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Re: Fighting iguanas photo

From: Ben Creisler

A couple of articles that may be relevant:

D.I. Hamasaki (1968)
Properties of the parietal eye of the green iguana.
Vision Research 8(5): 591–599
doi: http://dx.doi.org/10.1016/0042-6989(68)90100-4

The ERG evoked by achromate stimuli was used to study the properties
of the parietal eye of the Green Iguana. The response consisted of a
positive component (positive on-response and a negative off-response),
and a negative component (negative on-response and no response at off)
which were independent and had different properties. The negative
component was more sensitive and had a long refractory period whereas
the positive component had a higher threshold but had a very short
refractory period. The parietal eye of the iguana studied had
properties which were more like those of the lateral eyes of nocturnal
reptiles (gecko and caiman) than those of its own lateral eye.


Seiji Wada, Emi Kawano-Yamashita, Mitsumasa Koyanagi & Akihisa Terakita (2012)
Expression of UV-Sensitive Parapinopsin in the Iguana Parietal Eyes
and Its Implication in UV-Sensitivity in Vertebrate Pineal-Related
PLoS ONE 7(6): e39003.

The pineal-related organs of lower vertebrates have the ability to
discriminate different wavelengths of light. This wavelength
discrimination is achieved through antagonistic light responses to UV
or blue and visible light. Previously, we demonstrated that
parapinopsin underlies the UV reception in the lamprey pineal organ
and identified parapinopsin genes in teleosts and frogs of which the
pineal-related organs were reported to discriminate light. In this
study, we report the first identification of parapinopsin in the
reptile lineage and show its expression in the parietal eye of the
green iguana. Spectroscopic analysis revealed that iguana parapinopsin
is a UV-sensitive pigment, similar to lamprey parapinopsin.
Interestingly, immunohistochemical analyses using antibodies specific
to parapinopsin and parietopsin, a parietal eye green-sensitive
pigment, revealed that parapinopsin and parietopsin are colocalized in
the outer segments of the parietal eye photoreceptor cells in iguanas.
These results strongly suggest that parapinopsin underlies the
wavelength discrimination involving UV reception in the iguana
parietal eye. The current findings support the idea that parapinopsin
is a common photopigment underlying the UV-sensitivity in wavelength
discrimination of the pineal-related organs found from lampreys to

On Sun, Oct 13, 2013 at 3:44 PM, Jura <pristichampsus@yahoo.com> wrote:
> The pineal eye should just be a light detector. It is pretty much directly 
> wired into the pineal gland/sac and functions in Circadian rhythm. The only 
> way I can think it would help with detecting aerial predators is that it 
> might alert the animal to a sudden shadow passing overhead. Having raised 
> iguanas I can certainly attest to their jumpiness when it comes to sudden 
> shadows passing over them. Of course their two regular eyes should be more 
> than capable of seeing the shadow too. :)
> Jason
> ----- Original Message -----
>> From: "quailspg@frii.com" <quailspg@frii.com>
>> To: Dinosaur <dinosaur@usc.edu>
>> Cc:
>> Sent: Sunday, 13 October 2013 5:47 PM
>> Subject: Re: Fighting iguanas photo
>> Stunning!
>> The text mentions that the lizards can detect aerial predators with the
>> "parietal eye." I had thought that the opening and lens were to
>> monitor
>> light for detecting changes in the seasons, or some other very basic use.
>> Can it actually "see" approaching objects?
>> -- Donna Braginetz
>>>  OK--they're not dinosaurs but New Scientist has a photo of two
>>>  fighting iguanas that should be seen:
>> http://www.newscientist.com/data/images/ns/cms/mg22029380.100/mg22029380.100-1_1200.jpg
>>>  text:
>> http://www.newscientist.com/article/mg22029380.100-fighting-iguanas-are-reallife-game-of-thrones-dragons.html#.UloifVA_sbl