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一些深海鲨鱼可以浮动与传统观点相反

Researchers at University of Hawaii, Manoa in collaboration with a team from the University of Tokyo were surprised to find not one, but two species of deep-water sharks that have positive buoyancy。 Most sharks have a negative buoyancy, meaning if they stop swimming they’;ll sink to the bottom, and some researchers have posited that there may be some species with neutral buoyancy。 Finding sharks that defy this conventional wisdom is definitely an important discovery。 Now the researchers are trying to find out how the positive buoyancy is attained and whether other shark species have this ability。

Floating sharks

The prickly shark, Echinorhinus cookei, is a large predatory shark with a pan-Pacific distribution。 Prickly sharks are amazing looking and have a traditional shark body type although they are a bit thicker around the middle than many other species。 Photo: Wikipedia

The prickly shark, Echinorhinus cookei, is a large predatory shark with a pan-Pacific distribution。 Prickly sharks are amazing looking and have a traditional shark body type although they are a bit thicker around the middle than many other species。 Photo: Wikipedia

Sharks’;  cartilaginous skeletons are less dense than bones, and most employ an oil-filled liver to increase buoyancy。 Despite this, sharks can’;t float and have to start swimming at some point to avoid sinking to the bottom of the ocean。 Some scientists have considered that maybe some species are neutral buoyant based on observations of some species which live in austere environments (low oxygen, few food resources)。 You can imagine how remarkable it was for the Hawaiian researchers to discover that the  sixgill and prickly sharks have slightly positive buoyancy which helps them slowly rise to the surface without any effort。

The team strapped cameras, lights and sensors to the several specimens from each species。 Each 30 seconds, a strobe would turn on and light the shark’;s surroundings, while a camera instantly took a picture。 Meanwhile, sensors recorded the temperature and depth of the water。 To record when the shark began to swim and measure the effort that went into the process, an accelerometer was also added。 After a predefined time, the whole pack detached from the shark and rose to the surface from which it was collected by the researchers。

本文源自: 环亚娱乐游戏

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