Are there any theories on how hollow teeth (or spines) and venom sacs
evolved? I myself can't come up with the vaguest notion how this might have
happened, in any animal.
Harry Greene's book "Snakes: the Evolution of Mystery in Nature"
(University of California Press, 1997) contains a discussion of this
subject of starting at page 91, under the heading "The evolution of venom
injection mechanisms". This is part of an extensive chapter on venoms and
their delivery mechanisms, with very thorough descriptions of the differing
types in snakes. He points out that than the glands appear to have derived
from Duvernoy's gland, a widespread feature of both venomous and
nonvenomous snakes. These glands, and true venom glands, are "derived
embryonically from tissues that produce tooth enamel... As for venom
conducting teeth, the formation of a groove, or closed canal, obviously
facilitates the flow of secretions into a victim's tissues. The initial
evolutionary enlargement of rear teeth, however, could simply have aided in
holding prey prior to the origin of specialized glands or even made it
possible to puncture the puffed-up bodies of toads as well as enhance the
inoculation of toxic secretions. In any case, two large adjacent teeth
also might have formed together a crude groove (e.g., as in some litter
snakes), thus further exposing tissue to... gland secretions."
--
Ronald I. Orenstein Phone: (905) 820-7886
International Wildlife Coalition Fax/Modem: (905) 569-0116
1825 Shady Creek Court
Mississauga, Ontario, Canada L5L 3W2 mailto:ron.orenstein@rogers.com