Insects - hormones in growth and reproduction, Biology

Insects - Hormones in Growth and Reproduction

In insects hormones regulate moulting and metamorphosis. The larvae or nymphs which hatch out of the eggs undergo regular moulting that is followed by growth, as in crustaceans and ultimately they become adults. The change in form from larva to adult is termed as metamorphosis. In insects such as cockroach, grasshopper etc., (hemimetabolous insects), the change in form is gradual. Though in some other insects like moths, butterflies, houseflies etc., (holometabolous insects), the change is much more conspicuous during the later period of the life history and the adult that emerges from the pupa is quite different. As in crustaceans, the hormone which brings about moulting in these animals is as well ecdysone but in insects it is secreted through prothoracic glands. How is metamorphosis in insects brought about? In insects the hormone that is accountable for preventing the animal from metamorphosing is juvenile hormone secreted by the corpus allatum. Actually, as the name implies, juvenile hormone keeps the insect juvenile. Thus in effect it inhibits metamorphosis. We have previously seen that the prothoracic glands in immature insects secrete ecdysone. This hormone causes the insect to moult. As long as the larva moults in the existence of high titres of juvenile hormone, it moults into another larva. If the moult occurs when the titres of JH are low in the blood, it results in a pupa. Finally when there is no JH circulating in the blood, the pupa moults into adult. So the concentration of JH in blood determines the type of resulting individual. It is as well known that JH causes the repression of those genes that are accountable for adult differentiation.

Posted Date: 2/4/2013 8:13:28 AM | Location : United States







Related Discussions:- Insects - hormones in growth and reproduction, Assignment Help, Ask Question on Insects - hormones in growth and reproduction, Get Answer, Expert's Help, Insects - hormones in growth and reproduction Discussions

Write discussion on Insects - hormones in growth and reproduction
Your posts are moderated
Related Questions

In some protozoans, food is always ingested at the same place on cell surface, cytostome (cell mouth). Undigested food is removed at a cytoproct, or cell anus. All of this is simil

whatis a prokaryotic cell? explain its structure and description with images

Explain Pure Culture Techniques We learnt the techniques involved in sub-culturing, i.e., the process involved in transfer of culture from one medium to another or transfer of

Q. What is the substance produced in the liver that acts in the small intestine during digestion? How does that substance act in the digestive process? Bile is an emulsifier li



What is Hyperhomocysteinaemia ? Homocysteine has been considered as a risk factor for Cardio-vascular diseases because of many epidemiological and observational studies showing

To verify the effect of intra-specific competition on the growth of saplings of Eucalyptus dives, an experiment was designed in which two sets of pots were used. In the first set o

An impermeable membrane separates one liter of a 0.01 M glucose solution in water in the left compartment from one liter of a 0.1 M glucose solution in water in the right compartme