Kevin, your absolutely right, being new to the uniondae I haven't figured
the whole lot out , could be the lack of information as most collectors
ignore the fresh water bivalves . Mark James Bethke
-----Original Message-----
From: Kevin S. Cummings <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: Friday, June 26, 1998 12:28 PM
Subject: Re: CONCH-L Digest - 24 Jun 1998 to 25 Jun 1998
 
 
>>Date:    Thu, 25 Jun 1998 19:54:18 -0700
>>From:    Scott E Jordan <[log in to unmask]>
>>Subject: sexual dimorphism
>>
>>This is a topic that I have found myself wondering about before.  I don't
>>believe that I have ever seen distinctions made indicating morphological
>>differences between the shells of a molluscan specie's male and female.
It
>>is certainly common amoungst chordates.  Anyone out there who can
enlighten
>>us on instances in the molluscan fauna?
>>
>>Scott Jordan
>
>>Date:    Thu, 25 Jun 1998 23:39:19 -0400
>>From:    mark <[log in to unmask]>
>>Subject: Re: sexual dimorphism
>>
>>Good question, in the case of fresh water mussels (unionidae) the male
>>shells are generally fatter then the females. This seems to be typical in
>>most fresh water bivalves. Mark James Bethke
>
>Mark,
>
>This is a bit of an over simplification.  First, most unionids (or Hyriids,
>Mutelids, Mycetopodids, and Etheriids, for that matter) are not obviously
>sexually dimorphic.  Most of the dimorphic species are are members of the
>unionid subfamily Lampsilinae (if this is really a monopyletic subfamily).
>The vast majority of Anodontines and Amblemines are not dimorphic.  As for
>males being "fatter" than females, I would say that the opposite is true.
>Most females have a post basal expansion and are more inflated than males
>in order to provide room for the eggs and glochidia.
>
>Kevin
>
>Kevin S. Cummings
>Illinois Natural History Survey
>607 E. Peabody Drive
>Champaign, IL 61820
>[log in to unmask]
>http://www.inhs.uiuc.edu/cbd/collections/mollusk.html
>