Jennifer Finne
11/4/13
C
Literature Review Outline
Importance of Startle Response
Animals react to cues from predators, and avoiding them can prevent harmful encounters.
Time spent avoiding predators or watching for them can negatively affect other activities like
feeding and mating. Therefore anti-predator behavior needs to aid animals in survival, yet still
allow them to carry out other important activities (Rosier & Langkilde, 2011). Animals including
humans have a limited amount of attention, and survival can greatly depend on correctly
distributing attention to the surrounding stimuli (Elwood,1995)
Behavior is the way someone or something acts. Flight can be defined as animals
retreating from harmful situations, and the actions animals take to protect themselves is
defensive behavior. The response to new stimuli that causes investigation or readiness to escape
is orientating response, also named reflex or startle response. Escape behavior is defined as an
animal’s movement when faced with certain stimuli, while orientation response is movement
from one place to another (Barrows 2000).
Stress response in the form of fight or flight is designed to aid in survival. When an
organism senses a threat, bodily functions that are essential for survival heighten such as
increased blood pressure, breathing and heart rates, and brain activity. Functions that are not
essential for immediate survival including the reproductive system and the immune system are
repressed (Olpin &Hessin, 2012).
The difference in a specimen’s behavior is named intraindividual variation in behavior
(IIV). Animal personality is repeated behavior for each specimen during different situations and
over periods of time. Behavioral syndromes occur when there are relationships between different
times and tests. To ensure consistent research there are guidelines for personality traits. Shyness
or boldness is for familiar yet dangerous situations. Exploration or avoidance is for new
situations, and aggressiveness and sociability can also be measured. Activity is the amount of
movement during normal situations. (Watanabe et al, 2012) Organisms can show habituation, or
a decreased likelihood to respond to certain repeated stimulus. Sensitization can lead to
heightened responses and it can precede habituation. Extreme stimulus can lead to the reversal of
habituation, or dishabituation. Sensitization is prone to occur with dishabituation (Stahlman et al,
2011).
Flight initiation distance (FID) is the closeness people or other animals can reach to an
animal before it escapes. Captive animals with greater FIDs are difficult to interact with and care
for. Tameness is the measure of an animal’s tolerance towards humans. Untamed animals avoid
and will not go near humans. Tamed animals are unlikely to avoid people and will approach
them. Taming is learned throughout life and aids in management and interactions in captivity. In
the wild it is helpful for animals to fear new places and stimuli (Price, 2008).
In an experiment with mink bred for decreased fear towards humans, mink had less fear
of new objects and unfamiliar minks, and mated more often while in captivity. Domestic animals
raised in the wild can be as tame as wild animals. In an experiment with wild rats handled daily
in captivity when they were young, rats were almost as tame as domestic rats (Price, 2008).
Coenobita clypeatus startle response
Several recent studies of hermit crabs have focused on startle response. Multiple tests with
different species show that subjects respond more rapidly when given correct visual and auditory
cues. Hermit crabs are more prone to go into their shells slowly if the auditory stimuli they
receive does not correspond with the visual stimuli. Subjects are less likely to freeze during
trials that do not correspond, and they have quicker responses during concordant trials
(Elwood,1995). Louder noise produces heightened responses and dishabituation. Other
experiments show that noise at the same time as visual stimuli may result in split attention
(Stahlman, et al, 2011).
Figure 1. For an experiment involving concordant and
discordant auditory stimuli, the hermit crab (Coenobita
clypeatus) is clamped down (Ryan, et al, 2012).
Nociception allows animals to respond to harmful stimuli. It is often related to pain,
which is can be difficult to demonstrate in animals. Pain is often shown by behavior that is
learned. Additionally animals will avoid body parts that are injured and groom them. Pain can
also be a motivation for an animal to change its behavior. Anesthetics will limit behavior
associated with pain. Responses caused by pain can include increased heart and breathing rates
and stress behaviors such as fight or flight ( Appel & Elwood, 2009).
Other experiments involve placing hermit crabs with the shell opening facing upwards on
a wash cloth. Researchers measured the time from when the hermit crabs were placed to when
the walking legs emerged. Another experiment involves placing the hermit crab with the shell
opening down in an open, blue, wooden box. Researchers measured the time it took for the
walking legs to emerge. An additional experiment involved clamping hermit crabs in front of an
LCD monitor. Over seventeen seconds an image of a raptor moved down the screen and
enlarged, while the time it took for a hermit crab to hide and emerge was measured with a
camera. The experiment was repeated until the crab no longer hid. Another experiment involved
shocking hermit crabs in a Skinner box.
The repeatability for the time to emerge for both the cloth and box experiments was high,
and the repeatability for emergence time before and after the shock was high. Subjects responded
differently from each other, but each individual showed consistency during the experiments.
Testing for the same behavior such as emergence in the box and before the predator can yield
different results. Behavioral experiments must take into account newness and risk during trials.
