A renSime has only the one Selyn system that is for the sole purpose of sustaining the sime's life. RenSimes have no conscious control of their selyn system, except to "augment" -- to increase speed and strength for short periods, burning more selyn than their basal rate, thus shortening their Need Cycle and under some circumstances, Life Expectancy.
The fanzine, A COMPANION IN ZEOR #13 contains Jacqueline's CHANNEL'S LIFE EXPECTANCY CHART --- http://www.simegen.com/sgfandom/rimonslibrary/cz/cz13/sgchl.html
In transfer or Kill, renSimes do not have control over their selyn draw speed as the channels do. Such control is a property of the interaction of the channel's primary and secondary selyn transport nervous systems via the connection between them at the vriamic node. See Vriamic functions. The vriamic functions define the difference between channel and renSime.
When written renSime is spelled with a small 'r' unless it is the first word in a sentence. (e.g: renSime vs RenSime).
RenSime body operates on selyn, not calories. Simes eat only to replace body-building materials.
(Source: Jacqueline Lichtenberg e-mail March 4, 2013) Technically "renSime" is a catch-all term for a whole range of complicated sub-mutations that don't have the channel's dual-nervous-system. The observable characteristic is that a renSime can not control selyn draw speed, and can not prevent him/herself from Killing a Gen.