Changes in turn alternation pattern in response to substrate-borne vibrations in terrestrial isopods

Abstract

The present study focuses on the relationship existing between the phenomenon of turn alternation and substrate-borne vibrations in woodlice. Armadillo officinalis was utilized as a behavioral model in comparison to Armadillidium vulgare so as to assess its capability of perceiving external vibrations too. A T-maze with multiple exits was used to collect information on the pattern of turn alternation in i) adult individuals of A. officinalis exposed, and ii) not exposed to micro-vibrations, and iii) adult individuals of A. vulgare exposed to micro-vibrations. Turn alternation was assessed as the number of times that an animal turned on the opposite side in the T-maze. Our results showed a statistically significant association between turn alternation pattern and both exposure to micro-vibrations and species of the animals. According to our best-fitting model, A. officinalis not exposed and A. vulgare exposed to substrate-borne vibrations have 97% and 98% lower odds, respectively of being in a higher category of turn alternations compared to a lower category than exposed individuals of A. officinalis. A. officinalis seems to be very reactive to substrate-borne vibrations, unlike A. vulgare. This different reactivity might be related to a more complex defense mechanism developed as an evolutionary adaptation to the xeric environment, and/or to a means of communication mediated by substrate-borne vibrations, like in insects.