231
15.4.2 Vertebrates
Many vertebrates inhabit wetlands from the
surrounding land. The grass snake ( Natrix natrix )
is a common hunter of frogs and insects in the
reed swamp margin in Europe. It is also an active
swimmer. Nevertheless, it is equally at home and
try to prey upon the small mammals and other
denizens of dry grassland. Many of these dry
grassland mammals also penetrate the upper reed
swamp. Amongst the herbivores, the harvest
mouse, common vole and bank vole ( Micromys
minutus, Microtus arvalis and Clethrionomys
glareolus ) are common, while the insect-hunting
shrews ( Sorex spp.) differentiate little between
reed swamp and tall grassland.
Wetter reed swamp with open-water pools provides the habitat of other more nearly obligate
wetland vertebrates, e.g. the common frogs and
toads (e.g. Rana and Bufo spp.), which depend on
water as a secondary habitat for their tadpoles.
Otherwise, they roam and hunt throughout the
wetland and its terrestrial fringes, which also
comprise of a large number of tropical forest- fl oor
faunas. Many reptiles including numerous species
of water snakes (subfamily Homalopsinae) and
the sub-aquatic turtles (superfamily Testudinoidea)
are characteristics of the water- edge throughout
the world.
A few species of fi sh are adapted to the mud
and shallow-water swamp environment. However,
a normal fi sh may be asphyxiated while adjusting
with less oxygenated water. Most typically, they
are part of the fauna of tropical swamps which
occasionally dry out completely and may cause
large-scale fi sh mortality. Those which survive,
may aestivate or migrate overland. They belong
to the polygenetic group of air-breathing fi sh.
The swamp-dwelling catfi shes ( Clarias
mossambicus, C. batrachus ) are air-breathing
fi shes capable of migrating overland. They also
possess blood haemoglobin which has an
exceptionally high oxygen affi nity combined
with tolerance of large concentrations of CO 2
in the blood. A few temperate zone fi sh are also
able to migrate overland, e.g. the eel ( Anguilla
anguilla ), which shows some respiratory gas
exchange through the skin.
Amongst the mammals, the water vole
( Arvicola amphibius ) of northern Europe and
North American muskrat ( Ondatra zibethicus )
are both herbivores. They often graze heavily on
Phragmites, Typha, etc., reed swamp. Eat-outs by
geese ( Anser spp. and Branta spp.), in North
American salt marshes, cause formation of pools.
The reed swamp provides cover and refuge
particularly for nesting water birds. They construct nests amongst the reed stems or on a
mound of felled reeds, hidden from view and
shaded by the surrounding vegetation. Many of
these reed swamp-nesting and roosting birds
hunt fl ies whose larvae are detritivores in the
adjacent water.
Tropical reed swamps support much large
herbivorous mammals. In Africa, the hippopotamus
( Hippopotamus amphibious ) feeds voraciously on
the grass Vossia cuspidata in company with an antelope, the puku ( Kobus vardoni ). Sometimes, they
cause damage to the habitat. The rather long high
rainfall season imposes an interesting cycle of
animal migration in these riverine and lakeside
tropical swamp grasslands. The Amazonian manatee ( Trichechus inunguis ) feed voraciously on
aquatic vegetation. It has been suggested as a biological control for the water hyacinth ( Eichhornia
crassipes ). The reed swamps and forests of the
warmer parts of the world support aquatic large reptiles, notably the crocodiles and alligators. These
reptiles may prey upon the animals which are
attracted to the water margin to drink, fi sh or feed.
15.5 Wetland Fishes
15.5.1 Ichthyodiversity
Fish constitutes almost half of the total number of
vertebrates in the world. They live in almost all
conceivable aquatic habitats. c 21,723 living species of fi sh have been recorded out of 39,900 species of vertebrates (Jayaram 1999 , 2010 ). Of
these, 8,411 are freshwater species and 11,650
are marine. Let us consider India as an example.
