Author
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Fielding, Dennis |
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Defoliart, Linda |
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Submitted to: Physiological and Biochemical Zoology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 6/21/2007 Publication Date: 9/7/2007 Citation: Fielding, D.J., Defoliart, L.S. 2007. Growth, development, and nutritional physiology of grasshoppers from subarctic and temperate regions. Physiological and Biochemical Zoology. 80:607-618. Interpretive Summary: Grasshopper outbreaks occur only sporadically, but they can cause heavy losses of crops and forage. The factors leading to population outbreaks of grasshoppers are not well understood, but it seems likely that nutrition plays an important role. Understanding the nutritional basis of growth and development in grasshoppers will help to enable us to predict, and thus, prepare for major outbreaks of grasshoppers. The migratory grasshopper, Melanoplus sanguinipes, has a very broad geographic range, from the southern U.S. to the interior of Alaska. Comparing life history traits of these grasshoppers from different regions may give us clues to important determinants of their population dynamics. Experiments showed that grasshoppers from Alaska developed more quickly from egg hatch to adult than those from Idaho. This rapid development was achieved through more rapid weight gain and by maturing at a somewhat smaller size. Alaskan grasshoppers supported their more rapid growth by increased rates of consumption and by greater assimilation of nitrogen. The higher assimilation of nitrogen from their food suggests a higher protein requirement for rapidly growing grasshoppers. Nevertheless, the Alaskan grasshoppers performed as well as the Idaho grasshoppers when reared on a low nutrient diet, because of the efficiency with which the Alaskan grasshoppers assimilated and utilized the nutrients in their diet. Technical Abstract: The evolution of key life history traits may be strongly influenced by season-length and food resource quality. This study examined inter-population differences in developmental rates, growth rates, and size at maturity of grasshoppers, Melanoplus sanguinipes F. (Orthoptera: Acrididae), from two contrasting geographical regions. One population was from Alaska, USA, where the growing season is short, but summer precipitation is common, if not abundant. The other population was from Idaho, where the growing season is relatively long and hot, with very little precipitation. We hypothesized that the Alaskan grasshoppers would show more rapid growth and development, but would be more sensitive to food quality, than grasshoppers from Idaho. On a diet of lettuce and wheat bran, grasshoppers from Alaska developed from egg hatch to adult more rapidly than those from Idaho at each of three different temperatures regimes. Averaged over all temperature treatments, Alaskan grasshoppers weighed about 5% less than the Idaho grasshoppers at the adult molt. Feeding and digestive efficiencies were determined for the final two instars using two meridic diets: one with a high concentration of nutrients, and the other with the same formulation, but diluted with cellulose. Alaskan grasshoppers again developed more rapidly, weighed less, and had faster growth rates than grasshoppers from Idaho. Alaskan grasshoppers supported their more rapid growth by increased rates of consumption, greater assimilation of nitrogen, and, on the high quality diet, by greater efficiency of conversion of digested matter to biomass. There was no evidence that performance of Alaskan grasshoppers suffered any more than that of the Idaho grasshoppers on the low quality diet. |
