Gymnothorax melanosomatus, Loh, Kar-Hoe, Shao, Kwang-Tsao & Chen, Hong-Ming, 2011

Loh, Kar-Hoe, Shao, Kwang-Tsao & Chen, Hong-Ming, 2011, Gymnothorax melanosomatus, a new moray eel (Teleostei: Anguilliformes: Muraenidae) from southeastern Taiwan, Zootaxa 3134, pp. 43-52 : 44-50

Gymnothorax melanosomatus new species

New English name: Black body moray eel ( Figures 1–2 , Tables 1–2)

Holotype: TOU-AE 1991, 11 Aug. 2008 (male, 496 mm TL), off-shore from Changbin, Taitung, Taiwan, longline, 50–100 m, collected by Captain J.S. Chiou.

Paratypes: 7 specimens. ASIZP 0072170, 27 Jul. 2007; TOU-AE 0 627, 28 Oct. 2004; TOU-AE 1879, 6 Oct. 2005 (3 males, 433–522 mm TL); ASIZP 0 0 72171, 2 Aug. 2005 (female, 407 mm TL), all from Changbin, Taitung, longline, 50– 150 m. TOU-AE 3774, 16 Nov. 2006 (male, 504 mm TL); TOU-AE 3775, 16 Nov. 2006; TOU-AE 5095, 11 Aug. 2008 (female, 447–504 mm TL), all from Shihtiping, Hualien, longline, 70– 180 m. All collected by Captain J.S. Chiou.

Diagnosis. Body greatly elongate, depth at gill opening 33.2 (27.1–44.8) in total length, anus behind midbody; body and fins unpatterned, uniformly black-brown; preanal length 1.71 in TL, head length 10.30 in TL. Maxillary and dentary teeth uniserial, few in number, long and needle-like. Mean vertebral formula 6-108-207.

Description. The proportions as percentage of total length or head length, vertebral counts, teeth counts and gonadal type of the type series are provided in Table 1. Tail length 2.4 (2.3–2.5) in TL, trunk length 1.9 (1.9–2.1), depth at gill opening 33.2 (27.1– 44.8), depth at anus 45.2 (35.9–46.6), head length 10.8 (9.5–10.8); Length of upper jaw 2.4 (2.4–3.1) in HL, length of lower jaw 2.6 (2.6–3.2), interorbital width 7.9 (7.1–10.8), snout length 5.1 (4.9–6.7), eye diameter 8.6 (8.6–12.1).

Teeth uniserial ( Figure 3 ), median intermaxillary teeth counts are different in each sex, 2–3 in female, 0 in male; maxillary teeth uniserial 6 (6–7), each side of intermaxillary teeth 6 (4–8), vomerine teeth uniserial 4 (0–7), each side of dentary teeth uniserial 11 (10–12). Head pores typical, three superorbital pores, four infraorbital pores, six mandibular pores. Two small branchial pores before gill opening. Gill opening below midside. Total vertebrae 207 (201–211), predorsal vertebrae 5 (4–7), preanal vertebrae 109 (105–109).

Color. When fresh, head and body mostly black in color, without any spots or pattern; and irises of eyes yellow. Body color after preserved in formalin or alcohol would be blackish or grey, irises become white.

Distribution. From southeastern Taiwan: off Changbin, Taitung to Shihtiping, Hualien City. Depth range is from 50–180 meters.

Biology. A small bodied species with maximun length 522 mm TL in adult male and 504 mm TL in adult female. Three females (407–504 mm TL) all were gravid, distended with 1.0– 1.2 mm diameter eggs, and fecundity 2960 ± 818 eggs respectively.

Etymology. The species name is from the Greek melano (black) and somat- (body), in reference to its black body color.

Remarks. Gymnothorax melanosomatus new species is clearly distinct from its closest congener, G. prolatus Sasaki and Amaoka (1991) , in the following character combinations, given as mean (range): (1) longer preanal length 58.5 (56.6–59.5) [vs. 48.9 (46.6–50.4)] % of total length; (2) shorter snout length 17.8 (14.9–20.5) [vs. 20.0 (17.3–21.4)] % of head length; (3) interorbital width 12.2 (9.2–14.1) [vs. 14.3 (10.7– 17.8)] % of head length; (4) more preanal vertebrae 108 (105–109) [vs. 80 (74–86)]; (5) more total vertebrae 207 (201–211) [vs. 183 (174– 190)]; and (6) black [vs. brown] body (Table 2).

The new moray eel is easily distinguished from the other similar species Strophidon sathete ( Hamilton, 1822) , by the following features, (1) longer preanal length 58.5 (56.6–59.5) [vs. 43.7 (42.2–45.4)] % of total length (Table 2); (2) longer trunk length 50.1 (48.8–51.8) [vs. 34.7 (32.8–36.2) % of total length; (3) longer snout length 17.8 (14.9–20.5) [vs. 11.1 (9.7–13.9)] % of head length; (4) longer interorbital width 12.2 (9.2–14.1) [vs. 9.0 (7.3– 11.4)] % of head length; (4) more preanal vertebrae 108 (105–109) [vs. 81 (78–83)]; (5) more total vertebrae 207 (201–211) [vs. 194 (188–200)]; and (6) maxillary and dentary teeth uniserial vs biserial.

We place the new species in Gymnothorax senso latu but not Strophidon based on its dentition (uniserial vs. biserial jaw teeth), larger eye diameter (8.2–11.7 vs. 2.9–6.8 % of HL), eye position (mid-jaw vs. far forward in upper jaw), shorter tail (40.5–43.4 vs. 54.6–57.8 % of TL).

We also note that the new species differs from another related species, G. polyspondylus Böhlke and Randall (2000) by its longer preanal length 58.5 [vs. 43.3] % of total length, more preanal vertebrae 109 [vs. 89], fewer total vertebrae 207 [vs. 233] (Table 2); and fewer intermaxillary teeth 4–8 [vs. 11-11].

Figures

FIGURE 1. Holotype of Gymnothorax melanosomatus, TOU-AE 1991, 496 mm TL, male.

FIGURE 2. Head of holotype of Gymnothorax melanosomatus, TOU-AE 1991, 496 mm TL.

FIGURE 3. Diagrams of dentition and placement of jaw pores from the type specimens of Gymnothorax melanosomatus, new species: A, Holotype, male, TOU-AE 1991, 496 mm TL; B, paratype, female, TOU-AE 5095, 447 mm TL.