Sixth Sense, the platypus

Consider our five senses of perception which allow us to interact and perceive our environment: smell, touch, hear, see, and taste.  But what about a six sense that would give us an extra range of perception, perhaps electroreception?  Groups of animals known to use electroperception, or the ability to perceive electric stimuli, include elasmobranches (sharks, skates, rays), but less known, the platypus (Ornithorhynchus anatinus) belonging to the odd of order of egg-laying mammals known as monotremes.  Aside from their unique ability to perceive changing electrical stimuli surrounding them, platypuses can deliver a nasty dose of venom from the spur of their hind foot. 

Mucus covered electroreceptors dot the outside of the Platypus bill and are highly sensitive capable of detecting electrical field producing  20 µV cm−1.  According to a paper by John Pettigrew, platypuses have up to 40,000 electroreceptors along their bills.  Afferent signals from the these electroreceptors are processed  in the somatosensory cortex and then are integrated and created to a mental topographical map in the neocortex.  Based off of given strength from each receptor and difference in time of signals received from each receptor leads to the creation of a spatial map.  From this mental spatial map, platypi are able to determine the direction of prey. 

Mechanoreceptors parallel the electroreceptors send afferent signals to the somatosensory cortex as well helping to aid in forming the visuo-spatial map.  Interestingly, the platypus is able to negate most of the electrical feed generated from its own body movement .  Cropping and accumulating incoming sensory information sounds familiar to the processes associated with accumulating information like hearing.

 Below is a short clip of these bizarre animals foraging.  

Cited Sources:

http://jeb.biologists.org/content/202/10/1447.long

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1692303/pdf/9720113.pdf

http://www.ncbi.nlm.nih.gov/pubmed/14667847

http://en.wikipedia.org/wiki/Electroreception

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