Heteroconger fugax, Koeda & Fujii & Motomura, 2018

Koeda, Keita, Fujii, Takuma & Motomura, Hiroyuki, 2018, A new garden eel, Heteroconger fugax (Congridae: Heterocongrinae), from the northwestern Pacific Ocean, Zootaxa 4418 (3), pp. 287-295 : 288-294

Heteroconger fugax sp. nov.

New standard Japanese name: Nigemizu-chin'anago New English name: Shy Garden Eel Figures 1 ¯4; Table 1

Heteroconger lentignosus (not Böhlke & Randall 1981): Senou et al. 2007:48, fig. 2 (Irabu-jima island, Miyako Islands, Japan, underwater photograph only).

Holotype. KAUM –I. 95673, 729.0 mm TL, off Shirahama , Setouchi , Amami-oshima island, Amami Islands, Kagoshima, Japan (28°12ʹN, 129°16ʹE), 32.5 m depth, 11 November 2016, coll. by hands, T. Fujii and K. Koeda.

Diagnosis. A species of Heteroconger with the following combination of characters: body extremely slender, depth 1.2% TL and 1.0% TL at gill opening and anus, respectively; pre-dorsal-fin and pre-anal-fin vertebrae 8 and 67, respectively, total vertebrae 197; origin of dorsal fin slightly posterior to tip of appressed pectoral fin; numerus small conical cirri on chin; 2–3 rows of dark spots above and below lateral line; 6–7 rows of dark spots on interorbital space; large distinct white rectangular blotch on opercle; number and density of spots on head greater than those on body; lips spotted; ground color of body uniformly cream, without microscopic dark speckles.

Description. Pre-dorsal-fin vertebrae 8; Pre-anal-fin vertebrae 67; total vertebrae 197; lateral-line pores before pectoral fin 7; lateral-line pores before anus 65; pectoral-fin rays 9; dorsal-fin rays before anus 182; total dorsal-fin rays 590; anal-fin rays 425; caudal-fin rays 9 + 8. Head pores (left side): supraorbital series 1 + 4; infraorbital series 3 + 3; preoperculomandibular series 5 + 3; supratemporal series 3.

As percent of TL: HL 3.4%; Snout-anus length 30.1%; pre-dorsal-fin length 4.0%, trunk length 26.4%; tail length 67.4%; depth at gill opening 1.2%; depth at anus 1.0%. As percent of snout-anus length: HL 11.5%; predorsal-fin length 13.7%. As percent of HL: snout length 16.8%; eye diameter 19.2%; mouth width 24.5%; gill opening 9.1%; interbranchial distance 21.4%; depth at gill opening 34.2%; depth at anus 27.9%.

Body extremely elongate, body depth similar throughout; greatest depth at gill opening. Body slightly compressed laterally along head, progressively more so to tail tip; tail much longer than body, anus at about 30% total length. Head slightly compressed ventrally; snout short, rounded. Mouth with fleshy lips; distinct fold extending to end of lips; upper lip confluent medially, enclosing anterior nostrils; posterior nostril located just in front of eye; no flap around posterior nostril; mouth strongly oblique, posterior margin of upper lip reaching below anterior rim of pupil; numerous conical cirri on chin ( Fig. 2 ). Eye large, oval, weakly intruding into dorsal profile. Throat with developed folds extending to branchial aperture. Gill opening vertically slit, located before pectoral fins.

Pectoral fins a small rounded flap; origin of dorsal-fin posterior to tip of appressed pectoral fin; dorsal and anal fins very low; tip of tail hardened, inflexible; caudal-fin rays not readily visible.

Teeth small, numerous, in broad multi-serial patches anteriorly on jaws and vomer ( Fig. 3 ); patches narrowing posteriorly to a point on vomer, or to 1 or 2 rows on jaws; posterior portion of maxillary patch flared laterally; anterior intermaxillary-vomerine teeth larger than other teeth.

Live and fresh coloration ( Figs. 1 , 4 ). Body and head with small, round, discrete dark spots overlying a uniformly cream ground color, without microscopic dark speckles; dark spots in 2 or 3 irregular rows above and below lateral line; spots more numerous and crowded over entire head, smaller ventrally; ca. 20 spots surrounding eye; 6–7 rows of spots across interorbital area; a large distinct white rectangular blotch on opercle; three dark spots just anterior to white blotch confluent with each other to form an inverted fiddle-shaped blotch; fins semitransparent. Tip of numerous small conical cirri on chin dusky.

Coloration of preserved. Coloration of body and head almost unchanged from live and fresh; dark spots on body and white blotch on opercle clearly distinguishable from background.

Etymology. The specific name of the new species, fugax , means “shy” in Greek, in reference to their bashful nature.

Distribution. Heteroconger fugax sp. nov. is currently known from the northwestern Pacific Ocean. The holotype was collected off Shirahama on the south coast of Amami-oshima island, Ryukyu Archipelago ( Japan), facing the Oshima Strait; no other specimens appear to have been collected. Underwater photographs of colonies of the species were taken at the type locality in depths of 28.0– 32.5 m ( Fig. 4 ), in addition to underwater photographs of single individuals taken off Irabu-jima island, Miyako Islands ( Japan)(KPM-NR 67322, 10– 11 m depth), off northern Mindoro Island ( Philippines)(KPM-NR 88296, 10 m) and Mabul Island, northeastern Borneo (KPM-NR 23927, 12 m).

Habitat and ecological notes. Heteroconger fugax sp. nov. forms colonies in muddy bottoms at depths of ca. 30 m off Amami-oshima island, being absent from shallower or deeper areas around the type locality. However, photographic records from other localities were taken over sandy bottoms at depths of 10– 12 m.

