CATDOLL : CATDOLL: How do shells give birth to smaller shells?

1. How do shells give birth to small shells?

In the breeding season, male and female shellfish release sperm and eggs into the water respectively. With the movement of water, these sperm and eggs will automatically recognize and combine, thus achieving the purpose of reproduction. I found some information that can explain it more clearly: Let's take oysters as an example. Oysters have two types of reproduction: larval and oviparous. Oyster: The general name of the oyster family of the order Ostreae of the class Bivalvia of the phylum Mollusca. Also known as sea oysters. In the breeding season, the parent of the oviparous oyster discharges mature sperm and eggs from the body. The sperm and eggs are fertilized in the seawater. After a period of floating life, they attach to other objects and metamorphose into juveniles after fixation. Most of the cultured species belong to this type. When the larval oyster reproduces, the parent discharges mature reproductive cells into the water outlet cavity. Relying on the action of the mantle and gill muscles near the drainage hole, the reproductive cells are pressed into the gill cavity and fertilized here. After the embryo develops into a veliger larva, it leaves the mother body and goes through a free-floating stage in the seawater, and then attaches and metamorphoses into juveniles. The dense-scaled oyster belongs to this type. The gonads of oysters mature and begin to reproduce when they are one year old. There are two types of reproduction: larval and oviparous. The dense-scaled oyster is a larval type. After the eggs mature, they are discharged into the mother's mantle cavity between the gills for fertilization and hatching. After developing to the veliger larvae stage, they are discharged into the seawater for floating life, and then metamorphose into adults for fixed life. The long oyster is oviparous and fertilized in vitro. Most of the long oysters are hermaphroditic, and a small number are hermaphroditic. When the gonads mature, the males are milky white and the females are light yellow. When the water temperature in the natural sea area rises to 16℃, the gonads of long oysters begin to mature, and the spawning peak is when the water temperature reaches 24-25℃. The peak breeding period in the Yueqing Bay sea area of ​​Zhejiang Province is from June to July. Oyster spawning is mostly carried out during the high tide. When the water temperature is 23℃, the fertilized eggs develop into D-shaped larvae after 20-22 hours. Under the condition of water temperature of 23-26℃, after about 20 days of cultivation, the average shell length of the D-shaped larvae can reach more than 280μm, and 40%-50% of the larvae have eyespots. At this time, the attachment base should be put in so that the larvae can metamorphose and attach.

2. How do mollusks like scallops and oysters reproduce? Do they have shells when they are born?

Mollusk, a phylum of coelomectins. It belongs to the protostomes, true coelom, and terminal cell stem. Gastropods have a second left-right asymmetry due to the twisting of the visceral mass, while the systems of other classes are left-right symmetrical. The body consists of the head (not in the Bivalvia), feet, and visceral mass. The epidermis of the visceral mass extends to form the mantle, which wraps the main part of the body. The space between it and the visceral mass is the mantle cavity, which contains gills, and the end of the digestive organs and the excretory organs open here. There is no body segment structure at all. The irregular gaps in the body are the blood cavity. The true coelom becomes narrower due to the development of mesenchyme, forming only the pericardial cavity, the inner cavity of the kidney duct, and the inner cavity of the gonad (genital cavity). The head has sensory organs such as eyes and a mouth. The foot, as a locomotion organ, has smooth muscles, which is related to its slow movement. There are oblique striated muscles on the wall of the ink sac. The mantle secretes shells outward. The number and shape of shells vary in different classes. The digestive tract is long, and there are generally radulas and salivary glands in the mouth. The midgut gland opens into the stomach. Generally, there is one pair of gills, and the heart has two atria and one ventricle. However, species with two pairs of gills in the cephalopoda have four atria. Due to the twisting of the visceral mass, some gastropods have only one gill (the heart has one atria and one ventricle), and some species have lost all their gills and replaced by mantle gills. In the terrestrial gastropoda, part of the mantle of the pulmonary snails has evolved into lungs. It is an open vascular system, and the respiratory pigment is mostly hemocyanin. Clams, flat spiral snails, etc. have hemoglobin. The excretory organ is mainly the nephric duct (Boyena's organ), but there are also species with Kieber's organ (branchi). The nervous system is a special type. In addition to the one pair of head ganglia on the esophagus, there are also one pair of lateral ganglia, foot ganglia and visceral ganglia. Each pair of similar ganglia is connected by transverse nerves, and the head ganglia are connected to other ganglia by longitudinal nerves. Hermaphroditic or heterosexual. Sexual conversion is seen in oysters, shipworms and abalone. Except for cephalopods, all other species undergo spiral cleavage, going through the trochophore larvae and veliger larvae stages; however, the cleavage of cephalopods is bilaterally symmetrical and develops directly.

3. How do shells give birth to small shells?

Shells are the outer shells of shellfish. Shellfish reproduce by laying eggs, and the eggs develop into small shellfish in the water.

4. How do shellfish reproduce?

During the breeding season, the parent of the oviparous oyster discharges mature sperm and eggs from the body. The sperm and eggs are fertilized in the seawater. After a period of floating life, they attach to other objects and metamorphose into juvenile shellfish after fixation. Most of the cultured species belong to this type. During the reproduction of the juvenile oyster, the parent discharges mature reproductive cells into the water outlet cavity. Relying on the action of the mantle and gill muscles near the drainage hole, the reproductive cells are pressed into the gill cavity and fertilized here. The embryo develops into a veliger larva and leaves the mother body. After a free floating stage in the seawater, it attaches and metamorphoses into juvenile shellfish. The dense-scaled oyster belongs to this type.