Robin Wilson rwilson at
Mon Feb 12 18:26:35 EST 1996

On Mon, 12 Feb 1996, Gary R. Gaston wrote:

> Jerry McLelland and I have been working on some Aricidea recently, and we
> noticed that adult specimens usually are packed posteriorly with fairly
> large sand grains.  This makes their posterior ends, which are thin walled,
> easily lost during washing of samples.  Question:  Can they pass these sand
> grains?  We have not been able to maintain any specimens in culture, but it
> appears impossible that these sand grains pass through the anus, and they
> are so far posterior that I doubt they can be regurgitated.  Perhaps the
> sand grains have some function in digestion, but without much muscle in this
> region I doubt it.  Anybody seen this before or have any experience with it?
> No personal testimonials, please, we're talking worms only.
> Gary R. Gaston
> Biology Department
> University, Mississippi 38677
> (601) 232-7162


I have noticed the same thing here (paraonids from the continental shelf 
of southern Australia).  I would have to dig around to find a provisional 
generic identification, though.  The shelf sediments are mainly poorly 
sorted carbonate (lots of bryozoan fragts, etc), and they pack the 
thin-walled posteriors of paraonids in just the way you describe.  It only
registered subliminally with me that these animals must be accumulating a 
painful excretion problem. Maybe they use their "sandbag rear ends" to 
kosh one another in defense of territory?!  More seriously, if the coarse 
fragments cannot be eliminated, maybe the quantity of trapped sediment is 
a measure of the age of the worm?

I would be very interested to hear progress reports if you do any work on 



Robin Wilson				rwilson at
Museum of Victoria			
71 Victoria Crescent			telephone 61-3 9284 0216
Abbotsford  Victoria			fax       61-3 9416 0475
Australia  3067

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