Different species of whale use different mechanisms to counteract the harmful effects of ultraviolet (UV) radiation, a paper published in Scientific Reports suggests. Further work is needed to investigate the long-term effects of UV exposure on whales.
Previous research has indicated that UV rays can cause skin lesions in whales. Mark Birch-Machin, Karina Acevedo-Whitehouse and colleagues investigated the effects of UV exposure at a genetic level, linking damage to migratory patterns. The team measured mitochondrial DNA (mtDNA) levels in skin samples from blue, fin and sperm whales as a marker of DNA damage.
The authors found that higher melanin levels tended to be correlated with lower levels of micro lesions and mtDNA damage, which suggests that melanin may confer protection against the sun. They found that blue whales could modify their skin pigmentation in response to UV rays. This ability to alter melanin levels (to ‘tan’) in response to UV exposure may be linked to the migratory pattern of blue whale, as they migrate annually from higher to lower latitudes, moving into a higher UV environment. Fin whales permanently occupy a high-UV region and demonstrate a reduced ability to modify skin pigmentation, instead maintaining consistently higher levels of melanin. Fin whales have the lowest recorded incidence of sunburn of the whales studied.
Sperm whales, which can spend up to six hours at a time at the sea surface, respond differently, activating genotoxic stress pathways in response to UV exposure. Higher levels of HSP70, one of the proteins expressed as part of this response, were found to correlate with a lower incidence of mtDNA lesions in sperm whales, suggesting that these pathways may bestow protection against UV damage.