Squids feed on everything they can grab – from plankton to large fish and even their brethren. The gluttony of these cephalopods is phenomenal. For example, the Humboldt squid, reaching a length of more than 3.5 m and numerous along the western coast of South America, rises at night to the surface in search of prey. These oceanic “wolves” quickly leave nothing but bones from 200-250 kg of marlin or swordfish caught on a longline hook.
As a carnivorous predator, squid needs sharp eyesight. His eyes are very similar to the human eye, and for certain functions – they are even better. Some squid have one eye several times larger than the other, each of which is adapted to a different intensity of light.
Most squid of medium depths have glow organs. Light is formed as a result of a chemical reaction similar to that which creates a “cold” glow of fireflies. Individual species may even flare up periodically. Some of the luminous squid organs are just dots, others reach the size of a 5-ruble coin. In a number of squids, luminescence organs are simple formations, consisting of lenses that produce tissue and reflector light. In other species, the luminescence organs are equipped with diaphragms, focusing mechanisms and filters. There are squids that can produce even light of several colors.