First discovery of lipids in auditory system of an insect

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Researchers have discovered a lipid synthesizing organ in the auditory system of a tree weta, an insect endemic to New Zealand, which has a fossil record dating back 270 million years. Very little is known about the hearing abilities and modes of communication of most weta species. Studies and observations indicate they communicate using both far-field hearing and vibration. Weta produce sound by stridulation and the calls produced are broadband with frequency peaks between 2–14 kHz, depending on the type of stridulation being produced. Weta are thought to produce four different behavioural stridulations. However, a complete repertoire of sound is only known for one weta species, Hemideina crassidens. The aim of this research project was to understand the role the hemolymph channel plays in the sensitivity of an insect auditory system and if it contributes to further frequency discrimination of this auditory system. While investigating this role, researchers were surprised to discover that complex tibial organs are not actually bathed in hemolymph, but in a medium comprised principally of lipid from a new class as determined by mass spectrometry. Further investigations into the function of the lipid revealed a previously undescribed tissue structure, additional to the known complex tibial organs, sitting within the lipid-filled channel; the researchers refer to this structure as the olivarius. “Our study is the only example of a lipid being associated with an auditory system outside of the cetaceans,” say the authors. “However, the lipids contained in the cetacean and weta auditory systems are distinctly different.” In the cetaceans, they allow sound amplification in the water environment. “Results from our study indicate that the lipid plays a different role in the auditory system of the weta compared to cetaceans…The auditory threshold, however, is increased upon removal of the lipid.” Further studies are needed to elucidate the role played by this novel lipid in the auditory system of the weta.

Source: Lomas KF et al. Discovery of a Lipid Synthesising Organ in the Auditory System of an Insect. PLoS ONE. 2012 ; 7(12): e51486.

Rose Simpson & Katia Delaval