Parental care in amphibia

A topic of chordate.

1. PARENTAL CARE IN AMPHIBIA - By Sampriya Ghosh

2. DEFINITION:- Looking after the eggs or the youngs untill they are independent to defend themselves from predators is known as PARENTAL CARE . By comparison with birds and mammals, amphibians generally have been thought to exhibit little parental care . However, in recent years both field and laboratory studies have provided evidence for an astonishing array of parental care in amphibians. Parental care may be defined as any behavior exhibited by a parent toward its offspring that Increases the offspring’s chances of survival ( Trivers . 1972 ). Anurans show greater diversity than Urodales or Apodans .

3. Parental is divided in to two broad catagories :- 1. PROTECTION BY NESTS,NURSERIES OR SHELTERS. 2. DIRECT CARING BY PARENTS .

4. 1. PROTECTION BY NESTS,NURSERIES OR SHELTERS:- SELECTION OF SITE :- 1. Some amphibians lay their eggs in safe and moist land, very near to water. 2.   Rhacophorus schlegli  of Japan, lays eggs in a hole on muddy bank of river or pond with foamy mucus cover to prevent the eggs from drying. 3. In   Gyrinophilus  the eggs are laid under the stones in stream. Sometimes, the eggs are taken up on the body. 4. In case of  Hylodes , eggs are laid on the under surface of leaves hanging above water. 5. In   Triton  the eggs may be fixed with the aquatic weeds by glues.

5. 2. FROTHING OF WATER:- Some Anurans just after laying eggs, surrounding water is made frothy by wringgling movements of the hind limbs, so that the eggs are prevented from desiccation and can escape the site of enemies. 3. FOAM NEST :- Rachophorus maculatus secretes a jelly like secretion with eggs from time to time which is beaten by the cross wise movement of the hind limbs of the female partner only resulting in formation of frothy mass. First this frothy mass looks white but gradually truns yellowish. This mass with eggs called FOAM NEST. With in few hours this mass the outer surface hardens gradually.

6. 4. Formation of Nests: Some amphibians build nests for deposition of eggs. 1.Mud Nest : Brazilian   Hyla fabre  digs small holes in the mud for deposition and development of the eggs.

7. 2.Leaf Nest:  In a South American tree frog   Phyllomedusa hypochondrales , margin of the leaves are folded and glued(cloacal secretion) together which acts as nest for the eggs .

8. 3.Shoot Nest:   Triton   construct the nest by fixing the shoots with a gelatinous secretion . 4.Gelatinous bags :- In Phrynixalus biroi large eggs are enclosed in sausage shaped transparent gelatinous membranous bags. 5.Communal nest:- The toad Nectophyrinoids malcolmi prepare communal nests in which the eggs are deposited by several females. This nest is guarded by a single male.

9. DIRECT CARING BY PARENTS i )  Coiling around eggs: Ø    Amphuima , Ichthyphis  females after laying eggs guard them by coiling body till the eggs hatch. Ø   In Japaneese salamander   Megalobatrachus maximus , the males perform the same function.

10. ii) Transferring tadpoles to water:     Phylobates , Pelobates (both are terrestrial)  species inhabiting tropical Africa and South America hold the newly hatched tadpoles with their mouth and transport them from land to water. Anthroleptis males carries the tadpoles from one pond to another.

11. iv) Eggs glued to the body: Salamander   Desmognathus fuscus   females carry cluster of eggs glued to their body. In Sri Lankan tree frog,  Rhacophorus reticulates , the eggs are glued to the belly of the females. In a European frog,  Alytes obstericans , instead of female’s parental care, the male entangles the eggs around his hind legs .

12. iv) Eggs in back pouches :- In   Hyla goeldii , the females carry the eggs on their back. In  Desmognathus , the females carry the eggs and live in underground hole . In  Pipa pipa , the eggs are carried by females on the back . In  Cryptobatrachus evansi  the dorsal skin contains many small pockets for lodging of eggs . In  Pipa dorsigera , the eggs are developed in the pits on the back of the females. During breeding season, the dorsal skin becomes soft, spongy, and vascular. Embryonic development occurs within the pits and physiological exchanges takes place between the females and the larva.

13. v) Organs as brooding pouches :- South American male frog of  Rhinoderma darwinii  keeps fertilized eggs in his vocal sacs where they undergo complete development. In   Hylambates breviceps , the female carries eggs in her buccal cavity . Australian frog Rheobatrachus the female keeps the egg in her stomach, tadpoles expelled through mouth after metamorphosis.

14. vi)   Viviparity : A special type of reproductive behavior is observed in  Salamandra atra  and  S. maculosa . The eggs are placed inside the uterine cavity where the entire development takes place. The uterine wall functions physiologically as primitive placenta .