Environmental Engineering Reference
In-Depth Information
to feed on the marine algae, which got exposed
only during low tide. Although it was a foreign
food, but its subsequent generations resisted and
persisted this condition. This caused the present-
day iguana to be completely different from its
relatives on the mainland.
The marine iguana is 3-feet-long lizard and is
entirely black; some are mottled red and black
showing some hint of green during the breeding
season. This dark colouration allows them to
absorb more heat energy to raise their body tem-
perature so that they can swim and feed in the cold
Paci
lay their eggs. Like the ancient ichthyosaurs,
females of the remaining species are ovovivipa-
rous, retaining their eggs within their body until
they hatch. The young that emerge are able to
swim and feed immediately.
Although all sea snakes breathe air, some
species can remain submerged for several hours.
The animal
s single lung reaches almost to its
tail, and its trachea has become modi
'
ed to
absorb oxygen, thus acting as an accessory lung.
Sea snakes can also exchange gases through their
skin when they are under water. These adapta-
tions allow the sea snakes to absorb large
amounts of oxygen in a very ef
c waters. They are very good swimmers,
using lateral undulations of their body and tail to
propel them through waters. They avoid heavy
surf and rarely venture more than 10 m from shore.
When leaving the water, they tend to ride in with
the swell and then swiftly crawl up the rocks. If
they do not
cient manner.
Sea snakes are able to lower their metabolic rate
so that they consume less oxygen when sub-
merged, and some species may even be able to
extract oxygen from swallowed water. Special-
ized valves in the snake
nd their territory immediately, they
touch the rocks with their tongues and carry scent
to a receptor in the roof of the mouth. When they
locate their own scent, they follow it to their ter-
ritory, where they rest on the rocks, lying almost
motionless above the high tide.
s nostrils prevent water
from entering when they are submerged.
Most sea snakes remain close to the shore, but
the yellow-bellied sea snake (
'
)
is pelagic, feeding on surface sh. On several
occasions, it has been sighted hundreds of miles
from land. This species has migrated east and
west from the coast of Asia and can be found off
the east coast of Africa and the west coast of
tropical America. Most of the other species are
found in warm coastal waters from the Persian
Gulf to Japan and east to Samoa.
The mangrove swamp of Sundarbans at the
apex of western Bay of Bengal is the homeland
of several reptiles (Table
2.16
) that are either
aquatic or semi-aquatic in nature. Many species
are well adapted in the upper estuarine stretch,
where the salinity reaches zero during monsoon.
Palamis platurus
Sea Snakes
Snakes are descendants of lizards that have lost
their limbs as an adaptation to maintain a bur-
rowing lifestyle, a lifestyle that was later aban-
doned by many species. Although most species of
snakes are terrestrial or arboreal, there are about
50 species that live in the marine environment,
each one bearing venomous fangs. Sea snakes are
less tied to the land than other marine reptiles, with
only about half of the species coming onto land to
Table 2.16
List of reptilian fauna reported from Indian Sundarbans region
Species
Family
Habitat
Lissemys punctata
(Bonaterre)
Trionychidae
Aquatic
Varanus bengalensis (Daudin)
Varanidae
Wetland associate
Varanus flavescens
(Gray)
Varanidae
Wetland associate
Enhydris enhydris
(Schneider) smooth water snake
Colubridae
Aquatic
Xenochropis piscator
(Schneider) checkered keelback
Colubridae
Aquatic
Cerberus rhynchops
(Schneider) dog-faced water snake
Colubridae
Aquatic
Naja naja kaouthia (Lacepede) monocellate cobra
Elapidae
Wetland associate
