or
How does a land snail look like in infrared photography?
Abstract
I have corroborated the hypothesis that Mollusca are poikilothermic. It is possible to detect snails with infrared camera, at least in some environmental conditions and especially if snails are moving.
Introduction
Some snakes, such as pit vipers (subfamily Crotalinae) and some pythons (family Pythonidae) and some boas (family Boidae), have a pit organ, a sensory organs for infrared radiation (IR). Therefore they can detect thermal radiation emmited by their prey and from their environment. True vipers (subfamily Viperinae) also may have less sensitive thermal radiation receptors (within supranasal sac). Dmitrijev (1988) hypothetized, that similar thermal organs have all snakes.
This is important for snakes, that are hunting at night. For example this Iwasaki’s Snail-eater (Pareas iwasakii, family Colubridae) movie 1, movie 2 was apprently filmed at night. Did it use eyes or sense of smell (Jacobson’s organ) or thermal organ (if it has any)?
If I was a snail-specilized snake with a proper thermal radiation sensory organ (I have no idea if such snakes exist), would it be possible to “see” snails at night?
Methods
I have taken photos with Flir 3 infrared camera:
Gastropods:
juvenile Cepaea hortensis with the shell width of 11.5 mm;
adult Cepaea vindobonensis with the shell width of 24 mm.
Results
Photos from the common camera are not from the exactly same moment because I can not take photos from two cameras simultaneously.
Infrared photos of a Cepaea vindobonensis on a plastic box placed on a cold floating floor:
Photo of a Cepaea vindobonensis on a plastic box:
Another infrared photo and normal photo of a Cepaea vindobonensis on a plastic box:
Photos at the sunny day on another plastic box:
Note the mucous track visible on the IR photo:
Infrared photos of a juvenile on Cepaea hortensis on a cold floating floor:
A photo of the same specimen of juvenile on Cepaea hortensis on a cold floating floor:
Both snails on the same photo:
Discussion
There are very few published information about infrared photography of marine and freshwater gastropods. I have found no infomations about infrared photography of land snails and slugs.
This infrared camera takes photos with resolution 240×240 pixels.
I think that there would be hardly possible to see gastropods smaller than 10 mm with this camera because of its low resolution.
References:
(in Czech) Dmitrijev J. 1988: Obojživelníci a plazi známí i neznámí pronásledovaní chránění. – Lidové nakladatelství, Praha. 168 pp. p. 54.
Krochmal A. R., Bakken G. S., & LaDuc T. J. (2004). Heat in evolution’s kitchen: evolutionary perspectives on the functions and origin of the facial pit of pitvipers (Viperidae: Crotalinae). – The Journal of Experimental Biology 207: 4231–4238.
Wikipedia contributors. Infrared sensing in snakes. – Wikipedia. accessed 30 May 2012
Masaki Hoso, Yuichi Kameda, Shu-Ping Wu, Takahiro Asami, Makoto Kato & Michio Hori 2010: A speciation gene for left–right reversal in snails results in anti-predator adaptation. – Nature Communications 1(Article number: 133). doi:10.1038/ncomms1133
gastropods 