Limpets on Atlantic Shores

At northern latitudes cold-water gastropod species are on the move: rising sea temperatures from global warming are causing a northward migration of at least 57 species, including limpets.  Limpets and other gastropods are the dominant grazers of algae on coastal areas.  They determine the net productivity of a system as well as its landscape characteristics in terms of an algal mosaic.  Understanding factors that determine a grazing species distribution is fundamental to understanding the influence of changing sea temperatures on coastal zones.  In the eastern North Atlantic Tectura testudinalis is the only limpet species that grazes the rocky intertidal.  Its foraging association with the crustose coralline algae Clathomorphum circumscriptum is well-documented, though its non-foraging movements and preferences are unknown.  Here limpet abundance was tracked during non-foraging time periods and compared to multiple substrates in Nahant, MA.  Limpets were found to preferentially select bare rock substrates for their non-foraging resting sites.  There is likely a relationship of the distance between the bare rock substrate and the closest coralline algae patch, where limpets select bare rock 10-20 cm from small patches of C. circumscriptum.

The common limpet Patella vulgata is the most understood limpet worldwide.  Its foraging patterns and strong homing activity are well-documented in diverse parts of the world.  P. vulgata is a good model organism for determining non-foraging aspects of homing, the behavior in which an individual limpet returns to the same home scar after each daily foraging excursion.  The movement of 10 tagged limpets was tracked using time series photography in a tide pool on the north shore of Bermuda.  Limpets were dislodged at diurnal low tide every day for four days, and photographs were taken at 20 minute intervals during the first two hours after dislodgement.  Individual movement was tracked as well as general group movements.  There were no differences in the average movements between individuals over four days.  The total amount of movement decreased continuously over the four day period.