Although sometimes exiting vertically more than 30 cm from their burrows, individuals immediately disappeared into the burrow when approached, their head holding steadily at ca. several centimeters depth (still visible from directly above the burrows).

As a result of poor water visibility at the type locality (<10 m), an accurate count of individuals in the colony was difficult. However, about 40 individuals were estimated for each colony, from a combination of underwater photographs and number of burrows.

Remarks. Heteroconger fugax sp. nov. resembles H. tomberua Castle & Randall 1999 , both species having a very slender body with numerous small dark spots on the body and head, about 200 vertebrae, and similar counts of head pores ( Castle & Randall 1999). However, a comparison of H. fugax with the holotype and the original description of H. tomberua (USNM 349761: Fig. 5 ) showed that the former can be distinguished by the dorsal fin originating posterior to the appressed pectoral-fin tip (vs. anterior in H. tomberua ), numerous conical cirri on the chin (vs. absent) ( Fig. 2 ), a large distinct white rectangular blotch on the opercle (vs. none), dense dark spots over the entire head, including lips (vs. absent on throat, snout and lower jaws), and lacking microscopic dark speckles on the body (vs. present) ( Fig. 1 ). In addition, H. fugax differs from H. tomberua in having slightly higher counts of preanal vertebrae (67 in H. fugax vs. 58–64 in H. tomberua ), lateral-line pores before the anus (65 vs. 56–63), and shorter head length (11.5% in HL vs. 12.5–16.3%) and eye diameter (19.2% in HL vs. 22.8–27.6%) ( Table 1).

Heteroconger cobra Böhlke & Randall 1981 , H. mercyae Allen & Erdmann 2009 and H. tricia Castle & Randall 1999 all have> 196 vertebrae (as does H. fugax ). However, the coloration of these species, e.g. large black saddle on the head enclosing a U-shaped white marking, and pair of widely spaced black saddles with white central bar on the anterior body in H. cobra ; zebra-like pattern of black and white bars in H. mercyae ; and two rows of large round spots on the body in H. tricia ; are very different from that of H. fugax . The remaining eight Heteroconger species have <175 vertebrae ( Castle & Randall 1999; Allen & Erdmann 2009, 2012).

Heteroconger chapmani (Herre 1923) was regarded as “unidentifiable” in the revision of the subfamily Heterocongrinae because of an inadequately description (of 2 poorly preserved Philippine specimens), compounded by a lack of type specimens, color description or vertebral counts ( Castle & Randall 1999). The species was omitted by Allen & Erdmann (2009) in their comparison of a newly undescribed species with valid congeners, and we followed their opinion.

Senou et al. (2007) reported H. lentiginosus Böhlke & Randall 1981 from Irabu-jima island in the Miyako Islands, Japan, based on an underwater photograph (KPM-NR 6 7322). The photograph shows clearly a large distinct white rectangular blotch on the opercle (vs. absent in H. lentiginosus ), circular numerous dark spots (vs. freckles) and head uniformly covered by spots (vs. uniformly dark brown), and is identical with H. fugax .

Biswas et al. (2012) reported a species resembling H. fugax from Kalakkam, east coast of India, as H. tomberua , based on a specimen (ZSI F-10575/2) collected from the traveling water screen of the seawater cooling system of the nearby nuclear power station. The specimen was similar to H. fugax , having an extremely slender body (depth 1.16% of TL), 191 total vertebrae, dark spots on the head and body, a large distinct white blotch on the opercle, spots on the head more numerous and denser than on the body, lips spotted, and body ground color uniformly cream, lacking microscopic dark speckles. However, H. fugax differed in having the dorsal-fin origin posterior to tip of the appressed pectoral fin (vs. above middle of pectoral fin), 2–3 rows of dark spots above and below the lateral line (vs. 3–4 rows of dark spots restricted to anterior half of body, faint or lacking posteriorly), 6–7 row of spots across interorbital area (vs. 11–13 rows of spots), and numerous crowded dark spots over entire head (vs. ventral half of head lacking dark spots) all from Biswas et al. (2012). Clearly, Biswas et al.’s (2012) specimen is distinct from H. fugax , as well as from all other known species of Heteroconger , and remains to be formally identified.

Figures

FIGURE 1. Fresh holotype of Heteroconger fugax sp. nov. from Amami-oshima island, Japan. KAUM–I. 95673, 729.0 mm TL.Red and green arrows indiCate vertiCal positions of tip of appressed peCtoral fin and origin of dorsal fin, respeCtively.

FIGURE 2. Numerous small ConiCal Cirri on the Chin of the holotype of Heteroconger fugax sp. nov. KAUM–I.95673, 729.0 mm TL.

FIGURE 3. Dentition of upper and lower jaws of the holotype of Heteroconger fugax sp. nov. KAUM–I. 95673, 729.0 mm TL.

FIGURE 4. Underwater photographs of a Colony (A) and single individuals (B–D) of Heteroconger fugax sp. nov. A: off Amami-oshima island, Japan; B: off Irabu-jima island, Miyako Islands, Japan, 10–11 m depth (KPM-NR 67322); C: off Mindoro Island, Philippines, 10 m depth (KPM-NR 88296); D: off Mabul Island, Malaysia, 12 m depth (KPM-NR 23927)

FIGURE 5. Preserved holotype of Heteroconger tomberua. USNM 349761, 401 mm TL. Red and green arrows indiCate vertiCal positions of tip of appressed peCtoralfin and origin of dorsal fin, respeCtively.