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 malabar
n. sp.
Figures 11–12
,
Tables 1
,
4
Holotype
. AMS I.19426-001,
414 mm
, female,
Australia
, New South
Wales
, off
Malabar
(
33°58’S
,
151°17’E
), Sta. 3
Malabar
Benthic Survey,
66 m
,
26 March 1973
.
Paratypes
.
3 specimens
,
240–363 mm
. AMS I.19427-001,
240 mm
,
Australia
, New South
Wales
, off
Malabar
(
33°58’S
,
151°17’E
),
44–46 m
, collected by benthic trawl,
14 March 1973
. AMS I.19428-001,
343 mm
,
Australia
, New South
Wales
, off
Malabar
(
33°58’S
,
151°17’E
), Sta. 16, 49–
55 m
, collected by D. Hoese using a benthic trawl,
2 January 1973
.
CAS
234253 (previously AMS I.19428-002),
363 mm
, collected with AMS I.19428-001.
Diagnosis
. An elongate species with: tail 1.9–2.2, head 18–19, and body depth
52–77 in
total length; 3 preopercular pores and 5 pores in supratemporal canal; teeth conical, uniserial on jaws and vomer; 6 vomerine teeth; body mostly pale in preservative; and MVF 78–158, total vertebrae 155–162 (n=4).
Counts and measurements (in mm) of the
holotype
.
Total length 414; head 23.4; trunk 174.6; tail 216; body depth at gill openings ~6.7; body width at gill openings ~4.9; body depth at anus ~5.0; body width at anus ~4.9; head depth at branchial basket 6.9; head width at branchial basket 6.5; snout length 4.1; tip of snout to rictus 7.4; tip of snout to tip of lower jaw 3.6; eye diameter 1.8; interorbital distance 2.0; gill-opening length 2.9; isthmus width ~1. Vertebral formula 73–155. Lateral-line pores difficult to count accurately due to small size and waxy exudate, 6 pores in branchial region.
FIGURE 11.
Head of holotype of
Apterichtus malabar
, AMS I.19426-001, 414 mm. Drawn by Corlis Schneider.
Description.
Body elongate, nearly cylindrical throughout, snout and tail tip sharply pointed; depth at gill openings
52–77 in
TL. Branchial basket slightly wider and deeper than body. Head and trunk
1.8–2.1 in
TL; head
18–19 in
TL, 7.5–9.0 in trunk. Snout pointed, its underside somewhat rounded and bisected by a groove (
Figs. 11–12
). Lower jaw included, its tip slightly in advance of eye. Slope of dorsal surface of snout approximately 40° 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,
4.1–5.5 in
upper jaw and
13–17 in
head, its anterior margin above tip of lower jaw, its center well in advance of middle of upper jaw. Anterior nostril within a tube, approximately one-third 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. 11
) small but apparent. Single median interorbital and temporal pores. Supraorbital pores 1+4, infraorbital pores 5+2 (
holotype
has 6+2 left), supratemporal pores 5, lower jaw pores 4, preopercular pores 3. Lateral-line pores difficult to count accurately due to small size and waxy exudate, 6 pores in branchial region.
FIGURE 12.
Dentition of holotype of
Apterichtus malabar
, AMS I.19426-001, 414 mm. Drawn by Corlis Schneider.
TABLE 4. Counts and proportions (in thousandths) of the holotype and 3 paratypes of
Apterichtus malabar
n. sp.
TL = total length. HL = head length.
| holotype |
mean |
range |
| TL (mm) |
414 |
--- |
240–414 |
| HL/TL |
56 |
54 |
52–56 |
| Head and trunk/TL |
478 |
515 |
478–543 |
| Tail/TL |
522 |
485 |
457–522 |
| Upper jaw/HL |
316 |
344 |
316–381 |
| Snout/HL |
175 |
188 |
175–204 |
| Eye/HL |
77 |
72 |
59–77 |
| Interorbital/HL |
85 |
84 |
74–88 |
| Gill opening/HL |
124 |
98 |
88–124 |
| Isthmus/HL |
47 |
52 |
47–56 |
| Depth at gill opening/TL |
16 |
16 |
13–19 |
| Width/depth at gill opening |
731 |
831 |
731–960 |
| Preanal vertebrae |
73 |
78 |
73–80 |
| Total vertebrae |
155 |
158 |
155–162 |
Teeth (
Fig. 12
) uniserial, small, conical and slightly recurved. Intermaxillary with a chevron of 7 teeth (the largest in the jaw), followed by a short gap and a linear row of 6 small vomerine teeth. Jaw teeth nearly subequal, small, 17–18 teeth in each side of upper jaw and 18–19 teeth in each side of lower jaw, the posteriormost 6–7 irregularly biserial.
Body mostly colorless (presumably faded) in isopropanol.
Size
. The largest specimen examined is
414 mm
, a gravid female (ova
0.8–1.1 m
diameter).
Etymology
. Named
malabar
, in reference to its location of capture, to be treated as a noun in apposition.
Distribution
. Known only from the
type
specimens which were captured off
Malabar
, NSW,
Australia
, at
44–66 m
depth.
Remarks.
As
explained in the previous description of
Apterichtus dunalailai
,
A. malabar
shares the cephalic pore configuration of 5 supratemporal pores and 3 preopercular pores with
A. dunalailai
,
A. klazingai
and
A. moseri
.
It differs significantly from all but
A. dunalailai
in having more total vertebrae (160 vs. 131–145).
Apterichtus malabar
is most similar to the deep water
A. dunalailai
but differs in having a shorter head (5.2–5.6% vs. 6.0–6.2% of TL), a shorter and deeper snout (19.8–21.2% vs. 17.5–20.4% of HL) (compare figures 6 and 11), and more preanal vertebrae (73–80 vs. 68–74).
It is notable that eastern
Australia
also has
Apterichtus flavicaudus
and
A. klazingai
in its shallow water ichthyofauna, generally occurring at overlapping depths.