Feeding responses of the horsefly, Tabanus nigrovittatus, to physical factors, ATP analogues and blood fractions |
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Authors: | W G FRIEND J G STOFFOLANO Jr |
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Institution: | Department of Zoology, University of Toronto, Canada;*Department of Entomology, University of Massachusetts, Amherst, U.S.A |
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Abstract: | ABSTRACT. Wild-caught female horseflies, Tabanus nigrovittatus Macq. (Diptera: Tabanidae), were presented solutions of seven analogues of ATP in 0.15 m NaCl, or various blood fractions, either as free liquids at 22 or 38 C or covered with a Parafilm M membrane at 38 C. Warming the diet, so that it can stimulate the insects' heat receptors, or presenting it warmed and covered with a membrane, which the flies can pierce and thus deploy their mouthparts as they would when blood-feeding, enhances the response to gorging stimulants. ADP (ED50 45 μM) was the most potent chemical phagostimulant. There were no significant differences between the potencies of AMP, A(TETRA)P, AMP-PCP, AMP-PNP or AMP-S, which were 3.5-5 times less potent than ADP. Cyclic AMP had no phagostimulatory activity at concentrations of 400 or 1000 μM. The ED50 for washed red blood cells (RBC) in saline was 4.5% (one tenth the concentration found in blood). RBC-free plasma caused only 10% gorging but plasma with 0.5% RBC caused 61% gorging, indicating synergism between RBC and plasma. |
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Keywords: | Tabanus nigrovittatus horsefly Diptera blood-feeding phagostimulation ADP plasma red blood cells |
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