Jellyfish: Jellyfish is a kind of lower invertebrate zooplankton and carnivore, which belongs to Acanthoptera and Cephalopoda in taxonomy, with about 250 known species. The term jellyfish also refers to jellyfish-shaped (bell-shaped or dish-shaped) stinging animals, such as hydra jellyfish, tube jellyfish, Deming jellyfish (including capuchin jellyfish), comb jellyfish and sea urchin, which do not belong to the class of algae-eating.

Jellyfish: The genus Jellyfish (Jellyfish), rhizomes and jellyfish. Plankton in the camping ocean. The bulge of adult umbrella is hemispherical, the umbrella surface is smooth and the rubber layer is thick. The diameter of the umbrella is 300 ~ 600 mm, and the longest can reach 1 m. There are eight notches on the edge of the umbrella, and each notch has 14 ~ 22 tongue-shaped side lobes. No umbrella tentacles. Eight mouths and wrists, three wings.

Each wrist has about 150 ~ 180 filaments and 30 ~ 40 rods. The big mouth disappears, and small animals and plants are sucked away by the small suction port on the edge flap. The inner umbrella has developed annular muscles.

Second, the morphological characteristics

Jellyfish: Hydromedusae is large in size, and the diameter of umbrella rim is generally 2-40 cm, and the diameter of some large species can reach 1-2 m, such as jellyfish. Umbrellas are disc-shaped, such as jellyfish, or conical, semi-circular, butterfly-shaped and so on, depending on species. Due to the color of gonads or other gastric sacs in the body, the body appears local pink and orange in transparency.

The body is also divided into an upper umbrella surface and a lower umbrella surface, and there is a circle of tentacles without membrane at the edge of the umbrella. The number of tentacles of different species is different. The tentacles are solid or hollow, long or short, and a few species have no tentacles, such as Rhizopus. There are sensory organs on the umbrella rim, also called tentacle sacs, the number is 4 or multiple of 4, and there are 8 jellyfish with gaps, so the umbrella rim is 8 pieces.

The end of the vertical lip in the center of the lower umbrella extends outward to form four or eight cuffs, and one side of the cuffs facing the center is provided with a groove.

Jellyfish: Jellyfish looks like a mushroom and is divided into two parts: umbrella part and mouth and wrist part. Umbrella (jellyfish skin) is more than hemispherical, with a diameter of 300 ~ 600 mm and a maximum length of1m. The outer umbrella has a smooth surface and a thick rubber layer, which is crystal clear. There are 8 sensors at the edge of the umbrella, and 1/8 umbrellas have 16 ~ 22 flaps.

Three. Living habits

Jellyfish: Jellyfish are carnivores, feeding on plankton, small crustaceans, polychaetes and even small fish. Due to the mechanical and chemical stimulation of food, hydra elongate their tentacles, release stinging silk sacs to entangle, paralyze and poison their prey, and then send food into their mouths.

Mucus secreted by gland cells in oral area is beneficial to food swallowing. After food enters the gastric cavity, the gland cells in the gastric layer begin to secrete protease, which decomposes and digests food to form many peptides. At the same time, food can be mixed and promoted in the gastric cavity due to the flagella movement of nutritional muscle cells.

Jellyfish: The aquatic mother of jellyfish lives in the ocean and inhabits the offshore waters, especially near the Xiqi estuary. The water depth in the distribution area is generally 3-20m, sometimes up to 40m, and the water temperature is 8-30℃. Suitable water temperature 13-26℃, salinity 12 ‰-40 ‰, and suitable salinity 14.

Wind direction, wind current and tide have obvious effects on the horizontal distribution of jellyfish.

Fourth, the distribution range.

Jellyfish: They exist in tropical waters, temperate waters, shallow waters, oceans about 100 meters deep, and even fresh water areas. The vast majority of marine products, only a few species are produced in fresh water, and the shallow waters of tropical and subtropical oceans are the most abundant.

Jellyfish: widely distributed in China's coastal areas, with Zhejiang and Fujian as the most. From August to September every year, they appear on the sea in droves.

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