Body size range

Craig McClain mcclainc at
Fri Apr 1 21:45:40 EST 2005

On Mar 30, 2005, at 8:37 PM, Geoff Read wrote:

>> I am currently developing a chapter on patterns of body size for marine
>> invertebrates for upcoming volume on patterns of body size.      

> Hello,
> Since this is your field of expertise, would you be able to educate
> annelida listers with an idea of why this is interesting to you and what
> factors are important?  I imagine maxima are controlled by more than just a
> 'limit to growth' due to physiological constraints on a body plan, but it
> is a long time since I was at uni having this stuff explained. Are there
> existing books, reviews? 
> Geoff
> (annelida moderator)

There are number of reasons.  First geographic patterns in body size have 
recieved little attention in invertebrates (especially marine invertebrates) 
except for insects.  The work on body size in mammals, birds, reptiles, and 
amphibians is enormous.  Yet, many hypotheses about what limits body size are 
presented as generalities, without test of them among the inverts.  Take for 
example the volume I am contributing a chapter to...there are entire chapters 
about body size of mammalian orders but two on inverts (mine on marine inverts 
and one on insects by Gaston and Chown).  At first this may seem biased, yet 
the research to synthesize on body size patterns in marine invertebrates is 
just lacking.  Knowing what limits body size also speaks to what may be 
limiting ranges, diversity, abundance, biomass, and host of other ecological 
variables.  To specifically address your question why are size ranges 
important.  One, only general textbooks on inverts. present this kind of 
information yet what they present is very vague and lacking for some groups.  
Perhaps more importantly, it begins to address what constrains size in 
different groups and the enormous variation in size in these groups.  Take for 
example the group I typically work with.  The size range for marine gastropods 
is much larger than terrestrial gastropods.  At the upper end the ease at 
which a large, heavy shell can be carried submerged underwater is much greater 
than can be carried on land.  At the lower end, small terrestrial snails are 
much more prone to desiccation, yet marine snails can occupy smaller sizes 
because of living in the aquatic medium.  I urge your readers (can you forward 
this along to the listserv) to share their thoughts on body size in annelids 
with me (including limits to size, geographic variation in size, and the 
largest and smallest species).  


Craig R. McClain, Ph.D.
Department of Biology
University of New Mexico
MSC03 2020
Albuquerque, NM 87131-0001

phone: 505-277-6437
email: mcclainc at

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