Mystery of ageing lobsters is SOLVED: Scientists develop a new DNA-based technique to reveal the age of crustaceans
- Researchers identify changes in DNA of the European lobster to work out its age
- The DNA-based technique could help manage lobster fisheries more sustainably
- It had previously not been possible to accurately work out a living lobster’s age
A new DNA-based technique can accurately reveal the age of lobsters, a study reveals – something that scientists have struggled to do until now.
The researchers, at the University of East Anglia (UEA), identified changes in the DNA of the European lobster (Homarus gammarus) that accumulate with age.
The changes can be identified in living lobsters, meaning the crustaceans – still sought after as a delicacy – no longer have to be killed to find out their age.
Previously, it has not been known exactly how old lobsters can get. Some experts have estimated they could live on the ocean floor for as long as a century or more.
But the new DNA-based technique could help manage lobster fisheries more sustainably, the UEA researchers report.
The new study follows revelations from the British government in July that it will ban the act of boiling lobsters alive for consumption.
The research team used a method that relies on quantifying DNA changes that accumulate with age within a European lobster (Homarus gammarus, pictured). Lobsters raised from eggs by the National Lobster Hatchery, so that the exact ages of individuals was known, allowed the researchers to calibrate their methods
THE EUROPEAN LOBSTER
Homarus gammarus, known as the European lobster, is a large lobster that can grow more than three feet in length.
It is found at all British and Irish coasts on rocky substrata, living in holes and excavated tunnels from the lower shore to nearly 200 feet in depth.
It is blue-coloured above with coalescing spots and yellowish below.
The first pair of walking legs carry massive (but slightly unequal) pincers which can be ‘formidable and dangerous’.
Identifying features include large eyes, large claws and a short and spiny rostrum.
‘Until now, a lobster’s age has usually been estimated using its size,’ said study author Dr Martin Taylor from UEA’s School of Biological Sciences.
‘But this is inaccurate as individual lobsters grow at different rates.
‘For a long time, it appeared that there was no accurate way to quantify a lobster’s age.
‘Some research suggested that you could tell a lobster’s age by counting the rings in parts of their eyestalks and stomach – a little like counting tree rings – but you can’t do that for a living lobster.’
Previously, it has been ‘very difficult or impossible’ to age a lobster without killing it, and even then it is quite controversial, Dr Taylor told MailOnline.
For the study, the researchers obtained lobsters raised from eggs at the National Lobster Hatchery in Padstow so they would know their exact age.
Once fully grown, they took tissue samples from the lobsters’ claws and measured DNA methylation, which is known to decrease with age.
Methylation of the DNA is the addition of a methyl group to one of the four DNA bases (in this case, cytosine).
DNA is made up of four building blocks called nucleotides – adenine (A), thymine (T), guanine (G), and cytosine (C).
Homarus gammarus, known as the European lobster, is a large lobster that can grow more than three feet in length. This specimen is 4-5 years old
A European lobster between 1-2 months. Previously, it has not been known exactly how old lobsters can get
‘These changes are often referred to as epigenetic changes and sites within the DNA may become more or less methylated with age, frequently in a clock-like manner,’ Dr Taylor told MailOnline.
‘We selected markers that best correlated with known age to build an ageing model that was then used to age unknown age samples.
‘A similar method has been used to determine chronological age in humans.’
Ministers are planning to ban boiling lobsters alive as they look to extend new animal sentience laws to include crustaceans.
The Government’s new Animal Welfare (Sentience) Bill – which is currently making its way through Parliament and will recognise animals as sentient beings – currently only covers vertebrates.
But the legislation will reportedly be extended to also cover invertebrates, formally recognising that lobsters, crabs and octopuses feel pain.
Boiling lobsters alive is already illegal in some countries like Switzerland, Norway and New Zealand.
Read more: Ministers will ban lobsters from being boiled alive
The researchers identified a very strong relationship between age and these DNA modifications, allowing them to accurately estimate the ages of individual lobsters.
When they applied this method to wild lobsters it predicted ages that generally aligned with minimum estimates of age based on size.
The researchers say further validation is required across a wider range of known-age individuals and tissue types before the model can be used in fisheries management.
The lobsters used in the study were up to around four years, but it’s thought the European lobster can live until it’s even more than 70 years old, and the American lobster (Homarus americanus) until it’s 100 years old.
