repugnatorial

Repugnatorial is an adjective derived from the Latin repugnatorius, meaning opposed or resisting, and is used in general language to describe something repugnant or arousing disgust. In biology, repugnatorial describes glands or secretions used for defense by certain organisms, especially arthropods, that produce a repugnant odor or irritant to deter predators. The term is often applied to repugnatorial glands, paired defensive organs found in some millipedes and isopods, which emit foul-smelling chemicals when threatened.

The chemical composition of repugnatorial secretions varies widely and can include sulfur compounds, terpenoids, benzoquinones, phenolics, and other substances. These secretions may be sprayed, smeared, or expelled from specialized openings and may deter predators through odor, taste, or irritation. The exact mechanism and chemistry can differ among taxa, reflecting adaptations to specific ecological pressures.

In zoological literature, repugnatorial glands are described in contrast to other defense mechanisms and are often referred to as defensive or spray glands depending on the organism. The term’s usage is largely descriptive, with some authors favoring more precise naming of the gland type or its secretion. As a cross-taxon descriptor, repugnatorial highlights the defensive function rather than a single, uniform gland lineage.

Etymology: From Latin repugnatorius, meaning opposed or resisting.