The word dolphin comes from the Greek word “delphis” which means “spirit of the sea”. It is a generic term that does not define a particular species but more than thirty different species that belong to marine mammals. The dolphin is a marine mammal with teeth and a long rostrum.
You said marine mammal? And yes, the dolphin is a mammal whose life is entirely dependent on water. All mammals, whether marine or terrestrial, have in common: aerial breathing, breastfeeding, warm blood and the presence of hair at some point in their lives. In marine mammals there are animals as different as whales, dolphins, seals, dugongs and, more surprisingly, the polar bear and the marine otter. The dolphin belongs to the order of the cetaceans of the Greek “ketos” which means big fish of sea.
How many species of dolphins exist? Dolphins alone represent more than 30 species of varying sizes and shapes. It can be seen in virtually every ocean and even in some rivers. Whether small or large, gray or pink, its kindness and peaceful nature make it an extraordinary animal, demonstrating exceptional anatomical, behavioral and organizational adaptability. These characteristics are also its weaknesses with regard to the threats weighing on it.
The origins of the dolphin:
The dolphins have the originality to have for ancestor a terrestrial mammal, an ungulate (animal that always walks on the tips of his fingers, terminated by very thick nails, hoofs). The descendants of this ancestor have gradually adapted to aquatic life, initially giving amphibious animals, then animals perfectly equipped for a strictly aquatic life. It took more than 50 million years for the terrestrial ancestor to adapt to marine life and finally resembles a dolphin.
The body :
The dolphin with its hydrodynamic body is perfectly adapted to aquatic life.
In order to facilitate their movement in water, the body is torpedo-shaped and all the protruding parts have disappeared.
The ear horn is non-existent and the ear canal is presented as a simple needle hole on the side of the head.
The nipples are placed at the bottom of a slit and only protrude when breastfeeding.
In the male, except during erection, the penis is completely retracted inside the body.
Effective fins: dolphins are forced to breathe regularly on the surface. Consequently, their movements are mainly from bottom to top, and vice versa.
The horizontal caudal fin is the ideal tool for these movements, since it is used for propulsion.
The pectoral fins play an essential role in stabilization and orientation.
Finally, the dorsal aileron also serves as a stabilizer
Skin with variable geometry: to facilitate the swimming, the dolphin’s skin lost its hairiness to become smooth and slippery. It consists of a smooth and elastic epidermis and a dermis traversed by numerous orifices, in order to avoid the formation of vortices or turbulences which can slow the displacements. In addition, the skin cells secrete tiny drops of oil, a real lubricant that allows dolphins to slip better into the water. However, all these particularities do not explain, on their own, the extraordinary speeds of the dolphins, able to swim at more than 50 km / h! To date, the man fails to explain such a performance (for comparison, an Olympic champion hardly reaches 10 km / h).
