Editing Platypus (section)

=== Electrolocation ===
[[File:Platypus electrolocation.svg|thumb|upright=2<!--for readability of svg text-->|The platypus has secondarily acquired [[Electroreception and electrogenesis|electroreception]]. Its receptors are arranged in stripes on its bill, giving it high sensitivity to the sides and below; it makes quick turns of its head as it swims to detect prey.<ref name="Electro1"/>]]

[[Monotremes]] are the only mammals (apart from the [[Guiana dolphin]])<ref>{{cite journal |last1=Czech-Damal |first1=Nicole U. |last2=Liebschner |first2=Alexander |last3=Miersch |first3=Lars |last4=Klauer |first4=Gertrud |last5=Hanke |first5=Frederike D. |last6=Marshall |first6=Christopher |last7=Dehnhardt |first7=Guido |last8=Hanke |first8=Wolf |date=22 February 2012 |title=Electroreception in the Guiana dolphin (Sotalia guianensis) |journal=Proceedings of the Royal Society B: Biological Sciences |volume=279 |issue=1729 |pages=663–668 |doi=10.1098/rspb.2011.1127 |pmc=3248726 |pmid=21795271}}</ref> known to have a sense of [[electroreception]], and the platypus's electroreception is the most sensitive of any monotreme.<ref>{{cite journal |last1=Proske |first1=Uwe |last2=Gregory |first2=J. E. |last3=Iggo |first3=A. |year=1998 |title=Sensory receptors in monotremes |journal=Philosophical Transactions of the Royal Society of London |volume=353 |issue=1372 |pages=1187–1198 |doi=10.1098/rstb.1998.0275 |pmc=1692308 |pmid=9720114}}</ref><ref name="Electro1">{{cite journal |last=Pettigrew |first=John D. |year=1999 |title=Electroreception in Monotremes |url=http://jeb.biologists.org/cgi/reprint/202/10/1447.pdf |url-status=live |journal=The Journal of Experimental Biology |volume=202 |issue=Part 10 |pages=1447–54 |doi=10.1242/jeb.202.10.1447 |pmid=10210685 |archive-url=https://web.archive.org/web/20060928054253/http://jeb.biologists.org/cgi/reprint/202/10/1447.pdf |archive-date=28 September 2006 |access-date=19 September 2006 |doi-access=free|bibcode=1999JExpB.202.1447P }}</ref> Feeding by neither sight nor smell,<ref name="draft_genome" /> the platypus closes its eyes, ears, and nose when it dives.<ref>{{cite journal |author=Gregory, J.E. |author2=Iggo, A. |author3=McIntyre, A.K. |author4=Proske, U. |date=June 1988 |title=Receptors in the Bill of the Platypus |journal=Journal of Physiology |volume=400 |issue=1 |pages=349–366 |doi=10.1113/jphysiol.1988.sp017124 |pmc=1191811 |pmid=3418529}}</ref> Digging in the bottom of streams with its bill, its electroreceptors detect tiny electric currents generated by the muscular contractions of its prey, enabling it to distinguish between animate and inanimate objects.<ref name="Electro1" /> Experiments have shown the platypus will even react to an "artificial shrimp" if a small electric current is passed through it.<ref name="Manning">{{cite book |author1=Manning, A. |url=https://archive.org/details/introductiontoan0000mann_m2z8 |title=An Introduction to Animal Behaviour |author2=Dawkins, M.S. |publisher=Cambridge University Press |year=1998 |edition=5th |url-access=registration}}</ref>

The [[electroreceptor]]s are located in rostrocaudal rows in the skin of the bill, while [[mechanoreceptor]]s for touch are uniformly distributed across the bill. The electrosensory area of the [[cerebral cortex]] is in the tactile [[somatosensory]] area, and some cortical cells receive input from both electroreceptors and mechanoreceptors, suggesting the platypus feels electric fields like touches. These receptors in the bill dominate the [[somatotopic map]] of the platypus brain, in the same way human hands dominate the [[Cortical homunculus|Penfield homunculus map]].<ref name="sensory_platypus">{{cite journal |last1=Pettigrew |first1=John D. |first2=P. R. |last2=Manger |first3=S. L. |last3=Fine |title=The sensory world of the platypus |journal=Philosophical Transactions of the Royal Society of London |pages=1199–1210 |issue=1372 |year=1998 |pmid=9720115|pmc=1692312 |doi=10.1098/rstb.1998.0276 |volume=353 }}</ref><ref name="Ancestors_Tale">{{cite book |first=Richard |last=Dawkins |author-link=Richard Dawkins |title=The Ancestor's Tale, A Pilgrimage to the Dawn of Life |chapter=The Duckbill's Tale |publisher=Houghton Mifflin |location=Boston, Massachusetts |year=2004 |isbn=978-0-618-00583-3 |title-link=The Ancestor's Tale }}</ref>

The platypus can feel the direction of an electric source, perhaps by comparing differences in [[signal strength]] across the sheet of electroreceptors, enhanced by the characteristic side-to-side motion of the animal's head while hunting. It may also be able to determine the distance of moving prey from the time lag between their electrical and mechanical pressure pulses.<ref name="Electro1" />

Monotreme electrolocation for hunting in murky waters may be tied to their tooth loss.<ref name="Masakazu Asahara 2016">Masakazu Asahara; Masahiro Koizumi; Thomas E. Macrini; Suzanne J. Hand; Michael Archer (2016). "Comparative cranial morphology in living and extinct platypuses: Feeding behavior, electroreception, and loss of teeth". Science Advances. 2 (10): e1601329. {{doi|10.1126/sciadv.1601329}}.</ref> The extinct ''[[Obdurodon]]'' was electroreceptive, but unlike the modern platypus it foraged [[pelagic zone|pelagically]].<ref name="Masakazu Asahara 2016" />