Posts: Links / Parasites: Another incredible radiolab podcast.

Just finished listening to the first half of the podcast on parasites. I was unaware about the cockroach although the ant one was in Dennet's book, Breaking The Spell. It is insane to think of the gruesome and cruelty of nature.For Darwin his lose of faith was a gradual one and examples such as these really struck Darwin as indication against a direct Creator. Why would such a benevolent almighty God create such monstrosities? On the other hand as dreadful as these guys are there is a sheer beauty in their ability to manipulate, as the guy in the podcast they literally perform brain surgery on the cockroach. Behaviors implicitly enacted fine tuned over millions of years. Utterly amazing.

Something else that caught my attention was the monogamous behavior in parasites. I will definitely need to read more on this but it sounded like females are selective and once pair-bounded they mate for life. If your thinking that the parasite are better at fidelity and commitment than us humans keep in mind that it helps to stay attached at the abdomen for years.


This made me think about what type of selection pressures were around to cause these parasite to pair-bond. Typically species that pair bond invest in offspring that have a longer juvenile period on average. Something I was thinking about was the fact that they are confined to one location. It would seem almost unnecessary unless their are many different types all living in their. I will have to read more about it.

So how do you think this behaviour might have evolved? Do you think the ancestral wasps were just giving the roaches a fatal "coup de grâce"? Then perhaps the wasps that were more likely to hit the roach brain in the right place had more success because it meant a live roach to incubate their offspring. Eventually the only wasps left were these micro-surgeon types. I can't really come up with any other way the behaviour might have appeared.

So how do you think this behaviour might have evolved? --I think all behavior evolved so I am not sure what the alternative would be. Unless you are referring to whether I think this behavior is adaptive or just a by product.

I have read others far more elegant then myself (Dawkins & Dennet) both give good assumptions as to how these types of behavior evolved. My gist on this would be that the wasp and cockroach have been battling for thousands of years. Each time one evolves a better strategy the other evolves a counter strategy. Over time these strategies increase in complexity.

As for the wasp...he might not be as good as a neurosurgeon as you think for the cockroach's brain is spread throughout it disgusting body. The head holds a bit of a nervous system, while the rest of the brain is scattered along the ventral part of its body. Which is why if you cut the head off a roach it does not die right away. So if the brain is scattered throughout the body the wasp only needed to accidentally sting it on various parts of it's body until it found the sweet spot and over time wasps that were better at it survived and eventually the behavior became hardwired into the brain.