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 mysi
n. sp.
Figures 13–14
,
Tables 1
,
5
Holotype
.
BPBM
11843, 298 mm
, male, Marquesas Islands, Fatu Hiva
Island
, off point at N end of Hanauu Bay (
10o29’26”S
,
138o38’56”W
), depth
35 m
, captured using rotenone over sand bottom by J.E. Randall, D. Cannoy and R. McNair,
21 Apr. 1971
.
Paratypes
.
9 specimens
,
167–301 mm
.
BPBM
41104, 277 mm
, gravid female, and
CAS
234136, 298 mm
, collected with the
holotype
.
BPBM
11908, 249 mm
, Marquesas Islands, Tahuata
Island
, off point at S end of Vaitahu Bay (
09o57'S
,
139o05'W
), depth
35–40 m
, captured using rotenone over sand and rubble bottom by J.E. Randall
et al
.,
23 Apr. 1971
.
BPBM
11891, 241 mm
, Marquesas Islands, Nuku Hiva
Island
, Baie Hatuarua, off Nuka River (
10o29'S
,
138o38'W
), depth
53–59 m
, captured using dredge by D.M. Devaney,
18 Sept. 1967
.
MNHN
2001-1089, 5 (
167–301 mm
), Nuku Hiva, depth
45–64 m
,
24 Aug. 1997
.
FIGURE 13.
Head of holotype of
Apterichtus mysi
, BPBM 11843, 298 mm. Drawn by J. McCosker.
FIGURE 14.
Dentition of holotype of
Apterichtus mysi
, BPBM 11843, 298 mm. Drawn by J. McCosker.
Non-paratypes.
MNHN
2014-2819
, two specimens, 160+ and 240+ mm (extrapolated total lengths ~
190 mm
and
280 mm
), badly damaged during capture but identifiable as this new species.
Diagnosis
. An elongate species with: tail 2.2–2.4, head 17–18, and body depth
58–69 in
total length; snout moderately pointed in lateral view, dorsal profile
ca.
45–50o above lower jaw; 3 preopercular pores and 3 pores in supratemporal canal; teeth conical, uniserial on jaws and vomer; 5–6 vomerine teeth; body mostly pale in preservative, with fine brown speckling on the dorsal surface of body and tail; and MVF 75–148, total vertebrae 146–153 (n=10).
Counts and measurements (in mm) of the
holotype
(those of the
paratypes
summarized in
Table 5
).
Total length 298; head 17.3; trunk 147.7; tail 133; body depth at gill openings 4.9; body width at gill openings 4.0; body depth at anus 4.0; body width at anus 3.6; head depth at branchial basket 5.7; head width at branchial basket 4.7; snout 3.4; tip of snout to rictus 3.2; tip of snout to tip of lower jaw 2.5; eye diameter 1.3; interorbital distance 1.6; gill-opening length ~1.8; isthmus width ~1.0. Vertebral formula 76–151. Lateral-line pores difficult to discern,
6 in
branchial region, ~80 pores before the anus.
TABLE 5. Counts and proportions (in thousandths) of the holotype and 7 paratypes of
Apterichthus mysi
n. sp.
TL = total length. HL = head length. Vertebral counts are based on all 10 types.
| holotype |
mean |
range |
| TL (mm) |
294 |
--- |
241–301 |
| HL/TL |
58 |
57 |
55–58 |
| Head and trunk/TL |
554 |
554 |
546–565 |
| Tail/TL |
446 |
446 |
425–454 |
| Upper jaw/HL |
358 |
346 |
327–366 |
| Snout/HL |
197 |
181 |
172–197 |
| Eye/HL |
75 |
75 |
66–81 |
| Interorbital/HL |
93 |
93 |
83–104 |
| Gill opening/HL |
104 |
112 |
96–128 |
| Isthmus/HL |
58 |
52 |
39–61 |
| Depth at gill opening/TL |
16 |
15 |
12–17 |
| Width/depth at gill opening |
816 |
845 |
790–935 |
| Preanal vertebrae |
76 |
74.9 |
72–78 |
| Total vertebrae |
151 |
147.9 |
146–153 |
Description.
