Unlike most fish, shark's reproductive strategy is to cultivate a few advanced larvae, rather than quantitative advantage. The duration of pregnancy varies from species to species. Generally, the spiny shark takes about 2 years, the basking shark takes 3 years, and the wrinkled shark even takes 3.5 years!

Extended data:

The crested shark (scientific name: Chlamydoselachus anguineus (Garman, 1884) is a shark of the genus crested shark. The frilled shark, also known as eel-shaped mackerel, is the most primitive shark, with no subspecies differentiation, and is known as a "living fossil". There are six branchial fissures on both sides of the body, and the branchial interval is extended and folded, covering each other, so it is named wrinkled gill shark.

The reason why gill fold sharks have more gill slits than other sharks is probably because most of them live in deep-sea environment, where the oxygen concentration is relatively low and more gill slits are needed for gas exchange.

Most frilled sharks live in the deep sea, and the distribution range is almost all over the world but very scattered. The fringed shark has a long gestation period, low fecundity and productivity, and its population is very rare. It has important ecological value and has been included in the Red List of Species in China and the Red List of Endangered Species in the World Conservation Union.

References:

Baidu encyclopedia entry-wrinkled shark

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