[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: MORE FEATHERS & NEKKID MAMMALS



On Nov 3,  2:07pm, Jeffrey Martz wrote:

>      Also, would anyone care to explain why so few endothermic animals
> are poisionous, when such a huge percentage of ectotherms are?

If we're talking about terrestrial ectotherms, there are 2 different traits you
could be talking about - amphibian skin secretions (poisons, ie toxins absorbed
through mucous membranes/gastric system) and reptile venoms (ie toxins
injected into blood stream).  Venomous animals are not necessarily poisonous -
you can swallow snake venom without too much danger.

I would have thought amphibian poisons were a shared derived character
of the Lissamphibia, i.e. mammals never evolved poison skin glands.
Producing enough poison to deter a predator would make a mess of your
fur - difficult to clean it up without poisoning yourself...

Reptile venoms (which have probably evolved more than once in Lepidosaurs)
seem to be an associated with swallowing large prey whole.  There is good
reason to think they evolved (from salivary secretions) as an aid to digestion.
As endotherms tend to dismember prey before eating it there is no selection
pressure favouring the evolution of increasingly powerful saliva.

Tony Canning
tonyc@foe.co.uk