Hypsirhina jagorii – Morice, 1875 Coup
d'Oeil sur la Fauna de la Cochinchine Francaise, p. 58.
Hypsirhina Iagorii (sic)
– Mocquard, 1907 Revue Coloniale, p. 51.
Hypsirhina enhydris subtaeniata
Bourret, 1934 Bulletin Genéral de
l’Instruction Publique, 9-10, Figure 3. Lectotype herein designated: MNHN
1958.04.74. Type locality: Kompong Speu, Cambodia. 1936 Bourret, 1936:278 [in
part]. Bourret (1934) described the lectotype from Kompong Speu [Cambodia] (~11°27’N
104°32’E, elevation 39m) and illustrated it in Figure 3. He then listed four
other specimens from Soc Trang, Vietnam (~09°36’N 105°58’E, elevation 0.9 m)
and gave ventral and subcaudal counts as well as measurements. He does not
apply the term “type” to any specific specimen nor does he exclude any of these
specimens from being a type. Ivan Ineich (personal communication) has suggested
that this specimen be designated the lectotype. The type locality is therefore
Kompong Speu, Cambodia.
Enhydris jagorii – Smith, 1943: Fauna of British India, Reptilia and
Amphibia, 3:384.
Enhydris jagori – Taylor, 1965 The serpents of Thailand and adjacent waters,
p. 917.
Hypsirhina enhydris
enhydris – Deuve, 1970 Serpents du Laos, pp. 173-175, Pl. 18, Figures
4-5.
Comment: This
species has been long confused with Enhydris
jagorii (Peters) and most of the literature references, particularly those
outside of Thailand, to Enhydris jagorii
actually refer to this species.
Etymology: The
name subtaeniata may be derived from
the Latin sub meaning under, and taenia meaning ribbon. Thus it most
likely refers to the several stripes that form a pattern on the belly.
Distribution:This
snake is widely distributed in the Mekong drainage, and inhabits Laos,
Thailand’s Korat Plateau, Vietnam, and Cambodia. It escaped the Mekong drainage
basin, possibly with human assistance, and colonized the Bung Boraphet area (Chao
Phraya drainage) in central Thailand.
Redescription of the Lectotype of Hypsirhina enhydris subtaeniata
Juvenile
female (MNHN 1958.0474, Bourret’s field number, M.388) total length of 202 mm,
tail 35 mm (17.3%). Rostral pentagonal, broader than tall. Nasals semi-divided;
cleft contacts first labial on each side. Prefrontal scales paired; scale on
the right longitudinally divided, as illustrated in Bourret’s Figure 3;
prefrontal scales about equal in diameter to nasal scales. Frontal pentagonal,
slightly less than the length of the parietal. Loreal single; contacted by
first three upper labials on both sides (contrary to Bourret’s Figure 3 showing
only the first two upper labials contacting the loreal). Ocular ring composed
of a supraocular, a preocular scale, two postocular scales, and upper labial
number four enters orbit. Temporal formula 1 + 2 + 3. Upper labials eight with
6th tallest; lower labials 10, the 6th largest. First three lower
labials contact the anterior pair of chin shields. Three pairs of chin shields,
anterior pair greatest in length. Gular scales 10 between chin shields and
first ventral. Dorsal scale rows 23 - 21 - 21. Ventral scales rounded, 139;
subcaudals 54/55. Colour and pattern of specimen obscure; nape stripe present;
head uniform brown. Ventral scales brown with zigzag stripe on outer edge and
edge of dorsal scale row one; ventrals on posterior third of the body have a
central spot which combine to form a medial stripe. Scale rows 1 - 3 a light
stripe; scale rows 4 - 6 have dark lateral spots; spots involve 2 - 4 scales
and fuse into a stripe on the tail, the spots number 52/47. Dorsum has
scattered pigment suggesting distinct spots present in life.
Systematic Status of Hypsirhina enhydris subtaeniata Bourret
1934
Morice
(1875) reported H. jagorii from
Cochinchine (=Vietnam) as did Müller (1887), and Mocquard (1907). Bourret
(1934) described Hypsirhina enhydris
subtaeniata on the basis of a specimen from Kompong Speu, Cambodia and four
specimens from Soc Trang, Cochinchine (= Vietnam). Smith (1943) placed Hypsirhina enhydris subtaeniata Bourret
in the synonymy of Enhydris jagorii.
