TURN ALTERNATION IN RESPONSE TO SUBSTRATE VIBRATION BY TERRESTRIAL ISOPODS, PORCELLIO LAEVIS (ISOPODA: ONISCIDEA) FROM RURAL AND URBAN HABITATS IN NEW JERSEY, U.S.A

Abstract

Terrestrial isopods are known to increase alternating maze turns in response to adverse environmental conditions, a behavioral pattern presumably associated with efficient escape. The present study investigates whether turning behavior in response to vibration disturbance differs between natural populations inhabiting disturbed and undisturbed areas. Some specimens were collected from urban habitat characterized by construction and heavy automobile traffic, and others from relatively undisturbed rural habitat less than 10 kilometers distant. We examined maze turn alternation in three groups: rural and urban terrestrial isopods exposed to vibration during testing, and rural isopods not exposed to vibration. As predicted, rural isopods exposed to vibration made significantly more turn alternations than rural isopods not exposed to vibration. However, rural vibration-exposed isopods also exhibited significantly greater turn alternation than vibration-exposed urban isopods. There was no significant difference between rural non-exposed and urban vibration-exposed isopods. These results indicate that isopods increase turn alternation when disturbed, but that previous exposure to disturbance is associated with a reduction in the effect. Whether this is due to acclimated or evolved behavioral mechanisms is presently unknown.