Data from: Salivary digestion extends the range of sugar-aversions in the German cockroach

Saliva has diverse functions in feeding behavior of animals. However, the
impact of salivary digestion of food on insect gustatory information
processing is poorly documented. Glucose-aversion (GA) in the German
cockroach, Blattella germanica, is a highly adaptive heritable behavioral
resistance trait that protects the cockroach from ingesting
glucose-containing-insecticide-baits. In this study, we confirmed that GA
cockroaches rejected glucose, but they accepted oligosaccharides.
However, whereas wild-type cockroaches that accepted glucose also satiated
on oligosaccharides, GA cockroaches ceased ingesting the oligosaccharides
within seconds, resulting in significantly lower consumption. We
hypothesized that saliva might hydrolyze oligosaccharides, releasing
glucose and terminating feeding. By mixing artificially collected
cockroach saliva with various oligosaccharides, we demonstrated
oligosaccharide-aversion in GA cockroaches. Acarbose, an alpha-glucosidase
inhibitor, prevented the accumulation of glucose and rescued the
phagostimulatory response and ingestion of oligosaccharides. Our results
indicate that pre-oral and oral hydrolysis of oligosaccharides by salivary
alpha-glucosidases released glucose, which was then processed by the
gustatory system of GA cockroaches as a deterrent and caused the rejection
of food. We suggest that the genetic mechanism of glucose-aversion support
an extended aversion phenotype that includes glucose-containing
oligosaccharides. Salivary digestion protects the cockroach from ingesting
toxic chemicals and thus could support the rapid evolution of behavioral
and physiological resistance in cockroach populations.