Even when everything is right, it can still go so wrong. Hermit crabs with multiple limb loss and other deformities require a certain kind of extra care than that of normal, healthy crabs. Below we will cover their dietary needs, how to properly care for them, and what causes these issues to arise.
Causes Of Limb Loss In Hermit Crabs
When we say limb loss, we specifically mean a hermit crab that is missing a main limb, such as walking legs, claws, antennae or eye stalks. The most common limb loss is the walking legs. So how do they actually lose them?
Fighting or Shell Jacking
One of the more common reasons for limb loss is due to fighting between hermit crabs or an attempted or successful shell jacking. A shell jacking is when one crab forcefully tries to remove another crab from their shell.
During fighting (whether it be for food sources, shells, over mating, or just plain aggression) hermit crabs will use their main cheliped (claw) as a weapon to nip at another crab, often pulling on their limbs. A crab's claws are very sharp and strong and can easily remove another crab's limb.
When one crab attempts to take another crab's shell, they will open their main claw and clasp down on the other crabs' legs or claws and try to remove them from their shell. Most hermit crabs would rather be torn in half, than forcefully removed from their shell. If another crab has a death grip on their limb and is pulling, often a leg or claw will be removed in the process.
This is why it is so important to supply an ample number of shells in appropriate sizes for each crab! Not only does this reduce the chances of a shell jacking, but if a crab fits inside their shell comfortably, they can use their large claw to protect themselves from intruders. Hermit crabs that are too big for their shells have nowhere to hide during a shell jacking attempt.
Stress
When a hermit crab is stressed due to tank conditions, being handled often, inappropriate diet, or living in an overcrowded tank, they will often drop a limb. The limb is not severed, they simply drop it. Similar to that of a lizard dropping their tail. It's common to see pet store hermit crabs with limb loss, as well as rescues who have come from inappropriate conditions.
Surface Moulting
So much can go wrong during a surface moult, because moulting is NOT supposed to take place on the surface. Moulting should always take place below the substrate and is an activity that the hermit crab should face alone.
During surface moulting, a lot of stress is placed upon the crab's body, being out of their dark moult cave and moulting on the surface surrounded by bright lights and sounds can cause a lot of things to go wrong. A common issue with surface moulting crabs is limb loss, when trying to shed their old exoskeleton, they drop limbs in the process.
Moulting Complications
Sometimes everything can start off right, your crab is moulting beneath the substrate the way it is supposed to. And still, things can go wrong. Unfortunately, we have no control over the moulting process once it has started and all we can do is hope that they are successful. Moulting is an extremely delicate time in a crab's life and many things can go wrong, remember that this is the weakest your crab will ever be.
Being Dug Up Mid Moult
A common issue when digging up moulting hermit crabs is that they are mid moult (they have not completely shed their old exoskeleton yet) and being dug up, removed from their moult cave and handled can cause their limbs to fall off with their old exoskeleton. This is why we never dig up hermit crabs, mid moulting hermit crabs are at high risk of limb loss, deformities and death.
What To Do When You Find a Crab with Limb Loss
It can be very overwhelming and upsetting when you find a crab who is missing limbs. But knowing how to care for them properly will ease your mind and make the process much easier.
The care you provide will depend on what limb is missing and how many limbs are missing.
Crabs missing one leg
If your crab is only missing 1 of their 4 walking legs, this isn't anything to worry about. Generally, they will still be able to get around with their 3 remaining walking legs and 2 claws. They should not need to be isolated and can stay in the general population tank. They will grow their missing leg back over multiple moults. You may notice them eating more and moulting more often, this is a good sign.
Offer them a diet rich in protein, calcium and omega-3 to support the healthy growth of their new leg.
Crabs missing multiple walking legs
If your crab is missing multiple walking legs, it may be harder for them to get around the tank. It depends if the legs are missing all on one side or if they are missing some on both sides. If they appear to be able to get around the tank okay, you can leave them in the main tank.
If they are missing all walking legs on the same side, you will notice they will struggle to walk and may often drag themselves around and go in circles. If they are struggling to move around the tank, it is best to isolate them into a smaller tank alone. By offering them a smaller tank, they do not need to travel as far to find food, water and shelter.
The tank should be a minimum of 20L with deep substrate (15cm) and pools with extremely easy access in and out. Try to keep everything close together so they can easily access their pools and foods. They will need a diet rich in protein, calcium and omega-3 to support the healthy growth of their new limbs.
