Scientists solve mystery of a fish called Mary's 'virgin' birth

A female stickleback fish, nick-named ‘Mary’, has produced offspring from eggs that appear to have been fertilised while they were still inside her, according to scientists at the University of Nottingham.

The team of researchers from the School of Life Sciences collected Mary on an expedition to the Outer Hebrides to gather wild sticklebacks which are fully genome-sequenced models for a wide range of scientific research. 

In a paper published in Scientific Reports they present the first ever discovery of internal fertilisation and development of babies inside a normally egg-laying species, and their successful delivery. 

The three-spined stickleback, Gasterosteus aculeatus, is a small fish that is common to both fresh and coastal waters in the Northern Hemisphere. In normal reproduction, the male stickleback builds a nest and, by performing a zig-zagging dance routine, lures a female to lay her eggs inside it. The male then chases the female away and fertilises the cluster. He then guards and takes care of the eggs by fanning them with his fins to aerate them for around 2 weeks until they hatch. 

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