These experiment tested shyness or boldness and exploration or avoidance (Watanabe, 2012).
Coenobita clypeatus biology
Hermit crabs use shells or other objects to protect their bodies. They can be found on land or
in marine waters, and different species live in various areas around the world. They have five
pairs of legs where the first pair is chelae that are used to cover the shell. The fourth and fifth
pairs hold the shell and the second and third pairs provide mobility. Hermit crabs also have two
pairs of antennae (Hermit crab, 2013).
Coenobita clypeatus are from the order decapoda, the class malacostraca have bodies with 14
sections, the subphylum crustacean which have 5 pairs of parts on their heads, and the phylum
arthropoda which have exoskeletons (Karis, Wood & Parr). Coenobitidas is a family with the
two genera Coenobita and Birgus (The Caribbean Terrestrial, n.d.).
Figure 2. The anatomy of a hermit crab (Coenobita clypeatus)
(Hermit Crab Anatomy, 2013).
Coenobita clypeatus are often called purple pincher crabs or Caribbean crabs.
Maxillipeds bring food to the mouth and groom. Hermit crabs have exoskeletons with hair called
setae on them. The cephalphorax is the back and head of the crab. Claws are named chelipeds,
and crabs use the larger one to defend and the smaller one to eat and drink. Pereiopods are the
legs and there are four pairs besides the chelipeds. Hermit crabs walk with the second and third
pairs, move in and out of shells with the fourth and clean the inside of the shell and the gills with
the fifth. The gills must be kept moist in order to function. The abdomen is vulnerable and is
inside the shell. Uropods keep the crab in its shell. Females keep eggs on pleopods (Hermit Crab
Anatomy, 2013).
Figure 3. There is a notable difference between the anatomy of female and male hermit crabs
(Coenobita clypeatus) (Hermit Crab Anatomy, 2013).
Coenobita clypeatus ecology
The natural habitat of Coenobita clypeatus can be in Bermuda, Brazil, and from Southern Florida
to Venezuela. The species is found at altitudes of 887 meters (2,300 ft) and inland areas with dry
ground. Coenobita need humidity but they do not prefer habitats that are always humid. Hermit crabs
closer to the shore face greater competition for food from other crab species (The Caribbean
Terrestrial, n.d.). Coenobita clypeatus are tropical and require high humidity to breathe through their
gills (Karis, Wood & Parr, n.d.).
Ideal temperatures for the species are between 93 and 72 degrees Fahrenheit. Temperatures
below 65 degrees cause hermit crabs to become slow and tired. Coenobita can prevent from drying
out by storing water in their shell. Properly fitting shells can provide a great advantage by preventing
dehydration and allowing the animals to survive without water for an increased time period. The
outer body appendages of the crab are calcified and form a seal at the aperture of the shell which
aids in decreasing evaporation (The Caribbean Terrestrial, n.d.).
Coenobita clypeatus are nocturnal and will hide and bury themselves for the day. These hermit
crabs are social and forage together, although they will attack each other for shells. During molts
hermit crabs can re-grow limbs. There are four phases to molting including saving water stores,
shedding the old exoskeleton, growing and strengthening a new exoskeleton, and a phase between
molts. Molts are anywhere between 3 weeks and 3 months long and are related to size (Karis, Wood
& Parr, n.d.).
Coenobita prefer water with traces of salt. The animals can drink ocean water, but the water in
their shell needs to be close to fresh. These omnivorous hermit crabs will consume flesh, droppings,
vegetables, and fruit (The Caribbean Terrestrial, n.d.). Coenobita clypeatus are scavengers that eat a
wide variety of food, and chelipids take food to the hermit crab’s mouth (Karis, Wood & Parr, n.d.).
Coenobita clypeatus as pets
Hermit crabs have been officially distributed as pets to the public beginning in 1953. There are
no cases of humans contracting diseases from Coenobita clypeatus. Florida Marine Research had
labs in Florida conduct research regarding this. (The Caribbean Terrestrial, n.d.).
Common attitudes involving hermit crabs as pets are that they are low maintenance pets that do
not live very long. They are also inexpensive which results in hermit crabs being viewed as things
that can be thrown away. Hermit crabs have little rights and are kept in poor conditions by both pet
stores and other vendors. New owners are rarely given the information they need to care for their
hermit crabs properly (Jacobs, 2000).
Post purchase stress (PPS) condition occurs when hermit crabs are unable to adapt to rapid
changes in their environment such as from a natural habitat to shipment to being sold to being kept
as pets in captivity. There is a high risk of death from physical stress because of lack of appropriate
food, water sources, and habitat, in addition to changes in heat and humidity. Hermit crabs also
experience stress when changing from very poor conditions to ideal conditions. Therefore, new
owners are advised to gradually improve conditions to reduce stress (Latell, 2006).
In captivity it is important for the survival of Coenobita clypeatus that ideal conditions are met.
