Sᴘɪᴛᴛɪɴɢ cobras may have evolved unique ᴠᴇɴᴏᴍ
What’s in the ᴠᴇɴᴏᴍ? One expected finding, one surprising finding. When it comes to ᴠᴇɴᴏᴍᴏᴜs snakes, usually we think of these creatures as using ᴠᴇɴᴏᴍ to kill and eat their prey. However, a new study suggests that in one group of snakes, known as Sᴘɪᴛᴛɪɴɢ cobras, evolution had a new purpose in mind for their ᴠᴇɴᴏᴍs. Cobras are fascinating and ꜰʀɪɢʜᴛᴇɴɪɴɢ creatures. These snakes are most well known for their characteristic defence mechanism called hooding, when the sides of their neck ꜰʟᴀʀᴇ out in a dramatic display.
However, hooding isn’t the only defensive behaviour in a cobra’s arsenal. Some species of cobra have modified fangs with small, front facing orifices. These allow them to forcibly eject ᴠᴇɴᴏᴍ as a spray or “sᴘɪᴛ”, which can ʜɪᴛ the eyes of a target up to 2.5 metres away. For this behaviour, they are known as Sᴘɪᴛᴛɪɴɢ cobras. Convergent evolution provides insights into the selective drivers underlying evolutionary change. Snake ᴠᴇɴᴏᴍs, with a direct genetic basis and clearly defined functional phenotype, provide a model system for exploring the repeated evolution of adaptations. While snakes use ᴠᴇɴᴏᴍ primarily for ᴘʀᴇᴅᴀᴛɪᴏɴ, and ᴠᴇɴᴏᴍ composition often reflects diet specificity, three lineages of cobras have independently evolved the ability to sᴘɪᴛ ᴠᴇɴᴏᴍ at ᴀᴅᴠᴇʀsᴀʀɪᴇs. Using gene, protein, and functional analyses, we show that the three Sᴘɪᴛᴛɪɴɢ lineages possess ᴠᴇɴᴏᴍs characterized by an up-regulation of phospholipase ᴛᴏxɪɴs, which potentiate the action of preexisting ᴠᴇɴᴏᴍ cytoᴛᴏxɪɴs to activate mammalian sensory neurons and cause enhanced ᴘᴀɪɴ. While most snakes use ᴠᴇɴᴏᴍ for ᴘʀᴇʏɪɴɢ on other animals, Sᴘɪᴛᴛɪɴɢ cobras use it purely for defence. In a new study, we tested the ᴠᴇɴᴏᴍ of Sᴘɪᴛᴛɪɴɢ cobras to see what ᴛᴏxɪɴs could be found, to work out what might have caused this defensive behaviour to evolve. The results show it might have been to ward off ᴀᴛᴛᴀᴄᴋs from our human ancestors. Sᴘɪᴛᴛɪɴɢ cobras may have evolved unique ᴠᴇɴᴏᴍ to defend from ancient humans.
Cobras are fascinating and ꜰʀɪɢʜᴛᴇɴɪɴɢ creatures. These snakes are most well known for their characteristic defence mechanism called hooding, when the sides of their neck ꜰʟᴀʀᴇ out in a dramatic display.