Do parasites affect burrowing depth and habitat choice of sand hoppers, Talorchestia quoyana (Amphipoda: Talitridae)?

Talorchestia quoyana is the most abundant sand hopper (Amphipoda: Talitridae) on New Zealand's beaches. These supralittoral detritivores are host to a parasitic mermithid nematode, Thaumamermis zealandica. In other systems, mermithids have been found to manipulate host behaviour to facilitate the continuation of their lifecycle. The aim of the present study was to determine if the burrowing behaviour of T. quoyana showed evidence of manipulation by T. zealandica. Two studies were conducted to assess the spatial and temporal patterns in sand hopper burrowing under field and laboratory conditions. Sand hopper burrowing behaviour showed considerable variation, related to sand hopper length, sand hopper distribution, month of collection, and experimental moisture conditions. The presence of parasites was not a significant factor in determining sand hopper burrowing behaviour, a result contrary to previous laboratory findings for this system. This study illustrates the benefits of combining both field and laboratory experiments to evaluate whether or not parasites alter host behaviour.