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Female beaked whales' teeth are hidden in the gums and are not visible, and most male beaked whales have only two short tusks. Narwhals have vestigial teeth other than their tusk, which is present on males and 15% of females and has millions of nerves to sense water temperature, pressure and salinity.
The skim-feeders are right whales, gray whales, pygmy right whales, and sei whales (which also lunge feed). To feed, skim-feeders swim with an open mouth, filling it with water and prey. Prey must occur in sufficient numbers to trigger the whale's interest, be within a certain size range so that the baleen plates can filter it, and be slow ...
Beaked whales have several anatomical adaptations to deep diving: large spleens, livers, and body shape. Most cetaceans have small spleens. However, beaked whales have much larger spleens than delphinids, and may have larger livers, as well. These anatomical traits, which are important for filtering blood, could be adaptations to deep diving.
Filter feeding is very beneficial as it allows baleen whales to efficiently gain huge energy resources, which makes the large body size in modern varieties possible. [37] The development of filter feeding may have been a result of worldwide environmental change and physical changes in the oceans.
Narwhals also have a comparatively high amount of myoglobin in their body, which helps to facilitate deeper dives. [28] It has a dense layer of blubber , around 50 to 100 mm (2.0 to 3.9 in) thick. This fat accounts for a third of the body mass and helps insulate from cold ocean temperatures.
The beluga's body size is between that of a dolphin and a true whale, with males growing up to 5.5 m (18 ft) long and weighing up to 1,600 kg (3,530 lb). This whale has a stocky body. Like many cetaceans, a large percentage of its weight is blubber (subcutaneous fat).
Sperm whales have the largest brain mass of any animal on earth, averaging 8,000 cm 3 (490 in 3) and 7.8 kg (17 lb) in mature males, in comparison to the average human brain which averages 1,450 cm 3 (88 in 3) in mature males. [44] The brain to body mass ratio in some odontocetes, such as belugas and narwhals, is second only to humans. [45]
Homologous structures - structures (body parts/anatomy) which are similar in different species because the species have common descent and have evolved, usually divergently, from a shared ancestor. They may or may not perform the same function. An example is the forelimb structure shared by cats and whales.