CUTTLEFISH, a marine invertebrate animal related to the octopus and placed in the molluscan class Cephalopoda (q.v.). The name has been regularly given to members of the family Sepiidae; but it has also been ap plied to other cephalopods, e.g., to various kinds of squid. It is considered to be more desirable, however, to maintain the more precise usage, when possible, and to avoid confusing the cuttlefish (Sepiidae) with squids. The most characteristic feature of the cut tlefish is the internal calcified shell or "cuttle-bone," and it is this structure which affords the best means of distinguishing the cuttlefish from other forms, which on account of certain structural resemblances, are asso ciated with it in the suborder Sepioidea of ten-armed Cephalo poda. These forms (e.g., Sepiola, Rossia, etc.) have a horny "shell." The interesting genus Spirula is regarded by some zoologists as allied to the cuttlefish ; but the shell of Spirula is not wholly in ternal and its structure is not comparable with that of the Sepiidae. The Sepiidae include the widely distributed genus Sepia, in which the common European cuttlefish (Sepia offi cinalis) Sepiella, Hemisepius, and a few other genera are placed. These animals have a somewhat flattened body (visceral mass) edged by a pair of rather narrow fins. In the common cuttlefish the body is ornamented with a number of zebra-like stripes. The remarkable Sepiella ornata has a series of longitudinal patches (ocelli) down each side. Five pairs of arms encircle the mouth in all cuttlefish. One pair of these is specialized for capturing prey. These are longer than the rest and can be withdrawn into two pouches. The suckers of the shorter arms are arranged in transverse rows of four suckers each down the entire length of the arms, except on one of the ventral arms of the male (kec tocotylized arm), from which they are absent towards the base. On the tentacles the suckers are restricted to an expanded pad (the "hand") at the tip of the arm. (For the general anatomy of these animals see Cephalopoda.) The cuttlefish are active muscular animals. They swim usually by means of the fins, which perform undulating movements ; but on being alarmed or attacked the animal can dart violently back wards by expelling a jet of water from the mantle-cavity through its funnel (q.v. in article CEPHALOPODA). In common with the majority of the Cephalopoda the cuttlefish secretes a dark sub stance ("ink"), the value of which as a means of protection is discussed in the general article on the Cephalopoda.
About ioo species of cuttlefish are known at the present time. They are found in most tropical and temperate seas, but only rarely in high latitudes. According to Grimpe the European spe cies are not found further north than the Skager Rak. Among the more noteworthy species are Sepia rouxii and Sepia hierreda, which are found in the Indian ocean and the Atlantic respectively and attain a length of over aft.; Sepiella ornata from West Africa, the colouring of which has been already alluded to, and the squid-like members of the subgenus Doratosepion. One of these, Doratose pion con f usa, has its fins prolonged backwards in two long "streamers" in the male and furnished with two organs of unique structure and unknown function. The cuttlefish are mainly in habitants of shallow coastal waters. Certain species (e.g., the common European Sepia officinalis) seem, however, to perform regular migrations into deeper water during part of the year, and there is not much doubt that these movements, as in the case of some other marine animals, are related to various phases in the reproductive cycle. From Cuenot's account of the migrations of S. officinalis it seems certain that this cuttlefish enters the Bassin d'Arcachon (Bay of Biscay) during the spring, summer, and autumn for the purpose of breeding and egg-laying, and that all the individuals, young and old, depart for deeper off-shore water in the winter. Grimpe, however, has observed an additional periodicity in the occurrence of S. officinalis in the North sea, for there are apparently years in which this cuttlefish is far more frequent in that area than at other times. Grimpe and Cuenot have likewise recorded the occurrence of seasonal dimorphism in S. officinalis. The former states that a plump summer form ("S. filliouxii") replaces the slender ("S. officinalis") winter form in the North sea.
The pear-shaped eggs of Sepia are enclosed in tough capsules and are dark in colour. They are deposited in clusters on f rag ments of coral, the tubes of marine worms and the stems of plants. Le Bianco observed that in the Gulf of Naples Sepia officinalis prefers submerged land plants, such as Pistacia, for this purpose.
The breeding habits of the common cuttlefish have been re cently studied by Grimpe, who records that, at least in captivity, the animal is monogamous.
The food of Sepia mainly consists of crustacea, though fishes are also eaten by it. J. T. Cunningham has described the capture of prawns by S. officinalis in the aquarium of the Marine Bio logical Station at Plymouth. The cuttlefish marks down a prawn that is poised on a projecting ledge of rock and stalks it with great caution. When it is within striking distance the cuttlefish shoots out its tentacles and drags the prawn into the circlet of shorter arms, by which it is held as it is dismembered by the "beaks" or horny jaws of its cap tor. In all probability the enemies of the cuttlefish are large fishes; but exact observations on the special enemies of these animals are wanting.
Cuttlefish are eaten by men in various parts of the world, e.g., in Italy, Greece, India and Japan.
In the Gulf of Naples Sepia offi cinalis is caught with various kinds of tackle, and the Neapoli tan fishermen in the breeding season of this animal sometimes tow a female Sepia behind their boats and catch the males which invariably follow her. It has been found that some species of sepia which are partly nocturnal in their habits are attracted by light, and in various countries fishermen lure them into their nets by torches or lanterns. In Naples the flesh of Sepia is not so much esteemed as that of Octopus and Loligo; but it is obtained and sold in great quantities in the Gulf of Naples and additional supplies are obtained from the Adriatic and Gulf of Manfredonia.
The "ink" secreted by these animals is used as the well known brown pigment "sepia." It is made by dissolving the dried secre tion of the ink-sac (q.v. in article CEPHALOPODA) in dilute am monia or soda and re-precipitating it with hydrochloric acid. The "cuttlebone" or internal shell has been used, either powdered or whole, as a dentifrice, for fine polishing, for taking casts in metal work, as an agricultural fertilizer, for "pouncing" (dusting un sized paper to prevent ink spreading on it) and for feeding cage birds. It was also used as a cosmetic by Roman women of fashion.
The modern cuttlefish make their appearance in the Miocene period. They are undoubtedly derived from a Belemnite-like an cestor, Belosepia, which lived in the Eocene seas and is found in a fossil state in the London clay.