Many veteran and novice crabbers alike engage in the practice of
actively bathing their hermit crabs frequently, some as often as once
or twice per week. Most adopt this practice because it is printed on
care sheets (like the one FMR puts out), they hear about it from
other crabbers in online forums, or read it in a hermit crab care
book. The idea behind bathing is that hermit crabs as a genus were
once aquatic animals that have adapted to terrestrial life. The
thought is that regular bathing has the benefits of helping them keep
their gills moist, keeping the crabs well hydrated and cleaning out
their shells of dirt, debris and feces.
Many have also adopted the practice of adding Stress Coat to the bath
water for the moisturizing benefits of the aloe contained in it and
the thought that it will help condition their exoskeleton and replace
some of the natural oils and slime coating they may have in the wild.
This can be easily accomplished by offering an appropriate and varied
diet, including some whole fish (like sardines in spring water or
other fish with skin intact, just be leary of fish known to have
higher mercury levels, or fish that has been processed or cooked).
Commercial diets like FMR also provide for essential oils. Vertebrate
feces, such as that from a tortoise, can also be beneficial in
providing additional nutriment in the form of undigested plan matter,
animal proteins sloughed off from the GI tract and beneficial
bacteria found in their digestive tract. One caveat here is to use
only feces from a healthy animal that has been screened for
parasites; though the gastric mill of the crabs likely provides
adequate defense to most common parasites. (Adapted from Greenway
2003, pg. 18 under "Feeding and Diet"). Another use for Stress Coat
is as an aid in rehydrating/rehabilitating injured and/or dehydrated
specimens, which I will comment on later.
The information presented here is adapted from two main sources, the
book "Biology of the Land Crabs", edited by Burggren and McMahon, and
the research paper, "Terrestrial Adaptations in the Anomurans
(Crustacea: Decapoda)". Here is a link to this article:
http://www.museum.vic.gov.au/memoirs/do ... enaway.pdf
What is known from these sources, which are based upon scientific
research, is that hermit crabs maintain their shell water at salt
levels that are isosmotic (equal to) salt levels in their bodies.
Hermit crabs are separable by species with regard to their preferred
salt levels, with each species having its own preferred range of salt
levels. Beach dwelling species like C. perlatus (the Strawberry
Hermit Crab) tend to maintain salt levels that are actually of a
higher concentration than seawater, while species that live more
inland like C. clypeatus usually do not have access to seawater, and
therefore tend to have salt levels well below the concentration of
seawater. (adapted from Greenaway, 2003)
It has been well documented that the more inland species prefer
dilute water unless they are depleted of salt. (Greenaway, 2003 as
referenced from de Wilde, 1973). This would explain reports by
crabbers who actively bathe their hermit crabs that even their C.
clypeatus (considered a "more inland" species) have been observed or
noted to have "drained" their salt water dish on a regular basis.
Certainly crabs will increase water intake prior to molting, but for
C. clypeatus to frequently drain the salt water dish is likely an
indication of salt depletion due to frequent bathing in water
hyposmotic (lower in comparison) to their blood and body tissues.
This information is a very brief summary of the information found in
the article linked above starting on page 16, column 1 with the
heading "Salt and Water Balance".
Now, let me discuss the practice of actively bathing hermit crabs and
the effect it can have on their salt regulation. The procedure most
use when they bath their crabs is to submerge them, some placing them
upside down so that when they come out of their shell to turn over,
the bath water flows into their shell and rinses out dirt and feces.
Others wait until the crabs come out to walk around and then move
them around under the water to rinse out the shell. In these
processes, their shell water is swapped out for the bath water (for
some, chemically treated Stress Coat water). The net effect is that
their shell water which was once isosmotic (equal) with their blood
concentration of salt is now hyposmotic to the concentration of salt
in their blood (salt level in their shell water lower than that in
their blood and body tissues). Through osmosis, a higher
concentration will always move toward a compartment with a lower
concentration; as a result, the concentration of salts in their blood
and body tissues is lowered as some salt is lost through osmosis to
the lower concentrated shell water. This presents a problem,
potentially dropping their body salt level below the range that is
preferred for each species, especially in a beach dwelling species
like C. perlatus, which tends to be "saltier" than others for lack of
a better term. It has been noted that the renal organs of hermit
crabs (analogous to our kidneys) possibly plays a large role in their
osmoregulation through exchange of ions:
Quote:
"In aquatic species adjustments to ion content are made principally
by salt transport across the gills, and the renal organ makes only a
minor contribution. In terrestrial animals the gut and renal organs
become the main sites of ionic regulation."
Source: Biology of the Land Crabs, Burggren and McMahon, pg 213.
Since we do not know the long term effects on their body systems and
organs of the wide swings in salinity levels that can occur with
frequent bathing, perhaps we should make adjustments to the captive
care of these animals, with the goal being minimizing the overall
disturbance of their salinity levels.
Certainly, the crabs can adjust their salinity levels by selective
drinking/bathing in their habitat, and through the promotion of
evaporation (Greenaway, 2003), but again we don't know the long term
effects of wide swings in salinity levels on their osmoregulatory
systems overall and specifically their gut and renal organs.
Furthermore, one of the world's leading experts in herpetology and
captive animal husbandry, Philippe De Vosjoli recommends against
actively bathing hermit crabs for much the same reason in his
book, "The Care of Land Hermit Crabs".
The next issue to be dealt with is in regard to adding Stress Coat to
the bath water. Recently, a fellow crabber contacted the manufacturer
of Stress Coat to ask about the safety of adding it to their drinking
water. The answer was that it has not been studied and cannot be
recommended. The crabber noted that many crabbers also add it to
their bathing water. Again, the answer was this has not been studied
and cannot be recommended by the manufacturer. One point that many
Stress Coat bathers don't often realize is that their crabs are
likely exposed far longer than they think to the chemicals in Stress
Coat.
