Innervation of copepod antennules investigated using laser scanning confocal microscopy

Abstract

The antennules of calanoid copepods compose one of the primary organs for remote sensing of mechanical and chemical environmental stimuli. To better understand how these sensory structures interface with the 3-dimensional fluid environment, it is necessary to understand both their functional morphology and their physiology. These appendages possess setae which are the suspected sites of signal transductlon. Ultrastructural studies reveal that the setae differ in their patterns of innervat~on, and it is believed that these dissimilarities reflect differences in function. In this study, we label the sensilla of copepod antennules using a fluorescent carbocyanine dye, Dil, which becomes inserted in the lipid bilayer of neuronal cell membranes. Aesthetascs on the antennules can then be identified using standard fluorescent microscopy. Because the copepod exoskeleton is transparent to the laser, we were able to utilize laser scanning confocal microscopy to identify other neuronal structures and patterns of musculature within the antennule, while simultaneously visualizing the orientation and larger scale structure of the sensilla.