Cuticular Permeability, Percent Body Water Loss, and Relative Humidity Equilibria Comparisons of Four Termite Species

Abstract

This study compared percentage of total body water (%TBW), water loss rate under desiccative conditions, and cuticular permeability (CP) of four termite species (Order: Blattodea, Infraorder: Isoptera) from different habitats, including one subterranean termite, Coptotermes formosanus Shiraki (Blattodea: Rhinotermitidae), one dampwood termite, Neotermes jouteli (Banks) (Blattodea: Kalotermitidae), one 'wetwood' termite, Cryptotermes cavifrons Banks (Blattodea: Kalotermitidae), and one drywood termite, Cryptotermes brevis Walker (Blattodea: Kalotermitidae). There was no consistent pattern associated with the habitat relative humidity (RH) levels and the %TBW among the four termite species tested. Because C. formosanus forage for food, its lowest %TBW may be due to its ability to access water sources, and its need to be more mobile than kalotermitids that remain in wood. Body water loss rate and CP were lower for xeric species such as Cr. brevis than hydric species such as N. jouteli. An RH equilibrium represents the capacity of termite water retention mechanisms that may include the physical structure of cuticular layers, behavioral manipulation of natural openings, and physiological means. As with water loss rate and CP data, RH equilibria were lower for xeric species such as Cr. brevis than hydric species such as N. jouteli. Moreover, RH equilibria for dead individuals of the four termite species were significantly higher than those of live individuals, indicating dead termites lost more water after losing their physiological and behavioral means of retaining water. RH equilibria represent termites' capability in water retention, and there is a strong linear relationship between RH equilibria and CP values. Hence, RH equilibria may offer simpler alternatives to CP estimates.

Keywords: dampwood termite; desiccation; drywood termite; subterranean termite.