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| Image of Rhabdophis tigrinus including insets of feed behaviour and chemical structure of commonly sequestered toxin. |
The
primary goal for most organisms is to reproduce. However passing on genes to the next
generation is pointless if they don’t survive the onslaught of predators in their
new world. Animals that are pregnant and support the development of young
internally also become susceptible to predation due to a greater size and
changed behavior, eg sun baking
for longer (Mori & Burghardt. 2001).
The Tiger Keelback (Rhabdophis tigrinus) along with others of the same genus have developed an unusual strategy to enhance survive rates of both it and its young by having the best of both worlds being venomous and poisonous (for an explanation see Venomous Anurans ;Hutchinson et al. 2007).
The Keelbacks (Rhabdophis genus) of Asia have developed a row of paired glands along the back of the neck. These glands sit just below the surface and release their toxin if pressure is applied. The poison is variable as it is sequestered by the snake from toads which they feed on (Hutchinson et al. 2007).
The Tiger Keelback (Rhabdophis tigrinus) along with others of the same genus have developed an unusual strategy to enhance survive rates of both it and its young by having the best of both worlds being venomous and poisonous (for an explanation see Venomous Anurans ;Hutchinson et al. 2007).
The Keelbacks (Rhabdophis genus) of Asia have developed a row of paired glands along the back of the neck. These glands sit just below the surface and release their toxin if pressure is applied. The poison is variable as it is sequestered by the snake from toads which they feed on (Hutchinson et al. 2007).
These snakes are oviparous
meaning they produce eggs. It has been shown that pregnant snakes with
ready access to the toxin producing toads in their diet consume a higher
proportion of these toads.This leads to an increase in poison availability which
provides two benefits;
-A female often left more susceptible to predation now
has a better defensive capability.
-The female is also enabled to pass on the poison to
the young, which can in turn use them for defence. This gives them a greater chance for survival after birth when they are most
vulnerable.
The Keelbacks also biosynthesise (as apposed to
sequester) as venom which is delivered through the rear mouth fangs.The venom
is produced in the Duvernoy's gland
and the most significant effects of envenomation include coagulopathy and renal failure.
Reference
Hutchinson, D.A., Mori, A., Savitzky, A.H., Burghardt, G.M., Wu, X., Meinwald, J. and Schroeder, F.C., 2007."Dietary Sequestration of Defensive Steroids in Nuchal Glands of the Asian Snake Rhabdophis tigrinus." Proceedings of the National Academy of Sciences, Vol:104 No:7, pp.2265-2270.
Mori, A. and Burghardt, G.M., 2001."Temperature Effects on Anti‐Predator Behaviour in Rhabdophis tigrinus, a Snake with Toxic Nuchal Glands." Ethology, Vol;107, No:9, pp.795-811.
Reference
Hutchinson, D.A., Mori, A., Savitzky, A.H., Burghardt, G.M., Wu, X., Meinwald, J. and Schroeder, F.C., 2007."Dietary Sequestration of Defensive Steroids in Nuchal Glands of the Asian Snake Rhabdophis tigrinus." Proceedings of the National Academy of Sciences, Vol:104 No:7, pp.2265-2270.
Mori, A. and Burghardt, G.M., 2001."Temperature Effects on Anti‐Predator Behaviour in Rhabdophis tigrinus, a Snake with Toxic Nuchal Glands." Ethology, Vol;107, No:9, pp.795-811.
A very interesting post What kinds of toads do these snakes eat? Are they similar to cane toads?
ReplyDeleteToxins are sequestered from Bufonidae species.Cane toads also belong to this family but are not present within the range of R.tigrinus.
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