The mysterious “love hormone” released in humans when they fall head over heels for someone causes starfish to turn their stomachs inside out, scientists have discovered.
Oxytocin is an ancient hormone that has different functions across species – previous studies have shown it makes mice lose their appetite and makes some birds more generous.
In the latest research, scientists injected the chemical into starfish and found it triggered their mechanism of “everting” – turning out their stomachs in the posture they use for eating.
Researchers from Queen Mary University of London said the experiment could help control the feeding patterns of the starfish species called the crown of thorns. This species feeds on coral and has “a devastating impact” on Australia’s Great Barrier Reef.
Lead author Professor Maurice Elphick said: “Our study has provided important new evidence that oxytocin-type molecules are important and ancient regulators of feeding in animals.
“So oxytocin is much more than a ‘love hormone’ – perhaps especially for animals like starfish that don’t fall in love.”
Dr Esther Odekunle, formerly a PhD student at the university, added: “This research may provide a basis for the development of novel chemical methods to control their appetite for coral.”
Oxytocin-type molecules have been acting in the nervous systems of animals for more than half a billion years.
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The third in a series of three grey seals found on a Norfolk beach with frisbees embedded in their necks
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The injury to the seal was so severe that it had to remain in the care of the RSPCA for three months
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A turtle found wrapped in plastic netting in Tenerife, Canary Islands
Eduardo Acevedo/UPY 2019
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This turtle was caught in a plastic six-pack ring when young and became deformed as it grew while still trapped in the ring
Missouri Department of Conservation
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Sharks and turtles caught in a discarded plastic net
PA
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A shortfin mako shark tangled in fishing rope. The rope has caused scoliosis of the back in the shark
PA
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A hermit crab uses a plastic toy as a shell
Alamy
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Found in September 2017, a grey seal dubbed Mrs Frisbee was the first in a series of seals to be found off the Norfolk coast with frisbees around their necks
Friends of Horsey Seals
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The third in a series of three grey seals found on a Norfolk beach with frisbees embedded in their necks
PA
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The injury to the seal was so severe that it had to remain in the care of the RSPCA for three months
PA
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A turtle found wrapped in plastic netting in Tenerife, Canary Islands
Eduardo Acevedo/UPY 2019
In humans, oxytocin molecules bind with receptors in the brain and in doing so influence maternal care, social interactions and stress and anxiety levels. The hormone has also been suggested as a treatment for anxiety, depression, addiction, anorexia and schizophrenia owing to its ability to promote social and bonding behaviour.
Starfish were injected with the hormone and within a few minutes started bending their arms and adopted a “humped” posture, similar to that used when feeding – and the stomach was then everted from the mouth.
The animals feed by climbing onto shellfish and adopting this posture, then using the tiny tube feet under their arms to pull apart the two valves of their prey.
The starfish then evert their stomach into the gap they have created, before digesting the soft tissues into a soup-like mixture and drawing this back into their body to eat, according to the study published in the journal BMC Biology.
Professor Elphick said: “What is fascinating is that injecting the hormone in starfish induces what is known as fictive feeding. The starfish are behaving as if they are feeding on a mussel or an oyster but no mussel or oyster is there to be eaten.”
The researchers also found the effect of oxytocin was so powerful it made starfish two to three times slower at righting themselves when flipped over – an important defence mechanism when they are upturned by strong waves.
They also found that the hormone exists naturally in regions of the starfish body – including the central nervous system and the stomach – and its effects appeared to be consistent with the oxytocin-type molecules.
