Blog: The wonder of venomous animals

For BIAZA Vital Venoms and Practical Poisons week, we’re highlighting the work of individuals across the sector who contribute to advancing venomous species research and appreciation.

Today, Steve Trim – BIAZA TIWG Hazardous Invertebrate Co-Chair and Chief Scientific Officer at Venomtech Ltd, takes us through the enormous diversity and insight derived from venoms...

There are many medicines on the market that owe their origin to venoms. Now this may seem counter intuitive, but in the same way that medicines are toxic when you take too much, venoms can also be beneficial if you have the right part and in the right dose.
These excellent achievements have taken many years to develop (more than 10 years for each) and are excellently summed up by my hazardous invertebrate co-chair Phil Robinson a Senior Aquarist at The Deep. But this is not the end of the story, drug discovery (the process of finding new medicines) goes on and there are many new opportunities to use venoms to treat diseases of humans and other animals. This is down to the power of evolution and the benefits an organism gets from developing a venom system.

Most groups of venomous animals are distantly related with no shared venomous ancestor between them. Take spiders and scorpions as an example, they are both arachnids and therefore quite closely related in the overall scheme of things, however their venom systems are at either ends of their bodies and thus have evolved independently.

In fact, venoms are thought to have evolved over one hundred times independently. In nearly every case when a venom evolves such as a toxin appearing in a salivary gland or at the base of a spine, the host species undergoes increased diversity leading to new closely related species evolving. This adaptive radiation has led to the fantastic diversity of venomous species, and they are still evolving.

As a biologist it is important to make the distinction between venom and poison as they are quite different in their evolution and thus of different utility in drug discovery. Venoms have evolved to be actively injected such as from teeth and spines whereas poisons are passive defences such as skin secretions. Several years ago I would have said that amphibians are poisonous with many having toxic skin secretions, however in recent years scientists have discovered a venomous frog that headbutts venom into victims with modified skull spines and a newt that uses its ribs! Within arthropod species there is a clear divide between poisonous millipedes and venomous centipedes. Millipedes sequester toxins from the plants they eat and only use this poison if they are disturbed or attacked by a predator, while centipedes produce their own venom in modified front legs and actively inject it into their prey and careless people.

It is also important to realise that not all venoms, in fact only a few, are actually medically significant to humans. This is because they have evolved to subdue their prey or just warn their predators, where venoms are lethal to predators it is only those that choose not to prey on the venomous animals that will survive.

The diversity of toxicity in venoms is vast, all scorpions are venomous but only those of the family Buthidae (with the odd exception) are actually toxic to humans, all, but one, species of spider are also venomous and all Cnidaria (jellyfish, anemones and corals) are venomous. Scorpion venom is exquisite at causing pain, even in the commonly captive species such as the emperors (Pandinus imperator) and the Asian forest scorpions (Heterometrus spinnifer), the initial part of their venom contains potassium salt (like that in low sodium table salt) this causes pain, like getting salt in a wound, and then the real clever part is the venom stops the pain switching off. The technical name is inward rectifying potassium channel blockers and these are really useful in science. Many people that enjoy examining rock pools and have had the joy of seeing sea anemones and noticing that they appear to stick to your finger, this is actually an envenomation and yet it is totally innocuous to us humans.

It is these very forces of natural selection that shape venom into the useful tools they are. It is becoming a cliché to say venoms are complex mixtures but it is true, for the most part, as most venoms have hundreds and sometimes thousands of components. The diversity of the species that have evolved venoms and their complexity may surprise many people. Shrews, including those native to the UK contain very simple venoms with less than ten components, whereas the blue mountains funnel web spider (Hadronyche versuta) is currently the owner of the most complex venom with 1,000 different components detected.

Venom complexity is often due to gene duplication events that allow higher rates of protein production and thus more venom. As venoms have evolved to subdue predators and deter prey, the targets they bind to in the recipients have also evolved into genes that are involved in human disease and this is the root of when venoms are useful as new medicines.

The future is very exciting for new therapies from venoms, Chlorotoxin from the death stalker scorpion (Leiurus quinquestriatus) that helps surgeons identify brain tumours in humans and dogs, an exciting powerful anti-inflammatory peptide from the Asian forest scorpion (Heterometrus spinnifer) that is human clinical trials of psoriasis and exciting new biopesticide that biodegrades is on its way from spider venom.

With many venoms yet to discover we need to protect the global biodiversity for our own sake as well as that of the natural world.

Steve Trim
Chief Scientific Officer at Venomtech Ltd.
BIAZA TIWG Hazardous Invertebrate Co-Chair

All blogs reflect the views of their author and are not a reflection of BIAZA's positions.