Temperatures should be kept above 75 degrees, but too much higher can be detrimental. Ideal
humidity should be at least 70%. Ideally substrate needs to be thick enough that hermit crabs can
bury themselves, and it can be sand, coconut fiber or a combination of the two. Coenobita clypeatus
travel together and do not tolerate isolation, so when kept as pets there should be at least two.
Chlorine is detrimental to their health because it damages their gills, which can cause suffocation.
Water used for the hermit crabs should be free of chlorine. Hermit crabs should be able to enter the
water, but the depth needs to be monitored to prevent drowning. Sponges can aid in effectively
maintaining a constant humidity, which is a major factor in survival because hermit crabs breathe
through modified gills. Also, for safety concerns hermit crabs should be picked up from behind
(Wilkin, 2011).
Literature Cited
Appel, M., and Elwood, R.W. (2009). Gender differences, responsiveness and memory of a
potentially painful event in hermit crabs. Animal Behaviour, 78 (6), 1373-1379.
Barrows, E. M. (2000). Animal Behavior Desk Reference A Dictionary Of Animal Behavior,
Ecology, and Evolution, Second Edition. CRC Press. Doi: 10.1201/NOE0849320057
Briffa, M., Bridger, D., and Biro, A. P. (2013). How does temperature affect behavior?
Multilevel analysis of plasticity, personality and predictability in hermit crabs. Animal
Behaviour, 86 (1), 47-54
Karis, R., and Wood, J. B., and Parr, M. (n.d) Purple Pincher Hermit Crab (Coenobita clypeatus).
Retrieved November 10, 2013, from
http://www.thecephalopodpage.org/MarineInvertebrateZoology/Coenobitaclypeatus.html
Hermit Crab Anatomy. (2013). Retrieved September 19, 2013 from
http://www.hermitcrabpatch.com
Hermit crab. (2013). In Encylopaedia Britannica. Retrieved September 19, 2013, from
Encylopeadia Britannica Online: www.britannica.com
Jacobs, N. (2000). “Just a Hermit Crab”(The Throw Away Pet) Retrieved December 1, 2013,
from http://nanjacobs.com/crab.txt.html
Latell, S. (2006). PPS (Post Purchase Stress) Minimizing the Impact. Retrieved November 31,
2013, from http://crabstreetjournal.org/wp/blog/2013/02/21/pps-post-purchase-stressminimizing-the-impact/
Olpin, M. and Wadsworth, M.H. (2013) Stress Management for Life: A Research-Based
Experiential Approach. Belmont, Ca: Cengage Learning. Retrieved from
http://faculty.weber.edu/molpin/healthclasses/1110/bookchapters/stressphysiologychapter
.htm
Price, E.O. (2008) Principles and Applications of Domestic Animal Behavior: An Introductory
Text. Cambridge, Ma: CABI North American Office. Retrieved from
http://books.google.com/books?id=Ww07sIWTYAAC&pg=PA228&dq=%22taming+is
%22+animal&hl=en&sa=X&ei=TZ70UNWPDqfDigLs6oC4BA&ved=0CDoQ6AEwAg
#v=onepage&q=%22taming%20is%22%20animal&f=false
Rosier, R. L. & Langkilde, T. (2011) Behavior Under Risk: How Animals Avoid Becoming
Dinner. Nature Education Knowledge 2(11):8
Ryan, K. M., Blumstein, D. T., Blaisdell, A.P., and Stahlman, W.D. (2012). Stimulus
concordance and risk-assessment in hermit crabs (Coenobita clypeatus): Implications for
attention. Behavioural Processes, 91(1), 26-29. doi:10.1016/j.beproc.2012.05.002
Stahlman, W. D., Yim-Hol Chan A. A., Blumstein, D. T., Fast, C. D., and Blaisdell, A. P.
(2011). Auditory Stimulation dishabituates anti-predator escape behavior in hermit crabs
(Coenobita clypeatus). Behavioural Processes, 88 (1), 7-11. doi:
10.1016/j.beproc.2011.06.009
Thacker, R. W. (1996). Food choices of land hermit crabs (Coenobita compressus H. Milne
Edwards) depend on past experience. Journal of Experimental Marine Biology and
Ecology, 199, 179-191 doi: 10.1016/0022-0981(95)00192-1
The Caribbean Terrestrial Hermit Crab Coenobita Clypeatus (herbst, 1791). (n.d) Retrieved
November 10, 2013 from www.fmrpets.com
Watanabe, N. M., Stahlman, W. D., Blaisdell, A. P., Garelick, D., Fast, C. D., and Blumstein, D.
T. (2012). Quantifying personality in the terrestrial hermit crab: Different measure,
different inferences. Behavioural Processes, 91 (2), 133-140.
doi:10.1016/j.beproc.2012.06.007
Wilkin, C. (2011). Basic Crab Care. Retrieved September 19, 2013, from http://www.hermitcrabs.com