【英语时差8,16】独角鲸（下）（在线收听）

 Researchers from Harvard’s School of Dental Medicine think the giant tooth might also act as a sensory organ. With an electron microscope they discovered that the surface of a narwhal tusk is covered with millions of tiny nerve endings. These nerves connect to the narwhal’s brain through a network of tiny tubes in the tooth. The scientists believe that the narwhal use the sensitive tusks to detect changes in temperature, salt content, and flow patterns in the environment around them. But since only males grow tusks, it’s likely that the tusks did not evolve primarily as a sensory organ. More research is needed to really understand why narwhals have tusks and how they use them.