Nugulata is a bilaterally symmetrical, three germ layer, non coelomic multicellular animal.Linear FaunaIt is a multicellular animal with three germ layers and pseudocoelom.byPlatyhelminthesOne side door.
Nympheta has a long and narrow body in a flat band, with a body length of 5~20cm in general and up to 30m in some species.The back and abdomen are flat, and the body extends into a new belt, so it is named.The digestive tract has mouth and anus.There is a long kiss on the back of the front section.Excretory organIt is the primary renal tube.Most occur in the sea, and a few in fresh water and wet soil, also have parasitic life.Fossils are scarce.Jurassic to modern.
classification
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Anopla (Anopla)
Paleonema(Paleonemertea): For exampleTubular Neozoa。
Enopla (Enopla)Hoplonemertea (Hoplonemertea): For exampleAmphiporus (Amphiporus)、Neozoa corpusca，Terrestrial Neozoa(Geonemertes), etc.
Vermiculinae(Bdellonemertea): There is only one family and one genus.
Nugular structure
Leech Newworm(Malacobdella): There are 4 species.
Morphological structure and function
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The new-born body is long, cylindrical, or flat and banded (see figure).The head is not obvious, and the front end often has eyespots and other sensory organs.The internal structure has some segmentation, but there is no segmentation on the surface.The body surface has cilia.The mouth is on the ventral side of the proximal end.The front end has a kiss hole.Kiss can be turned out when hunting.The anus is behind the body.The structure of the dermatomuscular sac is similar to that of the flat animalsEpidermal cellAnd muscle layer, covering the whole body;Muscles usually have two or more layers of circular and longitudinal muscles.Some also have some connective tissue between the epidermis and muscle, called the lower cortex.The number and arrangement of muscle layers is an important basis for classification.The digestive tube is divided into foregut and midgut. Food passes through the digestive tube from the mouth, and the residue is discharged from the anus at the rear end.There are many lateral caecum in the midgut, which are symmetrically arranged on the body side at the interval between the anterior and posterior gonads, so there is a false segmentation phenomenon.The snout is on the back of the digestive tube, which is a tubular blind sac in the snout cavity.The compression of the kiss cavity can make the kiss turn out of the body.The end of the snout has thorns and poison glands, which are used to prey on small animals.InitialClosed loop, including one back blood vessel and two side blood vessels, three blood vessels are connected in front and back, blood flows from back to front in the back blood vessels, and from front to back through the two side blood vessels.Except for a few kinds of blood cells with red pigment, the blood of common newworms is colorless.The respiratory function of Newworms andFlatfishSimilarly, gas exchange is carried out through the skin.The excretory system consists of the original kidney.The nervous system is quite developed,central nervous systemIt is composed of the cerebral ganglion at the rostral end and the bilateral nerve cords following it.There are transverse nerves connected between the nerve cords on both sides in a "ladder" shape.The central nervous system sends out many nerves and connects with various parts of the body.
The snout of a newworm
Reproduction and development
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Most newworms are dioecious, with many testes and ovaries, which are located between the lateral caecum of the intestine and are segmented.Most Newworms are fertilized in vitro, but a few are fertilized in vivo.There are two kinds of development of newworms: direct and indirect.Indirect development goes through the larval stage. This larva is called a cap shaped larva, which is helmet shaped, and has a drooping flap on both sides of its mouth;There are cilia on the body surface and hair follicles on the top;The digestive tube has a mouth and an anus.
Taxonomic evolution
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Nugulates are very similar to flatworms in appearance, body surface cilia, skin muscle sac, excretion and nervous system, as well as cap larvae and Mullerian larvae.However, from the perspective of having anus and circulatory system, they are higher than flat animals in the evolutionary system.This phylum is divided into two classes: Anapla and Enopla.