When their shell water is swapped out for Stress Coat treated water
through frequent bathing, the chemicals are now in their shell water,
and likely remain there for days after bathing, if not straight
through until the next bath all together. Even if the crabs add to
their shell water, all they are doing is diluting the chemicals. If
they are able to partially or fully submerge themselves in the
drinking water (salt and fresh) in their habitat, then some of the
chemicals no doubt wind up in their drinking water. Even changing
water every day as most crabbers do, you are likely to wind up with
some chemicals in the drinking water on a day to day basis in a set
up with multiple crabs, as each will visit the water dish on their
own schedule. Chances are somebody with Stress Coat water in their
shell will visit the water dish on a daily basis.
With these thoughts in mind many crabbers, including myself, have
opted for a more "passive" method of bathing our hermit crabs. That
is, providing basins of salt and fresh water large and deep enough to
allow the crabs to at least partially, if not fully submerge
themselves in them. One issue here is that you need to provide
adequate climbing surfaces (i.e. rocks, coral, etc.) in the basins to
ensure that even the smallest crabs can climb out from the bottom.
Some crabbers, including myself, have added a filter to their basins
in order to cut down on daily maintenance.
There are several filters that can work for this application, but you
need a water depth of about 3" to accommodate them. Penn Plax has a
Small World filter that operates off of an air pump, and they also
have a submersible filter called the Sand Shark. I have tried both
and prefer the Sand Shark. It is only a little more than the Small
World once you factor in the air pump you need for the Small World,
is much quieter, and circulates water better, creating a sort of wave
motion effect. Other brands that offer similar filters are Fluval,
Duetto and ZooMed. The most common application for these is in semi
aquatic terrariums for turtles, frogs and other semi aquatic
creatures, and most have an adjustable flow rate, making it possible
to use them in relatively small basins. To find appropriate sized
basins, measure your habitat and come up with a reasonable size that
will fit and allow for at least partial, if not full submersion. Then
visit your local pet store and look for that size dish, or visit the
tupperware isle at a local department store and measure the dishes
until you find some of appropriate size. One point to note if you
switch to a filtered basin, is that you will lose some water through
evaporation and will likely have to replace some every few days. Take
care to monitor the salinity level of the water to keep it within an
acceptable range for seawter (generally considered 1.020-1.024
specific gravity). I usually add fresh or brackish water to replace
evaporative losses so as not to increase the overall salinity. You
can monitor this with a simple hydrometer purchased at a pet store
that handles salt water fish at a cost of $10-12.
Maintenance can be an issue if you cannot filter; however, since most
crabbers change their water daily, it is not a big deal to change
water in a larger dish every day if you have to go up in size. One
problem to overcome is how does one recoup lost land surface area in
their crabitat if they have to add larger basins to accommodate
passive bathing? My answer was to landscape the terrarium so that
there is a high level of substrate at one end, molded over makeshift
caves and leveled off. What you wind up with is a natural second
level, and more surface area by way of the caves buried underneath. I
believe this can be accomplished with the smallest of crabitats and
will be happy to assist anyone with suggetions on how to do this in
their size tank. Here is a link to some photos that will show some
ideas for caves. Note the photo near the bottom of the second link
showing my C. perlatus bathing himself in a filtered saltwater basin:
http://www.kazabee.com/html/hermit_crab_stuff.html
http://www.kazabee.com/html/hermit_crab_stuff_2.html
As a matter of fairness, active bathing may be acceptable if one
cannot provide for passive bathing for the crabs in their habitat.
Active bathing would be preferable to not bathing at all, especially
if the crabs have small, shallow water dishes, or in some cases a
small shell dish with only a moist sponge (the latter of which I
certainly do not advocate), and/or if the humidity levels are low or
borderline in the crabber's home and/or the crab's habitat. If active
bathing is deemed necessary, care should be taken to minimize the
overall disturbance the crabs experience. This could mean modifying
your practices by bathing them less frequently, cutting down on the
frequency of Stress Coat use or limiting it to use for injured
specimens or those in need of rehabilitation/rehydration, and lastly
adjusting the salinity of the bath water to try to more closely match
what is likely in the shell of each species; for example, bathing C.
perlatus in full strength salt water as opposed to fresh water. There
is a chart in the Greenaway article referenced above that shows the
relative salinity levels for each species (page 17, table 3).
In closing, every crabber who actively bathes their crabs should ask
themselves the following questions:
1. How long does the Stress Coat treated water stay in my crabs'
shells
after they are bathed in it?
2. Are they exposed almost every day to Stress Coat water and the
chemicals in it as a result of my bathing because it is left in their
shell water between baths? We know crabs ingest their shell water
from time to time, they will also absorb chemicals through their
skin. Also, if they readjust by submerging in their drinking water,
the Stress Coat chemicals are likely to wind up there as well.
3. How much and how often do they actually drink when left to their
own
devices? Are they getting a bulk of their weekly drinking water
intake done at bathing time, causing them to ingest Stress Coat and
its chemicals on a regular basis?
4. What is the potential long term effect of wide swings in salinity
levels caused by once or twice weekly bathing? What is the long term
effect on the bodies of hermit crabs of constantly having to readjust
their levels-- not minor adjustments that occur through their own
natural bathing and drinking behaviors, but major adjustments
necessitated by shell water constantly being hyposmotic to blood
levels due to frequent bathing?
Give yourself honest answers to these questions. We have the
responsibility to care for these animals to the best of our ability.
This should include simulating their natural environment and giving
them the facilities they need to properly care for their own needs in
as natural a manner as possible.
Copyright 2004, Kazabee, Inc. All rights reserved.
