Bascanichthys ryukyuensis Hibino, Yamashita & Sakurai, 2022

Hibino, Yusuke, Yamashita, Kenta, Sakurai, You & Ho, Hsuan-Ching, 2022, Two new species of the snake eel genus Bascanichthys (Anguilliformes: Ophichthidae) from the northwestern Pacific, Zootaxa 5189 (1), pp. 103-113 : 106-110

Bascanichthys ryukyuensis Hibino, Yamashita & Sakurai , sp. nov.

New standard Japanese name: Kazura-umihebi

New English name: Vine-like Sand Eel

Figs. 3‒4 ; Table 1

urn:lsid:zoobank.org:act:4B91D8E3-F13A-4B4A-9FDC-6F4F51049E26

Bascanichthys sp. : Hibino et al. 2021: 17, fig. 6a (Okinawa-jima Island, Japan).

Holotype. FRLM 52250, 627 mm TL, female, Yakena , eastern coast of Yokatsu Peninsula , Okinawa-jima Island, Ryukyu Islands, Japan, stranded specimen found at beach (0–1 m depth) around seagrass bed, 26 Jan. 2016, coll. K. Yamashita.

Paratype. FRLM 52251, 516 mm TL, male, collected with holotype .

Diagnosis. An extremely elongate species of Bascanichthys with the following combination of characters: head 3.7–4.3% TL; tail 43.3–44.2% TL; predorsal-fin length 40.7–45.4% of head length; snout length 11.3–13.1% of head length; body pale brown, head without distinct dark bands after preservation; lateral-line pores anterior to anus 114–118; total vertebrae 207–216, mean vertebral formula 2-116-212; and dorsal-fin origin slightly before middle of head and before first lateral-line pore.

Description. Counts and measurements are shown in Table 1 . Body extremely elongate ( Fig. 3A ), subcylindrical, tail laterally compressed posteriorly, its depth at gill opening 83‒91 times in TL. Skin generally smooth, with weak longitudinal wrinkles dorsally; tail shorter than head and trunk, preanal length 1.8 in TL. Head small, skin with many longitudinal wrinkles except snout; dorsal contour smoothly curved; branchial basket convex, well-expanded, its deepest depth 2.4–2.7 times in HL.

Snout stout and broad, tip weakly pointed and relatively pointed from dorsal view ( Fig. 3B, C ), its length 7.6–8.8 in HL; posterior half of snout bisected by a deep groove ventrally; interorbital region smooth, slightly convex. Eye small, positioned about mid-jaw, its diameter 3.8–5.0 in upper jaw length and 18.4–19.7 in HL; interorbital space narrow, its width 1.6–2.1 times eye diameter and 9.4–11.6 in HL; numerous papillae present on snout, interorbital space, temporal and lips, rather dense in holotype but scattered in paratype; anterior nostril tubular, extending downward; posterior nostril a hole covering by a compressed thin skin, its opening towards posteroventrally; upper lip with several fleshy thorn-shaped barbels ( Fig. 4A ), one between nostrils, very minute barbels along with the barbel in left side of holotype; and two posterior to posterior nostril (three in left side of paratype); rictus relatively short, behind posterior margin of eye; lower jaw short, distance from tip of snout to anterior end of lower jaw slightly longer than eye diameter; gill opening lateral, located at ventral half of body.

Sensory pores small but conspicuous ( Fig. 4B ); supraorbital pores 1 (ethmoid)+3; infraorbital pores 3+3, 1 between nostrils, 2 below eye along upper jaw, and 3 behind eye in a vertical row; mandibular pores 5, the last pore slightly behind rictus; preopercular pores 2; interorbital pore 1; supratemporal pore 3 (single mid-temporal pore). Lateral line nearly completed, pores conspicuous, 0 pore before dorsal-fin origin, 8 anterior to gill opening, 118 anterior to anus and total 207 in holotype (0, 9, 114 and 195, respectively, in paratype), the last just before tip of tail about 1/3 HL.

