Parental Care
in Amphibia
Looking after eggs or young until they
become capable to protect themselves from the predator is called as parental
care. Many animals, especially vertebrates are actively involved in the caring
of their young ones. Many amphibians are involved in parental care by
protecting eggs during early stage of development and the young by various ways
to maintain their population in an ecosystem.
In Amphibians parental care is carried
out by two methods.
1.
Indirect method
2.
Direct method.
1. Indirect method
of parental care involves construction of nest, nurseries or shelter.
The different modes of protection are
given below in the three important orders of class Amphibia.
A number of different species of frogs
and toads construct nests or shelters of leaves or other materials in which the
eggs are deposited and the youngs are developed.
A.
Mud Nests:
Tree forg Hyla
faber found in Brazil construct shallow nest of nursery on the border of pond.
The female of Hyla faber scoop out mud up to the depth of about 7 to 10
cm with the help of flattened webbed hands. The bottom is leveled by hands and
belly. The margin of nest remain above water level. In this nest female lay
eggs and protect the eggs and tadpoles from predators. During rain wall of nest
get destroyed and larva goes into water.
B.
Foam Nests:
Male and female
Japanese tree frog Rhacophorous bury
themselves into mud at edge of mud and make hollow chamber just above the water
level. In this hole female secret gelatinous secretion through cloaca, Which is
beaten into froth or foam, in this foam or froth female releases eggs at the same time male releases
sperm. After oviposition in foam, male and female get separate and make exit
gallery towards pond of ditch. The opening of chamber is obliquely downwards
toward water. In foam, eggs hatches into tadpole, that start undulating movement
that liquefies the froth which help to sliding of tadpole into water below for further development. In this way
eggs and tadpoles are protected in foam nest.
C.
Tree Nests:
Indian tree
frog Rhacophorus malabaricus and South American tree frog Phyllomedusa glued
tree leaves hanging over water body in which female lay eggs in gelatinous
fluid. After hatching, tadpole directly falls into water below.
Tailed
amphibian Autodx lays about 10 to 20 eggs in hole on tree up to 10 meters above
the ground. The male and female remain the hole to protect the eggs and larvae.
Both parents taking care and also moisten the eggs to avoid desiccation. Thus,
youngs remain with their parents for substantial period.
D. Gelatinuous Bags:
Female of large frog Phytynixalus biroi
secrete sausage shaped transparent bag in which eggs are laid by female.. the
bag is left in the stream. The full
development of young is takes place with in the eggs and after complete
development little frog come out of eggs with all development.
Tailed amphibian (Urodale)
Salamanderlla keyseriligi deposits eggs in gelatinous bag which is attached to
aquatic plant below water level. Thus, youngs are protected by gelatinous
bag.
E. Eggs under stone:
Many species of American tree frogs
lays their eggs in damp places under the stones of mosses outside water. The
eggs contain large amount of yolk which helps young for complete development
within the eggs. After, complete development tiny frog hop out from the egg.
2. Direct Nursing by the Parent:
A. Tadpoles on the back:
South American small frog Phyllobates
and Dendrobates lay egs on groung. After hatching of tadpole it get adhere to
the back of their parents with the help of sucker like lips and flattened
abdomen. In this way the tadpoles are
carried from one place to the another place of from one pond to anther pond
when one pond is to dry up.
Small South American frogs Phyllobates
and Dendrobates and tropical African frogs Arthroleptis and Pelobates lay their
eggs on ground. The hatched tadpoles adhere by their sucker-like lips and
flattened abdomen to the back of one of their parents and, thus, they are
carried from one place to the other and in this way they can even go from one
pool to the other and this is particularly when one pond is to dry up.
Eggs on the body:
Male of Alytes frog in Europe, wind the string of eggs around hind legs. This
eggs retained until the tadpole are ready to be hatched.
Female of Sri Lankan tree frog,
Rhacophorous reticulatus carries the eggs to her belly.
The female of Desmognathus fusca
salamander bound string of eggs on body. The eggs are nourished at
comparatively dry place.
Eggs in Back Pouches:
(i) Exposed:
In a Brazilian tree frog, Hyla goeldii,
eggs are carried in to emerged brood pouch during breeding season in which the
eggs remain exposed.
In Nototrema eggs are taken over back
in single large brood pouch which open
posteriorly infront of cloaca.
(ii)
In Cell-Like Pouches:
In toad Pipa americana, during breeding
season the back of female become thick, highly vascular and gelatinous. After
egg laying eggs are carried on the back of mother. Male toad help to placing
and spacing the eggs.
E. In the Mouth or Gular Pouch:
(i) By the Male:
In small South American frog Rhinoderma
darwini, the eggs are taken into vocal sac by male. The
complete development of frog is takes place there.
In Arthroleptis, male frog keeps the larvae in
his mouth.
(ii) By the Female:
The female of a West African tree-frog,
Hylambates breviceps, carries the eggs in to the mouth. Female of Australian frog Rheobatrachus silus keeps her eggs in to the stomach. The tadpoles
are ejected through mouth after metamorphosis.
F. Coiling Around Eggs:
In tailed amphibian Plethodon, the eggs
are laid in small groups of about five beneath the stones or in the rotten log.
The mother coils round them.
Female
Amphiuma salamander coils round the eggs laid in burrows in damp soil.
Ichthyophis are oviparous, lay eggs in burrows
in damp soil and coil round them until they hatch.
G. Viviparous or Viviparity:
East African toads, Pseudophryne
vivipara are known to be viviparous,
give birth to young ones.
Caecilians like Typhlonectes, Gymnopis,
etc. are ovoviviparous. In these Caecilians (Limbless Amphibians) eggs are laid
into the uterus and development of larvae is also takes place in uterus. Hence
they are called as ovi-vivparous.
