Expert: Dana Krempels, Ph.D. - 10/6/2011

Question
Dr. Krempels,

I am curious to know if there is some molecular reason why some animals such octopi (octopusses?) have an eight-based radial symmetry, while other animals have a five-based symmetry (starfish), and other animals still other kinds of number based symmetry.

I apologise for the "roughness" of this question, as I am not a specialist in biology, but I am curious to know whether there is some protein structure or another that has something to do with how radially symmetrical animals are constructed?

Answer
Dear Eleanor,

This is one of the HUGE questions in evolutionary biology.  There is not a single protein involved in the process of developing different types of radial symmetry (pentaradial, octaradial, or whatever).  Rather, there is a developmental cascade that starts with the throwing of the still mysterious "switch" genes that control the expression of other genes during development, turning them on at some point and off in another.  Or turning them on in one tissue, not in another, and for varying lengths of time.

While different labs are working on these questions, the precise answer is not yet known.  

Interesting question, though!

Dana