Anatomy of finfish and shellfish

Unit 13 - Mollusca

13.3.1. Distribution
The genus Loligo has a world-wide distribution in the warmer seas. In America, Loligo pealli is one of the most common squids, found along the Atlantic coast, from Nova Scotia to Florida, while Loligo apalesens is a common sight along the entire Pacific coast of the United States. Squids are quite aboundant in the Indian coastal waters, but they hunt in great shoals in the inland waters such as the Gulf of Kutch, the Gulf of Mannar and the Palk Bay and Strait. etc. Fossil remains indicate that squids were once very abundant during prehistoric times.
Habits and Habitat
The squids are the most active of the cephalopods occurring in coastal waters, in deeper waters, and in the abysses. Their winter habits are little known, but in the spring and in the early summer they swim in large schools of 10 to 100 or more, to lay eggs, when they are netted in great quantities. They can move swiftly both forwards and backwards by the combined actions of the fins and the funnel. When attacked they can emit through the funnel a cloud of black ink to make good their escape. The integument also has a great power of rapid chame¬leon-like colour changes, which also serves for protection. The skin contains pigment cells filled with various colours. When these cells become larger or smaller, the colours of skin change rapidly as though the animal were blushing. The colour changes harmonise with the colour of background, resulting in concealment of the animal. By examining a young squid under the low power of the microscope, one can observe how this colour ohange is accomplished. Small squids of the deep sea become visible in the dark by means of lurninous organs of various colours. The ink of deep sea liquid is also luminecent as it has to be if it is to serve its pur¬pose in the dark waters of the deep sea.