title: Tolerance for nutrient imbalance in an intermittently feeding herbivorous cricket, the Wellington tree weta.
abstract: Organisms that regulate nutrient intake have an advantage over those that do not, given that the nutrient composition of any one resource rarely matches optimal nutrient requirements. We used nutritional geometry to model protein and carbohydrate intake and identify an intake target for a sexually dimorphic species, the Wellington tree weta (Hemideina crassidens). Despite pronounced sexual dimorphism in this large generalist herbivorous insect, intake targets did not differ by sex. In a series of laboratory experiments, we then investigated whether tree weta demonstrate compensatory responses for enforced periods of imbalanced nutrient intake. Weta pre-fed high or low carbohydrate: protein diets showed large variation in compensatory nutrient intake over short (<48 h) time periods when provided with a choice. Individuals did not strongly defend nutrient targets, although there was some evidence for weak regulation. Many weta tended to select high and low protein foods in a ratio similar to their previously identified nutrient optimum. These results suggest that weta have a wide tolerance to nutritional imbalance, and that the time scale of weta nutrient balancing could lie outside of the short time span tested here. A wide tolerance to imbalance is consistent with the intermittent feeding displayed in the wild by weta and may be important in understanding weta foraging patterns in New Zealand forests.
authors.affiliation: Ecology Group, Institute of Agriculture and Environment, Massey University, Palmerston North, New Zealand.
authors.forename: Priscilla M
authors.initials: PM
authors.lastname: Wehi
authors.affiliation: Institute of Natural Sciences, Massey University, North Shore, Auckland, New Zealand ; The Charles Perkins Centre and Faculty of Veterinary Science and School of Biological Sciences, The University of Sydney, New South Wales, Australia.
authors.forename: David
authors.initials: D
authors.lastname: Raubenheimer
authors.affiliation: Ecology Group, Institute of Agriculture and Environment, Massey University, Palmerston North, New Zealand.
authors.forename: Mary
authors.initials: M
authors.lastname: Morgan-Richards
mesh_terms: D000818:Animals; D002149:Energy Intake; D005260:Female; D006135:Gryllidae; D060434:Herbivory; D008297:Male; D009520:New Zealand; D014197:Trees