The venom system of bloodworms

Recently, we published a paper with the title “Comparative analyses of glycerotoxin expression unveil a novel organization of the bloodworm venom system” and with this “behind-the-paper-style” blog I want to give some insights how we came to our conclusions. The paper was published by Richter et al. (2017) in BMC Evolutionary Biology and is open access.

Venoms and venom systems evolved many times independently across the animal tree of life. That spiders or snakes can be venomous is well-known. Also, the venom of the iconic cone-snails has been investigated in detail. However, venomous annelids have been (mostly) neglected so far. There are around 20,000 annelid species, but only few of them have been convincingly shown to be venomous. E.g., fireworms (Amphinomidae) can burn like hell if you touch them, which is due to an inflammation-inducing substance called complanine. However, this is passively delivered when their chaetae break and therefore these animals should be regarded as poisonous (which still make them an interesting target for studying the content and evolution of their toxins). In contrast, venomous are those animals which actively deliver their toxin cocktail,. e.g., for predation, defense or competition. Only glycerids and leeches are convincingly demonstrated to represent venomous annelids (von Reumont et al. 2014). For several other annelids (e.g., chrysopetalids, polynoids or sigalionids) it has been speculated that they might be venomous, however, our own dissections could not reveal convincing evidence of venom glands or an apparatus to deliver the venom in several investigated taxa. Nevertheless, different groups of scale-worms (e.g., Pisione spp., Pholoe spp.) remain good candidates to include venomous species, but desperately need to be studied in detail. And I also would not be surprised if more examples from other annelid taxa will be discovered in the future. Continue reading The venom system of bloodworms