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Sweet problems: insect traits defining the limits to dietary sugar utilisation by the pea aphid, Acyrthosiphon pisum

Douglas, A.E., Price, D.R.G., Minto, L.B., Jones, E., Pescod, K.V., François, C.L.M.J., Pritchard, J. and Boonham, N. (2006) Sweet problems: insect traits defining the limits to dietary sugar utilisation by the pea aphid, Acyrthosiphon pisum. Journal of Experimental Biology, 209 (8). pp. 1395-1403. ISSN 0022-0949

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Plant phloem sap is an extreme diet for animals, partly because of its high and variable sugar content. The physiological and feeding traits of the pea aphid Acyrthosiphon pisum that define the upper and lower limits to the range of dietary sucrose concentrations utilised by this insect were determined principally using chemically defined diets containing 0.125–1.5 mol l–1 sucrose. On the diets with 0.125 mol l–1 and 1.5 mol l–1 sucrose, the aphids died as larvae within 8 and 14 days of birth, respectively. On the other diets, 60–96% of aphids developed to adulthood, and the 0.5 mol l–1 and 0.75 mol l–1 diets supported the highest fecundity. The diet with 0.125 mol l–1 sucrose was ingested at 36% of the rate of the 0.25 mol l–1 sucrose diet, but >90% of ingested sucrose-carbon was assimilated on both diets. This suggests that the lower limit is dictated by the aphid feeding response, specifically, a requirement for a minimal concentration of sucrose for sustained feeding. The haemolymph osmotic pressure of aphids on diets with 0.125–1.5 mol l–1 sucrose was up to 68% higher than on 0.125–1.0 mol l–1 sucrose diets, but diet consumption and sucrose-carbon assimilation was not reduced on the very high sucrose diets relative to 1.0 mol l–1 sucrose. This suggests that failure of the osmoregulatory capacity of the insects on high sucrose diets may define the upper limit to the range of dietary sucrose utilised by the aphids. The mean haemolymph osmotic pressure of aphids on plants with phloem sap containing 0.37–0.97 mol l–1 sucrose was 1.61±0.063 MPa (mean ± s.e.m.), not significantly different from that (1.47±0.059 MPa) on diets with 0.25–1.0 mol l–1 sucrose. It is concluded that the osmoregulatory response of aphids to diets and plants are comparable, and, more generally, that the feeding and osmoregulatory capabilities of the aphids are compatible with the phloem sugar levels commonly encountered by aphids feeding on plants.

Item Type: Article
Keywords: Acyrthosiphon pisum, osmoregulation, phagostimulation, phloem sap, sucrose
Institution: The University of York
Academic Units: The University of York > Biology (York)
Depositing User: York RAE Import
Date Deposited: 03 Aug 2009 14:07
Last Modified: 03 Aug 2009 14:07
Published Version: http://dx.doi.org/10.1242/jeb.02148
Status: Published
Publisher: The Company of Biologists Ltd
Refereed: Yes
Identification Number: 10.1242/jeb.02148
URI: http://eprints.whiterose.ac.uk/id/eprint/6643

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