Crabs missing a claw
If one claw is missing, this isn't too much of an issue, they will simply use their other claw to feed themselves. They can stay in the main tank and should be offered a diet rich in protein, calcium and omega 3.
Crabs missing both front claws
If your crab is missing both of their claws, this is a worry. Your crab will no longer be able to feed themselves or break apart foods. This requires isolation into a smaller tank. They will also require a special diet that is in a very fine powder form, or liquid form. This is so they can use their maxillipeds to feed themselves. Because they cannot use their claws to break apart their food, it needs to be very fine, either a powder form or a liquid form. They will require a shallow food bowl and a diet rich in protein, calcium and omega-3. You can grind up their food to a powder form in a blender. Do not offer them hard foods, things like cuttlefish bone powder, greensand, worm castings, and protein and omega-3 foods finely ground. Alternatively, you can add a small amount of primed water to the powders to make a slurry. This is also a good time to offer them an SOS food and crab pastes such as Chubby Crab Paste (owned by The Happy Hermie) these foods do not need to be broken apart.
You can also mix their powdered foods with molasses or honey to make a paste like consistency. You do not want their food to be too sticky, as this can coat their gills and suffocate them.
Crabs missing all 4 walking legs and both front claws
This is a major limb loss for your crab. They will no longer be able to get around their tank and will no longer be able to feed themselves. This requires immediate isolation in their own small tank. Due to having no legs at all, your crab will no longer be able to dig or climb. This means that they will be forced to surface moult until their limbs grow back. Expect them to be in isolation for a long time. Crabs with no legs or claws require a very specialized care. You will need to hand feed them a diet rich in protein, calcium and omega-3.
Every day you will need to place your crab into its food bowl, sitting directly over its powdered/slurried food so that they can feed themselves. They need to gain enough energy to be able to moult. Offering them honey and molasses on a toothpick and placing it directly under their maxillipeds so they can bring it to their mouth can help give them an energy boost.
Because your crab can no longer get itself in and out of its pools, you will need to offer them very shallow pools to prevent drowning, but so they can still drink.
You may think that your crab will never survive this trauma, and it is highly likely that they may pass away eventually due to their injuries, however it has been done before. A person in the US came across a crab in a parking lot that had all 4 walking legs and both claws missing. They successfully nursed it back to full health and it has now grown back all of its walking legs and claws and is thriving in captivity. So, it can certainly be done!
Some people may not have room for an isolation tank in their house, we totally understand that not everyone has the room and that's totally okay. Alternatively, you can isolate them in a small container and place that inside their main tank so that other crabs cannot access them, but the injured crab still has access to heat and humidity.
Perhaps you don't have the time or resources to nurse an extremely injured crab back to health and you are feeling awful that you cannot help them, leaving them to die in the tank is not the right way to go. Your crab is suffering. You can either rehome them to an owner who has the time and resources to nurse them back to health or you can humanly euthanize them.
This is not something that we recommend people do and not something that is commonly spoken about within the crab community as we are passionate about giving all crabs a chance at life. However, we will discuss humane euthanasia below. PLEASE DO NOT try to euthanize a healthy crab with no issues, this is not fair on the crab, if you can no longer care for your crabs, please surrender them to a local crab rescue (they are located in VIC, WA, NSW, ACT and TAS) or rehome them to someone else.
Humane Euthanasia
This should ONLY be used as a very last resort and only after all avenues have been exhausted.
The aim of this is to reduce their pain and suffering, and essentially put them into a deep sleep that they will never awake from.
Isolate your injured crab into a container and place them into a refrigerator, this will slowly start to cool the crab down and their body functions will also begin to slow down, as we know if crabs are kept below 18.c degrees, they can be forced into an unnatural hibernation.
Leave your crab in the container, inside the fridge for 24 hours, the cooling of the body will force them into a deep sleep (hibernation) after 24 hours, place the crab into the freezer. This process will euthanize the crab while they are asleep so they will feel no pain during the process.
Please note - that at The Happy Hermie, we personally do not support euthanasia for a limbless crab, as we know they can be brought back to health with the right care. We do, however, believe it to be the best method to stop their suffering and sometimes may need to be used as a last resort if a crab is heavily injured during an attack with another crab that we know they will not be able to heal from.
Growing Back Limbs
Hermit crabs can actually regenerate their limbs! Magical right?
