A review of the finless snake eels of the genus Apterichtus (Anguilliformes: Ophichthidae), with the description of five new species
Author
Hibino, Yusuke
text
Zootaxa
2015
3941
1
49
78
journal article
10.11646/zootaxa.3941.1.2
9a54c25b-e43f-4e60-881a-fd262e98310f
1175-5326
288211
ECDCBC06-96AC-4D91-9C24-7A0A30A3E375
Apterichtus jeffwilliamsi
n. sp.
Figures 8–10
,
Tables 1
,
3
Holotype
.
USNM
363869, 305 mm
TL, female, Vanua Lava
Island
, Banks Islands,
Vanuatu
(13°.7461’S, 167°.4061’E), depth
9–16 m
, rippled sand bottom, collected by J.T. Williams, D.G. Smith, R.D. Mooi, and D.J. Bray,
23 March 1997
.
Paratypes
.
Four specimens,
112–283 mm
TL.
USNM
427494 (formerly
USNM
363869), two specimens,
112–283 mm
TL, collected with
holotype
.
USNM
350117, two specimens,
149–178 mm
TL, Ranon Bay, Ambrym
Island
,
Vanuatu
(16°.1406’S, 168°.1167’E), depth
4–7 m
, collected by J.T. Williams and D.G. Smith.
Diagnosis.
An elongate species with: tail 1.7–1.8, head 13–16, and body depth
65–73 in
total length; 4 preopercular pores and 5–9 pores in supratemporal canal; teeth conical, uniserial on jaws and vomer; a single vomerine tooth; anterior nostril non-tubular, a hole; snout sharp, slope approximately 30° relative to underside; body coloration pinkish white, with numerous brown to orange spots less than eye diameter; and MVF 58–140, total vertebrae 138–142.
Counts and measurements (in mm) of the
holotype
.
Total length 305; head 18.8; trunk 106.9; tail 179.3; body depth at gill openings 4.5; body width at gill openings 3.9; body depth at anus 3.9; body width at anus 4.1; head depth at branchial basket 5.8; head width at branchial basket 3.9; snout length 3.3; tip of snout to rictus 9.2; tip of snout to tip of lower jaw 4.0; eye diameter 1.4; interorbital distance 1.1; gill-opening length 2.1; isthmus width 0.8. Vertebral formula 58–141. Lateral-line pores 59, 7 pores in branchial region.
Description.
Body elongate (
Fig. 8
), subcylindrical throughout, snout and tail tip sharply pointed; depth at gill openings
65–73 in
TL. Branchial basket slightly wider and deeper than body. Head and trunk
2.3–2.4 in
TL; head
13–16 in
TL,
4.6–5.7 in
trunk. Snout pointed, long, almost equal to twice eye diameter, weak ridges on one-third of mid-lateral snout; short median groove ventrally on snout, beyond anterior edge of posterior nostril. Slope of dorsal surface of snout approximately 30° relative to underside of snout. Lower jaw included, its tip located between verticals through anterior margin and center of eye; snout extends beyond tip of lower jaw, distance from tip of snout to anterior tip of lower jaw almost equal to twice eye diameter; upper and lower lips meet when mouth is closed. Mouth moderately elongate. Rictus well behind rear margin of eye. Edge of upper lip smooth, a distinct crease extending from a vertical through rear margin of eye to end of rictus; a crease on lower lip same as on upper in adult specimens (
283–305 mm
TL), extending from a vertical through rear margin of eye to just before preopercle. Eye moderately developed,
5.1–6.5 in
upper jaw and
11–15 in
head, its anterior margin slightly beyond tip of lower jaw, its center in advance of middle of upper jaw. Anterior nostril non-tubular, small, hole-shaped with a pair of small flaps, located in anterior third of snout, invisible from above. Posterior nostril opens in outer lip beneath anterior margin of eye. Branchial openings low, ventral; branchial region modestly expanded, creating a bulbous region in posterior half of head.
FIGURE 8.
Holotype of
Apterichtus jeffwilliamsi
, USNM 363869, 305 mm, showing fresh coloration. Photograph by J. Williams.
FIGURE 9.
Head of holotype of
Apterichtus jeffwilliamsi
, USNM 363869, 305 mm. Drawn by Y. Hibino.
