NEMATODA
Charachteristics of Nemotoda:
1)Bilaterally symmetrical
2)Body has more than two cell layers, tissues and organs.
3)Body cavity is a pseudocoel, body fluid under high pressure.
4)Body possesses a through gut with a subterminal anus.
5)Body covered in a complex cuticle.
6)Has a nervous system with pharyngeal nerve ring.
7)Has no circulatory system (no blood system)
8)Reproduction normally sexual
9)Feed on just about everything.
10)Live just about everywhere,
Nematodes are the most speciose phylum after the arthropods, they occur in nearly every habitat including as parasites in all sorts of plants and animals. One species is known that can live in old vinegar and another that as only been found in German beer mats. Though only about 80, 000 species have been described some scientists estimate there may be as many as a million species all told. They can occur in very dense numbers in the soil and rotting vegetation, as many as 90 000 have been found in a single rotting apple, while millions occur in the top 3cm (1 inch) of a square metre of good quality soil. While there are a huge number of free living Nematodes there are also a large number of parasitic species, many of which cause diseases to man and other animals as well as to plants, nearly every living organism has been found to be parasitised by one species of nematode or another. Most nematodes are reasonably small, they range in size from 100 micrometres in length (1/10th of a mm or 1/250th of an in
Digestive System
The nematode digestive system is generally divided into three parts, the stomodeum, intestine, and proctodeum. The stomodeum consists of the “mouth and lips”, buccal cavity, and the esophagus . Each of these parts are used a lot in taxonomy and classification of nematodes, as well as giving as indication of feeding habit or trophic group. For example, the buccal cavity of plant parasitic nematodes is modified in the form of a hollow spear, adapted to penetrate and withdraw the contents of host cells. Some nematodes often have a buccal cavity characterized by teeth or hook-like projections. Nematodes have a linear digestive system. Digestion is mostly extracellular and nutrients are absorbed by the thin wall of the intestines.