By Josh Davis, Natural History Museum at South Kensington,
U.K Science News First published 8/16/2019
India has an impressive diversity of reptiles, with over 600
species recorded to date. But snakes and lizards remain poorly studied there,
and new species are continually being described.
Deepak
Veerappan, Marie Curie Post-Doctoral Fellow at the Museum, specialises in
south Asian reptiles. He has recently been involved in a host of papers
describing three new species, a new genus and a new subfamily of snakes from
across India.
Deepak has
helped to describe the first new species of
pit viper from India in 70 years, found in the northeastern province of
Arunachal Pradesh, which borders Bhutan and Tibet.
Deepak was drafted in thanks to his specialised skillset.
'My colleagues needed help with a couple of things,' he says. 'One of these was
inverting the hemipenis from a preserved specimen. This is a difficult task,
and I have become quite good at it.’
Most male lizards and snakes possess what is known as a
hemipenis. This is the organ roughly analogous to the penis in mammals, except
it is formed of two branches and works in a slightly different way.
'Relatively speaking, the study of hemipenis morphology is
only very recent,' explains Deepak. 'Studies began in the 1960s when people
actually started to understand what it was. But later in that decade, it was
realised that there are some groups of reptiles in which the characteristics of
the hemipenis are important.
'When people started looking in more detail, it turned out
that in some cases you can even use the hemipenis to identify individual
species.’
Trimeresurus arunachalensis is the first new species of
pit viper from India to have been described in 70 years.
For different species of pit vipers, the shape and structure
of the hemipenis is highly distinctive. To get a good look at it, the organ has
to be inverted from the snake. While this is fairly straightforward in recently
dead snakes, in preserved specimens it gets a bit trickier. This is where
Deepak's skills came in.
When compared to its closest relative - the new species'
hemipenis was distinctive in that it was unforked and remarkably smooth.
T. arunachalensis lives on the ground and not in trees, and
looks unlike any other pit viper in the region. These factors combined
suggested that this animal was new to science.
The species is only known from a single specimen, so DNA
sequencing was needed to confirm the finding.
'We have also described a new species of vine snake from
eastern and central India,' says Deepak. 'My colleague in India found the first
specimen around nine years ago, but since then he has surveyed a lot in the
same area and has found only three more individuals.’
The species belongs to a group that is fairly well known,
making the discovery even more surprising.
Despite only having a few specimens to go on, to the
researchers saw it was clear that it is a new species, now named Ahaetulla
laudankia. It has distinctive colouration, pattern of scales and DNA analysis.
The snake is a rich chestnut brown on its belly, and it has black speckles
running all over its body.
Found in the Eastern Ghats, Ahaetulla laudankia is distinguished
by its distinct colouration.
It is also unlikely to be the only new species of vine
snake. 'There are definitely more new species hidden within this group of
snakes,' Deepak says. 'But it is difficult for many people to come to
collections such as the Museum and check.
'So in the study we've published all the raw data, hoping
that people from different parts of Asia can then look at it all and help
uncover these other species.'
A group of burrowing snakes from south western India have
long been an oddity. Belonging to the genus Xylophis, the three species of
snake burrow through the soil and leaf litter in search of worms and other
small creatures.
Limited to the Western Ghats, a region renowned for its
biodiversity, the burrowing snakes are unlike others in the
area.
Deepak says, 'They looked similar to some of the natricine
snakes, a group that includes many more common species like the European grass
snake. But some people had speculated it to be something else.’
By sampling the DNA of two of the Xylophis species, the team
were able to finally place these unusual reptiles on the evolutionary tree,
though the results were not what they expected.
v
'Nobody in their wildest dreams thought that this burrowing
species found only in the Western Ghats would be related to tree-climbing
specialist feeders in southeast Asia,' says Deepak.
Despite living underground, the closest living relatives of
Xylophis live up in the trees.
It turned out that their closest living relatives were
another group of strange snakes known as the snail-eaters. As their name
suggests, these animals climb trees to feed primarily on snails, and their
skulls having become astonishingly specialised in the process.
'This particular group has become so specialised to scoop
out snail flesh that their head shape is unlike anything else, their heads are
modified in a really dramatic way,' says Deepak.
This makes it all the more surprising that the
ground-dwelling burrowing snakes are their closest relatives of Xylophis.
'We estimated that the split between the groups occurred
around 40-50 million years ago, which makes sense as this is about the time
that most of the animal and plant exchange happened between southeast Asia and
peninsula India,' Deepak continued.
The Western Ghats is also home to a group of natricine
snakes known as Rhabdops. These semi-aquatic snakes are found in small forest
streams, feeding on frogs and other reptiles. But included in this group is
another species, Rhabdops bicolor, living far away in northeastern India.
The new genus was named Smithophis in honour of Malcolm
Arthur Smith.
'This is quite interesting, because biogeographically they
are found in two different areas, and yet are species of the same genus,'
explains Deepak. 'So the obvious question is how are the Western Ghats snakes
related to the one found in the northeast?’
Museum collections combined with new samples revealed that
the two separate populations are actually two separate genera, with those in
the northeast now belonging to the new genus Smithophis, named in honour of
Malcolm Arthur Smith, who published three influential volumes on reptiles and
amphibians of the Indian subcontinent.
Additionally,
this new genus is not made up of a single
species but two. The new snake species has been named
Smithophis atemporalis.
The work being carried out by Deepak and his colleagues in
India goes some way to highlighting just how much there is still to discover in
the forests of Asia, and the importance of historic Museum collections that can
be used as vital references.
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