It will take multiple moults for the missing limb to fully grow back. After their first moult, you may notice a small gel like nub where their limb once was. This is the beginning of the limb growing back.
Over several moults the limb should fully grow back, and they will be as good as new! You may notice once the limb as finally grown back that the exoskeleton colour of that particular limb is a different colour to the rest of their limbs.
From experience, I have noticed that freshly grown legs tend to be a more translucent/creamy white colour. As time goes on, their limbs will become the same colour and you won't even know which leg was grown back.
Offering The Right Diet For An Injured Crab
All captive crabs should be offered a fully balanced diet daily, however injured crabs need an extra special diet.
High Protein -
A diet high in protein is super important during this phase. Protein aids in their growth, without protein, there will be little to no growth of the crab. And if your crab is trying to grow back a limb, they need to do a lot of growing! Meat based proteins hold the highest source of protein and should make up 50% of their diet.
High Calcium -
Calcium supports a healthy exoskeleton, and aids in the new exoskeleton hardening. Offering them high amounts of calcium constantly is very important. You can offer this with the use of cuttlefish bone powder, powdered leafy vegetables such as kale and spinach, powdered down sea urchins and star fish and liquid molasses. Without a constant source of calcium, there will be complications in the exoskeleton hardening.
High Omega-3 -
Omega-3 Fats help to support a successful moult and conditioning the exoskeleton. Lots of healthy fats are important for a crab needing to grow back limbs. These can be found in oils, avocado, oily fish, nuts and seeds, coconut etc.
Deformities In Hermit Crabs
Deformities are caused when moulting goes wrong. There can be a number of reasons why moults can go wrong, including unbalanced diet and poor nutrition, being disturbed mid moult, movement during moulting, surface moulting and sometimes for unknown reasons.
Types of deformities include crooked and twisted legs, tips of legs missing, or crooked antennae.
The most common cause of deformities is crabs either getting stuck inside their old exoskeleton, or movement while the crab is still soft. This can often happen when a crab is dug up mid moult, if their limbs are not inside the shell in the position they are supposed to be in and the exoskeleton can harden while the soft limb is not at the right angle, hardening it to a permanent position. Sometimes crabs can just move on their own while they are waiting for their exo to harden, and this can cause the limbs to become deformed.
Deformities are usually a quick fix and will correct themselves during their next moult. You may notice your crab will moult again quite quickly after the moult that went wrong. These crabs should not need to be isolated; it may just take them a little longer to get around the tank and climb. If the deformities are quite severe and the crab truly struggles to move around the tank, you can isolate them into a smaller tank. Ensure they have easy access to foods and pools. Hermit crabs with deformities still require a fully balanced diet to support their overall health.
• The leg is facing in an upward position and can not be brought back into the shell when retracting. This crab was left alone and moulted beneath the surface, the crab has clearly moved during moulting and the exoskeleton has hardened with the leg in this position.
• Photo belongs to The Happy Hermie Rescue & Adoption
• This Hermit Crab has a deformed lower leg where the tip is angled, it is also missing a leg and its main large claw.
This crab was dug up during a rescue and transported to a local Rescuer where it moulted. The stress from being dug up and relocated caused this crab to drop limbs and have moult complications.
Photo belongs to Mykayla Bone
• This crab has come up from a recent moult with one leg missing, it appears the crab has had one of its legs stuck inside its old exoskeleton and has dropped the limb to remove itself from its old exoskeleton during moulting.
• A Hermit crab with a lower leg deformed. The tip of the leg sticks outwards. This will fix itself with its next moult.
Photo belongs to Tammy Gledhill
• Hermit Crab with a translucent/creamy white leg (top right side) that has previously grown back.
Photo belongs to The Happy Hermie Rescue & Adoption
• Hermit Crab with no legs or claws at all. This crab requires consistent hand feeding.
Photo found through Reddit - owner unknown
• A gel limb has started to grow.
Photo sourced through Crab Street Journal
• A pet store crab who surface moulted in the pet store tank and has been injured by another crab while their exoskeleton was still soft, here the exoskeleton has hardened, and a scar is visible. This will correct itself next moult.
• This crab is missing both walking legs and its main large claw all on the same side. This occurred due to being dug up mid moult during a tank flood. This crab was isolated immediately to surface moult, however the damage had already been done.
• An injured hermit crab being spoon fed an emergency mix, the mix has been placed onto a plastic spoon and placed directly under the crab so they can use their one remaining claw to bring the food up to their mouth.
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