Nematodes have successfully adapted to almost type of ecosystem: from salt water to fresh water, from soil to polar and tropical regions. They are ubiquitous in freshwater, saltwater and terrestrial environments. They are more numerous than other animals just by taking single species and are found in different places such as mountains, deserts and ocean trenches. They are found all over the earth's lithosphere, even at great depths (0.9-3.6 km) below the surface of the Earth, in gold mines in South Africa. They represent 90% of the animals on the ocean floor. Their numerical dominance, often greater than one million people per square meter, so as to represent about 80% of all individual animals on earth, their diversity of life cycles and their presence at various trophic levels, points to play an important role in many ecosystems. The many parasitic forms include pathogens in most plants and animals (including humans). Some nematodes can undergo cryptobiosis.
Shape and structure
Roundworms are thin worms. They typically have a thickness ranging from 5 to 100 microns (up to 0.1 millimeters). THE nematodes smaller are microscopic, but some species can even reach more than one meter in length. The body is often decorated with a crest, or with rings, bristles or other. Its head is relatively distinct: whereas the rest of the body has a bilateral symmetry, the head is radially asymmetrical, with sensory bristles. The mouth has three to six lips, in which they have a series of teeth on the inner edges. The epidermis is either a syncytium or a single layer of cells, and is covered with a thick cuticle of collagen. The cuticle often has a complex structure and may have two or three distinct layers. Under the epidermis there is a layer of longitudinal muscle cells.
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Most nematode species are dioecious, i.e. there are male and other female species. Both sexes have one or two tubular gonads. In males, sperm are produced at the end of the gonad and migrate along its length when mature. The testicle opens into a large seminal vesicle and then, during sexual intercourse, into a glandular and muscular ejaculatory duct via a vas deferens to the cloaca. In females, each ovary opens an oviduct and then into the glandular uterus. Reproduction occurs through a sexual act, even though hermaphroditic nematodes are capable of self-fertilizing. Males are usually smaller than females and often have a tail that is usually folded or fan-shaped to hold other intercourse.
Nematodes: What they attack and how to fight them
Nematodes attack plants belonging to the Solanaceae, Composite, Cucurbitaceae families as well as various vegetables, such as corn or beetroot, and fruit. They, as parasites, sting, injecting dangerous viruses, and sucking up the tissues, giving way to infestation. Attacked plants develop late, as parasites prevent the supply of nutrients from reaching the roots, causing poor production both in terms of quality and quantity, and also makes the plant more sensitive to attack by other pathogens (such as fungi or bacteria). In order to attack, nematodes need favorable climatic conditions and humidity, so that they can lay their eggs on the plant. Usually they are fought with chemical agents that are administered to the soil, or through the overheating of the soil (which can occur during the summer season). Then you have to cover the ground with clear plastic to create a greenhouse effect.