The humidity responses of Bathysciola derosasi and Leptodirus hohenwarti, two species of troglobitic Bathysciinae showing different degrees of adaptation to cave environment, have been studied. Intact and antennectomised subjects were tested using choice-chambers with various combinations of relative humidity alternatives (i.e. 20-100%, 50-100%, 90-100%, 50-90% and, as controls, 100-100%) to investigate the role played by the sense organs situated on the 7th, 9th and 10th antenna segments. The results show that intact-antenna subjects of both species are very sensitive to humidity gradients and that their intensity of reaction varies according to the intensity of stimulus, as previously reported by Argano, Sbordoni and Cobolli Sbordoni (1969). The antennectomy experiments show that receptors situated on the 7th, 9th and 10th antenna segments (Hamann’s organ) are involved in hygroreception. In Leptodirus, insects antennectomised below the 9th segment show a reduced intensity of reaction, while those antennectomised below the 7th segment show no positive response at all. This seems to indicate that receptors in the 9th and 10th antennal segments have additive roles beyond that of the 7th. Further research is needed to ascertain whether the antennal organs of Bathysciinae may have yet further additional sensory roles (e.g. chemioreception) as their complex structure suggests.
Lucarelli, Marco and Valerio Sbordoni.
Humidity responses and the role of Hamann's organ of cavernicolous Bathysciinae (Coleoptera Catopidae).
International Journal of Speleology,
Available at: http://scholarcommons.usf.edu/ijs/vol9/iss2/9