All teeth small, conical, and relatively pointed; teeth on maxilla in holotype arranged uniserial, in paratype partly biserial but generally uniserial ( Figs. 4B, C ); dentary teeth biserial; 5 intermaxillary teeth arranged as chevron; vomerine teeth biserial in holotype, mid-part of vomer partly triserial in paratype.

Dorsal and anal fins very low, ending at near tip of tail, end of anal fin slightly behind that of dorsal fin; dorsalfin origin before middle of head, right behind the mid-temporal pore and before the first lateral-line pore; pectoral fin extremely minute, flap-like, located at anterior corner of gill opening, its length 13.1–20.4% HL and base height 26.2–44.1% HL.

Color when fresh condition (after refrigeration; Fig. 3 ): body purplish pale brown, darker dorsally; head yellowish, snout and lower jaw deep, tip of snout yellowish brown; fins dusky white. Color in preserved condition: purplish and yellowish color faded. Body pale brown, darker dorsally; head slightly paler than body, in paratype tip of snout dark brown and pale dusky white band between tip of snout and eye; fins dusky white.

Etymology. The specific name ryukyuensis is derived from the type locality.

Distribution. Only known from the two specimens collected from shore of Okinawa-jima Island, Ryukyu Islands, Japan.

Ecological note. The present specimens were collected as stranded specimens caused by the extremely low temperatures by a serous cold wave coming from the Arctic ( Hibino et al. 2021). In the type locality, several species of Muraenidae , Ophichthidae , Apogonidae , Syganidae, etc., were also collected at the same time.

Figures

FIGURE 3. Bascanichthys ryukyuensis Hibino, Yamashita & Sakurai, sp. nov., holotype, FRLM 52250, 627 mm TL, Okinawajima Island, Ryukyu Islands, Japan. A, whole lateral view; B, lateral view of head and anterior trunk; C, dorsal view of head and anterior trunk.

FIGURE 4. Drawings showing the head pores and tooth pattern of Bascanichthys ryukyuensis Hibino, Yamashita & Sakurai, sp. nov., from the holotype (A, B) and paratype, FRLM 52251, 516 mm TL, collected with holotype (C). A, head pores; B, tooth pattern on upper jaw (left) and lower jaw (center); C, upper jaw (right). Arrows indicate the interorbital pore (left) and med-temporal pore (right).

Tables

TABLE 1. Counts and measurements of two new Bascanichthys described in this study.

	B. kabeyawan sp. nov.	B. ryukyuensis sp. nov.
	Holotype	Holotype	Paratype
Total length (TL, mm)	526	627	516
Counts
Predorsal vertebrae	4	2	3
Preanal vertebrae	103	118	114
Total vertebrae	224	216	207
Lateral-line pores before gill opening	10	8	9
Lateral-line pores before anus	104	118	114
Total lateral-line pores	214	207	195
Measurements
As % ofTL
Head length (HL)	4.6	3.7	4.3
Preanal length	47.7	56.7	55.8
Tail length	52.3	43.3	44.2
Predorsal length	2.7	1.5	1.9
Body depth at gill opening	1.1	1.1	1.2
Body width at gill opening	0.7	1	1.0
Body depth at mid-anus	0.8	1.1	1.3
Body width at mid-anus	0.6	1	1.2
As % ofHL
Predorsal length	58.4	40.7	45.4
Snout length	10.9	13.1	11.3
Eye diameter	5.0	5.1	5.4
Upper-jaw length	19.8	25.4	20.9
Gill-opening length	12.3	10.2	10.9
Interorbital width	7.2	10.6	8.6
Isthmus width	7.4	14	15.4
Body depth at gill opening	23.6	30.5	29.0
Body width at gill opening	14.2	26.3	23.1
Body depth at mid-anus	16.3	28.4	31.3
Body width at mid-anus	13.4	27.1	28.6
Pectoral-fin length	2.6	7.6	5.0
Pectoral-fin base	5.4	3.8	2.3