Did you know there is a shark looking like it is wearing stripped pajamas? The pyjama shark is a species of catsharks (the largest family of sharks), named after their cat-like eyes: horizontally oval eyes with elongated pupils and a nictitating membrane (an additional, transparent lower eyelid). Catsharks lay egg cases called mermaid’s purses with curly tendrils at each end, enable the female shark to fasten the egg case to underwater structures.
When threatened, the pyjama shark sometimes curls like the (remote) related shyshark (my very first shark of the week) into a circle with its tail covering its head. It is a relatively small (up to 1.1 m -3.6 ft- long), attractive shark and survives shipping via air freight and captivity, what makes it a popular exhibit in public aquaria.
The nocturnal pyjama shark spends most of the day lying motionless, hidden in caves on the bottom of the kelp forest. Usually living in South African coastal waters no more than 5 m -16 ft- deep, it has been found in 108 m -354 ft- deep waters and at the Madagascaran coast, too. Since near-shore waters are subject to wide fluctuations in salinity, pyjama sharks are able to actively regulate their internal saltiness. They maintain an internal osmotic pressure slightly higher than that of the surrounding water by concentrating nitrogenous wastes (for instance urea) in its tissues.
Pyjama sharks feed from everything, even fish offal, but are partial to squid. During the peak breeding season of the South African Chokka Squid, the pyjama sharks switch to daytime hunting and hide motionless among squid egg strands (the stripes help to break up their outline into unrecognizable shapes, thus camouflage the shark). Since Chokka Squids are known to tear off at high speed after spawning, this behavior is putting the shark in a perfect position to ambush the distracted squids from close range, like other catsharks and rays do.