Ghost shark egg find a treat

The spindle-shaped egg of a ghost shark also known as a mermaids purse.

Fish Hoek resident Margie Olson was thrilled when she picked up a couple of strange-looking shark eggs on Fish Hoek beach a few weeks ago and decided to share her find with the Echo.

The Echo spoke to Tinus Beukes, operations manager at Two Oceans Aquarium, to find out more about them.

Sharks can be oviparous (laying eggs outside the body) viviparous (giving birth to live young) or ovoviviparous (the embryos develop inside an egg that hatches inside the mother’s body).

Mr Beukes looked at photographs of Ms Olsen’s find and confirmed the spindle-shaped egg was that of a ghost shark (Callorhinchus capensis), also known as elephant fish or St Joseph shark.

The black egg, he said, belonged to a pajama catshark (Poroderma africanum).The ghost shark was the most interesting of the two he said.

Ghost sharks show seasonal abundance in False Bay, but people are mostly unaware of their existence as they are not a common catch on rod. They can be found from shore to depths of more than 200 metres.

The egg cases for the ghost shark wash up quite regularly, especially on the West Coast, Durban and Namibia.

All shark eggs contain an embryo and yolk sac similar to a chicken’s egg. It is encased in a leathery watertight sac to protect it from predators as the mother swims away after laying eggs.

Mr Beukes said the spindle shape of the ghost-shark egg allowed it to be wedged in the sand or between rocks to protect it and prevent it from floating in the water.

Despite its name, the ghost shark is neither fish nor shark, although it shares a common ancestor with sharks.

They are smooth and scaleless, silvery white in colour with trunk-like flexible snouts that serve a sensory function. They have four gill openings and no spiracles. Water for respiration is taken in through the nostrils. Ghost sharks have spines and two dorsal fins that can be erected.

The mouth is located just behind the snout and the eyes are large and set high on the head.

It has classic characteristics of a fish and a shark, and like a shark it has a spiral valve instead of a true stomach and has a cartilaginous skeleton instead of the bony one a fish has.

Adult males have clasping organs on the head and pelvic fins, which hold the female in place during copulation. After internal fertilisation, the females deposit one or two brown egg capsules on the sea bed.

Mr Beukes said eggs could take up to a year to hatch.