The egg cases of catsharks are purse-shaped with long tendrils at the corners that serve to anchor them to structures on the sea floor. Some catsharks (Scyliorhinidae) and the finback catsharks in the genus Proscyllium are the only members of their order that lay eggs. The egg cases are oval and covered with adhesive fibers that serve to secure them to the bottom. The bamboo sharks (Hemiscylliidae) and the zebra shark (Stegostomatidae) lay eggs on the bottom, while the other carpet sharks give live birth. Egg case of a brownbanded bamboo shark Carpet sharks As a member of the order Heterodontiformes, the whitespotted bullhead sharks is thought to be oviparous, but egg cases have never been observed. The egg case of the Mexican hornshark features a tendril and more rigid flanges, suggesting that egg case design of this species is evolving towards anchoring with tendrils and away from wedging into crevices. The Female Japanese bullhead shark has been known to deposit their eggs in one location along with other females, called a "nest". Bullhead shark eggs typically hatch after 7 to 12 months, depending on the species. Hatchlings are considered large for sharks, reaching over 14 cm in length by the time they leave the egg case. ![]() This allows the egg cases to become wedged in the crevices of rocky sea floors, where the eggs are protected from predators however, some bullhead sharks deposit their eggs on sponges or seaweed. Bullhead sharks īullhead shark egg cases are shaped like an auger, with two spiral flanges. Oviparous sharks are known to regularly produce unfertilized eggs when kept in captivity without males. It is thought that viviparity is the ancestral condition for sharks, and that it evolved through the elongation of retention time of retained oviparity. With retained oviparity, eggs are kept within the oviduct for a period of time before depositing outside of the body as an unhatched egg case. With single oviparity, the egg cases are extruded soon after fertilization. Oviparity in sharks can be categorized as single or retained. The embryo fans its tail constantly to promote exchange with surrounding water. After a period of development, typically a week or two, small slits open on each side of the egg case to aid water flow. Gestation can take anywhere from a few months to over a year. Egg cases are typically produced in pairs, each with one fertilized embryo inside, with the exception of a few species that produce egg cases with more than one viable embryo. Shortly after the egg case finishes developing, it is deposited outside the body common locations include kelp forests and rocky seafloors. After the ovum enters, the rest of the egg case forms around it. Shortly after internal fertilization, the fertilized ovum enters the partially formed egg case located in the oviduct. Depending on the species, egg cases may have one or more tendrils. With the exception of bullhead shark eggs, egg cases are typically rectangular in shape with projections, called horns, at each corner. ![]() Egg cases without a fibrous outer layer can be striated, bumpy, or smooth and glossy. Some egg cases have a fibrous material covering the outside of the egg case, thought to aid in attachment to substrate. ![]() Description Įgg cases are made of collagen protein strands, and are often described as feeling rough and leathery. Oviparity is completely absent in the superorder Squalomorphii. Egg cases typically contain one embryo, except for big skate and mottled skate egg cases, which contain up to 7 embryos. ![]() Natural collagen casing found encompassing some aquatic lifeforms' fertilized eggsĮgg case of a skate Embryo active inside egg case.Īn egg case or egg capsule, often colloquially called a mermaid's purse, is the casing that surrounds the eggs of oviparous sharks, skates and chimaeras.
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