Delphininae

a subfamily of mammals of the family Delphinidae of the order Cetacea. The body measures 1.2–3 m long, with some species reaching 10 m. Most species have a dorsal fin, a snout elongated into a beak, and numerous teeth (more than 70). The animals orient themselves superbly in the water with the aid of echolocation (sonar) and extremely sensitive hearing, which is capable of discerning vibrations from a few tenths of a hertz to 150–196 kilohertz. The Delphininae have complex voice signalization and a sound signaling organ (which is the echolocation organ) located in the single blowhole; the blowhole is connected to three pairs of air sacs, which are supplied with a system of muscles. The frequencies of emitted signals measure as much as 170 kilohertz. The Delphininae have a highly developed central nervous system: the brain is large and round, and the cerebral hemispheres have numerous convolutions (the cerebral cortex numbers up to 30 billion nerve cells). Owing to the large size of the brain, the Delphininae can process large quantities of acoustic and other data; like parrots, they are able to imitate words uttered by man. They are found in many oceanariums and dolphinariums. Since they can be easily trained, the Delphininae are used as circus and laboratory animals, and the possibility of domesticating several species is being studied.

The Delphininae are rapid swimmers, reaching speeds of up to 50 km per hour. They are herding animals with extremely streamlined and highly maneuverable bodies. The pectoral, dorsal, and caudal fins (particularly the latter) have variable elasticity, which changes with the swimming velocity and is regulated by complex blood vessels (hydroelastic effect). The Delphininae feed on fish, on cephalopods, and less frequently on crustaceans. After a gestation period of 10–12 months, one calf is born. It is large, sometimes half the length of the mother’s body. The mother nurses it for 4–6 months; it reaches full maturity at 3–5 years.

There are sedentary and migratory Delphininae; their migrations have been poorly studied. The large animals live as much as 50 years, while smaller ones live up to 30 years. Currently the Delphininae are undergoing evolutionary growth. The subfamily includes 20 genera that comprise 48 species. Of these, 12 genera (15 species) live in the seas of the USSR. There are three species in the Black Sea: the bottle-nosed dolphin (Tursiops truncatus), the common dolphin (Delphinus delphis), and the harbor porpoise (Phocaena phocaena). They are widely distributed in oceans. Some species (for example, the false killer whale [Pseudorca crassidens]) are cosmopolites. The Delphininae are particularly numerous in warm ocean waters, and some species live only in such waters: all seven species of the genus Sotalia, the black finless porpoises (Neomeris phocaenoides), and most species of the genus Cephalorhynchus. New genera have been described recently, the Sarawak dolphin (Lagenodelphis) in 1956 and the broad-beaked dolphin (Peponocephala) in 1966.

The hydrodynamic perfection of the body’s form, the structure and the antiturbulence properties of the skin, the controlled hydroelastic effect in the fins, the ability to dive to great depths, the dependability of the echolocation, and many other anatomical features of the Delphininae are of great interest to bionics. From the point of view of physiology and medicine, a number of adaptations in breathing and blood circulation are of special interest (the abundance of myoglobin, the ability to hold the breath for long periods, the insensitivity of the respiratory center to accumulation of carbon dioxide in the blood, the slowing of the pulse and redistribution of blood flow during diving, the well-developed rete mirabile, and the peculiarities of the renal blood circulation and water-salt exchange). In US laboratories attempts are being made with the help of various factors (overburdening, nutritional and nerve effects) to cause rheumatic, cardiovascular, and ulcerous diseases in the Delphininae. Large funds are being expended to study the animals. Their use for locating fish schools, driving fish schools into nets, communications, and assisting aquanauts in various underwater projects is being envisioned. With the aid of attached transmitters, they are being trained to gather data on radioactivity, salinity, temperature, and currents at various ocean depths. The taming of the animals offers man the opportunity to more fully use the riches of the sea.

Abroad, the Delphininae are also being studied for military purposes: the possibility of using them to locate mines, torpedoes, and sunken vessels and to patrol ocean sectors and detect submarines is being ascertained.

Some species are used commercially. Members of the genera Stenella and Lagenorhynchus are used for food in Japan and the Solomon Islands, where both the flesh and oil is eaten. In the USSR, the commercial use of the Delphininae has been banned since 1966.