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Objective
Abstract
Introduction
Discussion / Future Directions
Results
Methods
References / Acknowledgements
The objective is to determine if its nocturnal
activities are endogenous and self-sustaining
or exogenous and not self-sustaining, 7 crabs
were placed in constant light conditions with
food and water while another 7 were placed
in constant dark conditions with food and
water before observing both for activity at
random times for a few weeks.
Fourteen hermit crabs, Coenobita clypeatus, were
purchased from pet stores that had a 12 hr: 12 hr
light-dark cycle. Seven crabs, large and small,
were placed in separate containers in constant
light conditions with pellet hermit crab food, fresh
water, and salt water (13 ppt). Another seven,
large and small, were placed in separate
containers in constant dark conditions with pellet
hermit crab food, fresh water, and salt water (13
ppt) before observing both for activity at random
times for a few weeks. The location of the crab in
the container was recorded as was its activity. A
crab was scored as inactive if it was not moving
and in its shell without its legs exposed. A crab
was scored as active if it was moving and out of its
shell with its legs exposed. The location of the
crab in the container was recorded to determine if
the crab moved since the last time that it was
observed. The percentage of active crabs was
calculated by dividing the number of active crabs
by the total number of crabs and multiplying by
100. The percentage of inactive crabs was
calculated by dividing the number of inactive
crabs by the total number of crabs and multiplying
by 100..
The activity of hermit crabs in constant light conditions ranged from 17% to 20% during the
evening but was 100% inactive during the day (Figure. 1). The activity of hermit crabs in
constant dark conditions was 43% during evening but ranged from 29% to 100% active during
the day (Figure 2).
The results suggest that although hermit crabs in constant darkness were
more active than crabs in constant light conditions, they were active at times
not expected for nocturnal animals and had activities that were exogenous
and not self-sustaining. Hermit crabs in constant light conditions, although
not as active as those in constant dark conditions, were active at times
expected for nocturnal animals and had activities that were endogenous and
self-sustaining. Based on these findings future studies on nocturnal hermit
crabs should test them in both constant light and constant dark conditions.
THE ACTIVITY OF HERMIT CRABS DEPENDS ON THE CONSTANT CONDITION
Bushra Tahhan*, Zemirah Hendley, and Dr. Marion McClary, Jr.
School of Natural Sciences, Fairleigh Dickinson University, Teaneck-Hackensack, NJ
The hermit crab, Coenobita clypeatus, is a semi-terrestrial and tree-
climbing hermit crab that is nocturnal. To determine if its nocturnal
activities are endogenous and self-sustaining or exogenous and not
self-sustaining, 7 crabs were placed in constant light conditions with
food and water while another 7 were placed in constant dark
conditions with food and water before observing both for activity at
random times for a few weeks. The activity of hermit crabs in constant
light conditions ranged from 17% to 20% during the evening but was
100% inactive during the day. The activity of hermit crabs in constant
dark conditions was 43% during evening but ranged from 29% to 100%
active during the day. These results suggest that although hermit
crabs in constant darkness were more active than crabs in constant
light conditions, they were active at times not expected for nocturnal
animals and had activities that were exogenous and not self-
sustaining. Hermit crabs in constant light conditions, although not as
active as those in constant dark conditions, were active at times
expected for nocturnal animals and had activities that were
endogenous and self-sustaining. Based on these findings future
studies on nocturnal hermit crabs should test them in both constant
light and constant dark conditions.
•Amesbury, S.S. 1980. Biological Studies on the Coconut Crab (Birgus latro) in the Mariana Islands. University of Guam Technical Report 17 and 66. 46 pgs.
•Drickamer, L., Vessey, S., and Jakob, E. 2001. Animal Behavior: Mechanisms, Ecology, Evolution. McGraw-Hill. 432 pgs.
•Funded by the National Science Foundation (NSF) via the Garden State (GS) Louis Stokes Alliance for Minority Participation (LSAMP) in STEM Grant
Biological rhythms occur when animal activities and
behavior patterns can be directly related to distinct
environmental features that occur with regular
frequencies. Circadian rhythms are biological
rhythms with a duration of about 24 hours that are
governed by self-sustaining internal pacemakers. If a
self-sustaining internal pacemaker exists, a biological
rhythm is endogenous. If a self-sustaining internal
pacemaker does not exist, a biological rhythm is
exogenous. A biological rhythm is endogenous if the
behavior pattern exists in constant conditions and in
the absence of environmental features that occur with
regular frequencies. If the behavior pattern does not
exist in the absence of environmental features that
occur with regular frequencies, the biological rhythm is
exogenous. The hermit crab Coenobita clypeatus, is a
nocturnal semi-terrestrial tree-climbing hermit crab.
0
10
20
30
40
50
60
70
80
90
100
2/20 12p 2/21 1p 2/29 7p 3/4 4p 3/4 8p 3/11 1p 3/13 3p
Fig. 1. % of active crabs in constant light
0
10
20
30
40
50
60
70
80
90
100
2/20 12p 2/21 1p 2/29 7p 3/4 4p 3/4 8p 3/11 1p 3/13 3p
Fig. 2. % of active crabs in constant dark