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.
Figure 1. Clark University students working in Nahant, MA
Figure 2. The rocky intertidal behind Tobacca Bay, Bermuda