Pre Molt Symptoms

Coenobita perlatus digging

Coenobita perlatus digging

Observed Premolt Symptoms

by Marie (aka ladybug15057)

At times, crabbers become concerned due to certain actions their hermit crabs are beginning to display. Often, they are concerned that the hermit crab is ill, or has another form of complication happening that needs attention. Where, as on occasions, the symptoms they are observing may be due to a stressful situation, whether it be from their past or current living conditions, there are many times that the hermit crab is displaying premolt symptoms. If one knows that he/she has provided the hermit crab with the essentials it needs to thrive (proper humidity level, proper temperature, proper diet, bacteria/mold and a pest-free environment, etc.), what you are beginning to observe may very well be premolt symptoms that the hermit crab is displaying. With the numerous molts we have had, I would like to share some of the premolt symptoms I have observed with our hermit crabs and hope it can be of some help to ease other crabbers concerns.

Please note that not all hermit crabs will display premolt symptoms prior to molting. Some will do a surprise molt displaying no symptoms, but here are some we have noted with our hermit crabs:

1. Gorging food for almost 2 weeks prior to molting.

C. variabilis eating avocado byLisa Dawson Dec 2015

C. variabilis eating avocado by Lisa Dawson Dec 2015


2. A few days–up to and including almost 2 weeks prior to molting–consuming no food at all.

3. Very restless behavior during the daylight and evening hours, including attempting to climb the glass walls inside of the crabitat as though they are looking for a way out.

4. Dragging their large cheliped almost under them as though it is too heavy to hold up, or in front of them as opposed to being slightly in front of them when they are scooting.

5. The V shaped eye stalks _/ as opposed to the typical parallel eye stalk shape. |_| The pupil of the eye stalk looks as though they are looking outward as opposed to straight ahead.

6. Eye stalks in a downward position as opposed to a standing up type position. When the eye stalks are in this position, this means that the hermit crab is very close to molting, or has already begun the actual molting process to remove its exoskeleton. By no means at this time should the hermit crab be disturbed in any way. By doing so, this could be lethal for the hermit crab.

Hermit crab pre molt eyes

Hermit crab pre molt eyes


7. The leg tips of the hermit crab turn lighter in color, along with a lighter whitish/beige coloring at the joints of the legs and the chelipeds. With some, the outer parts of the legs change to a whitish/beige in color with the very center of the legs and chelipeds having a darker coloring to them.

Hermit crab pre molt

Hermit crab pre molt


8. Along with the lighter coloring of the hermit crab’s exoskeleton, if one looks closely where the joints meet, you can at times see where the old exoskeleton is pulling away from the new body. When this happens, the new body underneath can be seen. This reminds me of when a human wears pants, and sits on a chair. You can see the ends of the pants, and usually the socks underneath.

9. When the hermit crab is scooting through the sand in the crabitat, its shell leaves a deep groove type impression in the sand. This dragging of the shell can also be observed when the hermit crab is out of the crabitat in a drip dry area where the shell being dragged along the bottom of the area can actually be heard.

10. When the hermit crab is scooting, its legs are out to their sides as opposed to being in an upright hermit crab style curve when walking. (This reminds me of the stepped-on bug effect look.)

11. When the hermit crab is picked up and it first comes partly out of its shell, one of its front legs stick straight out as though it has no control of it. Within a few seconds, the leg goes into a normal position like the other legs.

12. The premolter spends a lot more time than usual in, or around, the water ponds. This behavior has been observed around the ocean water pond as well as the fresh water pond. With our hermit crabs, it is observed that they frequent the ocean pond more than usual, and the ocean pond will need refilling a few times a day.

Coenobita perlatus submerged in water

Coenobita perlatus submerged in water


13. Some of the hermit crabs get an odor to them. This odor reminds me of the silicone that is put around a tub/shower. Some crabbers have related this odor to iodine, or butterscotch.

14. The hermit crab will attempt to find a secluded area away from its tank mates. Many will go into single hidey areas we have within our crabitats. Smaller hermit crabs have gone into larger extra shells–in their own shells– where they can hide. This reminds me of a shell plug within the larger shell opening.

15. The hermit crab has slow antenna movement and appears lethargic, or depressed. Unless they are picked up and moved, they remain in the same place they were put.

16. A behavior change is noted. A very shy, out-going hermit crab appears shy, or withdrawn. It is scooting about the tank most of the day as if in search of something. It becomes slightly or overly crabby with its tank mates. I have one hermit crab that never digs, but when in premolt she will begin to burrow.

17. The hermit crab appears to suddenly become uncomfortable with the shell it is wearing. It begins to change shells frequently, but just cannot seem to find that right fit regardless of what shell it has on. This behavior is more frequent than a normal hermit crab trying shells on for fun or entertainment.

Hermit Crab Shell shopping

Hermit Crab Shell shopping


18. The hermit crab will begin to dampen or wet the sand regardless of how perfect the humidity level is at the time.

19. The hermit crab will begin to remain about half way out of its shell when it is relaxing, as opposed to being mostly within its shell.

20. The hermit crab will have whitish, cloudy or hazy looking eyes. I have also observed the pupils of the eyes being a dull reddish brown in color as opposed to being the bright, shiny, almost black color.

Hermit crab pre molt eyes

Hermit crab pre molt eyes


21. With some of our hermit crabs, it has been their tank mates that let me know that they are in premolt. It would appear that the premolter is all of a sudden a very popular hermit crab. His/her tank mates will surround him/her, or block the entrance to the single hidey that it has chosen to try to seclude itself in. The tank mates stay next to him as though they were best buddies, or trying to protect his friend. (Mating takes place prior to molt and this could explain the unusual interest in the molter)

Antennae war

Antennae war


22. A water sac is observed on the hermit crab?s side within the shell. (This may not always be observed.)

Pre molt water sac

Pre molt water sac

Pre molt water sac

Pre molt water sac


23. If the hermit crab is missing a leg or cheliped, a gel limb will form. The gel limb appears to go through a sudden growth spurt the closer the hermit crab is to actually molting.

Gel limb big pincher regenerating by Lamont Darren Medley

Gel limb big pincher regenerating by Lamont Darren Medley


When I observe any of the behaviors mentioned above, I isolate the hermit crab from his tank mates for its own safety. I have found these to be premolt symptoms with our hermit crabs. This is not to say there are not other premolt symptoms that I have not included in this list, there very well could be, but these are some of the ones I have observed.

If any of these symptoms are noted on your hermit crabs, please act accordingly. It is not always true that a hermit crab will burrow to molt. To date, we have 82 hermit crabs and I have had 319 molts. All of our hermit crabs, C. Brevimanus, (Indos), C. Rugosus, (Rugs), C. Clypeatus, (PPs), C. Compressus, (Es), have molted above substrate without any attempts of trying to burrow, except for the one Ecuadorian who will begin to burrow when she is in premolt, and will molt within a bottle once she is in isolation. Of the 82 hermit crabs we have, I have four C. Prelates (Strawberry), hermit crabs that have lived with me for over a month and have not yet molted.

(Edited 2/1/2010) I had written this original article about December of 2004. Since then all 4 of my Strawberry’s have molted several times. An observation I have made is that they appear to spend prolonged period of time in the ocean pond prior to molting. I have observed them almost completely submerged up to about 20 minutes at a time.

Photo Credits:
Marie Davis
Michelle Stephen
Stacy Griffith
NarNar
Lisa Dawson
Lamont Darren Medley