Scorpions vs. Crayfish

Robert Robbins rrobbins at GDB.ORG
Sat Jun 18 11:58:33 CDT 1994


Scorpions (chelicerata) and crayfish (mandibulata) are a long way apart
evolutionarily.  My guess is that what you are seeing is equivalent to the
wiring differences between cephalopod and vertebrate eyes.  Simple physics
requires that certain features be acquired by devices that accomplish
similar functions, but whim, chance, and evolutionary caprice determine
the details of analogous structures.

Now let's see how long before someone with real knowledge on this jumps in
with the right answer.





On Fri, 17 Jun 1994, David Stuchkus wrote:

>      My name is Steve Byrd and I am a laboratory assistant at Clayton
> State College in Morrow, GA.  While researching in preparation of a
> comparative anatomy lab, I noticed an interesting difference between
> the crayfish and scorpion.
>
>     Both of these creatures have opposable "thumbs" on their chela.
> However, the opposable "thumb" on the crayfish is medial where the
> scorpion's is lateral.
>
>     If anyone has any idea as to what caused this evolutionary
> difference, I would by interested in hearing them.
>
>     Please respond to:
>
> stuchkus at gg.csc.peachnet.edu
>
> Thanks in advance,
> Steve B.
> Clayton State College




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