From Andrew Brierley
We should not perhaps be surprised that Randolf Raff and his colleagues were
able to cross-fertilise two sea urchin species that diverged 10 million years ago
(This Week, 17 April, p 7).
Donald Williamson has reported the development of a hybrid larva from a sea
squirt egg (Ascidia mentula, phylum Chordata) fertilised with
sperm of the sea-urchin (Echinus esculentus, phylum
Echinodermata).
So unorthodox were Williamson’s observations that his paper “Incongruous
larvae and the origins of some invertebrate life histories” was rejected by
seven journals before finally being published in 1988 (Progress in
Oceanography, vol 19, p 87).
The paper also reports that embryonic and larval forms have occasionally been
transferred between distinct evolutionary lineages as a result of
cross-fertilisations.
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