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Hi Everyone,
Star-nosed Moles are certainly not my specialty so I had a quick look on the net for information. Fascinating creature! The tendrils are jammed packed with touch receptors. One article I read estimated that they are about six times more sensitive than the human hand. What makes the Star-nosed Mole even more amazing is the speed with which it can detect an item, determine its suitability as food and react to capture and eat it. The estimates I found were in the 25 millisecond range. To put this into context, it takes a human about 600 milliseconds to see something while driving and react by pressing the brake pedal. So the mole reacts almost 25 times faster than a human can.
Regarding electroreceptors, I did come across a paper which described evidence that star-nosed moles use electrical fields to detect prey items however the authors point out that the results must remain tentative until further experimentation is done. A preview of the article can be found here:
http://www.jstor.org/discover/10.2307/1381909?uid=3738032&uid=2129&uid=2&uid=70&uid=4&sid=56056577503
Star-nosed Moles often hunt in aquatic environments and wet soil so this would fit with Steven and Dave's discussion about the limitations of the transmission of generated electrical body current.
All the best,
Lance
-----Original Message-----
From: naturens-owner@chebucto.ns.ca [mailto:naturens-owner@chebucto.ns.ca] On Behalf Of David & Alison Webster
Sent: Tuesday, April 17, 2012 8:09 PM
To: naturens@chebucto.ns.ca
Subject: EXTERNAL: Re: [NatureNS] re moles? re mounds on ground
Hi Steven & All, Apr 17, 2012
I don't know about moles & electroreceptors but there is plenty of water and ions in soils for establishment of electrical gradients down to soil moisture tensions of about 15 bar (roughly 15,000 cm of water) and moles would generally feed in soils at 30 cm tension or less.
Noise could be a problem in some soils in which oxidation/reduction potential gradients can be steep over distances of 1-2 mm but these potentials are associated with water films in most imtimate contact with the solid phase and (I would guess) potential generated by an animal would be expressed largely in the water layers more remote from the solid phase. Just guessing.
And perhaps the solid phase would distort fields around an animal beyond recognition. More guessing.
Some 40 years ago (gulp) I measured soil Eh at various depths in soils but don't even recall how continuity between the planted Pt electrodes and mobile Calomel was established (a KCl agar bridge ?).
Yt, Dave Webster, Kentville
----- Original Message -----
From: "Stephen R. Shaw" <srshaw@dal.ca>
To: <naturens@chebucto.ns.ca>
Sent: Tuesday, April 17, 2012 7:25 PM
Subject: Re: [NatureNS] re moles? re mounds on ground
> 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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