I was reading Wikipedia regarding deep-sea gigantism -- the fact that deep-sea species are often much larger than their shallow-dwelling counterparts. The article said,
Decreasing temperature is thought to result in increased cell size andincreased life span... both of which lead to an increase in maximumbody size.
The citation is:S F Timofeev Izv Akad Nauk Ser Biol. 2001 Nov-Dec:(6):764-8.[Bergmann's principle and deep-water gigantism in marine crustaceans]
I haven't tried to retrieve that article because I can't read Russian. Following up on "Bergmann's principle" doesn't help; it's just identifying ecographic patterns in gigantism.
From a surface area to volume ratio perspective, I can see how smaller cells are adaptive to cold temperatures. A huge amount of cellular processes are diffusion-driven. All of them, except for some potential electron or proton tunnelling processes, all mediated with thermal movements.
So let's say the transport of glucose into a given cell is driven by the concentration gradient (diffusion). At lower temperatures the diffusion rate is lower, so a cell of a given volume gets a reduced import of glucose. So it seems that increased surface-to-volume ratio (a smaller volume) would allow for a cell to compensate, and to accomplish the same rate of import as the warmer cell. This would also apply to some intracellular processes.
So assuming my thinking about diffusion processes is irrelevant to the real-life biology, as it predicts for colder temperatures that smaller cells are adaptive, is the point that metabolic processes are slower at lower temperatures? Then, a reduced rate of transport is not necessarily the limiting factor. Maybe the cellular volume can be scaled up until the total metabolic flux is comparable to the warmer-living cell? If there's more dissolved oxygen at lower temperatures, and if oxygen equilibrates well-enough, maybe no other nutrient or signalling diffusion is relevant?
This thinking does not at all seem consonant with this story by Curtis Deutsch and coworkers: Impact of warming on aquatic body sizes explained by metabolic scaling from microbes to macrofauna.
The model reproduces three key aspects of the observed patterns ofintergenerational size reductions measured in laboratory warmingexperiments of diverse aquatic ectotherms (i.e., the "temperature-sizerule" [TSR]). First, the interspecific mean and variability of the TSRis predicted from species' temperature sensitivities of hypoxiatolerance, whose nonlinearity with temperature also explains thesecond TSR pattern-its amplification as temperatures rise. Third, asbody size increases across the tree of life, the impact of growth onO2 demand declines while its benefit to O2 supply rises, decreasingthe size dependence of hypoxia tolerance and requiring larger animalsto contract by a larger fraction to compensate for a thermally drivenrise in metabolism. Together our results support O2 limitation as themechanism underlying the TSR, and they provide a physiological basisfor projecting ectotherm body size responses to climate change frommicrobes to macrofauna.
