Student Symposium: Alternatives to Chemical Control of Insects: The Versatility of Radiotracer Methods for Studying Insect Ethology and Ecology

Abstract

Isotope (nuclide) markers, tags, labels, or tracers can be radioactive or nonradioactive and include a wide diversity of nuclides that may be conservative (a mimic of biologically essential elements) or nonconservative. Detectable radiations include alpha or beta particles, or gamma or X-rays, or combinations thereof. Radiotracer half-lives range from hours to years, and stable-activable tracers can be permanent. Modes of application to the organism of interest include injection, dipping, wire or disc attachments, paints, ingestion, trans-life-stage transmission, and water culture. Tags have been ingested from labeled baits, other insects, living plants with topically applied or translocated labels, blood, and living host animals. Radiolabels have been transferred to the insect life stage of interest by being retained through molts and metamorphic processes. The unit labeled may range from selected individuals to entire populations and ecosystems. Communities studied have been aquatic, terrestrial, soil- or wood-limited, or combinations thereof. Radio- and stable-activable tracers have each been easily and rapidly applied to large insect populations. It is possible to design experiments for studying each and combinations of the following behaviors and ecological interactions: Dispersal and movement patterns, territoriality, food handling and consumption, vector-parasite associations, and food chains and webs. Conservative isotopes can simultaneously be employed to study physiological aspects of each labeled organism. Detectors for quantifying alpha, beta, gamma, X-ray, and Cerenkov radiations are available, and some are able to differentiate between several isotopes located within the same sample. Samples have been detected in the field or laboratory, manually or automatically, and with a wide range of detection methods that include portable ratemeters, Gieger-Muller tubes, liquid scintillation and solid scintillation crystals, semiconductor detectors, and autoradiographic emulsions. Samples can be analyzed while living, dead, or after conversion to any physical state. The versatility of radiotracers was shown to enhance their utility in research in contrast with conventional marking techniques.