Meeting Abstract

77.6  Monday, Jan. 6 09:30  Is the ability to gain carbohydrate driving the evolution and ecology of an insect herbivore, the grasshopper? CLISSOLD, F.J.*; RICHARDSON, A.; LENHART, P.; BEHMER, S.T.; SIMPSON, S.J.; The University of Sydney; The University of Sydney; Texas A & M University; Texas A & M University; The University of Sydney fiona.clissold@sydney.edu.au

Nitrogen is generally thought to limit the performance and fitness of herbivores. However, using chemically defined artificial diet it has been shown that growth, development and reproduction are maximized when insect herbivores are able to obtain an optimal blend of nutrients, especially the macronutrients protein and carbohydrate, rather than by maximizing the intake of any one or all of these. However, while the specific blend of nutrients for each herbivore can be ascertained in the laboratory, this information cannot simply be transferred to natural foods by grinding up plant tissues and measuring their chemical composition. The ability of an insect herbivore that chews plant leaves to absorb nutrients depends on how these nutrients have been packaged within the plant, in interaction with the insect’s food processing tools (typically the mandibles and gastrointestinal tract) and plasticity of its behavioural and physiological responses. We present morphological, physiological and behavioural evidence demonstrating that the ability to gain carbohydrate appears to be a major factor influencing host choice and the evolution of grasshopper mouthpart morphologies. Evidence suggests nitrogen may be limiting, not through being in short supply, but rather its excess relative to carbohydrate and the control it exerts over nutrient uptake through controlling gut emptying and intermeal intervals.