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RAY (Lat. raia)
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See also:RAY (See also:Lat. raia) . The rays (Batoidei) together with the sharks (Selachoidei) See also:form the suborder Plagiostomi of Elasmobranch fishes, and are divided into six families (see See also:ICHTHYOLOGY). The first See also:family, Pristidae, contains only the saw-fishes (Pristis), of which five See also:species are known, from tropical and sub- tropical seas. They frequent es- pecially estuaries and See also:river-mouths, and in some cases make their way over a See also:hundred See also:miles from the See also:sea. Although saw-fishes possess all the essential characteristics of the rays proper, they retain the elongate form of the See also:body of sharks, the tail being excessively See also:muscular and the See also:sole See also:organ of locomotion. The " saw " (fig. 1) is a See also:flat prolongation of the snout, with an endoskeleton which See also:con- sists of three to five cartilaginous tubes; these are the rostral See also:pro- cesses of the See also:cranial See also:cartilage and are found in all rays, though com- monly much shorter. The in- tegument of the saw is hard, covered with See also:shagreen; and a See also:series of strong See also:teeth, See also:sharp in front and flat behind, are em- bedded in it, in alveolar sockets, on each See also:side. The saw is a for- midable weapon of offence, by means of which the See also:fish tears pieces of flesh off the body of its victim, or rips open its See also:abdomen to feed on the intestines. The teeth proper, with which the mouth is armed, are extremely small and obtuse, and unsuitable for wounding or seizing animals. Saw-fishes are abundant in the tropics; in their stomachs pieces of intestines and fragments of cuttle-fish have been found. They grow to a large See also:size, specimens with saws 6 ft. See also:long and 1 ft. broad at the See also:base being See also:common. The rays of the second family, Rhinobatidae, See also:bear a strong resemblance to the saw-fishes, but lack the saw. Their teeth are consequently more See also:developed, flat, obtuse, and adapted for crushing hard-shelled marine animals. There are about twenty known species, from tropical and subtropical seas. The third family, Torpedinidae, includes the electric rays. For the See also:peculiar organ (fig. 2) by which the See also:electricity is produced, see ICHTHYOLOGY. The fish uses this See also:power voluntarily either to defend itself or to stun or kill the smaller animals on on the See also:left side has been removed to show the electric organ. which it feeds. To receive the See also:shock, the See also:object must See also:complete the galvanic See also:circuit by communicating with the fish at two distinct points, either directly or through the See also:medium of some conducting body. The electric currents created in these fishes exercise all the other known See also:powers of electricity: they render the See also:needle magnetic, decompose chemical compounds and emit the spark. The dorsal See also:surface of the electric organ is See also:positive, the ventral negative. Shocks from a large healthy fish will temporarily paralyse the arms of a strong See also:man. The species of the genus See also:Torpedo are distributed over the coasts of the See also:Atlantic, Pacific and See also:Indian Ocean, and at least one reaches the coasts of See also:Great See also:Britain (T. ~hebetans). On the See also:west See also:coast of See also:North See also:America T. californica occurs, while on the Atlantic coast there is found the See also:black crampfish (T. occidentalis). This latter is said to reach a See also:weight of ,200 lb, but such gigantic specimens are scarce, and prefer sandy ground at some distance from the See also:shore, where they are not disturbed by the agitation of the surface-See also:water. Seven genera with about fifteen species have been described, mostly from the warmer seas. All the rays of this family have, like electric fishes generally, a smooth and naked body. The See also:fourth family, Raiidae, comprises the skates and rays proper, or Baia. More than See also:thirty species are known, chiefly from the temperate seas of both hemispheres, but much more numerously from the See also:northern than the See also:southern. A few species descend to a See also:depth of nearly 600 fathoms, without, however, essentially differing from their surface congeners. Rays, as is indicated by their shape, are bottom-fishes, living on flat sandy I perfectly flat molars, adapted for crushing hard substances. In ground, generally at no great distance from the coast or the surface. They See also:lead a sedentary See also:life, progressing, like the flat-fishes, by an undulatory See also:motion of the greatly extended See also:pectoral fins, the thin slender tail having lost the See also:function of an organ of locomotion, and acting merely as a See also:rudder. They are carnivorous and feed exclusively on molluscs, crustaceans and fishes. Some of the species possess a much larger and more pointed snout than the others, and are popularly distinguished as " skates." The following are known as inhabitants of the See also:British seas: (a) See also:short-snouted species: (I) the thornback (R. clavata), (2) the homelyn or spotted ray (R. maculata), (3) the starry ray (R. See also:radiata), (4) the See also:cuckoo or sandy ray (R. circularis); (b) long-snouted species: (5) the common skate (R. batis), (6) the flapper skate or jumbo skate (R. macrorhynchus), (7) the See also:burton skate (R. See also:elba), (8) and (9) the shagreen skates (R. oxyrhynchus and R. fullonica). A few deep-sea species are known, including R. abyssicola from 1588 fathoms off the coast of British See also:Columbia. Most of the skates and rays are eaten, except during the breeding See also:season; and even the See also:young of the former are esteemed as See also:food. The skates attain to a much larger size than the rays, viz. to a width of 6 ft. and a weight of 400 and 500 lb. The members of the fifth family, Trygonidae or sting-rays, are distinguished from the rays proper by having the See also:vertical fins replaced by a strong spine attached to the upper side of the tail. Some fifty species are known, which inhabit tropical more than temperate seas, some species being found in great tropical See also:rivers over x000 m. from the sea. The spine is barbed on the sides and is a most effective weapon of See also:defence; by lashing the tail in every direction the sting-rays can inflict dangerous or at least extremely painful wounds. The danger arises from the lacerated nature of the See also:wound rather than from any specially poisonous See also:property of the mucus inoculated. Generally only one or two spines are developed. Sting-rays attain to about the same size as the skates and are eaten on the coasts of the Mediterranean and elsewhere. One species (Trygon pastinaca) is not rarely found in the North Atlantic and extends northwards to the coasts of See also:Ireland, See also:England and See also:Norway. The rays of the See also:sixth and last family, Myliobatidae, are popularly known under various names, such as " See also:devil-fishes," " sea-devils " and " See also:eagle-rays." In them the See also:dilatation of the body, or rather the development of the pectoral fins, is carried to an extreme, whilst the tail is very thin and sometimes long like a See also:whip-See also:cord (fig. 3). Caudal spines are generally See also:present and some of the eagle-rays the molars are large and See also:tessellated (fig. 4), similar to those of the sting-rays. In the enormous " sea-devils," sometimes classed as a See also:separate family (Mobulidae), the anterior See also:part of the pectoral fin is detached and forms a " cephalic " See also:lobe or pair of lobes in front of the snout. The dentition consists of in others extremely small. Of the twenty-seven species which are known, from tropical and temperate seas, the See also:majority attain a very large and some an enormous size: one mentioned by Risso, which was taken at See also:Messina, weighed 1250 lb. A foetus taken from the uterus of the See also:mother (all eagle-rays are viviparous), captured at See also:Jamaica and preserved in the British Museum, is 5 ft. broad and weighed 20 lb. The mother measured 15 ft. in width and as many in length, and was between 3 and 4 ft. thick. At Jamaica, where these rays are well known under the name of " devil-fishes, " they are frequently attacked for See also:sport's See also:sake, but their See also:capture is uncertain and sometimes attended with danger. The eagle-ray of the Mediterranean and Atlantic (Myliobatis See also:aquila) is occasionally found off the British coasts. (A. C. G.; J. G. Additional information and CommentsThere are no comments yet for this article.
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