India is one of the megabiodiversity countries in
the world and occupies 9th position in terms of
freshwater megabiodiversity (Mittermeier and
15.5 Wetland Fishes
15.4.2 Vertebrates
Many vertebrates inhabit wetlands from the
surrounding land. The grass snake ( Natrix natrix )
is a common hunter of frogs and insects in the
reed swamp margin in Europe. It is also an active
swimmer. Nevertheless, it is equally at home and
try to prey upon the small mammals and other
denizens of dry grassland. Many of these dry
grassland mammals also penetrate the upper reed
swamp. Amongst the herbivores, the harvest
mouse, common vole and bank vole ( Micromys
minutus, Microtus arvalis and Clethrionomys
glareolus ) are common, while the insect-hunting
shrews ( Sorex spp.) differentiate little between
reed swamp and tall grassland.
Wetter reed swamp with open-water pools provides the habitat of other more nearly obligate
wetland vertebrates, e.g. the common frogs and
toads (e.g. Rana and Bufo spp.), which depend on
water as a secondary habitat for their tadpoles.
Otherwise, they roam and hunt throughout the
wetland and its terrestrial fringes, which also
comprise of a large number of tropical forest- fl oor
faunas. Many reptiles including numerous species
of water snakes (subfamily Homalopsinae) and
the sub-aquatic turtles (superfamily Testudinoidea)
are characteristics of the water- edge throughout
the world.
A few species of fi sh are adapted to the mud
and shallow-water swamp environment. However,
a normal fi sh may be asphyxiated while adjusting
with less oxygenated water. Most typically, they
are part of the fauna of tropical swamps which
occasionally dry out completely and may cause
large-scale fi sh mortality. Those which survive,
may aestivate or migrate overland. They belong
to the polygenetic group of air-breathing fi sh.
The swamp-dwelling catfi shes ( Clarias
mossambicus, C. batrachus ) are air-breathing
fi shes capable of migrating overland. They also
possess blood haemoglobin which has an
exceptionally high oxygen affi nity combined
with tolerance of large concentrations of CO 2
in the blood. A few temperate zone fi sh are also
able to migrate overland, e.g. the eel ( Anguilla
anguilla ), which shows some respiratory gas
exchange through the skin.
Amongst the mammals, the water vole
( Arvicola amphibius ) of northern Europe and
North American muskrat ( Ondatra zibethicus )
are both herbivores. They often graze heavily on
Phragmites, Typha, etc., reed swamp. Eat-outs by
geese ( Anser spp. and Branta spp.), in North
American salt marshes, cause formation of pools.
The reed swamp provides cover and refuge
particularly for nesting water birds. They construct nests amongst the reed stems or on a
mound of felled reeds, hidden from view and
shaded by the surrounding vegetation. Many of
these reed swamp-nesting and roosting birds
hunt fl ies whose larvae are detritivores in the
adjacent water.
Tropical reed swamps support much large
herbivorous mammals. In Africa, the hippopotamus
( Hippopotamus amphibious ) feeds voraciously on
the grass Vossia cuspidata in company with an antelope, the puku ( Kobus vardoni ). Sometimes, they
cause damage to the habitat. The rather long high
rainfall season imposes an interesting cycle of
animal migration in these riverine and lakeside
tropical swamp grasslands. The Amazonian manatee ( Trichechus inunguis ) feed voraciously on
aquatic vegetation. It has been suggested as a biological control for the water hyacinth ( Eichhornia
crassipes ). The reed swamps and forests of the
warmer parts of the world support aquatic large reptiles, notably the crocodiles and alligators. These
reptiles may prey upon the animals which are
attracted to the water margin to drink, fi sh or feed.
15.5 Wetland Fishes
15.5.1 Ichthyodiversity
Fish constitutes almost half of the total number of
vertebrates in the world. They live in almost all
conceivable aquatic habitats. c 21,723 living species of fi sh have been recorded out of 39,900 species of vertebrates (Jayaram 1999 , 2010 ). Of
these, 8,411 are freshwater species and 11,650
are marine. Let us consider India as an example.
India is one of the megabiodiversity countries in
the world and occupies 9th position in terms of
freshwater megabiodiversity (Mittermeier and
15.5 Wetland Fishes