Impacts of toxic red tide algae Karenia brevis on shell selection behavior of the hermit crab Pagurus longicarpus

Abstract

Eutrophication and global climate change may be increasing the duration and severity of Karenia brevis red tide algal blooms around the world. This is problematic, as the brevetoxins released by K. brevis negatively impact many organisms' neurological capabilities. In this study, we sought to determine the effects of K. brevis on aspects of the shell selection behavior of the hermit crab Pagurus longicarpus. Naked and shelled hermit crabs were pre-exposed to either control artificial seawater or to suspensions of K. brevis (1000 cells ml−1 or 5000 cells ml−1) for either 1 or 3 h, and were then moved to an individual container with either the same respective K. brevis suspension or artificial seawater without any phytoplankton. Hermit crabs then were given a choice between two empty periwinkle (Littorina littorea) shells of the appropriate size, one that was intact and one that had been drilled by a predatory moonsnail (Lunatia heros). The hermit crabs' shell selection behavior was recorded at intervals for 3 h. Hermit crabs normally exhibit extreme aversion to drilled shells; however, individuals that had been pre-exposed to K. brevis were slower to occupy intact shells over drilled shells than those in the control group, regardless of K. brevis concentration or the duration of algal exposure. Hermit crabs that were pre-exposed to K. brevis while “naked” (not residing in a shell) took longer to occupy intact shells than those pre-exposed to K. brevis while occupying a drilled shell and then given the choice to exchange it for an intact one. Additionally, hermit crabs pre-exposed to K. brevis before being tested for shell selection in control seawater were slower to choose intact shells than the control group, indicating lingering impacts of K. brevis exposure. This study suggests that the presence of K. brevis in the plankton may impact the neurological decision-making capabilities of hermit crabs, which could have negative ecological implications for their survival during toxic algal blooms.