He considered E. jagorii to
have 116 - 145 ventrals and 38 - 61 subcaudal scales, ranges that encompass subtaeniata
and E. chanardi. A collection of
snakes purchased at the markets around Tonlé Sap, Cambodia contained Enhydris enhydris and a few specimens
labeled “Enhydris jagorii.” A
collection of snakes made in central Thailand contained specimens labeled “Enhydris jagorii” but in both cases the
snakes agree well with Hypsirhina
enhydris subtaeniata Bourret. Examination of additional museum material
labeled “Enhydris jagorii” found most
of them to be conspecific with Bourret’s Hypsirhina
enhydris subtaeniata. St. Girons (1972a) discussed “Enhydris jagori” from Cambodia and described it as having 127 - 149
ventrals and 48 - 68 subcaudals. His Plate 32 (a photograph) shows specimen no.
70-555, clearly a specimen conspecific with
subtaeniata. Voris et al.
(2002) used tissues from (FMNH 252506) “Enhydris
jagorii,” in a molecular study, which suggested it is the sister species to
Enhydris enhydris; this specimen is
also conspecific with Bourret’s subtaeniata.
Hypsirhina enhydris subtaeniata
Bourret 1934 is a valid species. It is sympatric with E. enhydris at many locations in Thailand, Vietnam, and Cambodia.
Its confusion with E jagorii
undoubtedly occurred because of the similar scale counts, scale arrangements,
and a pattern that includes lateral spots.
Diagnosis: There
are 21 scale rows at midbody; ventral scales number 136 - 153 (136 - 146 in
females and 143 - 153 in males), subcaudal scale counts were 46 - 69 (46 - 60
in females and 54 - 69 in males). The ventral counts will usually separate this
species from its sister species Enhydris
enhydris which has 153 - 174 ventral scales. Enhydris subtaeniata can have two or three pairs of chin shields
that are elongate, rather than the flared condition found in jagorii and its relatives (chanardi, innominata, and longicauda).
Both E. enhydris and E. subtaeniata have a stripe on scale
rows 1 - 3, and both have striated dorsal scales, but only E. subtaeniata has a row of spots on scale rows 4 - 6. Each spot
involves two or three scales, and these may fuse on the neck to form a stripe,
but are distinct at midbody. Additionally, scale row two in subtaeniata is salmon pink, this is
absent in all other known taxa except E.
enhydris. Enhydris chanardi, E. jagorii,
E. innominata, and E. longicauda, also all have 21 rows of
scales, but they all have 136 or fewer ventral scales, none of these have a
longitudinal stripe in their dorsal pattern above scale row 3, and none have
striated scales. E. subtaeniata has a
bold zigzag stripe at the outer edge of the ventral scales and dorsal scale row
one, and it has a series of midline spots on each ventral scale on the
posterior half of the body.
Size: The largest female (CUMZ 2002.227) had a total length of
870 mm with a 127 mm tail. The largest male (CUMZ 2002.234) had a total length
of 659 mm, with a 120 mm tail. The smallest specimen was a female (MNHN
1938.0142) with a total length of 159 mm with a 31 mm tail, this is probably
at, or near the size of neonates at birth. The range of 18 female SVLs was 128 -
743 mm (= 402 mm), the range of 19
males SVLs was 133 - 490 mm (= 397 mm). Females had tails
that were 17 - 23% of the SVL, and males had tails that were 22 - 30% of the
SVL. The largest specimens examined were from the Bung Boraphet population in
Thailand.
External Morphology
The
head is moderate in size and depressed, the body is cylindrical, and increases
in diameter posteriorly to a point near the vent. The eyes are dorsolateral,
and the orbit diameter is less than the eye-mouth distance, and about equal to
the eye-nostril distance.
