Are groupers, surfperches, guppies, and sharks viviparous or oviparous?
People habitually assume that fish are all oviparous, so are the newly appearing fish species on the market - the grouper, the surfperch, the guppy - and the traditional ocean overlord, the shark, oviparous or viviparous? According to relevant ichthyology data, the first three small fish are all oviparous, but the shark has three modes: viviparous, ovoviviparous, and oviparous.
1. Viviparous (placental viviparous): fertilized eggs enclosed in a horny shell develop in the uterus, and the nutrients needed for growth are obtained from the yolk sac placenta, and they are only born when the young sharks are almost fully formed, with dozens born each time. Most oceanic sharks are viviparous. Most sharks reproduce according to the seasons each year, and some large sharks reproduce every other year. Most sharks have a gestation period of 8-9 months, and the spiny dogfish's gestation period is even as long as 24 months. Generally speaking, large sharks give birth to more young sharks at one time, while small sharks are the opposite. Sharks also grow extremely slowly, not reaching sexual maturity until 5-10 years of age.
2. Ovoviviparous (non-placental viviparous): fertilized eggs develop in the uterus, with the yolk sac or eggs released from the ovary into the uterus as the source of nutrition, and no placenta is formed in the uterus. Except for the whale shark, which can produce more than 300 at a time, the rest produce at most dozens each time, and the fewest is the thresher shark (long-tailed shark), which produces only two each time.
3. Oviparous: generally adopted by large sharks. Shark eggs are very large, so there is no shortage of nutritional supply. The expelled eggs are wrapped in a flat, cushion-shaped sheath, and the cushion-shaped sheath is added around the egg as it passes through the oviduct. The outer skin of the sheath hardens after entering the water, and each corner of the sheath has a short, hollow horn-like structure through which seawater can enter, allowing the egg to obtain oxygen. The number of eggs laid each time is limited. The eggs are bag-shaped or spiral-shaped, and after being laid they are fixed in coral reefs, seabed plants, or rock crevices. The empty egg capsules of the spiny dogfish washed up on the coast are nicknamed mermaid's purses.
Appendix: The grouper is a deep-sea fish, also known as the stone scorpionfish, named for the red spots on its body. Hotels in Hong Kong, China and Guangdong often use it to make high-end dishes. The body is medium-long and laterally compressed, with highly variable coloration, usually brown or red, with stripes and spots. It is a famous specialty of Shengsi seafood and has long been praised by gourmets at home and abroad. The grouper is rich in the most important nutrient needed for growth and development——protein. Protein contains various essential amino acids and is a high-quality protein food for humans. It also contains linolenic acid, arachidonic acid, linoleic acid, and other essential fatty acids for the human body, as well as eicosapentaenoic acid and docosahexaenoic acid. It is not only a high-quality food and health nutritional product, but can also resist thrombosis, reduce blood viscosity, lower blood pressure, and can be used to prevent and treat myocardial infarction, coronary heart disease, vasculitis, cerebral arteriosclerosis, and many other diseases. At the same time, fish can activate brain nerve cells and improve brain function.
The surfperch is distributed in the western North Pacific. In China it is found in the northern Yellow Sea and the Bohai Sea. It belongs to the family Embiotocidae (jiujiu fish, sea perch).
The guppy is an omnivorous small fish species. Because guppies are extremely adaptable to the environment, they reproduce and are distributed in the lower reaches of rivers, lakes, marshes, and ditches in some tropical regions. Their wild habitats are diverse, mainly inhabiting freshwater basins and lakes and marshes. They can tolerate polluted waters and are gregarious. They are widely distributed. They are native to Venezuela, Guyana, the West Indies, northern Brazil, and other places in South America.