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NFC: Mystery isopods?

My attempt to anwer the mystery shrimp question generated more 

From Kaus Schoening:
> My question is, how do you know they aren't fairy shrimp?

From Tony Gustafson:
> Thanks for the info Thom. I guess my next question would be, If the
> mystery shrimp are isopods, and are "livebearers," then how do they
> survive the dry summers? Often times there's not an ounce of moisture
> in that pond!

First, I suppose they could be fairy shrimp, but the description of 
activity under the ice makes me think they must be isopods.  Tony's 
memory might settle this issue.  Tony, were the animals somewhat 
flattened and did they spend most of their time in your aquaria on 
the bottom?  If so they are isopods.  If they were not flattened and 
swam regularly in the water column, they were fairy shrimp.  For that 
size (1") I can't imagine they were anything else.

Second, isopods do very well in temporary creeks and ponds, 
especially in disturbed sites, such as along railroad tracks.  They 
do not produce resting eggs like fairy shrimp, daphnia, and brine 
shrimp.  Rather, they burrow and are apparently dessication 
resistant.  Note that the majority of isopod species are terrestrial. 
Sowpugs, pillbugs, and the like are terrestrial isopods.

Hope this helps!


Dr. Thomas J. DeWitt

Address until March 1, 1999:
  Center for Ecology, Evolution, & Behavior
  TH Morgan School of Biological Sciences
  University of Kentucky
  Lexington, KY 40506-0225

tel 606/323-4992; fax 257-1717; email dewitt at ceeb_uky.edu

After March 1, 1999:
  Department of Wildlife & Fisheries Sciences
  Texas A&M University
  College Station, TX 77843-2258

E-mail tdewitt at wfscgate_tamu.edu