Cat sharks and bioluminescience

Bioluminescence is linked above all to marine organisms that are sometimes taxonomically distant from each other

by Lorenzo Ciotti
Cat sharks and bioluminescience
© NOAA Ocean Explorer Wikimedia Commons

Cat Sharks can be distinguished by the elongated shape of their eyes and two small dorsal fins placed far back on the body. Most species are quite small, no more than 80 cm in length, but some, such as the Leopard, can reach 1.6 m in length.

Most species have patterns on their skin, ranging from broad stripes to simple spots. They feed on invertebrates and small fish. Some species are ovoviviparous, but most lay eggs enclosed in elongated transparent capsules that end in spiral filaments at each end, allowing them to cling to vegetation and not be carried away by the current.

These eggs known as mermaid purses allow the development of the embryo to be monitored during its incubation. Cat Sharks of the Cephaloscyllium genus have the curious ability to fill their stomachs with water or air, when threatened, increasing their girth by 2 or 3 times.

Cat Sharks are found in temperate and tropical seas around the world, ranging from shallow midshore waters to depths of 2,000 meters or more, depending on the species.

But what is bioluminescence?

Bioluminescence is linked above all to marine organisms that are sometimes taxonomically distant from each other, but it also concerns terrestrial animals, for example insects, such as beetles of the Lampyridae or Phengodidae families and fungi.

In marine organisms, light-producing organs are called photophores and are present above all in fish, cephalopods, cnidarians of the order Siphonophora and other invertebrates living in the bathyal plane and the abyssal plane as well as in numerous bathypelagic organisms.

The phenomenon of bioluminescence is also widespread in many bacteria, some of which give rise to the milky sea effect which occurs especially in the Indian Ocean, where the sea takes on an intense luminescence that gives it the white color of milk.

The principle underlying bioluminescence is the same as that of chemiluminescence, in which some molecules, produced in an excited electronic state, emit part of energy in the form of light radiation returning to the ground state.

Biochemical studies have shown that the mechanisms of light emission by living organisms are very varied and therefore, in all likelihood, this property has developed independently in the various biological groups.