Re: The Very Very Latest Paper From 2006!!!

[David Marjanovic <david.marjanovic@gmx.at>]

> Restating-- Large animals have low surface mass ratios, and therefore lose 
> heat more slowly on a mass specific basis than smaller animals. It follows 
> that direct ambient temperature effects on growth are more pronounced in 
> small animals more than large, and LAGs would therefore be less defined in 
> larger animals, and would disappear entirely at some size.

If any temperature has an influence on bone growth, then it's the 
temperature of the bone itself. Small mammals work harder tthan large ones 
at maintaining their body temperature constant and high -- but despite the 
higher cost they still succeed. Therefore we don't have any reason to expect 
more LAGs in small than in large mammals.

However, despite this expectation, the largest mammals apparently _have_ 
fewer LAGs than smaller ones. So this must have another reason; I guess the 
speed of growth.

> Due to the obvious seasonal effects on food intake of herbivorous animals,

Good idea, but doesn't explain why elephants have fewer LAGs.

> Also-- To change the subject slightly, would endotherms show a 
> proximal/distal limb bone LAG definition gradient?

I'd expect that endotherms with long, slim legs living in a seasonal climate 
would show more LAGs in distal bones. That's because such legs have inbuilt 
heat exchangers: the distal parts, which contain tendons but more or less no 
muscles, approach ambient temperature, so I'd expect them to stop growing in 
winter, while the proximal parts don't even stick out from the body wall and 
approach body core temperature.

However, this expectation, too, is wrong AFAIK.