Hair is important, if you’re a land-based mammal. Hair or fur keep you warm! But for whales, who evolved from hairier land-based creatures to return to the ocean, hair just gets in the way. What matters more in a marine environment is streamlining, allowing the ability to catch prey. A group of Nanjing, China, scientists have pinpointed the genes responsible for this hairless return to the ocean.
Guang Yang and his team at Nanjing Normal University found that natural selection put pressure on two genes responsible for hair creation and loss, called Hr and FGF5, which allowed whales and other cetaceans to swim hairless. Yang’s research appears in the February 9 issue of BMC Evolutionary Biology.
Hair is produced continuously in hair follicles; these follicles are regulated by several genes, including the “hairless” or Hr gene, and fibroblast growth factor 5, or FGF5. The Hr gene helps boost the first growth of hair, and when absent, results in complete baldness (a condition called alopecia in humans). FGF5, meanwhile, controls the cycle of creating and replacing hair, including the various stages of growth (or cessation of growth) as an organism ages.
Cetaceans (whales, dolphins, orcas and others) are unusual because they are the only mammals that returned to the sea after evolving into land-based creatures. Part of this process involved losing the hair and fur that were essential to survival on land. By studying the genes of seven cetaceans, Yang’s team found that changes to the Hr gene resulted in its loss of function in whales, thus halting the development of hair follicles. Meanwhile, the FGF5 gene was expressed (and possibly over-expressed) in cetaceans, accelerating the hair loss that normally comes with human aging.
Source: BMC Central
Chen, Z., Wang, Z., Xu, S., Zhou, K., & Yang, G. (2013). Characterization of hairless (Hr) and FGF5 genes provides insights into the molecular basis of hair loss in cetaceans BMC Evolutionary Biology, 13 (1) DOI: 10.1186/1471-2148-13-34
whale cetacean, endangered whale, facts about whales