Crustaceans - hormones in growth and reproduction, Biology

Assignment Help:

Crustaceans - Hormones in Growth and Reproduction

Arthropods have a tough and frequently hard exoskeleton made up of cuticle composed of chitin and protein. The cuticle imposes restrictions on the growth of the animal. If not the cuticle is shed, growth is not probable to any extent. The periodic shedding of cuticle is known as moulting. Thus, moulting is closely related to growth in arthropods. In crustaceans, two hormones control the moulting process. The Y-organ generates the moulting hormone, the ecdysone, a steroid. Under the effect of ecdysone the animal moults. So it is a moult-inducing hormone having a positive effect on moulting. Though, moulting in crustaceans is as well under the inhibitory control of another hormone produced by the X-organ and released at the sinus gland. This hormone has a negative effect on moulting. If the inhibitory hormone concentration in the blood dominates, the animal moults. It is the balance among the two hormones that determines moulting in crustaceans. However, it is not certain whether the inhibitory hormone acts on the Y organ decreasing the release of moulting hormone ecdysone or it acts directly at the level of the epidermal cells where ecdysone also acts. Anyway, the effect is similar. You will see that in many animals, two or more hormones of antagonistic effects may control very frequently one function, the balance determining the result. Reproduction in crustaceans is as well under hormonal control. The X-organ-sinus gland complex is involved here also. It is easy to remove the X-organ-sinus gland system of crustaceans, which are situated in the eyestalk. Removal of the eyestalk, termed as eyestalk ablation, would result in the removal of the endocrine structures. Removal of the eyestalk from the adult female crustacean results in the acceleration of yolk deposition in the oocytes; size and width of the ovaries will therefore increase. Occasionally it results in precocious egg-laying too. Injection of an extract of the eyestalks of the adult females into eyestalk-ablated animal will reverse the trend. Such kinds of experiments led to the conclusion that in common animals ovarian growth is inhibited by a neurosecretory hormone from the eye stalk, namely, X-organ-sinus gland complex. When the hormone is absent, the ovaries start growing, depositing yolk in the oocytes. Although a number of other hormones controlling ovarian and testis activity have been postulated, sufficient proof to prove their existence is tacking. An exception is the androgenic gland hormone of some crustaceans.


Related Discussions:- Crustaceans - hormones in growth and reproduction

Properties of fatty acid, A fatty acid having of a hydrocarbon chain and a ...

A fatty acid having of a hydrocarbon chain and a terminal carboxylic acid group that is shown in the figure.  Most  fatty  acids  are  in  biology  have  an  even  number  of carbo

Drug interactions, Amiodarone, quinidine, propafenone, and verapamil may in...

Amiodarone, quinidine, propafenone, and verapamil may increase digoxin levels up to 100 per cent. It is prudent to measure a blood level after 7-14 days (and at least 6 hours after

Advanced nervous systems - general trend in evolution, Advanced Nervous Sys...

Advanced Nervous Systems - General Trend In Evolution In higher groups of animals you will observe clear trends towards centralisation of the nervous system, to maximize effe

Data gathering - steps in nursing process, Data Gathering   It is the g...

Data Gathering   It is the gathering of information about client's physical heath, mental outlook, social circumstances, family and community life, and other factors. To p

Development of reserves - conservation of wildlife, Development of Reserves...

Development of Reserves - Conservation of Wildlife Establishment of Biological reserves, National parks, Forest reserves, Wildlife refuges and Biosphere reserves are effective

What are the illustrations of the criminal law, What are the illustrations ...

What are the illustrations of the criminal law? Illustrations of crimes' law: Illustrations of crimes are theft, reckless or murder behaviour. The major aim of illegal

Feline leukemia, Feline leukemia The disease is caused by a retrovirus and...

Feline leukemia The disease is caused by a retrovirus and is the most common naturally occurring lymphosarcoma and accounts for nearly 30% of feline tumors. Based on the location

Fats are essential for meeting nutritional need of essential, Why Fats are ...

Why Fats are essential for meeting nutritional need of essential? Fats are essential for meeting nutritional needs of essential, fatty acids like linoleic acid (n-6) and alpha

Biology in dispelling myths and misbeliefs, BIOLOGY IN DISPELLING MYTHS AND...

BIOLOGY IN DISPELLING MYTHS AND MISBELIEFS - Varieties of myths still exist in our society, and can be removed by the knowledge of Biology. Some of these are- 1.       Snake

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