Many animals have highly developed sensory organs. While much research has gone into understanding the sensory systems developed my mammals, Dr. H. Beckmann suggests researchers and innovative developers take a closer look at smaller organisms such as the fire beetle (Merimna) and snakes. These organisms use microbolometer systems to detect infrared radiation. Microbolometer systems are essentially thermosensors that measure the “temperature of an absorbing surface that is heated by IR radiation” (Beckmann 2004: 972). These microbolometer systems are complex systems compact enough to fit side-by-side on the ventrolateral sides of the second and third abdominal sternite of the beetle. These beetles (and snakes) have organs that are penetrated by a single neuron with its mass of dendrites attached closely; though the structural arrangement differs among species. When tested, the Melanophila beetles’ (another beetle that senses forest fires) sensors did not respond to light nor moderate air movements or changes in temperature near the organs. However, they did respond to IR stimuli, suggesting that these organs are highly developed for specific use. Understanding the function of these sensory organs can lead to development of more accurate and precise sensors.
“The Melanophila acuminata beetle is attracted to forest fires via a pair of infrared sensory organs composed of sensilla…Mathematical calculations showed that the physical properties of the sensilla are such that the expected temperature rise is insufficient for transduction of the infrared signal through mechanical means or as a thermal receptor as previously thought; hence the protein plays the pivotal role in perception of single photons and transmission of the signal within the sensilla.” (Israelowitz et al. 2011:129)
“The Melanophila acuminata sensilla are composed of lipids that may channel the photons to the protein region. Similar to high order polymers like dendrimers, which are nanometer-sized macromolecules with regular units, the lipids form regular layers with a thickness of 100 nm. The lipid layers insulate the scattering of collisional energy and direct the energy towards the IR-absorbing tulip-shaped protein region. Protein hydrogen bonds vibrate in response to infrared radiation at wavelengths around 3 µm and at wavelengths between 10 µm and 25 µm. This stretch resonance corresponds at 3 µm with the data for maximal IR absorption as well as with behavioral and sensory response of the Melanophila acuminata. The presence of this protein provides an explanation for high sensitivity and the specificity of the beetle towards the narrow infrared windows likely via a photo-effect since protein, by consequence of hydrogen resonance, absorbs in the infrared wavelength.” (Israelowitz et al. 2011:136)
Beetles of the genus Melanophila and certain flat bugs of the genus Aradus actually approach forest fires. For the detection of fires and of hot surfaces the pyrophilous species of both genera have developed infrared (IR) receptors, which have developed from common hair mechanoreceptors. Thus, this type of insect IR receptor has been termed photomechanic and shows the following two special features: (i) The formation of a complex cuticular sphere consisting of an outer exocuticular shell as well as of a cavernous microfluidic core and (ii) the enclosure of the dendritic tip of the mechanosensitive neuron inside the core in a liquid-filled chamber.