The sensory dorsal organ of crustaceans: Theme and variations

This report presents the results of a scanning electron microscope survey of sensory dorsal organs across a wide range of crustaceans. Sensory dorsal organs are widespread amongst the Crustacea but not ubiquitous. Although many of the organisms surveyed are only distantly related phylogenetically and there is some variation in the appearance of their sensory dorsal organs, a cluster of elements are all or nearly all present. This suggests not only that the sensory dorsal organ appeared very early in crustacean evolution, but that its function requires the elements to be retained in a relatively conservative manner.