Fragmentation and regeneration, Biology

Fragmentation and Regeneration

Both the situations mentioned above that is whether occurring naturally or accidentally, can in general, be categorized like fragmentation. Of these, the first one, of natural or innate fragmentation followed by regeneration generating complete individuals has already been covered in the previous sections. We shall here explain the second manner in which accidentally generated body fragments regenerate all the missing parts to produce complete individuals. Regenerative capacity is fairly well-developed and extensive in echinoderms, but to a different degree in dissimilar groups and species. Though echinoids or sea urchins are poorly endowed along with regenerative power, star fishes (asteroids), brittle stars (ophiuroids) and sea lilies (crinoids) have wide capacity to regenerate. Most of these, especially many star fishes and brittle stars, not just only regenerate lost arms or part of the central disc, but even an arm can regenerate a whole animal, including the other arms and the central disc. Some starfishes for example Linckia are able to cast off their arm, which will regenerate into a starfish. Some starfishes and some crinoids (e.g. Ophiactis) even normally reproduce asexually. This includes division of central disc so that the animal divides into two. This is known as fissiparity. The two halves will regenerate the missing half. Specific holothurians (sea cucumbers) are unique in showing what is called evisceration. On encountering any immediate danger of some intruder or enemy these can throw out the large masses of "tubules of Cuvier" attached to respiratory trees, or sometimes even almost all of their viscera by their cloaca and regenerate them later. In some species evisceration is a normal seasonal phenomenon. Spontaneous fragmentation of the body followed by regeneration of the body parts to form a new individual is a general form of asexual reproduction in polychaetes. In several syllids the point in the septa where the segment will fragment is predetermined and is dissimilar from other septa. In such species fragmentation and regeneration are highly organized and each fragment can develop into a complete individual. In some cases the original somite stay large and a head and tail regenerate at each end. These break off and the tail portion grows a new head, while the head grows a new tail.

Posted Date: 2/5/2013 12:42:29 AM | Location : United States







Related Discussions:- Fragmentation and regeneration, Assignment Help, Ask Question on Fragmentation and regeneration, Get Answer, Expert's Help, Fragmentation and regeneration Discussions

Write discussion on Fragmentation and regeneration
Your posts are moderated
Related Questions
Define Larval Stage of Taenia Cystcercus? The pork tapeworn (T: solium) and beef tapeworn (T : saginata , which are endoparasites of humans who are the final hosts

Q. What do you mean by Polyester? Polyester (ES) or polyethylene terephthalate (PET): PET is a very strong transparent glossy film, which has good moisture and gas barrier p

Motor Control in Annelids and Arthropods In annelids and arthropods generally, individual metameric ganglia of the ventral nerve cord are capable of initiating and keep locomo

KIDNE Y (RENAL FAILURE) - RF - Partial or total inability of kidney to carry excretory functions is called RF. It leads to uremia (excess of urea in blood), salt-water imba

Why is pattern baldness more common in men than in women? Pattern baldness is handled by the allele B. Testosterone interacts with the heterozygous genotype (BB′) to make baldn

What do you understand by Parapodia? Paired lateral, unjointed appendages of polychaete worms. Parapodia have a variety of shapes, and their appearance is related to their nume

Types of Osmotic Exchanges The osmotic exchanges that take place between an animal and its environment are of two different types: Obligatory exchanges and Regulated

What is the other name given to sex chromosomes? What is the function of sex chromosomes? Sex chromosomes are also known as allosomes (the other chromosomes that are not sex ch

Define the Energy Cost of Growth? The energy cost of growth has two components: 1) The energy needed to synthesize growing tissues; and 2) The energy deposited in these tis

How is the transport of substances done across the bryophyte tissues? How is this feature related to the general size of these plants? In bryophytes there are no water-conduct