Do iguanas have an amygdala?

[Malleus_Incus_Stapes]

Or the closest equivalent?

[Tamerlane]

Essentially, yes. It seems likely that it(or a functionally and structurally analogous organ )is an ancestral feature common to all vertebrates.

[Malleus_Incus_Stapes]

Huh. My boss at the petting zoo kept saying that snakes don’t have emotions because they don’t have an amygdala. So snakes have a proto-amygdala, then?

[thelurkinghorror]

The amygdala is a vertebrate thing. In humans, the amygdala is primarily involved in the emotion of fear and aggression as well as other things. It does not appear to have anything to do with happiness, sadness, surprise, or disgust. So lizards do not have as a “sophisticated” emotional system as humans, but it cannot be said that they lack them.

[Isilder]

@Malleus_Incus_Stapes

Huh. My boss at the petting zoo kept saying that snakes don’t have emotions because they don’t have an amygdala. So snakes have a proto-amygdala, then?

You can kill its whole family right in front of its face, and then feed it, and it will love you for feeding it.

While it clearly feels threatened, or feels safe, thats about as far as anyone can detect a feeling. I think that when it comes to reptiles, you are going to have to assume the amygdala only does fear.

[Malleus_Incus_Stapes]

Not true. She has an iguana, and he very clearly is affectionate and intelligent. He knows who he likes and who he doesn’t.

[Shagnasty]

@Malleus_Incus_Stapes

Not true. She has an iguana, and he very clearly is affectionate and intelligent. He knows who he likes and who he doesn’t.

Iguanas do bond with people. I don’t know if it is an emotional response but they definitely differentiate among people they know and those they don’t. Male iguanas in particular are known for bonding closely with female owners and can become territorial if someone else approaches. My ex wife and I had a very spoiled male iguana, Attila, that we raised from a tiny little thing and he was affectionate around both of us but did not like anyone else one bit. We couldn’t have him anymore when we expected to have kids because he was very large by that point and his tail could hurt even an adult badly if he decided to slap you with it.

[Wesley_Clark]

The amygdala is part of the limbic system, and my understanding is the limbic system is not present in reptiles.

[thelurkinghorror]

@Wesley_Clark

The amygdala is part of the limbic system, and my understanding is the limbic system is not present in reptiles.

I presume that’s based on MacLean’s theory (low “reptile brain”, middle “old mammalian brain” w/ limbic system, high “new mammalian brain”)? Evidence suggests that this is an oversimplification, and shouldn’t be treated as a hard division. Reptiles have a system of structures that work similar to a limbic system, no matter what name you actually give it.

@Wikipedia

However, while the categorization into structures is reasonable, the recent studies of the limbic system of tetrapods, both living and extinct, have challenged several aspects of this hypothesis, notably the accuracy of the terms “reptilian” and “old mammalian”. The common ancestors of reptiles and mammals had a well-developed limbic system in which the basic subdivisions and connections of the amygdalar nuclei were established. Further, birds, which evolved from the dinosaurs, which in turn evolved separately but around the same time as the mammals, have a well-developed limbic system. While the anatomic structures of the limbic system are different in birds and mammals, there are functional equivalents.