Auditory neural tuning of the tympanal organ when the lipids of the fluid channel are removed (red line).

<p>Frequency of best sensitivity is at 2 kHz, with a threshold at 55 dB SPL (<i>n</i> = 8). A threshold curve of an intact system (<i>n</i> = 9) has been overlaid to show the reduction in sensitivity (blue line). The error bars represent the standard error. Note, for some data points the error bar is too small to be seen.</p

The function of the lipid channel in sound transmission.

<p>Black arrows show direction of movement. In an intact system (A) pressure displacement due to a sound wave causes the thin region of the tympanal membranes (orange) to oscillate. The two enlarged tracheal vesicles between the membranes act like bellows, displacing the air within them dorsally toward the crista acustica (dark blue), but the lipid channel (yellow) acts as a solid mass preventing the crista acustica from moving dorsally, thus this force is sideways, stretching the receptor cell on the crista acustica. The thickened inner plate of the membrane (purple) acts as a further damper by restricting the amount of sideways movement at this point. When the lipid channel has been removed (B) the crista acustica is free to move dorsally with the trachea thus reducing the sensitivity of the system, as more movement is required to stretch the receptor cells laterally.</p

The front leg tibia showing the tympanum membrane with the lipid channel (highlighted in yellow) running from the top of the tympanum to the bottom of the tibia along the dorsal side of the leg.

<p>The front leg tibia showing the tympanum membrane with the lipid channel (highlighted in yellow) running from the top of the tympanum to the bottom of the tibia along the dorsal side of the leg.</p

The structure and placement of the olivarius organ in relation to the known auditory organs.

<p>(A) Cross sections (5 µm) showing a proximal view (1), middle view (2) and distal view (3) of the olivarius stained with Toluidine blue. Arrows point to blue lines corresponding to location of the section on the model. Scale 100 µm. (B) A 3D reconstruction from 519 cross sections, 5 µm thick constructed in Amira, shows the placement and size of the olivarius (O) is shown in yellow in relation to known auditory structures; the crista acustica (CA in blue) and associated sensilla (not modeled, the presentation is represented by the black line running down the centre of the CA), tympanal membranes (TM in orange), trachea (grey) and intermediate organ (IO in red). The subgenual organ, which sits proximal to the intermediate organ, is not revealed. The length of the model is approximately 2.5 mm. (C) A female <i>Hemideina thoracica</i>, the blue box boarders the location of the auditory structures (the white tympanal membranes can be seen) and the area model in the 3D reconstruction.</p

TLC plate of extracted weta leg segments containing the olivarius organ incubated with radiolabelled acetate, following extraction and solvent partitioning.

<p>The non polar phase was applied to silica solid phase extraction (SPE) and eluted fractions were applied to TLC and developed in hexane/ethyl acetate/acetic acid (20∶1:0.1 v/v/v). (A) Plate sprayed with 1% berberine sulphate in acetone/methanol (1∶1 v/v) showing standards: lane 1a, octacosane; lane 1b, tripalmitin; lane 3c, stearic acid; lane 3d, dipalmitin. Sequential SPE eluant fractions from weta leg extracts: lane 2, pentane; lane 4, dichloromethane/methanol 20∶1; lane 5, ethyl acetate. (B). The corresponding autoradiogram of the plate as a storage phosphor image after contact for 2.5 weeks. The red circle and arrows indicate the major lipid spot present as mass (A) and labeled with [¹⁴C]-acetate.</p

High resolution accurate mass spectrum of lipids found in the weta auditory system.

<p>(A) Full scan positive ion spectrum showing the new lipid cluster (shaded) and other more conventional lipids. (B) Insert, shows interpretation of related ions (adducts) to <i>m/z</i> 515.42468 the parent molecule.</p