By: Alison Cranage
Bats hold an exclusive place in our collective consciousness – as creatures of the night, of vampires and witchcraft. They are truly unique mammals, essential to our ecosystems, with much to teach us about human health and longevity.
One in every five living mammals is a bat. There are over 1,300 species, spread across the globe in a wide range of ecological niches. The largest bat is the giant golden-crowned flying fox, weighing 1.6kg with an impressive 1.7m wing span.
Near the other end of the scale is the common pipistrelle bat (Pipistrellus pipstrellus) – the UK’s most abundant species. It weighs just 5g, or the same as a 20 pence piece. If you see a bat darting through the twilight it is likely to be a pipistrelle hunting down moths.
Emma Teeling is Professor at University College Dublin and Founding Director of the Centre for Irish Bat Research. World renown expert, she is our collaborator on the pipistrelle bat genome, which we sequenced as part of our 25 Genomes Project.
She is studying the whole range of exceptional adaptations of the bat. They are the only mammals which can fly, and use laryngeal echolocate. They also possess vocal learning, a rare feature among mammals. Her most recent studies are into their unusual longevity.
A healthy life
The relationship between mammal size and lifespan is, on the whole, linear. Smaller mammals, with faster metabolisms, tend to have shorter lives. But some bat species live up to 10 times longer than would be predicted by their size. Not only do they live long lives, they live healthy ones. They can harbour a range of usually deadly viruses, including Ebola, SARS and rabies, yet they don’t get ill. Studying their immune systems could reveal new ways to treat these infections in people.
Bats are resistant to cancer too. In humans, the risk of developing cancer increases with age. Almost 9 in 10 cancer cases in the UK are in people aged 50 or over. Many other mammals also get cancer, but it is extremely rare amongst bats, naked mole rats, grey squirrels and elephants.
Secrets of the bat genome
Professor Teeling is combining a longitudinal study of one of the longest lived bat species with genomic and molecular analysis, to understand how bats age so healthily.
Her team visit Northern France every year to monitor a colony of about 700 Myotis bats – one of the longest lived species. Each member of the colony is tagged, and caught each year. A minute wing punch is taken and stored for later analysis, before the bat is released. One bat, first caught as an adult, has been caught again 42 years on, still healthy. The blood samples from the bats are used to study their genomes, cellular and gene function and immune system.
This enables the researchers to answer questions about the bat genome. Do they have the same age-related genes as other mammals? Do they regulate them differently? Or is there something else going on? Her work has already uncovered that genes involved in repairing the age-related damage at the ends of chromosomes may hold the key to bat longevity.
The pipistrelle bat lives five years on average. Comparing its genome to the longest lived species, like Myotis, will enable further discoveries.
|Bats pollinate the flowers of the agave plant – essential to making tequila|
|In 1999 the soprano pipistrelle was formally identified as a separate species from the common pipistrelle, based on differing echolocation signatures|
|Male bats sing to attract females|
|A pipistrelle can eat 3,000 insects in one evening|
Bats have the smallest genomes of all mammals. This could be an adaptation related to flight, as birds also have small genomes, but this is far from certain. Bats have highly active transposable elements in their genomes – these sequences of DNA copy and paste themselves, moving around the genome. In other mammals this leads to genomes growing over time as the copies stay – but bats must have a mechanism to remove them, because their genome has remained small. Studying bat genomes will help us understand this structural evolution, and uncover what is the minimal genome required to make a mammal.
Professor Teeling has set up the bat1k project – an effort to sequence the genomes of 1,000 different bat species. The sequence of the pipistrelle bat is just the start.
Usually out of sight, we perhaps don’t think about bats often. The pipistrelle is an iconic UK species, and highly adapted to live among us. The genome sequence will help researchers understand the native forna of the British Isles, as well as uncover the genetic basis of their unique features.
About the author:
Alison Cranage is a science writer for the Wellcome Sanger Institute.