Corpus allatum and juvenile hormone, Biology

Assignment Help:

Corpus Allatum and Juvenile Hormone

The corpora allata are rounded glands attached to the posterior side of every corpus cardiacum making a compact body just behind the brain. In a few (Hemiptera, higher Diptera) they are fused to make a single median structure. Experiments by Wigglesworth have shown that the CA secretes a hormone that determines the character of each larval instar by limiting the degree of differentiation in the direction of the development of the adult. He named this hormone like juvenile hormone (JH). This is also known as neotenic (youth substance), (Wigglesworth 1954) and gonadotropic hormone (Engelmann 1957). The juvenile hormone is identical in structure to terpenes. A large number of compounds with juvenile hormone activity have been isolated and several have been synthesized. Some synthetic ones appear much more potent than the naturally occurring ones. The juvenile hormones make sure the occurrence of larval moults and inhibit metamorphosis. Its existence or nonexistence determines whether the larva will moult into a larval/pupal stage or into adult stage. The main natural hormone isolated from the adult male Hyalophora cecropia moth has the following structure Figure.

1648_Corpus allatum (Singular) and Juvenile hormone.png

Figure:  Juvenile hormone isolated from Cecropia moth

The role of the corpus allatum and the juvenile hormones in metamorphosis has been proved via various experiments. It has been observed that if an extra corpora allata from a second stage larva is transplanted to the fourth instar last larval instar as compared to the moult does not generate a pupa or adult, instead an oversized larva develops. Removal of corpora allata early in larval life results in premature metamorphosis.


Related Discussions:- Corpus allatum and juvenile hormone

What are pericardium - pleura and peritoneum, Q. What are pericardium, pleu...

Q. What are pericardium, pleura and peritoneum? Pleura are the membrane that covers the inner wall and the lungs of the chest pericardium are the membrane that covers the heart

Show how adaptation affecting taste quality, Q. Show How Adaptation affecti...

Q. Show How Adaptation affecting taste quality? Adaptation - A low concentration solution will not give any sensation after tasting a higher concentration solution due to the a

Buffers in foods, Some foods are better able to resist changes in pH than...

Some foods are better able to resist changes in pH than others. These tend to resist changes in pH since these are buffered and the ability to resist changes in pH is known as bu

Assessment of megaloblastic anaemia, Assessment   On observation of a c...

Assessment   On observation of a child with this type of anaemia you will find that in addition to the symptoms  of iron deficiency anaemia there is hyper-pigmentation over knu

A light microscope with unlimited resolution, Theoretically you can build a...

Theoretically you can build a light microscope with unlimited magnification, but can you build a light microscope with unlimited resolution? Why or why not? (Hint: what really cont

Venous drainage of the heart, The coronary sinus is the main vein of the he...

The coronary sinus is the main vein of the heart and is about 3 cm. long. It lies in the coronary sulcus at the posterior surface of  the heart in the posterior atrio-ventricular g

Give an overview about operons, Normal 0 false false false ...

Normal 0 false false false EN-IN X-NONE X-NONE MicrosoftInternetExplorer4 Various protein-codi

What are the main characteristics of the age pyramids, What are the main ch...

What are the main characteristics of the age pyramids of developed countries? In a stabilized human population the age pyramid has a narrower base as the reproduction rate is

What do you mean by sex ratio, What do you mean by sex ratio? Sex Rati...

What do you mean by sex ratio? Sex Ratio is defined as "the number of females per 1000 males". Sex ratio is an important social indicator to measure the extent of prevailing e

What is rh typing of mother & fetus hemolythemolytic disease, What is the R...

What is the Rh typing of the mother and of the fetus in the hemolytic disease of the newborn? In a hemolytic disease of the newborn the mother is Rh- and the fetus Rh+. In thes

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd