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RESEARCH

The nursehound: small but fierce

Hiding in one of the smallest tanks in the Aquarium is perhaps one of the most spectacular species. Here we can see the birth of the Scyliorhinus stellaris, commonly known as the Nursehound or Bullhuss.

These small sharks are frequent visitors in the cold waters of our coastal seabed. Given its reduced size (between 16 and 150 cm), the nursehound is harmless to humans. However, these sharks can be quite fierce, and do not hesitate to use their 35 tiny teeth when it comes to defending their territory.

The nursehound is mainly nocturnal, sleeping on the sandy seabed during the day. This behaviour is similar to that of many other sharks, dispelling the myth that when sharks stop swimming, they die.

Inside the egg

The eggs of these sharks are quite curious. The hard translucent egg case allows us to see the minute embryos growing inside. This process will last around nine months, depending on the temperature. During this time the embryos will get their nourishment from a capsule located inside the egg called the viteline sac.

Though they may seem defenseless, these shark eggs are actually quite resourceful. The edges of the eggs have a series of tentacle-like protrusions which anchor them to the seaweed and keep them from being carried away with the current.

Nursehounds do well in captivity, which makes it possible for visitors to see up close how they lay their eggs and raise their young. In fact, nursehounds have been the subject of study at the Donostia-San Sebastián Aquarium for several years.