On
the head the rostral scale is pentagonal and broad, about twice as wide as it
is tall . The nasal scales are in contact, and they are
semi-divided with the nasal cleft extending to the first labial. They are
slightly larger than the diameter of the eye. The internasal is single,
posterior to the nasals and slightly penetrating between them. The prefrontals
are paired and about equal in their greatest diameter to the diameter of the
eye. The frontal length is about equal to the interocular distance and the
length of the parietals. It is hexagonal in shape. The loreal is singular and
more or less quadrangular. The supraocular is single; the preocular is single;
the postocular is usually divided into two scales with the more dorsal scale
being taller; and there are no subocular scales, upper labial number four
enters the orbit. Temporal scales number 1 + 2 + 3, or 1 + 2 + 4. The primary
is about as tall as it is broad and relatively small. The secondary and
tertiary temporals are small and similar to the occipital scales. The upper
labials usually number eight; the largest is usually the sixth. The first three
or four upper labials contact the loreal.
On
the chin the lower labials number 10 - 12, usually 11. The first three are in
contact with the anterior pair of chin shields. There are two or three pairs of
chin shields with the anterior pair being the largest, a characteristic that
will readily separate this species from Enhydris
enhydris. The gular scales number 9 - 11.
On
the body the dorsal scales are in 23 rows on the neck (rarely 24); dorsal scales
at midbody number 21; dorsal scales at posterior body number 19 - 21. The
ventrals number 134 in a Laotian specimen, but 140 - 153 in specimens from
elsewhere. These numbers are higher than those given by Bourret (132 - 140) for
his series from Soc Trang, Vietnam. Ventral scales at the anterior of the body
are 2 - 3 times the height of a nearby ventral, while ventrals at mid-body are
3 - 4 times the height of a nearby ventral, as are those posteriorly. Eighteen
females had 134 - 146 ventral scales (= 139), and 19 males had 143 -
153 ventral scales (=
146). Thus, the ventral scale counts are most likely sexually dimorphic in this
species. Subcaudal scales number 46 - 60 in 16 females (= 51.9) and 54 - 69 (= 62.8) in 17 males; the
subcaudal counts are also sexually dimorphic in this species when examined by
individual population, although they overlap when all populations are combined.
The anal plate is divided and
about the same length as the preceding ventral.
On
the tail the subcaudal scales are divided and number 46 - 69, a number that
agrees with Bourrett’s specimens. At the base of the tail the width is 81% of
the height, based upon the average of four specimens.
Color
and pattern. The outer edge of the ventral scales has dark brown pigment and
when combined with the dark brown pigment on the anterior edge of the first
scale row forms a zigzag stripe on each side of the belly. The posterior half
of the first scale row is cream. The second scale row and sometimes the bottom
portion of scale row three have a salmon pink or red stripe with some brown
pigment. In some specimens the salmon pink coloration is absent. Scale rows 4 -
18 are solid dark brown. Starting behind the parietal scales, there is a darker
stripe on four rows of scales, these become indistinct posteriorly. The midline
of the ventral scales frequently has a series of spots that form a midline
stripe on the posterior of the body, this is rarely absent, and rarely does it
extend to the anterior quarter of the ventral scales. There is a dark stripe on
the midline of the tail bordered by cream stripes above and below.
Habitat: This
aquatic snake uses streams impoundments, padi, ditches, klongs, ponds, and
probably many other aquatic microhabitats. There are several localities in
central Thailand where E. enhydris
and E. subtaeniata co-exists in
similar numbers and both species have been collected in the same gill net. The
population around Tonlé Sap, Cambodia also coexists with E. enhydris (Saint Girons and Pfeffer, 1972; Stuart et al. 2000).
In Cambodia, Saint Girons (1972) and Saint Girons and Pfeffer (1972) considered
this snake to be strictly aquatic and diurnal (see their comments about E. jagorii) and they suggest it migrates
with the water as the water levels in the lake undergo season fluctuations.
This snake has been collected from gill nets set in padi and in reservoirs.
Diet: One specimen was found to contain the remains of an
unidentified fish; another contained the remains of an anuran.
Reproduction: Litter
Size. Three females contained 7, 12, 20 oviductal eggs. The smallest gravid
female has a SVL of 572 mm. Deuve (1970) reported young born in April and May
with the first rains. This assumes his E.
enhydris account pertains to this species and not E. enhydris.
Relationships: E.
subtaeniata is the sister species to E.
enhydris (Voris et al. 2002).