Bowhead whales are the longest-living mammals on Earth, with an estimated lifespan of over 200 years. They are also among the largest animals, weighing up to 80 tons and measuring up to 18 meters in length. But how do they manage to live so long and avoid diseases like cancer, which are common in other mammals?
In this article, we will explore some of the fascinating facts about bowhead whales and their remarkable ability to resist cancer and ageing. We will also examine how their genome may be vital to unlocking their longevity secrets and what we can learn from them to improve human health and lifespan.
What are bowhead whales?
Bowhead whales are a baleen species belonging to the family Balaenidae and are the only living representative of the genus Balaena. They are named after their huge triangular skull, which they use to break through Arctic ice to breathe. They are the only baleen whale that lives exclusively in the Arctic and subarctic waters, where they feed on zooplankton by filtering water through their long baleen plates.
Bowhead whales are also known by other names, such as Greenland right whale, Arctic whale, steeple-top, and polar whale. They have a dark body with a distinctive white chin and no dorsal fin. They have huge heads representing almost one-third of their body length and the largest mouth of any animal. They also have the longest baleen plates of any whale, with a maximum length of 4 meters.
Bowhead whales are social animals that live in groups of up to 60 individuals. They communicate using a variety of sounds, such as clicks, whistles, moans, and songs. They are also very vocal during mating season, when males produce loud and complex songs to attract females.
Bowhead whales are migratory animals that follow the seasonal movements of sea ice and food availability. They typically spend the winter in areas with dense ice cover, such as the Bering Sea, and the summer in areas with open water, such as the Beaufort Sea. They can travel up to 10 kilometers per hour and dive up to 500 meters deep.
How do bowhead whales resist cancer?
Firstly – how does cancer work? Cancer occurs when cells in the body grow uncontrollably and form tumours that can damage vital organs and tissues. The risk increases with age, exposure to carcinogens, and genetic factors.
One would expect large animals like bowhead whales to have a higher risk of cancer than smaller animals because they have more cells that can mutate and divide abnormally. However, this is different. This unexpected phenomenon is known as Peto’s paradox, which states that there is no correlation between body size or lifespan and cancer incidence among different species.
In fact, many large animals have very low cancer rates, including bowhead whales, which are rarely affected by cancer despite living for over two centuries. This suggests that they have evolved some mechanisms to prevent or repair DNA damage that could lead to cancer-causing mutations. They contribute a lot to human health.
Scientists have recently sequenced the entire genome of the bowhead whale for the first time, hoping to find some clues about their cancer resistance and longevity. By comparing their genome with those of other mammals, including humans, cows, mice, and elephants, they discovered some unique features that may explain their remarkable health and cancer resistance ability.
One of these features is a set of mutations and duplications in genes that are associated with DNA repair, cell cycle regulation, cancer suppression, and ageing. These genes include ERCC1, PCNA, TP53, BRCA1, BRCA2, ATM, ATRX, WRN, BLM, XRCC1-6 , RAD51-54 , FANCA-G , MRE11 , NBS1 , CHEK1-2 , CDKN1A-B , RB1 , PTEN , NF1-2.
These genes are involved in various processes that help maintain the integrity and stability of DNA during cell division and replication, such as repairing DNA breaks, correcting DNA mismatches, removing DNA adducts, preventing DNA damage, arresting cell cycle progression, inducing apoptosis (programmed cell death), and inhibiting cell proliferation and migration. By having more copies or different versions of these genes, bowhead whales may be able to enhance their DNA repair capacity and avoid the accumulation of DNA damage that could lead to cancer or ageing.
Another feature that may contribute to their cancer resistance is their thick layer of blubber that helps insulate them from the cold and provides them with energy. This layer of fat may also protect them from harmful radiation and oxidative stress, which are major sources of DNA damage. Moreover, their low metabolic rate and slow growth rate may reduce the production of reactive oxygen species (ROS), which are by-products of cellular respiration that can damage DNA and other molecules.
How do bowhead whales resist ageing?
Ageing is a complex process involving gradually deteriorating biological functions and structures over time. Ageing is influenced by genetic and environmental factors and is associated with various diseases and disorders, such as cardiovascular disease, diabetes, neurodegeneration, arthritis, osteoporosis, cataracts, hearing loss, and dementia.
Bowhead whales do not show signs of senescence (age-related decline) or age-related diseases until very late in life. They also retain their reproductive capacity until old age, unlike most mammals that experience menopause or reduced fertility.
Scientists have identified some possible mechanisms that may explain how bowhead whales resist ageing.
One of these mechanisms is related to their genome stability and DNA repair ability. By preventing or fixing DNA damage, bowhead whales may be able to preserve their genomic integrity and avoid the accumulation of mutations that could impair their cellular functions and cause diseases.
Another mechanism is related to their gene expression patterns and epigenetic modifications. Gene expression is the process by which genes are turned on or off to produce proteins that perform various functions in the cell. Epigenetic modifications are chemical changes that affect the structure and accessibility of DNA without altering its sequence. These changes can regulate gene expression by making genes more or less active.
By analysing the transcriptome (the set of all RNA molecules produced by a cell) of bowhead whales and comparing it with those of other mammals, scientists have found some differences in the expression levels and epigenetic marks of genes involved in ageing and longevity. These genes include FOXO3 , SIRT1-7 , KLOTHO , IGF1 , IGF1R , IGFBP3-7 , AKT1-3 , MTOR , RAPTOR , RICTOR , AMPK , PGC1A-B , NRF1-2.
Frequently Asked Questions (FAQs)
1. How long do bowhead whales live?
Bowhead whales are the longest-living mammals on Earth, with an estimated lifespan of over 200 years. Some individuals may live even longer, as evidenced by the discovery of antique harpoons embedded in whale bodies.
2. How do bowhead whales survive in the Arctic?
Bowhead whales have several adaptations that help them survive in the harsh Arctic. They have a thick layer of blubber that insulates them from the cold and provides them with energy. Their large head allows them to breathe through ice up to 60 cm thick. They also have a keen sense of hearing that helps them navigate underwater and avoid predators.
3. How many bowhead whales are there in the world?
There are four distinct populations of bowhead whales in the world: the Bering-Chukchi-Beaufort population, the Hudson Bay-Foxe Basin population, the Davis Strait-Baffin Bay population, and the Svalbard-Barents Sea population. The total number of bowhead whales is estimated at around 25,000 individuals, with the Bering-Chukchi-Beaufort population being the largest and most stable.
4. What are the threats to bowhead whales?
Bowhead whales face several threats from human activities and environmental changes. These include commercial fishing and associated gear entanglement, industrial shipping and noise pollution, oil and gas exploration and development, climate change and sea ice loss, and orca predation. These threats vary in severity and impact among different populations and regions.
5. How can we protect bowhead whales?
International laws and agreements, like the International Whaling Commission (IWC), the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), and the Convention on Migratory Species (CMS), offer protection to bowhead whales. They are also managed by national and regional authorities, such as the U.S. Marine Mammal Protection Act (MMPA), the Canadian Species at Risk Act (SARA), and the Greenland Home Rule Government. In addition, Indigenous peoples have a special relationship with bowhead whales and play a vital role in their conservation through their traditional knowledge, culture, and subsistence hunting practices.