PARENTAL CARE IN AMPHIBIANS
In amphibians there are many devices for the protection during the early stages of development and in this way nature has practic- ed economy in the number of eggs, which varies in direct propor tion to the chances of destruction.
These devices fall under two heads, which may be found com- bined in some forms: firstly, protection by the parents, either by means of nest or nurseries, or by direct nursing; secondly, short- ening of the metamorphosis.
The different modes of protection are given below in the three important orders Anura of class Amphibia.
A. In enclosures in the water, e.g., Hyla faber.
B. In holes near water, e.g., Rhacophorus schlegellii.
C. In nests on trees or rocks overhanging the water, e.g., Phyllomedusa,Bhacophorus malabaricus.
D. In a transparent gelatinous bag in the water, e.g., Phrynizalus biroi.
E. On trees or in moss away from water, e.g., Hylodes, Rana opisthodon.
2. Direct nursing by the parents:
A. Tadpoles transported from one place to another by males, e.g., Phylobates, Dendrobates.
B. Egge protected by the male who covers them with his body, e.g., Mantophryne robusta,
C. Eggs carried by the parent.
(a) Round the legs by the male, e.g., Alytes.
(b) On the back of the female.
(i) Exposed, e.g., Hyla goeldii.
(ii) In cell-like pouches, e.g., Pipa americana.
(iii) In common pouch, e.g., Nototrema.
(c) On the belly, exposed, by the female, e.g., Rhacophorus reti. culatus.
(d) In the mouth, or in gular pouch.
(i) By the male, e.g., Rhinoderma darwini
(ii) By the female, a.g., Hylambates breviceps.
D. Viviparous or viviparity,
e.g.. Peeudophryne vivipara. Protection by Means of Nests and Nurseries
1. Protection by means of nest or nurseries :
A. In enclosures in the water:
A large tree frog (Hyla faber) known in Brazil as the "Ferreiro". It protects its progeny by building a basin-shaped nursery in shallow water on the border of the pond.
The female scoops mud to a depth of 3 or 4 inches and with the material thus removed a circular wall is built which emer- ges above the surface of the water.
The inside wall is smoothened by the webbed and flattened hands, the bottom is levelled by belly and hands.
The eggs and early larvae are thus protected from at- tack of many insects and fishes, etc., at least for some time, heavy rains later on destroy the wall and larvae go to the water.
B. In holes near water:
A still better mode of protecting the offspring during the early stages of development has been adopted by a Japanese tree frog Rhacophorus schlegelii.
The male and fe male in embrace bury themselves in the damp earth on the edge of ditch or flooded rice field, and make a hole or chamber, a few inches above water level.
The walls of this chamber are polished and during this process the gallery by which they enter into that cham- ber gets obliterated, oviposition begins.
The female first produces a secretion from cloaca which is beaten into a froth. The eggs are deposited into the froth.
Now the inactive male impregnates them, now both of them separate and make an exit gallery towards the ditch.
It is obliquely downwards towards the water, later on this is used by the larvae who come to the water to complete the develop- ment.
The bubbles collapse, the froth liquefies and this liquid acts as an efficient vehicle for transporting.
The larvae which are carried down the tunnel into the water.
C. In nests on trees or on rocks overhanging the water:
Some tree frogs like Phyllomedusa in South America, Rhacoph orus malabaricus in India, and Chiromantis in tropical Africa, deposit their spawn on trees, in nests of froth attached to one or many leaves stuck together and overhanging a pool for a few days.
The larvae move in froth and after losing the external gills, they fall in water to complete metamorphosis.
D. In transparent gelatinous bag in the water:
The eggs of Phrynixalus biroi are large which are enclosed in sausage- shaped transparent common membrane secreted by the female and is left in the mountain streams.
The whole development takes place within the eggs and little frogs go out in perfect condition.
No gills have been observed and the large tail serves as a breathing organ of young ones.