Body elongate, nearly cylindrical throughout, snout and tail tip sharply pointed, depth at gill openings
59–83 in
TL. Branchial basket slightly wider and deeper than body. Head and trunk
1.8 in
TL; head
17–18 in
TL,
7.8–9.2 in
trunk. Snout pointed, its underside somewhat rounded and bisected by a groove (
Figs. 13–14
). Lower jaw included, its tip slightly in advance of eye. Slope of dorsal surface of snout approximately 35° relative to underside of snout. Lower jaw included, its tip slightly in advance of eye; snout extends beyond tip of lower jaw by slightly less than lower jaw length; upper and lower lips meet when mouth is closed. Mouth moderately elongate. Rictus well behind rear margin of eye. An obvious crease extends posteriorly in upper lip from beneath eye to rictus. Eye moderately developed,
4.2–5.1 in
upper jaw and
12–15 in
head, its anterior margin behind tip of lower jaw, its center in advance of middle of upper jaw. Anterior nostril within a short tube, approximately one-fourth the diameter of the eye, its base in anterior third of snout and anterolaterally directed when viewed 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.
Head pores (
Fig. 13
) small. Single median interorbital and temporal pores. Supraorbital pores 1+4, infraorbital pores 5-6+2, supratemporal pores 3, lower jaw pores 4, preopercular pores 3. Lateral-line pores difficult to discern, 6 above branchial region, ~80 before anus.
Teeth (
Fig. 14
) uniserial, small, conical and slightly recurved. Intermaxillary with a chevron of 5–6 teeth (the largest in the jaw), followed by a short gap and a linear row of 5 small vomerine teeth. Jaw teeth nearly subequal, small, 11–12 teeth in each side of upper jaw and 11–12 teeth in each side of lower jaw.
Body mostly colorless in alcohol preservative (preserved in formalin and transferred to alcohol more than 15 years ago), however a fine brown speckling is present on the body and tail of some specimens.
Size
. The largest specimen examined is
301 mm
, a female with eggs ~
0.6–0.9 mm
in diameter.
Etymology
. Named in honor of
Mysi
Hoang of the California Academy of Sciences for her many contributions to ichthyology, to be treated as a noun in apposition.
Distribution
. Known from the Marquesas Islands, Polynesia, captured over sand with associated rock and coral reef bottoms using ichthyocides and dredges between
35–64 m
depth.
Remarks.
The new species differs from its congeners in the size and shape of its snout, the position of its eye, its cephalic pore configuration, and in its vertebral numbers. It is most similar to those species which share its cephalic pore condition of possessing 3 supratemporal pores and 3 preopercular pores, viz.
Apterichtus anguiformis
,
A. australis
,
A. equatorialis
,
A. flavicaudus
and
A. kendalli
.
It differs considerably from the New World species
A. equatorialis
and
A. kendalli
in having a shorter tail (2.2–2.4 vs. 1.8–2.0 in TL) and in having slightly more total vertebrae (146–153 vs. 137–145).
Apterichtus mysi
is most similar in cephalic appearance and vertebral number to
A. australis
and
A. flavicaudus
but differs from them in having a shorter and less acute snout (17–20% vs. 19–23% of HL), a shorter anterior nostril tube (approximately 4 times in eye vs. 3 times in eye) and the tip of its lower jaw is in advance of a line beneath the anterior margin of the orbit (vs. lower jaw tip beneath the anterior margin of the orbit). It differs from its other congeners in having fewer supratemporal and preopercular pores. The subtle differences between
A. mysi
and those congeners appear to fit a pattern that other Marquesan eels display. David G. Smith of the National Museum of Natural History advised
McCosker (2010:36)
“that widely-dispersed species of Indo-Pacific eels occasionally possess endemic forms in the Marquesas”, a pattern that has become more substantiated by subsequent collections and studies.
A
197 mm
specimen of
A. klazingai
was collected together with the new species at Nuku Hiva (MNHN 2001- 1089).