Like other domesticated animals the Carp is subject to variation; some individuals, especially when they have been bred under unfavourable circumstances, have a lean and low body; others are shorter and higher. Some have lost every trace of scales, and are called “Leather-carps;” others retain them along the lateral line and on the back only (“Spiegelkarpfen” of the Germans). Finally, in some are the fins much prolonged, as in certain varieties of the Gold-fish. Cross-breeds between the Carp and the Crucian Carp are of common occurrence. The Carp is much more esteemed as food in inland countries than in countries where the more delicate kinds of sea fishes can be obtained.
Carassius differs from Cyprinus in lacking barbels; its pharyngeal teeth are compressed, in a single series, 4–4.
Two well-known species belong to this genus. The “Crucian Carp” (C. carassius, “Karausche”) is generally distributed over Central and Northern Europe, and extends into Italy and Siberia. It inhabits stagnant waters only, and is so tenacious of life that it will survive a lengthened sojourn in the smallest pools, where, however, it remains stunted; whilst in favourable localities it attains to a length of twelve inches. It is much subject to variation of form; very lean examples are commonly called “Prussian Carps.” Its usefulness consists in keeping ponds clean from a super-abundance of vegetable growth, and in serving as food for other more esteemed fishes. The second species is the “Gold-fish,” Carassius auratus. It is of very common occurrence in a wild state in China and the warmer parts of Japan, being entirely similar in colour to the Crucian Carp. In a domesticated state it loses the black or brown chromatophors, and becomes of a golden-yellow colour; perfect Albinos are comparatively scarcer. Many varieties and monstrosities have been produced during the long period of its domestication; the variety most highly priced at present being the so-called “Telescope-fish,” of which a figure is annexed. The Gold-fish is said to have been first brought to England in the year 1691, and is now distributed over nearly all the civilised parts of the world.
Fig. 273.—Cyprinus auratus, var.
Catla.—Scales of moderate size. Dorsal fin without osseous ray, with more than nine branched rays, commencing nearly opposite to the ventrals. Snout broad, with the integuments very thin; there is no upper lip, the lower with a free continuous posterior margin. Symphysis of the mandibulary bones loose, with prominent tubercles. Mouth anterior. Barbels none. Gill-rakers very long, fine, and closely set. Pharyngeal teeth, 5. 3. 2.-2. 3. 5.
The “Catla” (C. buchanani), one of the largest Carps of the Ganges, growing to a length of more than three feet, and esteemed as food.
Labeo.—Scales of moderate or small size. Dorsal fin without osseous ray, with more than nine branched rays, commencing somewhat in advance of the ventrals. Snout obtusely rounded, the skin of the maxillary region being more or less thickened, forming a projection beyond the mouth. Mouth transverse, inferior, with the lips thickened, each or one of them being provided with an inner transverse fold, which is covered with a deciduous horny substance forming a sharp edge, which, however, does not rest upon the bone as base, but is soft and movable. Barbels very small, two or four; the maxillary barbels more or less hidden in a groove behind the angle of the mouth. Anal scales not enlarged. Pharyngeal teeth uncinate, 5. 4. 2.-2. 4. 5. Snout generally more or less covered with hollow tubercles.
About thirteen species are known from rivers of tropical Africa and the East Indies.
Discognathus.—Scales of moderate size. Dorsal fin without osseous ray, with not more than nine branched rays, commencing somewhat in advance of the ventrals. Snout obtusely rounded, more or less depressed, projecting beyond the mouth, more or less tubercular. Mouth inferior, transverse, crescent-shaped; lips broad, continuous, with an inner sharp edge of the jaws, covered with horny substance on the lower jaw; upper lip more or less distinctly fringed; lower lip modified into a suctorial disk, with free anterior and posterior margins. Barbels two or four; if two, the upper are absent. Anal scales not enlarged. Pectoral fins horizontal. Pharyngeal teeth, 5. 4. 2.-2. 4. 5.