Grant, TR & Temple-Smith, PD 1998, ‘Field biology of the platypus ( Ornithorhynchus anatinus): historical and current perspectives’, Philosophical Transactions of the Royal Society of London. And just to remind you that this post was about violence, here is a final video, of a cone snail attack.Ĭasewell, NR, Wüster, W, Vonk, FJ, Harrison, RA & Fry, BG 2013, ‘Complex cocktails: the evolutionary novelty of venoms’, Trends in Ecology and Evolution, vol. Those are just two of the remarkable venom-delivery systems to be found on the planet. The cone snail stretches its mouth open to cavernous, cartoonish proportions, engulfs the fish whole and draws the entire appendage back under its shell as if the fish never existed. The harpoon is a modified radula, the rasping organ that many molluscs use to scrape up food, and designed for one-time use only (Reece et al 2012). It actually looks like a harpoon, too (Schultz et al 2004). The process of evolution produces traits and strategies that are stranger than we can imagine – by building on things that have come before. Driven by a ballistic mechanism, the harpoon is released in less than a millisecond, drilling into the fish’s flesh and releasing the venom (Schultz et al 2004). The snail presses the tip of its proboscis against the fish’s scales.
The snail either digs into the sediment or crawls about on it at a sedate, snail-appropriate pace, gently waving around a thin tube called a siphon, which it uses to sniff out a juicy fish. The hunting strategy that revolves around this harpoon is quite appalling, in the most fascinating of ways. The weapon of choice for some in this group is a harpoon loaded with powerful toxins. Is this an example of two males attacking each other with their spurs?Ĭone snails ( Conus) are a genus of around 600 marine gastropods (Reece et al 2012). It’s time to remind you that this post is about violence with a video of a platypus fight. If males really are fighting over females, an intraspecific evolutionary arms race among platypuses could explain the strength of the venom.Įnd of speculation. Selection then favours even higher venom resistance – and on it goes. Stronger venom would negate the advantage. If platypuses are not killing each other in these duels, does this mean they are resistant to the venom? Increased venom resistance would give a male an advantage over another in a fight. Inflicting a little bit of pain or temporary paralysis would be enough to give one male the advantage over the other. A battle to the death would be, literally, overkill. To help answer this question, I would love to know what effect the venom has on another platypus. Why the venom needs to be so potent for this purpose is a mystery. Based on these observations Grant, Temple-Smith and others have suggested that males may use the spurs to fight each other for the right to mate with females. During this time they are often found with puncture mark injuries, especially near the tail (Grant & Temple-Smith 1998). In males the glands, along with the testes, increase in size for the breeding season. Female platypuses are born with spurs but lose them later (Ligabue-Braun et al 2012). The best answer to the first question so far seems to be “for the ladies”. Since platypuses don’t hunt rabbits – they much prefer benthic invertebrates that they don’t even kill with venom ( McLachlan‐Troup et al 2010) – why do they have spurs and venom at all? And what selection pressure makes the venom so strong? The venom is strong enough to kill rabbits when injected into their bloodstream ( Ligabue-Braun et al 2012). In humans the venom produces immediate local effects that are typically described as “torturous”, “agonising” and “excruciating”, words that are likely embellished with colourful adjectives I cannot repeat on this blog. The pointy end is a hollow spur on each rear ankle, fed through ducts by kidney-shaped venom glands (Grant & Temple-Smith 1998). Forget the duck beak and the beaver tail – the males of the species bear a pretty serious venom-delivery system. I’m going to take a look at two of my favourites. In this armoury there’s barbs, beaks, harpoons, nematocysts, pincers, proboscises, spines, sprays, spurs and stingers (Casewell et al 2013). The venomous animal kingdom offers an impressive weapons collection. Image by Unknown)Īt the midpoint of the semester I feel the need to let off some steam, and so this post will be all about the many violent ways to deliver venom. A platypus spur being displayed, I imagine, very carefully.
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