On 6 March 2014 15:47, Russell Standish <[email protected]> wrote:
> Could be - I have heard the factoid that some sharks need to keep > moving. What I don't know is whether it is an urban myth or not. > > As ever, the fount of all knowledge has the answer! >From http://en.wikipedia.org/wiki/Shark#Respiration Respiration Like other fish, sharks extract oxygen from seawater as it passes over their gills <http://en.wikipedia.org/wiki/Gill>. Unlike other fish, shark gill slits are not covered, but lie in a row behind the head. A modified slit called a spiracle <http://en.wikipedia.org/wiki/Spiracle> lies just behind the eye, which assists the shark with taking in water during respiration <http://en.wikipedia.org/wiki/Aquatic_respiration> and plays a major role in bottom-dwelling sharks. Spiracles are reduced or missing in active pelagic <http://en.wikipedia.org/wiki/Pelagic> sharks.[21]<http://en.wikipedia.org/wiki/Shark#cite_note-Gilbertson-21>While the shark is moving, water passes through the mouth and over the gills in a process known as "ram ventilation". While at rest, most sharks pump water over their gills to ensure a constant supply of oxygenated water. A small number of species have lost the ability to pump water through their gills and must swim without rest. These species are *obligate ram ventilators* and would presumably asphyxiate<http://en.wikipedia.org/wiki/Asphyxiate>if unable to move.Obligate ram ventilation is also true of some pelagic bony fish species. [32] <http://en.wikipedia.org/wiki/Shark#cite_note-32> <http://en.wikipedia.org/wiki/Shark#cite_note-32> -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/groups/opt_out.
