Suboptimal nutrient balancing despite dietary choice in glucose-averse German cockroaches, Blattella germanica

• Published in: Journal of insect physiology 2015-10, Vol.81, p.42-47
• Main Authors: Jensen, Kim, Schal, Coby, Silverman, Jules
• Format: Article
• Language: English
• Subjects: Animal Nutritional Physiological Phenomena; Animals; Blattella germanica; Blattellidae - growth & development; Blattellidae - physiology; Carbohydrate; Choice Behavior; Deterrence; Dietary Carbohydrates; Dietary Proteins; Feeding Behavior - physiology; Female; Fructose; Geometric framework; Glucose; Glucose aversion; Gustatory functioning; Oocyte development; Oocytes - growth & development; Optimal foraging; Protein; Taste adaptation; Toxin avoidance
• ISSN: 0022-1910; 1879-1611
• DOI: 10.1016/j.jinsphys.2015.07.001

[Display omitted] •Female glucose-averse cockroaches were given dietary choice from complementary foods.•Complementary foods were protein- or carbohydrate-rich but varied in sole sugar type.•Females reached their intake target when both foods contained fructose.•Intake was restricted to one imbalanced food when the other food contained glucose.•Failing to ingest a balanced diet came at the cost of slower development of oocytes. Insects have evolved fine-tuned gustatory and post-ingestive physiological mechanisms that enable them to self-select an optimal composition of macronutrients. Their ability to forage optimally among multiple food sources and maximize fitness parameters depends on their ability not only to taste and perceive the nutritional value of potential foods but also to avoid deleterious components; the strength of such avoidance should reflect the severity of the perceived hazard. In German cockroaches (Blattella germanica), glucose aversion has evolved in some populations in response to anthropogenic selection with glucose-containing insecticidal baits. In four feeding treatments, we gave newly eclosed glucose-averse female cockroaches free choice to feed from two artificial, nutritionally complementary foods varying in protein and carbohydrate composition, with glucose or fructose as the sole carbohydrate source in either food. After 6days of feeding, we measured diet consumption and the length of basal oocytes as an estimate of sexual maturation. The females did not compromise on their aversion to glucose in order to balance their protein and carbohydrate intake, and experienced lower sexual maturation rates as a consequence. Nutrient specific hunger via feedback mechanisms, and adjustments to gustatory sensitivity thus do not override the deterrence of glucose, likely due to strong selection against ingesting even small amounts of toxin associated with glucose in baits. In the absence of baits, glucose aversion would be expected to incur a fitness cost compared to wild-type individuals due to lower overall food availability but also to larger difficulty in attaining a nutritionally balanced diet.