It is probable that you have to tie growth lines with the individual
environmental situation.  In the study I referenced in Japan, there was a
substantial seasonal variation in temperature and presumably in the activity
level of the snail.  It might be that a rainy season and a dry season, if
such was a typical seasonal event, could have a similar impact on tropical
freshwater dwellers.  I was just hoping someone may have taken a look at
this.  If not, sounds like a great grant proposal for COA!

Tom E.

By the way, I will forward all responses to R.E. Taylor


>
>
> >Rings are often used as annular marks on unionids, although there is
> >evidence to the contrary. We have two Pyganodon grandis that we raised
> >from "off the fish" two years ago. Unfortunately they have 4
> "annular" rings.
>
>
>
>
> G. Thomas Watters, PhD
> Curator of Molluscs
> Museum of Biological Diversity
> Department of Evolution, Ecology & Organismal Biology
> The Ohio State University
> 1315 Kinnear Road
> Columbus, OH 43212 USA
> [log in to unmask]
> v: 614-292-6170
> f: 614-292-7774
>

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