FIGURE 10.
Dentition of holotype of
Apterichtus jeffwilliamsi
, USNM 363869, 305 mm. Drawn by Y. Hibino.
TABLE 3. Counts and proportions (in thousandths) of the holotype and 4 paratypes of
Apterichtus jeffwilliamsi
n. sp.
TL = total length. HL = head length.
| holotype |
mean |
range |
| TL (mm) |
305 |
--- |
112–305 |
| HL/TL |
62 |
70 |
62–80 |
| Head and trunk/TL |
412 |
425 |
412–441 |
| Tail/TL |
588 |
574 |
558–588 |
| Upper jaw/HL |
491 |
422 |
345–491 |
| Snout/HL |
178 |
151 |
134–178 |
| Eye/HL |
75 |
74 |
68–87 |
| Interorbital/HL |
56 |
45 |
25–57 |
| Gill opening/HL |
112 |
125 |
112–138 |
| Isthmus/HL |
40 |
35 |
22–43 |
| Depth at gill opening/TL |
15 |
15 |
14–15 |
| Width/depth at gill opening |
870 |
801 |
709–870 |
| Preanal vertebrae |
58 |
57.8 |
57–58 |
| Total vertebrae |
141 |
139.6 |
138–142 |
Head pores (
Fig. 9
) small but apparent. Single median interorbital and temporal pores. Supraorbital pores 1+6, infraorbital pores 5+5 (one
paratype
has 5+6 left), supratemporal pores 5 to 9 (
7 in
holotype
), lower jaw pores 5, preopercular pores 4. Lateral-line pores before anus 58-59, 7 pores in branchial region, almost complete to tail tip.
Teeth (
Fig. 10
) uniserial, small, conical and slightly recurved posteriorly. Intermaxillary with a chevron of 3-7 teeth (the largest in the jaw), followed by a short gap and a single vomerine tooth, same size as jaw teeth. Jaw teeth uniserial, small, 17-26 teeth in each side of upper jaw and 16-24 teeth in each side of lower jaw.
Ground color (
Fig. 8
) of head and body pinkish white, with numerous spots, reddish brown to orange toward tip of tail. In alcohol preservative head dark green, body yellowish brown. Body spots nearly fade out but remain as dark brown spots on head and breast.
Size.
The largest specimen examined is
305 mm
TL, a female with ripened eggs,
0.7-0.9 mm
in diameter.
Etymology.
Named in honor of Jeffrey T. Williams of the National Museum of Natural History (USNM), the collector.
Distribution.
Known only from the
type
specimens which were captured at
Vanuatu
, in
4-16 m
over a rippled sand bottom.
Remarks.
Apterichtus jeffwilliamsi
is most similar to
A. nariculus
in the shape and condition of its anterior nostril.
As
mentioned in the generic remarks section of this paper, these are the only species within the genus that lack tubular anterior nostrils. Their other characteristics are clearly shared by their congeners.
Apterichtus jeffwilliamsi
differs from
A. nariculus
in having a less obtuse and longer snout (profile is 30° vs. ca. 40°; length is equal to or more than twice eye diameter vs. equal to or less than twice eye diameter), a shorter trunk (35.0-36.2% vs. 40.0%. of TL), and more preopercular pores (4 vs. 3).
Apterichtus jeffwilliamsi
is similar to
A. klazingai
in its body coloration and in some proportional characters; the new species differs from the latter in having 4 preopercular pores (vs. 3), 5 to 9 supratemporal pores (vs. 5), a more acute and longer snout (its profile ca. 30° vs. ca. 40–45°; its length equal to or more than twice eye diameter vs. equal to or less than twice eye diameter), and the shape of its anterior nostril (a hole vs. a tube). The supratemporal pore condition of
A. jeffwilliamsi
is variable, ranging from 5 to 9 (5, n=1; 7, n=2; 9, n=2). Most species of
Apterichtus
have a singular supratemporal pore pattern (except for
A. moseri
, which has 5 or 6 pores,
Table 1
). One of the nine-pored specimens has an irregular row; the standard number of this species can be inferred to be 5 or 7, but it is unclear based on our limited material.