The other-worldly, bright orange, 5 limbed creature is instantly recognisable. Paddling on a Cornish beach, or rockpooling on the Isle of Mull at low tide – it’s pretty likely you’ll come across one.
Lurking in the shallow waters of the UK and across the North Atlantic, the common starfish (Asterias rubens) is one of 1,500 starfish species in the world.
Asterias rubens was nominated by the scientific community and won a public vote to sequence the genome as part of our 25 genomes project. The common starfish falls into our ‘cryptic’ category of creatures. Cryptic, because their behaviour and many hidden talents are not well understood.
Hidden talents
Starfish sperm
The DNA we collected for Asterias rubens was from its sperm. Professor Elphick’s lab in central London is home to some 200 starfish where he collected the sample for sequencing.
Possibly the most remarkable feature of starfish is their ability to re-generate limbs. If a starfish is attacked or is in danger, it can lose an arm in order to escape. It then grows a new one in its place. Nobody’s exactly sure how this works, but the key to finding out will be in its genome. Understanding the process would have huge implications for regenerative medicine.
The starfish genome could also help research into glue, including surgical adhesives that are used to heal wounds. Asterias rubens feasts on mussels and other molluscs. To get to the meat inside a mussel, it attaches its tube feet to the shell, by secreting a glue, and pulls it apart. Researchers are interested in that glue, and the genome sequence might reveal more about its production and structure.
Neuropeptides
Professor Maurice Elphick is working with us on the starfish genome. His research interests lie in neuropeptides. These tiny molecules act in the brain to control a whole range of processes including pain, reward, food intake, metabolism, reproduction, social behaviours, learning and memory.
Starfish don’t have a brain, but they are more closely related to humans than they are to most invertebrates. They do have neuropeptides – and his team have discovered many already. Several are involved in the unusual feeding behaviour of starfish.
To eat a mussel, once it’s forced open the shell, a starfish pushes its stomach out of its mouth. It partially digests its prey, takes up the resulting mussel ‘chowder’ and then retracts its stomach.
I’m interested in understanding the evolution of neuropeptide systems, and also want to compare their functions and to find out what homologous molecules are doing in very different biological contexts.
Maurice Elphick, Professor of Animal Physiology & Neuroscience, Queen Mary University of London.
One of the molecules they discovered triggers the stomach retraction. The equivalent molecule in humans clearly has a very different role. Professor Elphick explained: "Interestingly, we have also found that the neuropeptide behind the stomach retraction is evolutionarily related to a neuropeptide that regulates anxiety and arousal in humans."
Professor Elphick explained how the genome sequence will enhance their ability to discover and study more neuropeptides. Because neuropeptides are tiny, the genes encoding them are not always easy to find. The team will study the genome in places where other species are known to have neuropeptide genes, to see if they can pinpoint an equivalent in the starfish (an approach known as synteny). This is only possible because we are using ‘long-read’ technology in the 25 genomes project – so the genomes will be the best possible quality, with few gaps.
The future
The starfish genome is now sequenced and the raw data available for any researcher to use. Over the coming months, our partners at EMBL-EBI will be assembling and annotating it, marking the position of genes and other features.
The finished genome will enable researchers to answer their own questions. About evolution, glue, neuropeptides or growing new arms.
About the author
Alison Cranage is a science writer for the Wellcome Sanger Institute.
