Polypellum, a class of molluscs. Living in the sea. It is characterized by eight hard shells arranged in the inner ring and muscle tissue in the outer ring. The polycythranths include a variety of stone turtles, which are often seen on intertidal rocks after low tide. Edible. Polypellates are distributed worldwide, all seafood.
Representative animal: stone turtle
Latin name: Polyplacophora
Usually oval, flattened and symmetrical on both sides. The shell consists of 8 shell plates arranged in a tile-like arrangement. There is a ring of mantle membrane around the shell, also known as a ring belt. The feet are flat and wide, occupying the entire ventral surface of the body, and are suitable for adsorption on rocky surfaces or creeping crawls. The mouth has a well-developed tooth tongue, which can scrape algae and other plants from rocks. There are grooves on both sides of the foot, and there are gills in the grooves. Most species are up to 5 cm long. The stone turtle body is soft, stretched and flexed, can be snuggled in the stone crevice, and can be rolled into a ball when not attached to other objects. Attach it to the stone and force it to hurt it. More common in intertidal or shallow water (especially in warmer areas). Colder areas live in deep water. Mostly nocturnal. Juveniles (carrier-wheeled larvae) live freely and in large numbers, and are one of the important components of marine plankton. The stone turtle has large, roughly oval feet, a flat ventral surface, used to attach to or crawl on rock surfaces, and it crawls slowly, mostly at night. If there is enough food supply, they can stay at a fixed point for a long time. In the outer cavity around the feet of the stone turtle, a ring of feathered gills can be seen. The water flows from the water inlet holes on both sides of the front end of the turtle's body into the water inlet cavity, and then flows from the water inlet cavity through the gills to the water outlet cavity, and finally flows from the water outlet holes behind the body to the outside of the body. In this cycle, the stone turtle uses the seawater through the gills for gas exchange to complete the breathing and circulation.
The head of the stone turtle has no eyes. So, where do its eyes grow? Strange to say, its eyes are on the shell on the back of the body. Why do other animals have eyes on their heads while stone turtles grow on their backs? Because the head of the stone turtle is covered under the shell, only the shell is exposed and can contact the light, so the eyes are only useful in this part. This is an example of the unity of the body structure of a living organism with the conditions of the environment. The eyes of the stone turtle are very numerous, arranged on the shell in a certain order, and the most on the shell piece on the front side. Such eyes are small, about 0.06 to 0.07 mm in diameter, and cannot see objects. Some kinds of eyes can only feel the vibration or disturbance of the seawater. Although some species have corneas, crystals, pigment layers, omentums and other structures in the eyes, they can only sense light. The shell of the stone turtle is made up of eight shells arranged in a tile-like arrangement, so when stimulated, it can curl up like the larvae of many insects. Therefore, the collected specimen cannot be directly immersed in alcohol or formalin, and must be anesthetized to make it unconscious before immersion. Otherwise, they will shrink into a ball and will not be able to see their original appearance at all. There are many species of stone turtles, found in oceans around the world, and usually live on reef shores with normal salinity or at the bottom of oceans with high salinity. The body of the stone turtle is generally very small, and the length of the body of the common Species in China is about 2 to 3 cm. Since the stone turtle is the primitive type of shellfish, it has a certain significance in scientific research.
"Abalone Fraud"
Passing off dried stone turtles as dried abalone. Because the price of dried abalone in the market is not cheap, some unscrupulous traders use worthless "dried stone turtles" to sell them as "dried abalone" to make huge profits. Therefore, you must be careful when purchasing dried abalone, so as not to be deceived; abalone, like other shellfish, has a hard shell, but the shell part of the abalone shell is very small, the shell mouth is very large, and there is a small hole on the edge (commonly known as "nine-hole snail"). Its feet are well developed and the soles of the feet are flat. The dried abalone sold in the market has been hulled, slightly boat-like in shape, and has a very smooth side, that is, the sole part of the abalone. The "stone turtle" also has developed feet, the sole of the foot is also flat, so a little processing can be used to impersonate abalone, but as long as a careful identification will find that the "stone turtle" due to the thin flesh, drying will shrink and bend, and the edge of its foot is very rough. The biggest difference between "fake abalone" and "real abalone" is that the former has a shell plate in the center of the back, which is peeled off when processed and dried, but it always leaves obvious marks. Therefore, any "abalone" with obvious deep marks on the back is undoubtedly a fake abalone.