ANURAN PARENTAL CARE
The order Anura is an order in the class Amphibia that is comprised of toads and frogs which are referred to as tailless amphibians1. The word Anura is derived from a Greek an-without oura-tail hence tailless2. Frogs have no tails except for their larval stages called the tadpoles. They exhibit both terrestrial and aquatic lifestyles and depend on water for reproduction2. They are distributed in tropic and temperate areas of the world occupying diverse habitats. By evolving to live on land the frogs have adapted to escape the predation of their egg in the aquatic environment where they are more vulnerable than on land. On land they have also enemies which include invertebrates (especially ants and spiders) which feed on their eggs vertebrates like snakes and small mammals which feed on the young1.
Various methods have been adopted by anurans in order to protect their young and eggs predation and enhance chances of survival in terrestrial environments. This is a form of parental care exercised by the anurans. The Families Rhacophoridae, Hylidae, Hyperoliidae, Leptodactylidae and Myobatrachidae build foam nests that are used to harbour their young4. The genus Chiromantis which is found in
Others like Pipa carvoelhi (a toad) after mating have fertilised eggs picked by the male frog on the hind legs and spread on the female’s back where they are embedded and a membrane forms to cover them. The tadpoles hatch and develop and break from the skin. Others of the Genus Afrixalus (leaf folding frogs) lay eggs in leaves where they are fertilised and then the frogs fold the leave and sometimes grasses with a sticky substance which keeps them trapped till they hatch and the glue loosens and they are released into water3.
The Nectophrynoides of Western Africa have internal fertilisation and the eggs develop in the female’s oviduct to maturity and the frog gives “birth” to froglets. The Chilean frog Rhinoderma buries her eggs on moist ground and is guarded by the males who later take them into their mouths (vocal sacs) till they mature into little frogs. One of the poisonous Phyllobatids of South America lay eggs near males who guard them till they hatch. They later take the tadpoles on their backs and produce mucous which covers the eggs till they mature. An interesting method of parenting is practised by the Australian frogs Rheobatrachus silus and Rheobatrachus vitellinus. The female swallows the eggs after fertilization brooding them in her stomach for six weeks. To avoid the eggs being digested by the digestive juices it’s thought a substance (prostaglandin E2) is secreted by the egg capsules and then by the tadpoles which stops digestion. They feed from the
The African Breviceps is a burrowing group of frog which lives in arid areas but mate when there’s a heavy rain where also the female takes in a lot of water. They have bigger females and smaller males, and fertilisation occurs with the males gluing on the females back1, 4. In this position the female burrows and lays the eggs which are fertilised by the male. Constantly the female sprays moisture onto the eggs from her bladder till the froglets hatch4. The spade foot toads in the Western Deserts of
1. Duellman, W. E. and Trueb, L. 1986. Biology of Amphibians
2. Wikipedia contributors. Frog [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 4, 14:56 UTC [cited 2006 May 6]. Available from: http://en.wikipedia.org/w/index.php?title=Frog&oldid=51531477.
3. Carruthers V. 2001. Frogs and Frogging in
4. Knight, R. BCB Biodiversity chapter 2 The Invasion of the Land (Cited 2006 May 6) http://planet.uwc.ac.za/nisl/biodiversity/Chapter2/page_93.htm
VINCENT MUCHAI WAIRIMU
Biodiversity and Conservation Biology
University of the
Private Bag X17 Bellville