Saddleback Journal of Biology - Saddleback College

Fall 2009 Biology 3B Paper
The smallest mean shell sizes were found at the initial
location, with successively larger specimens being
found at increased distances down the coast. We were
able to establish statistical significance for the
difference between mean sizes at the first location and
size at all other locations, although this was not the
case for successive locations. This correlation, in
particular the results of the first location, can be
attributed to several factors. Although L. strigatella
possesses some locomotion abilities, it is primarily a
stationary organism, retreating back to a “home scar”
(Cook et al 1969). Ideally, the home scar is located
such that the limpet is in near constant contact with
water. However, in a polluted region (as was
encountered at Long Beach harbor), this ensures that
the limpet is also in constant contact with any
hazardous agents in the water. Whereas snails can
move in accordance with the tides, limpet locomotion
is restricted, ensuring that the limpet is either drying
out in the sun, or saturated with pollutants. This
accounts for the lack of growth at location one and to a
lesser extent location two. Also, it has been
demonstrated that limpets are particularly susceptible
to heavy metals in the water (Marchan et al 1999);
bradycardia results from copper concentrations of
0.1g/L after one day and death follows a few days later.
In areas of heavy pollution, such as Long Beach
harbor, this is not unreasonable. As the water quality
increases, L. strigatella does not receive any penalty
for being in constant contact with the water. L.
strigatella is also well suited to dealing with the
increased competition at these sites; limpets are
territorial and are known to physically ram organisms
out of their designated patch (Shanks 2002). This plays
a large factor in the success of L. strigatella in areas of
good water quality and high competition, found at
locations three and beyond.
Although our expectations for L. strigatella
were confirmed, we were surprised to find that T.
funebralis showed a negative correlation between size
and distance, meaning the average specimen size was
largest at our initial location. We found significant
differences in mean shell length between the initial
location and all four successive collection sites, and
also found significant differences in size between all
successive sites (two compared to three, three
compared to four, etc); meaning that the agent
responsible for the difference in sizes continued to be a
factor all the way down the coast. A number of factors
may be responsible. Watanabe (1984) asserts that the
highest amount of T. funebralis predation occurs in
deeper waters along the substrate bottom, with its main
predators being fish and benthic invertebrates (most
notably sea-stars). At our initial site, the water quality
could be considered noxious at best, with a noticeable
oil-slick and poor light transmission qualities caused by
visible amounts of inorganic debris. Because such
conditions play ill host to fish and sea-stars, a
possibility is that the proclivity of T. funebralis for this
location is due to the low amounts of predation. These
conditions were replicated in less extreme fashion at
location two, with water clearing up at locations three
and beyond. This can be seen in the temperature and
pH readings for these locations. These cleaner environs
prove less hostile to T. funebralis’ predators, which
may be responsible for increased predation and thus
demonstrated smaller organism size. Similarly, toxic
environments may give T. funebralis an advantage with
regards to spatial competition. As ideal vertical
location with regards to the tides is a key factor in
growth (Vermeij 1972), the ability to contest the
patches of tidal real estate with the correct exposure to
sun, water and nutrients becomes important,
particularly for the algae-feeding snails. Because
turban snails do not attach as strongly to their substrate
as mussels or limpets, they become increasingly
uncompetitive as the amount of competition for space
increases (Shanks 2002). This accounts for the lower
survivability and thus smaller sizes in locations three
through five, where the cleaner water results in higher
competition. However, in areas of low nutrient
availability and low competition (locations one and
two), T. funebralis’ mobility becomes an advantage,
allowing the turban snails to forage greater areas in
search of food.
Acknowledgements
We would like to thank Professor Steve Teh
for his help and wise counsel in our project. The
researchers would also like to thank Alex Tran’s aunt,
Stephanie Duong, for providing rulers, pH strips, and
thermometers needed for the completion of this project.
The lifeguards of Long Beach and Laguna Beach
should also be acknowledged for their aid in providing
information about tide pool organisms and safety rules.
Literature Cited
Cook, A., Bamford, O. S., Freeman, J. D., &Teideman,
D. D. (1969). A Study of the Homing Habit of the
Limpet. [Electronic version]. Animal Behaviour, 17(2),
330. doi:10.1016/0003 3472(69)90019-0.
Marchan, S., Davies, M. S., Fleming, S., & Jones, H.D.
(1999). Effects of copper and zincon the heart rate of
the limpet Patella vulgata L. [Electronic version].
Comparative Biochemistry and Physiology Part A:
Molecular & Integrative Physiology, 123(1), 89-
93.doi:10.1016/S1095 6433(99)00043-4.
Steen, R.G., & Muscatine, L. (1987). Low Temperature
Evokes Rapid Exocytosis of Symbiotic Algae by a Sea
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Saddleback Journal of Biology
Spring 2010