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How Do Cartilaginous Fish Reproduce?

Cartilaginous fish have skeletons made up of soft cartilage instead of hard bone, and movable jaws that are most often lined with sharp teeth. Cartilaginous fish include such species as sharks, rays, ratfish and skates. They reproduce in one of three ways -- through oviparity, ovoviviparity and viviparity. Fully mature at birth, young cartilaginous fish are released into the ocean to fend for themselves, as parental care after birth is is nonexistent.

Evolution
- Sharks, and other cartilaginous fish, have an evolutionary line that dates back many millions of years. While many other species of animals have evolved and changed completely within the last several million years, sharks in particular have not changed significantly in the last 150 million years. Through this time, the three types of reproductive methods evolved in cartilaginous fish have worked to ensure the propagation of each species' offspring.
Oviparity
- Oviparity is the process of laying eggs instead of giving birth to live young, according to Sharks.org. All egg fertilization is internal in cartilaginous fish, and once this occurs, the female fish will lay the eggs into the ocean. A yolk is provided within the egg pouch for nutrition and maturation. The eggs are often pushed into rock crevices to keep them out of the reach of predators. In addition, some species enclose the eggs in a thick case for added protection. The horn shark, zebra shark and bullhead shark all reproduce in this way.
Ovoviviparity
- Most cartilaginous fish are ovoviviparous, meaning that the eggs are fertilized internally and are formed and hatched inside of the female fish before they are born live into the ocean. One of the major advantages of this method of reproduction is that the young get a better chance at gaining strength and maturing to a point where they are better able to survive once they enter the ocean environment. Some ovoviviparous fish include the great white shark, angel sharks and mako shark.
Viviparity
- Viviparity is similar to ovoviviparity in that the eggs are fertilized inside of the female fish, with the difference being there is no yolk present for nutrition, and the fertilized eggs are provided nutrients to grow through the mother's placenta, according to Sharks.org. Young pups are born fully developed and strong, with an urgent need to get away from the mother as fast as they can, as she will view them as her next meal. Viviparous species include the hammerhead shark, bull shark and blue shark.

Animals & Science