2012 COURSE DATES: AUGUST 4 – 17, 2012 - Sirenian International

OUR INVESTIGATION
Introduction
We found L. variegatus to be quite common
along the sea wall on the west side of Spanish
Lookout Caye off the coast of Belize City,
Belize. While observing them, we noticed that
they were always hidden underneath rocks or
covered with seagrass or shells, perhaps done in
order to provide protection against predators or
to protect them from the sun or other physical
factors (Verling, 2004). The objective of this
research was to see if the size of the sea urchin
determined how fast the urchin recovered itself
with debris, or if the size was related to how far
they traveled away from their initial spot once
uncovered. Smaller sea urchins are in need of
more protection because they are more
susceptible to threats. Therefore, we expected
them to travel further or in less time in order to
find protection.
Methods
Over a four-day period, we noted abiotic
conditions and searched for different sized sea
urchins along the shallow sandy and rocky
bottoms. We removed all debris on 10 urchins
using tweezers and tested 3 additional control
urchins (n=13). Two controls were untouched,
and one was touched but no debris was removed.
Every two minutes for twenty minutes we
measured the distance each traveled from its
initial position. After observing for 20 minutes,
we measured the diameter of each urchin, not
including spines, and noted its coloration. Two
graphs were plotted to see if the size of the
urchins had an effect on the time of movement
or distance traveled in order to recover
themselves with debris.
Results
We found that there was no significant
relationship between size and total distance
(F(1,8)=1.32, P=0.28) (Fig 1) or size and time of
movement (F(1,8)=0.38, P=0.55) (Fig 2). We
tested a variety of juvenile-sized urchins, but
each urchin had its own individual response. The
control urchins suggested that there was no
relationship between human interaction and
individual urchin movement, only that they
sought protection. All urchins either recovered
themselves with debris or moved under rocks in
place of coverings within the 20-minute time
frame after we removed their initial debris.
Figure 1. Total Distance Moved vs. Size
Figure 2. Total Time of Movement vs. Size
Discussion
Time and distance traveled by each individual
urchin appeared to be to dependent on how
quickly they were able to recover themselves,
whether with debris or under a rock; not their size.
Further research should be done using a larger
sample size including adult urchins in varying
habitats. Since most of the urchins were juveniles
and found in shallow water, this might have
skewed our data and conclusions.
Literature
Barnes, Robert D. (1982). Invertebrate Zoology.
Philadelphia, PA: Holt-Saunders International.
Pp 961-981. ISBN 0-03-056747-5.
Jackson, J.B.C. (1997). Reefs since Columbus. Coral
Reefs: S23-S32.
Norris, Amy. (2003). Green Sea Urchin Lytechinus
variegatus. Marine Invertebrates of Bermuda:
1-7.
Verling, E. D.K.A. (2004). The dynamics of covering
behavior in dominant Echinoid populations
from American and European West coasts.
Marine Biology: 191-206.