Growing up you believe the world is meant to be the way it is. The older I get the more I realise that this is not the case. The world is full of injustices and atrocities that governments and the voice of faith expect us to accept, though with each passing year they grow fewer and fewer, at least one would hope. I have created this blog as a space for me to rant about all things science, politics, philosophy and religion, before it’s too late and the vessel of new atheism propelled by a growing surge in secularism solves all of the world’s problems for good.

Monday, 25 April 2011

The World's Only Known Poisonous Birds!



 The world’s first poisonous birds! They live in New Guinea and belong to the genus Pitohui. Though the genus was discovered way back in the 1830s by a French surgeon and naturalist named René Primevère Lesson, it was only in more recent years that it was discovered that this species has a form of toxic chemical defence by Dumbacher et al. It was previously thought that these toxic chemicals, batrachotoxins, were uniquely found in poison-dart frogs, genus Phyllobates. The occurrence of batrachotoxins in both birds and frogs is evidence that the ability to withstand and store the toxin was independently evolved by each group of organisms (aka, convergent evolution). Cool huh!?

This toxin is a neurotoxin and works by attaching to sodium voltage-gated receptors on cells and holding the gates open, preventing the cell from controlling its uptake and release of sodium ultimately leading to numbness from slight exposure all the way to paralysis and death in cases of extreme exposure.

The Hooded Pitohui obtains the toxins from eating a specific beetle, of the Melyridae family. This same beetle is also likely to be the same source of toxicity in the poison-dart frogs in Colombia. This toxin is stored in the feathers and skin of the birds with these beetles in its diet, in a similar way I’m guessing flamingos get their red colouration from the algae they each, which is subsequently stored in their skin and feathers as well. The original ancestor of the three species of Pitohui would have evolved a slightly different sodium voltage-gate in its cells to which the batrachotoxins could no longer bind. Much like trying to push a triangle through a square hole. This would’ve been an advantage for the birds as it opened up the ability to exploit a food source, the beetles, which other animals avoided due to their toxicity. On top of that, by storing the toxin in their skin and feathers they had acquired a form of defence against predators who would eat them. Over time, predator species would begin to avoid eating Pitohuis, those who did eat them would be poisoned and die, thus not passing their genes on, those who avoided them survived to reproduce. Much the same as is expected to be the case in the poison-dart frogs, which gained their bright colours as a way for predators to clearly differentiate the poisonous frogs from the edible ones.

Hooded Pitohui, Pitohui dichrous and Melyridae beetle


Here's a short clip of a lecture by Dumbacher on how these poisonous birds were discovered and their toxins. 


Pete.


3 comments:

  1. In answer to your question, yes. But only after signing in with my google account.

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  2. That is pretty amazing stuff. You always seem to find something interesting to share Pete :)

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