The thermo-photoelectric (TPE) properties of the hornet cuticle: correlation with the morphological structure.
The present study investigated thermoelectric phenomena in the cuticle of the Oriental hornet Vespa orientalis (Hymenoptera, Vespinae). This was done in dependence on the pigment extant at various cuticular region, that is, the brown cuticle in which the primary pigment is melanin and embedded within the cuticle, and the yellow stripes in which the yellow pigment is comprised of purines and pteridines that are located in special pockets between the upper part of the cuticle and the basement membrane. The yellow pigment could be separated from the cuticle proper, but the brown pigment was not thus separable. We found that all cuticular regions of the gaster evinced a thermoelectric response, in that with rise in temperature there was a rise in the thermoelectric current, and vice versa. Additionally, the intact hornet displayed a negative photoelectric response in each of its yellow segments, so that upon illumination with UV light, the maximal current dropped by about 40-50%. Measurements taken on individual stripes in the gaster segments revealed that the photoelectric response is elicited only in the yellow stripes. In all the latter the photoelectric response persists but the maximal current level is lower than in the intact whole hornet. If the yellow pigment is detached mechanically or by bacterial incubation, the photoelectric property of the cuticle is abrogated. Likewise the photoelectric property is abrogated upon immersion of the cuticle in alcohol, even though the yellow pigment is still retained. The specific heat of the yellow stripes in the cuticle is about twice as high as that of the same stripes that had been depleted of their yellow pigment, amounting to 1.8-1.9 J/g.K vs. 0.8 J/g.K.
Pertsis
Vitaly
V
Department of Physiology and Pharmacology, Sackler School of Medicine, Tel-Aviv University, Ramat-Aviv 69978, Israel.
Sverdlov
Anna
A
Ishay
Jacob S
JS
D000818:Animals; D003116:Color; D004583:Electrons; D006927:Hymenoptera / Q000033:anatomy & histology* / Q000737:chemistry*; D034582:Integumentary System / Q000033:anatomy & histology*; D010777:Photochemistry; D010858:Pigmentation; D013696:Temperature