The vertebrate transition from fin to limb is one of the juiciest mysteries in evolutionary biology, and this week, scientists may have identified another clue to the puzzle. Published online today (June 23) at linkurl:Nature,; a team of researchers describe two previously unknown proteins essential to fin development in bony fishes -- the loss of which may have been a key step in the evolution of fins to limbs during tetrapod development. "It's a very exciting piece of work," said linkurl:Paula Mabee,; an evolutionary biologist at the University of South Dakota. "Their conclusions are really intriguing and well justified."
Top: Pectoral fin bud of zebrafish embryo
showing the array of actinotrichia.
Bottom: Limb bud of an mouse embryo.
In contrast to the pectoral fin bud of
teleost fish, the mouse limb bud does
not contain actinotrichia.

Jing Zhang
The discovery happened almost by accident during a routine screen...
and3and4,and1and2,The Scientist.Gli3Acanthostega,and1and2,The Scientist.J. Zhang et al. "Loss of fish actinotrichia proteins and the fin-to-limb transition," Nature, published online June 23, 2010, doi: 10.1038/nature.09137.

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