A Scottish stickleback fish had a “virgin birth” after fertilising its own eggs internally, scientists have revealed. And researchers named her Mary after the mother of Jesus Christ, following the “miraculous” development of the offspring inside the normally egg-laying species. Female Scottish sticklebacks usually lay their eggs, which are then fertilised by a male. But it appears that Mary fertilised her eggs while they were still inside her ovaries.
Researchers from the School of Life Sciences collected Mary on an expedition to Scotland’s Outer Hebrides to gather wild sticklebacks which are fully genome-sequenced models for a wide range of scientific research.
Mary appeared to be unable to expel her eggs and was close to death when she was discovered.
The researchers made the decision to save the lives of her young by putting her to sleep and delivering the near-complete embryos by caesarean section.
All 54 embryos were successfully delivered and hatched into baby fish,.
They then grew to adulthood at Nottingham University where 20 still survive nearly three years later.
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And other, unrelated Scottish sticklebacks have themselves successfully bred from Mary’s offspring.
Dr Laura Dean, of the School of Life Sciences at Nottingham University, said: “We were astounded at what we found when we examined Mary in our lab in the Outer Hebrides.
“She looked like an ordinary egg-bound fish – so we couldn’t believe it when we found she had almost completely developed embryos inside her ovaries.
“This is pretty much unheard of in an egg laying species.
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“The embryos were perfectly healthy, not deformed in any way and most have gone on to live a normal adult lifespan.”
The three-spined stickleback, Gasterosteus aculeatus, is a small fish that is common to both fresh and coastal waters in the Northern Hemisphere.
The Scottish stickleback’s DNA has been fully mapped to aid an array of genetic research.
Populations in lakes with more fish predators develop more bony plates.
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Others sticklebacks lack spines or are much larger or smaller than the norm.
The evolutionary basis is thought to relate to be predation pressure.
The incident is the first recorded incident of this form of fertilisation and delivery of live offspring.
There are three known ways this abnormal type of reproduction might have occurred, two of which were dismissed.
The parthenogenesis process see the fish clone itself.
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The second process happens with hermaphrodite – fish born with both male and female sex organs.
Andrew MacColl, associate professor of evolutionary biology, said: “Although this almost accidental find revealed a vanishingly rare phenomenon, it might help us to understand a really important change that has happened throughout the tree of life.
“Most animals lay eggs, but some – including almost all mammals, but few fish – retain their eggs inside and give birth to live young.
“Although this appears to be a difficult thing to achieve in evolution, this one little fish seems to have got there almost by itself.”