Saturday, July 18, 2015

Oak Sap Analysis (SPME Head-space)

Following on from Matthew's very recent post (Sap Flows at Knepp!, dated 17th July), I thought some of you might like to see this new, very appropriate data. Last week I analysed a sample of Oak sap (plus a control, similar wood sample) by GC-MS SPME (Solid Phase Micro Extraction), Head-space analysis. Although a similar sap sample had previously been analysed by Omura (2000), my own data however has identified the consistent occurrence of a series of volatiles (red arrows), which differ only in the Carbon chain length of the compounds (C3-C16). This data gives direct support to the potential synergistic mechanism of attraction of such compounds as proposed by both Omura (2003) and also by Cosse (1996).

I confirm the validity of this new data with a biological assay showing a positive Proboscis Extension Reflex (PER) response (of both male and female Sasakia charonda specimens) of the sap sample against the negative PER response of the control (similar wood) sample.

As Matthew reports in his recent post, this newly acquired data has serious implications for the potential attraction of female as well as male Apatura specimens.

Omura, Honda, Hayashi (2000), Identification of Feeding Attractants in Oak Sap for Adults of Two Nymphalid Butterflies, Kaniska canace and Venessa indica, Physiological Entomology, 25, pp281-287.

Omura, Honda (2003), Feeding Responses of Adult Butterflies, Nymphalis xanthomelas, Kaniska cance and Vanessa indica, to Components in tree sap and Rotting Fruits: Synergistic Effects of Ethanol and Acetic Acid on Sugar Responsiveness, Journal of Insect Physiology, 49, pp1031-1038.

Cosse, Baker, (1996), House Flies and Pig Manure Volatiles: Wind Tunnel Behavioral Studies and Electrophysiological Evaluations, Journal of Agricultural Entomology, 13(1), pp301-317.

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