‘If we catch a lobster and we want to age it that’s 70 years, then we’re extrapolating a long way beyond our known age range, so it starts to become much more difficult to be certain,’ Dr Taylor told CBC.
Also, the method has been calibrated on the European lobster. ‘It could be developed for other species, but it would need a similar study using known age samples to calibrate the model,’ Dr Taylor said.
It was almost a decade ago that scientists in Canada reported being able to work out the age of a lobster by counting its rings, like a tree.
Tress can be aged by measuring their girth – specifically the rings that develop over time that increase that girth.
Lobsters and other crustaceans, like crabs and shrimp, grow one ring each year in hidden-away internal spots.
Before then, it was thought that when lobsters and other crustaceans moult, they shed all calcified body parts that might record annual growth bands, so scientists had tried to make educated guesses at the age of lobsters judged from their size.
‘Lobsters have hard, inelastic shells and so in order to grow they must shed their old shell and replace it with a new one,’ said study co-author Dr Eleanor Fairfield at UEA.
‘However, lobsters of the same age don’t always grow and moult at the same time.
The new study follows revelation from the British government in July that it will ban the act of boiling lobsters alive. Boiling lobsters alive is already illegal in some countries like Switzerland, Norway and New Zealand
‘For example, lobsters with more food or in warmer waters can grow more quickly, which makes it really hard to know how old lobsters actually are.
‘It is crucial to be able to estimate how many lobsters of particular ages are present in a given area so that they can be sustainably harvested.
Scientists have already used ribosomal DNA methylation levels to age mice, dogs and humans, but it had never been used in a wild, marine animal before, she added.
The researchers suggest the technique shows great promise as a tool for improved management of the European lobster where information regarding the age structure of stocks is missing.
‘Having an accurate indication of lobster age will help fisheries, scientists and conservationists alike to understand, manage and conserve our vulnerable lobster stocks, working hand-in-hand with proactive fisheries management strategies, such as stock enhancement,’ said study author Dr Carly Daniels, head of production science and development at the National Lobster Hatchery.
The technique – developed at UEA in collaboration with the Centre for Environment, Fisheries and Aquaculture Science and the National Lobster Hatchery – has been detailed further in the journal Evolutionary Applications.
DNA AND RNA EXPLAINED: THE MOLECULES THAT CONTAIN THE GENETIC INFORMATION FOR LIFE
DNA – deoxyribonucleic acid – is widely known as the molecule found in the nucleus of all our cells that contains genetic information.
It is shaped like a double-helix and made of small sections called nucleotides.
Each nucleotide contains a nucleobase, a sugar, and a phosphate group.
The sugar component in this particular molecule is called deoxyribose and makes up the D in DNA.
This is a cyclic carbon-based chemical with five carbon atoms arranged as a pentagon.
At the second carbon atom there is an attached singular hydrogen atom in deoxyribose.
This can also have an additional oxygen attached as well.
In this case, the oxygenated chemical then forms what is simply known as ribose – the R in RNA.
The deoxy prefix literally means without oxygen.
Shape of RNA and DNA
RIbose can do almost everything deoxyribose can and also codes for genetic information in some cells and organisms.
When the oxygen is present it drastically alters how the chemicals bonds and sits alongside other molecules.
When oxygen is present – in RNA – it can take a variety of shapes.
When oxygen is not present in this specific location – in DNA – the molecule forms as the iconic double helix.
Uses of RNA
DNA is often broken down into RNA and read by the cells in order to translate and transcribe the genetic code in order to make proteins and other molecules essential for life.
RNA uses three of the same base pairs as DNA: Cytosine, Guanine, Adenine.
The othe base pair, Thymine, is swapped out in RNA for Uracil.
RNA is also often found in simpler organisms, such as bacteria.
It is often also a virus, with Hepatitis, flu and HIV all forms of RNA.
All animal cells use DNA, with one notable exception: the mitochondria.
Mitochondrian are the powerhouses of the cell and turn glucose into pyruvate and then into Adenosine triphosphate (ATP) via the Krebs cycle.
This process is all done in this one organelle in the cells and ATP is the universal form of energy and used throughout every aerobic organism.
In the mitochondria there is a small strand of RNA which is unique in the animal kingdom.
It is passed down from the mother exclusively (the father’s lives in the sperm but is dissolved during fertilisation) and allows humans to trace their maternal lineage back throughout time.
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