Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.2 9/18/84 exptools; site ihnet.UUCP
Path: utzoo!watmath!clyde!burl!ulysses!mhuxr!mhuxn!ihnp4!ihnet!eklhad
From: eklhad@ihnet.UUCP (K. A. Dahlke)
Newsgroups: net.bio
Subject: Morphological Asymmetry
Message-ID: <295@ihnet.UUCP>
Date: Fri, 13-Sep-85 10:11:31 EDT
Article-I.D.: ihnet.295
Posted: Fri Sep 13 10:11:31 1985
Date-Received: Sat, 14-Sep-85 06:29:05 EDT
Distribution: net
Organization: AT&T Bell Laboratories
Lines: 31

< The line eater >

	What is the earliest animal (on the evolutionary scale)
that exhibits morphological asymmetry against a backdrop of
bilateral symmetry?
A friend nominated a particular crab
possessing one large claw, for fighting.
Certainly all mammals, birds, etc have the beating heart
on one side, and the liver on the other.
These popular asymmetries are consistent (i.e. the liver
belongs on the right).
There is a preferred (correct) orientation.
Are simple asymmetries, such as the crab's claw above, consistent?
What about that funny fish with his eyes on one side?
Is it always the same side?
Why did these asymmetries evolve?
Couldn't mammals have a beating heart behind the sternum,
and a small liver on each side?
Couldn't the crab have two fighting claws?
What biological mechanism begins the asymmetry in the developing embryo?
Is the mechanism different for consistent/inconsistent asymmetries?
What goes wrong in the few humans who are reversed
(i.e. liver on the left, etc)?  How common is this?
Has it been documented in other animals?

	I don't see much traffic on this newsgroup, which is unfortunate.
There are so many interesting things to talk about.

-- 
	This .signature file intentionally left blank.
		Karl Dahlke    ihnp4!ihnet!eklhad