[NatureNS] re moles? re mounds on ground

Date: Tue, 17 Apr 2012 19:25:06 -0300
From: "Stephen R. Shaw" <srshaw@dal.ca>
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Hi Jim,
Electroreceptors in SN moles? Only in water are electroreceptor  
systems believed to be usable at all, because only in water can  
significant external gradients of voltage exist around an animal,  
although these gradients are still really tiny (a few microvolts per  
centimeter).  Air is such a good insulator that virtually no loops of  
muscle current escape from the body that could be detected externally,  
in air. This is unlike the situation in water where electric fields  
can and do develop around the animal, mostly arising from its muscle  
activity, and is even used in active signalling in some groups.

So not out of the question in principle in these moles if they use  
their tentacles in water or wet soil, and apparently they do normally  
live in a partly wet environment. The star tentacles are known to be  
touch-sensitive with a high density of mechanoreceptors -- but then  
electroreceptors elsewhere are believed to have evolved from  
mechanoreceptor cells.  According to Ted Bullock, electroreception  
probably evolved independently at least six times in fish and is  
mostly confined to that group, but also is present in platypus and  
perhaps even in a dolphin. So, a resounding 'maybe'...
Steve, Halifax

Quoting "James W. Wolford" <jimwolford@eastlink.ca>:

P.S. Those 22? tentacle-like feelers making up the nose are extremely
>  sensory, allowing the moles to catch prey in situations with low or  
>  no light, and, if memory serves, the tentacles are also known to be  
>  electro-sensory (as are bottom-feeding sharks and skates?), so that  
>  they can sense the metabolic electricity of the prey animals...


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