2012年11月24日星期六
SeaWorld's Old "Dolphin Discovery" Show (in HD)
1. Dolphins are marine mammals closely related to whales and porpoises.
2. There are almost forty species of dolphin in 17 genera. They vary in size from 1.2 m
(4 ft) and 40 kg (90 lb) (Maui's dolphin), up to 9.5 m (30 ft) and 10 tonnes (9.8 long
tons; 11 short tons) (the orca or killer whale).
3. They are found worldwide, mostly in the shallower seas of the continental shelves,
and are carnivores, eating mostly fish and squid.
4. The familyDelphinidae is the largest in the Cetacean order, and evolved relatively
recently, about ten million years ago, during the Miocene.
5. Dolphins are among the most intelligent animals, and their often friendly appearance, an artifact of the "smile" of their mouthline, and seemingly playful attitude have made them very popular in human culture.
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Dolphins are marine mammals closely related to whales and porpoises. There are almost forty species of dolphin in 17 genera. They vary in size from 1.2 m (4 ft) and 40 kg (90 lb) (Maui's dolphin), up to 9.5 m (30 ft) and 10 tonnes (9.8 long tons; 11 short tons) (the orca or killer whale). They are found worldwide, mostly in the shallower seas of the continental shelves, and are carnivores, eating mostly fish and squid. The familyDelphinidae is the largest in the Cetacean order, and evolved relatively recently, about ten million years ago, during the Miocene. Dolphins are among the most intelligent animals, and their often friendly appearance, an artifact of the "smile" of their mouthline, and seemingly playful attitude have made them very popular in human culture.
回复删除Dolphins have a streamlined fusiform body, adapted for fast swimming. The tail fin, called the fluke, is used for propulsion, while the pectoral fins together with the entire tail section provide directional control. The dorsal fin, in those species that have one, provides stability while swimming. Though it varies by species, basic coloration patterns are shades of grey, usually with a lighter underside, often with lines and patches of different hue and contrast.
回复删除The head contains the melon, a round organ used for echolocation. In many species, elongated jaws form a distinct beak; species such as the bottlenose have a curved mouth which looks like a fixed smile. Some species have up to 250 teeth. Dolphins breathe through a blowhole on top of their head. The trachea is anteriorto the brain. The dolphin brain is large and highly complex, and is different in structure from that of most land mammals.
Unlike most mammals, dolphins do not have hair, except for a few hairs around the tip of their rostrum (beak) which they lose shortly before or after birth.[15] The only exception to this is the Boto river dolphin, which has persistent small hairs on the rostrum.[16]
Dolphins' reproductive organs are located on the underside of the body. Males have two slits, one concealing the penis and one further behind for the anus. The female has one genital slit, housing the vagina and the anus. Two mammary slits are positioned on either side of the female's genital slit.[17][18][19]
Though the exact methods used to achieve this are not known, dolphins can tolerate and recover from extreme injuries, such as shark bites. The healing process is rapid and even very deep wounds do not cause dolphins to hemorrhage to death. Furthermore, even gaping wounds restore in such a way that the animal's body shape is restored, and infection of such large wounds seems rare.[20]
A study at the U.S. National Marine Mammal Foundation revealed that dolphins, like humans, develop a natural form of type 2 diabetes, which may lead to a better understanding of the disease and new treatments for both humans and dolphins.[21]