Latin: Nereis

English: Common? Clam? Worm; A rag? insect

Also called (clam? Worm virus.

Annexure polychaete nereis annelids. Most of them are marine life, and most of them are freshwater life. Length 2.5? 90 cm (1 inch? 3 feet), usually brown, bright red or bright green. Probably the most advanced annelid, with a sharp retractable jaw on its head. 1 node has two short tentacles and four eyes, and node 2 has four pairs of tentacles. The number of body parts can exceed 200. Except for the first two paragraphs, each paragraph has a pair of wart feet for exercise. Breathe through the gills. They mainly eat other worms and small marine animals. Near the breeding season, sperm or eggs will swell out from the backs of most species. Usually at night, they leave shallow caves on the seabed to expel excretory cells near the sea surface. The fertilized eggs hatch into spherical larvae. Some species breed in caves. Females die after ovulation, are eaten by males, and are hatched by males. Some are hermaphroditic and self-fertilized. What is the most common species in North America? Limnicola, distributed in the Pacific and Atlantic coasts. n？ Virens can be as long as 80 cm (3 1.5 inches) and distributed on both sides of the North Pacific Ocean. ?

1 polychaetes. Long cylindrical, symmetrical on both sides, pointed at the back end, with many (80 ~ 200) individual nodes. It can be divided into head, trunk and tail. The head is developed and consists of two main parts: the front lobe of the mouth and the part around the stoma. The anterior lobe of the mouth is a round triangular or conical fleshy leaf protruding in front of the mouth, with two pairs of simple round eyes, 1 ~ 2 protruding head tentacles, and two large segmented tentacles on the ventral side of its front end. The perioral joint is a large annular joint, with a transverse mouth on the ventral surface and 3-4 pairs of tentacles on both sides, which can protrude muscle kiss from the mouth. The front end of the kiss has 1 pair of chitin jaws, and the kiss surface is smooth or has chitin jaw teeth or soft mastoid. The trunk has many body segments with similar structures, and both sides of each body segment have prominent fleshy flat protrusions, that is, wart feet. Most of the wart feet are bilobed, with thorns in the inner foot and prickly or sickle-shaped compound bristles outside; The tail is the last 1 segment or segments of the worm, also called anal segment, and there are a pair of anal whiskers and an anal orifice on the back of the end of anal segment.

Nereis is common in intertidal zone and also in deep sea. Nereis is the dominant invertebrate under rocks, cracks, algae, coral reefs or soft sediments. Except for a few species such as Nereis japonica, which live in fresh water or brackish water, the morphological changes of most species of Nereistidae before breeding are obvious, which is called Heteronereis. Some sexual nodes appear in the middle and back of the body, making worms appear in two different body areas. Some sexual knots such as Nereis and Nereis only occur in the middle of the body, which makes the worm show three obvious body areas: pre-sexual knot, neutral knot and post-sexual knot. The main changes in the body of Nereis nereis are: the tentacles and antennae of the anterior lobe of the mouth are shortened, the eyes are enlarged, and there are crystals. The wart feet only expand on the dorsal and ventral whiskers in the asexual joints. In the sexual joints, besides the bases of the dorsal and ventral whiskers, there are additional leaflike protrusions, and the bristle leaves become wide flat or fan-shaped, and the bristles are gradually replaced by swimming paddle bristles. There must be dentate papillae on the back of the male, and specialized sensory papillae grows in the anal segment. The internal changes include the decomposition and reorganization of muscles, the self-melting of digestive tract and the filling of body cavity by reproductive products, which leads to the changes of worm body (milky white for males and blue-green for females), which is beneficial to the transformation of Nereis from benthic to reproductive floating. Due to environmental influences (temperature, moonlight, etc.). ), the sexually mature female and male Nereis have left their habitat and floated on the sea to ovulate sperm. Multiple males revolve around females, which is a reproductive phenomenon called wedding dance. After the wedding dance, most men and women sank to the bottom of the sea and died. At present, there are 35 species of Nereis found in China.

The development of Nereis is complicated. The fertilized egg develops into an adult through spiral cleavage, trochanter, posterior trochanter, wart foot larva and rigid larva.

The adults and larvae of Nereis are the bait of economic fish and shrimp. Residents along the southern coast of China and Southeast Asia all have the habit of eating nereis. Nereis and Perinereis multidentata often live in rice fields and gnaw at rice roots. Nereis digging holes in salt fields will overflow brine, which is a kind of harm to salt industry. Nereis is also an important experimental material for teaching and scientific research. College animal teaching needs a large number of nereis as representatives every year to understand the system and structure of higher invertebrates. Another example is the infiltration mechanism of nereis to fresh water; The relationship between brain hormones and sexual maturity of Nereis: the development and settlement of Nereis larvae: the relationship between Nereis and the environment is a research topic in physiology, developmental biology and ecology. Therefore, Nereidae are extremely important marine and brackish water organisms.

Is that so?