E. On trees or in moss away from water:
In several species of tropical American genus Hylodes, the eggs are deposited in damp places under stones or moss or plant leaves and are of large size.
The metamorphosis is hurried up within the egg, there is a plenty of yolk in the egg and hence entire development takes place there and young frog hops out as an air breather with a vestige of tail which was fully developed and highly vascularized and ser- ved as a respiratory organ.
No gills have been seen.
X X
2. Direct Nursing by the Parent
A. Tadpoles transported from one place to another by males:
Small South American frogs Phyllobates and Dendrobates have been repeatedly observed carrying well-developed tadpoles on their back.
Tadpoles adhere by their sucker-like lips and flattened abdomen 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.
B. Eggs protected by male who covers with his body:
The eggs of Mantophryne robusta are strung together by an elastic gelatinous envelope.
They are seventeen in number and form a clump over which the male sits, holding it with both hands and development takes place there.
It may be outside water. The larvae have no gills, well developed legs, large tail which is vascular and respiratory.
(a) Round the legs by the male:
Alytes obstetricans was discovered in France in the middle of the eighteenth century in this very condition.
The pairing and oviposition takes place on land and when the eggs are deposited the male first leave the fe- male's waist and shifts hold to the base of head.
The eggs are passed out in two or three times at short intervals.
The male then binds the string and push them round the lega.
(b) On the back of female
(i) Exposed:
In a Brazilian tree-frog, Hyla goeldii it is the female which takes charge of the eggs, carrying them on the back.
How they are reached there is not known but probably male does it.
In Noto trema also this thing is seen.
(ii) In cell-like pouches:
In Pipa americana the eggs are carried on the back of the mother, but the skin thickens and grows round the eggs, until each is enclosed in a dermal cell, which is finally covered by a lid, believed to be formed by a secretion from the glands of the skin.
The eggs are about 100 in number and they develop in these pouches and the young leap out in the perfect condition.
The Pipa is a thoroughly aquatic and pairing of course takes place in water.
The male clasps the female round the waist.
How these eggs go to the back of the female has been obeserved in specimens kept in the London Zoological Gardena.
During egg- laying the cloaca projects as a bladder-like pouch directed forwards between the back of the female and the breast of the male and by means of this oviposition the eggs are evenly distributed over the whole back of the female.
How the eggs are fertilized are not known.
(iii) In common pouch:
In Noto trema the whole of the brood is sheltered in a common pouch.
It is a condition foreshado- wed by the lateral everted fold of Hyla goeldii.
This dorsal pouch develops only during breeding season.
How the eggs are introduced into the pouch is still unknown, the opening of this pouch is small and situated on the posterior part of the back.
(c) On the belly, exposed, by the female:
The female of the Ceylonese Rhacophorus reticulatus carries its eggs on the belly, which bears shallow impressions when the eggs are removed.
X X
(d) In the mouth or gular pouch
(i) By the male :
One of the most remarkable modes of nursing is that of the Chilian Rhinoderma darwini, a small frog.
It was first believed to be viviparous, but a more careful examination revealed the fact that the young about 10 to 15 in number, are sheltered and develop in the gular pouch which is a modified vocal sac.
(ii) By the female:
The female of a West African tree-frog, Hylambates breviceps, carries the eggs in her mouth.
These eggs are large and few in number.
D. Viviparous or viviparity:
Tw small East African toads Pseudophryne vivipara and Nectophryne tornieri are known to be viviparous, but no observations have yet been made on them beyond the fact that larvae are found in the uteri.
(Reference: Chordate Zoology by E.L.Jordan and P.S. Verma ,S.Chand and company limited, New Delhi.)
Fig.1. Parental care in amphibians ( A-Mud nests of Hyla. B-Ichthyo. phis coiling round the egg. C-Oryptobranchua ranei. D Deanog nathue with eggs. E-Gastrotheca, F-Alytea, G-Pipa pipa. H-Paqu doplacentation in Pipa dorsigera.)
View, Comments and share.....
0 Comments