This was probably the first snake to ever bite me. Not that others did not try, but these particular ones have quite a temper! Meet the parrot snake, Leptophis ahaetulla, a very widely distributed colubrid species. They roam from tree to tree, sleeping in the low vegetation by night (yes, they’re diurnal), going through life feeding on a broad menu of Hylid frogs, other reptiles, and sometimes birds. But you might be wondering what happened to me after that bite. Well, although this species is slightly venomous, their anatomy and physiology do not impose a big hazard for humans. Let me explain.
One of the ways to classify snakes is based on their dentition. Snakes that have fangs on the front part of their maxilla can be either Proteroglyphous (fixed) or Solenoglyphous (movable). Aglyphous snakes don’t have any specialized teeth (i.e. no fangs). And the fourth group, which is the case of this parrot snake, is Opisthoglyphous snakes: they have a pair of enlarged teeth on the back of the maxilla. This is why they are commonly called rear-fanged snakes and they are most of the extant species worldwide. So these ones need to handle their prey for a while in order to be able to reach them with the fangs! The same reason why it didn’t really get me, as my hand was never in too deep.
But how bad could this snake bite have been?
The venom of most Proteroglyphous and Solenoglyphous snakes has been studied for some time now, but colubrids had been quite ignored on the toxicological side (also because it’s hard to get good amounts of venom from their rear fangs). Sánchez et al. (2018) dug a little deeper on a Leptophis
The first two groups of snakes I mentioned (which mostly cover the families Viperidae, Elapidae and Atractaspididae) have big venom glands that are surrounded by strong muscular tissue. This muscular tissue provides the strength for their rapid injection system. This venom glands are modified salivary glands, so just as we are constantly producing saliva even after spitting, these snakes are also constantly producing venom. I just wanted to clear up the myth that “after a snake bites, it is depleted of venom for some time”. That’s just NOT true!
Our Opisthoglyphous friends, on the other hand, have what is called Duvernoy’s (venom) gland. Duvernoy’s gland is homologous to the other venom glands, but anatomically and functionally they’re something else. First of all, they are not surrounded by strong muscular tissue, so they lack this extra strength boost for the venom injection. The bio-active compounds produced here mostly show prey-specific toxicity. This is implied from the results from experiments in lab rats which showed low toxicity on them and the venom analysis which showed weak (<30kDa) proteins that are not usually harmful to mammals but could be for frogs and reptiles.
Overall it has weak neurotoxicity towards mammals and if the venom-injecting fangs had gotten me, according to some clinical publications, nothing THAT bad could have happened (some burning feelings and treatable itchiness).
It is important to remember that venom production for any species is energetically costly. If you encounter a snake and are not sure if it’s venomous or not, just stay away, they don’t want to harm you! Better said: they don’t want to waste their precious venom on a petty human instead of their lunch.
FunFact!
Sanchez et al. (2018) found a lot of melanin on the Duvernoy’s gland (see my previous post regarding reptiles skin coloration and how that happens). This amount of melanin might be because of the lack of thick muscle cover of Duvernoy’s gland. The melanin protects against UV radiation and thus prevents photo-detoxification of the venom components. This makes a lot of sense not only on melanin functionality but because parrot snakes are diurnal!
Also, if you want to read a nice sexual description of parrot snake reproduction check out this Scientific Note!
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- Sánchez, M.N., Teibler, G.P., López, C.A., Mackessy, S.P. & Peichoto, M.E. 2018. Assessment of the potential toxicological hazard of the Green Parrot Snake (Leptophis
ahaetulla marginatus ): Characterization of tits venoms and venom-delivery system. Toxicon. 148:202-212. - Lawson, R., Slowinski, J.B., Crother, B.I., Burbrink, F.T. 2005. Phylogeny of the Colubroidea (Serpentes): New Evidence From Mitochondrial and Nuclear Genes. Molecular Phylogenetics and Evolution 37(2005):581-601.