Horn sharks hatched

Source: Artis.nl, photo Ed Bierman
Animal keepers in Artis (The Netherlands) have peeled some eggs. It were remarkable eggs though: those of the horn shark. In the wild the eggs don't have to be peeled, because the scale becomes thinner by itself. But in aquaria they need some help.
Horn sharks (Heterodontus francisci) are a small shark species of about one meter long. They have a brown or gray colour with many dark spots and sharp spines just behind the dorsal fins. Their head is blunt, with high ridges over their eyes.

Horn sharks usually live solitary. They hunt at night and seek shelter during the day. Their prey consists of various crustaceans and shellfish, such as mussels, and all sorts of invertebrates and small fish. Younger sharks prefer softer prey such as lugworms and anemones. Horn sharks mostly live in rather shallow water of about 2 to 11 meters. Younger animals prefer a sandy bottom, older animals move to rocky reefs and algae beds. In wintertime the sharks move to deeper water.
In the period from February to April 24 eggs are laid. The scale (about 10 centimeters long) has the shape of a screw and in the wild the females wedge them into a crevice. In captivity the eggs are usually just laid on the bottom. In the wild the scales get increasingly thinner because snails eat from them. The young sharks can then free themselves after 6 to 10 months. Young sharks are 15 to 17 centimeters long when they hatch and they don’t need to look for food because of an internal yoke sac.
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