23 | 18–23 | 15–18 |
Branchial | 4 | 4 | 0 | 0 | 0 | 4–5 | 4–6 |
Trunk | 47 | 46–49 | 41–47 | 33–39 | 39–47 | 45–51 | 41–48 |
Tail | 11 | 9–11 | 7–10 | 6–10 | 7–12 | 11–14 | 11–14 |
Total pores | 76 | 74–82 | 75–81 | 57–67 | 68–79 | 81–92 | 74–82 |
Length in % of TL | |||||||
Prebranchial | 24.7 | 24.4–26.3 (25.3) | 33.3–35.5 | 30.5–32.6 | 29.2–32.0 | 25.2–29.6 | 20.1–25.9 |
Branchial | 5.9 | 5.2–5.8 (5.5) | 2.2–3.4 | 1.1–2.8 | 1.1–1.7 | 6.2–7.8 | 5.1–7.2 |
Trunk | 56.5 | 54.9–59.3 (56.9) | 45.9–50.8 | 49.5–52.6 | 53.2–54.9 | 47.6–55.0 | 50.6–55.9 |
Tail | 13.4 | 12.8–14.0 (13.5) | 13.2–16.7 | 15.0–18.0 | 12.2–15.6 | 13.2–17.0 | 13.9–18.3 |
Nostril to mouth | 3.4 | 3.7–3.8 (3.8) | – | – | – | – | – |
Nostril width | 1.7 | 0.8–1.5 (1.2) | – | – | – | – | – |
Nostril length | 0.6 | 0.7–1.6 (1.1) | – | – | – | – | – |
Mouth width | 3.2 | 3.3–3.8 (3.6) | – | – | – | – | – |
Pre-eyespot to nostril | 4.9 | 4.4–5.2 (4.8) | – | – | – | – | – |
Depth in % of TL | |||||||
w/VFF | 7.5 | 6.9–9.7 (8.3) | 8.1–9.0 | 15.0–15.5 | 6.9–10.4 | 4.7–8.5 | 7.1–11.4 |
Branchial region | 6.3 | 5.6–7.7 (6.7) | – | – | – | – | – |
Over caudal | 7.8 | 7.6–9.3 (8.6) | 7.6–10.2 | 8.9–10.1 | 6.5–10.0 | 5.1–8.5 | 5.3–11.6 |
Body elongated; laterally compressed at trunk and strongly compressed at tail (Fig.
Eptatretus wandoensis sp. nov. PKU 62167, prior to preservation A head dorsal view, white arrow indicates a white mid-dorsal line B head ventral view C gill apertures (GA) and pharyngocutaneous duct (PCD), note the location of GA and PCD D ventral view of body, black arrow indicates the ventral fin-fold (VFF) E dorsal region of body with a white mid-dorsal line.
Anatomical morphology of Eptatretus wandoensis sp. nov. PKU 62167. A palatine tooth, anterior unicusps (AUC) and posterior unicusps (PUC) B branchial region dissected, gill pouches (GP), median ventral aorta (MVA), separated ventral aorta (SVA), efferent branchial duct (EBD), pharyngocutaneous duct (PCD), dental muscle (DM), liver (L), and heart (H).
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.
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.
Southwestern Sea of Korea.
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.
The specific name, wandoensis, refers to the type locality, in Korea.
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
Comparison of meristic and proportional measurements among Eptatretus species occurring in Korean and Japanese waters.
Characters | E. wandoensis sp. nov. | E. atami* | E. walkeri | E. okinoseanus* |
---|---|---|---|---|
Gill aperture | 5 | 6 | 6 | 8 |
Gill pouch | 5 | 6 | 6 | 8 |
NSP | absent | absent | absent | absent |
Cusps | ||||
MUC | 3/2 | 3/3 | 3/2 | 3/2 |
AUC | 7–8 | 9–10 | 6–9 | 7–10 |
PUC | 8–9 | 8–10 | 7–9 | 7–10 |
Total | 40–43 | 47–52 | 36–44 | 40–49 |
Slime pores | ||||
Prebranchial | 14–18 | 12–19 | 15–22 | 13–17 |
Branchial | 4 | 0–1 | 0 | 6–8 |
Trunk | 46–49 | 43–47 | 40–48 | 54–61 |
Tail | 9–11 | 9–12 | 8–13 | 10–14 |
Total pores | 74–82 | 71–78 | 68–79 | 87–97 |
Length in % of TL | ||||
Prebranchial | 24.4–26.3 | 26.6–30.2 | 24.2–39.1 | 19.2–22.6 |
Branchial | 5.2–5.9 | 1.3–4.2 | 2.0–3.8 | 6.2–9.2 |
Trunk | 54.9–59.3 | 53.9–56.1 | 50.8–68.6 | 50.4–59.4 |
Tail | 12.8–14.0 | 11.1–14.2 | 10.7–16.1 | 12.7–15.5 |
Depth (mm) | ||||
w/VFF | 6.9–9.7 | 8.1–9.0 | 5.0–11.1 | 5.7–8.1 |
Over caudal | 7.6–9.3 | 7.4–8.8 | 6.3–11.4 | 6.2–9.0 |
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 (
Phylogenetic tree of hagfishes based on mitochondrial DNA sequences, constructed with the Neighbor-joining (NJ) method using Kimura 2-parameter distances A mitochondrial DNA 16S rRNA sequences B mitochondrial DNA cytochrome c oxidase subunit I (COI) sequences. Numbers above tree branches are bootstrap values based on 1000 replicates. Scale bar represent nucleotide substitutions per site.
Eptatretus wandoensis sp. nov. is one of many new hagfish species recently discovered in the northwest Pacific Ocean. Thus far, six hagfish species with five gill apertures have been reported worldwide (
In terms of geographic distribution, Eptatretus minor occurs in the Gulf of Mexico and Atlantic Ocean, while E. burgeri coexists with this new species in the same region of coastal Korea. In the comparison of depths, Eptatretus wandoensis sp. nov. is collected from depths between 60 to 80 m, and E. burgeri is known as between 5 and 270 m, and E. minor is known as between 300 and 400 m (
This research was supported by the Marine Biotechnology Program of the Korea Institute of Marine Science and Technology Promotion (KIMST) funded by the Ministry of Oceans and Fisheries (MOF) (No. 20170431).