Venomous

This being notice of the short glossy book from the Natural History Museum at reference 1 about the world of venomous animals. Around 200 pages organised into seven chapters. Lots of flashy pictures. A good introduction to the subject, even though the ‘popular’ style rather grates. There is also a fair bit of repetition. 

A book which turned up, by chance, in the course of looking into the outgroups which resulted in reference 2.

Venom is here defined as ‘a toxic secretion produced by specialised cells in one animal that is delivered to another animal via a delivery mechanism – typically through infliction of a wound – to disrupt normal physiological functioning in the interests of predation, feeding, defence, or other biological processes that benefit the venom-producing animal’.

A definition which includes all the many animals which feed on live blood, such as ticks, leeches and vampire bats. It also includes all the Cnidarians of reference 3, many insects; some snails, bats, fishes and snakes. Plus some oddities like the loris and the duck-billed platypus. 

The cnidarians have been around for a long time, say half a billion years, and it remains a puzzle to me that their complicated miniature harpoons (contained in cnidocytes) evolved so early. Another curious feature being that these cnidocytes are sometimes taken over by other animals for their own purposes.

Notwithstanding, the venomous animals that most of us think of first are the snakes, which, while they do not usually want to eat us, will deliver a painful, possibly fatal, shot of venom if disturbed, threatened or otherwise frightened.

Snakes must have been a serious problem for early humans because fear of snakes appears to be built into our genes; we do not have to learn about snakes to be frightened of them. We are also curious: we want to look and they pop-up in all kinds of places. Not least, plenty of horror films.

Snakes still cause a lot of damage and death in the tropics, particularly in sub-Saharan Africa, the Indian sub-continent and the rest of southeast Asia. Perhaps involving 400,000 amputations and 100,000 deaths a year. A lot of them in places where many people either do not have access to effective treatments or cannot afford them.

Odds and ends

Venoms are usually more or less complicated cocktails of peptides and proteins, that is to say gene specified strings of amino acids.

A lot of venoms are about blood (thinning it or clotting it), punching holes in cell walls, pain (causing it or stopping it), or neurotransmission. I was reminded that small changes in genes can make big differences: so some of the toxins to be found in venom can be rendered harmless by altering just one amino acid. Perhaps the one which locks onto an important ligand-gated ion channel, perhaps a channel on the nerves which are involved in getting arms, legs, ribs or diaphragms to move about.

Some venoms can bring on anaphylactic shock, with the shock sometimes killing before the venom finishes its work. Which can take some time; after all the point is often to immobilise the prey. The predator is not much interested in anything else and the killing is a side effect.

The authors do not have much time for traditional doctoring of snakebites, despite its thousands of years of history. They prefer the antivenoms made from the blood of horses injected with suitable doses of the toxins in question.

Given my fear of heights and injections, there was an interesting table about fears and phobias, quite possibly from the inaccessible reference 6, so I have snapped it from (page 157 of) the book instead. Oddly, while there is quite a lot of stuff about out there about fears and phobias, most of it is inaccessible, although I dare say a bit more work would start to turn up some freebies. Plus, I imagine they are tricky things to tackle from a statistical point of view.

And thinking of statistics, I suppose skunks with their stinking sprays are on the borderline of any classification. Not quite venomous, but there are venomous animals which spray.

And thinking of the systematics of reference 2, perhaps venom is an example where classification by behaviour is more helpful than classification by ancestry. The fact that venomous behaviour has evolved many times in many different parts of the tree of life is secondary.

Conclusions

A handy introduction to the subject. Also the sort of book that is handy for the advertisements breaks on television.

References 

Reference 1: Venom: the secrets of nature’s deadliest weapons – Ronald Jenner, Eivind Undheim – 2017.

Reference 2: https://psmv5.blogspot.com/2024/05/outgroups.html. 

Reference 3: https://en.wikipedia.org/wiki/Cnidaria.  

Reference 4: https://www.nhs.uk/conditions/anaphylaxis/.  

Reference 5: https://en.wikipedia.org/wiki/Ligand-gated_ion_channel.    

Reference 6: Specific fears and phobias in the general population: Results from the Netherlands Mental Health Survey and Incidence Study (NEMESIS) – Marja F. I. A. Depla, Margreet L. ten Have, Anton J. L. M. van Balkom, Ron de Graaf – 2008.