Infrared reception Flashcards
What is the optical window?
portion of EM spectrum which reached earth wo being absorbed by the atmosphere. responsible for how our visual systems evolved.
give an example of IR reception
insect cuticle absorbs IR emmission from forest fires at 425-1000 degrees.
many species approach fires and lay eggs on burned wood, larvae feed on colonising fungi. evolved IR sensing organs which detect fires at very far distance (up to 80km).
describe a specific IR sensitive receptor.
Melanophila beetles. pit organ on mesothorax.
many tiny domes covered in wax filaments to protect the receptor from changes in heat. 60 neurones.
domes have an apical indentation, and inside have many layers of cuticle. when heated, outer layers expand wo create pressure on the dendritic tip of sensory neurone attached at the base. similar morphology to mechanoreceptors in ears.
example of a simple IR detector
Merimna atrata beetle.
two organs on each side of the beetle.
mechanism unknown, but cells have many dendritic microvilli and mitochondria. thermal expansion probably plays a role.
70neurones and 800 dendrites
describe the strategy of Acanthocnemus nigricans
2 bilateral organs
high spontaneus rate of neural activity, and distinct inhibition when stimuli switched off.
soon returns to spontaneous firing.
organ is bowl shaped and internal cavity can be heated quickly and cools quickly, neurones detect IR radiation fast and accurately.
how sensitive are snakes IR detection?
sensitivity at 8-12micrometres, which is optimised to detect prey as the thermal emission of mammals is at 10micrometres. (hotter=shorter WL)
where are mosquito IR receptors found?
Tips of antenna, sensillum styloconicum. Has warm and cold cells which respond antagonistically
whats special about the tick IR receptor?
coeloconic sensillum
detects both water (hygroreception) and heat.
