David J. Bertsch, Joshua P. Martin, Gavin J. Svenson, and Roy E. Ritzmann
At any given moment behavior is controlled by a combination of external stimuli and an animal’s internal state. As physiological conditions change, vastly different behaviors might result from the same stimuli. For example, the motivation to hunt and hunting strategy is influenced by satiety. Here, we describe how sensory responsiveness and motor activity of a praying mantis (Tenodera sinensis) are changed as the insect feeds, leading to an altered hunting strategy. We further show that these changes can be induced by injection of insulin, which likely functions as a metabotropic indicator.
Praying mantises directed their attention toward real and simulated prey less often as they fed and became sated. The ranges of distance and azimuth at which prey was detected decreased as did pursuit of prey, while opportunistic close range attacks persisted. Together, these sensorimotor changes are indicative of a behavioral paradigm shift from “pursuit” to “ambush.” A similar effect was induced in starved praying mantises injected with 0.05 ml of 200 μg/ml bovine insulin. These experiments showed that insulin injection into the circulating hemolymph is sufficient to decrease prey orientation as well as in prey-directed locomotor behaviors (tracking and pursuit). The effects of both prey consumption and insulin injection were similarly dose-dependent. These results suggest that insulin is a signal of internal, physiological conditions that can modify responses to external stimuli. A change in hunting strategy thus results from coordinated effects of a neurohormone on a set of independent sensorimotor processes and the overall activity level of the animal.