Hermit crabs regenerate lost tissue when they molt their exoskeletons, which happens when hermit crabs regrow legs, chelipeds (claws), and eyes that have been shed, damaged, or severed.
Hermit crabs’ eye stalks can be regrown, but the renewal process could take 2-3 molts. Eye regrowth could take several years to complete, as hermit crabs only molt once every 18 months.
Hermit crabs rely on corneal lenses to see, which reflect light from within the eye stalk. These lenses regenerate, so once a hermit crab fully restores its eye stalks, it’ll be able to see again.
Losing an eye stalk is painful and traumatic. However, lacking one of both eyes won’t ruin a hermit crab’s quality of life, as they rely more on touch and scent through the antennae.
How Many Eyes Do Hermit Crabs Have?
Hermit crabs have two eyes on stalks at the top of the head.
These stalks are completely mobile, enabling a hermit crab to take in surroundings from every conceivable angle, though vision is arguably only the third most important sense to hermit crabs.
If your hermit crabs are happy, healthy, and intact, they’ll always have two eyes. While hermit crabs may shed legs or claws while stressed or sick, the eyestalks will not fall off or be shed.
If a hermit crab is missing an eye, something has caused this problem.
How Do Hermit Crabs See the World?
While hermit crabs use their antennae to detect threats, food, and obstacles in their path, eyesight still plays an important role in their lives.
Behavioral Processes confirms that hermit crabs respond to a visual threat by hiding in their shell.
Hermit crabs have compound eyes, dividing into tiny hexagons known as ommatidia. As a consequence, hermit crabs view the world through a kaleidoscope.
Hermit crabs’ eyes can differentiate between colors but struggle to tell the difference between shapes. According to the British Journal of Ophthalmology, these colors are determined by light entering the eye stalk and reflecting through a lens.
What Happens if a Hermit Crab Loses an Eye?
A hermit crab losing an eye will be extremely stressful.
As shedding the eye stalks isn’t natural, something traumatic caused the incident. ILAR Journal confirms that hermit crabs experience and remember physical pain.
Once hermit crabs adjust to life without one or both eyes, you’re unlikely to see much change. Hermit crabs aren’t reliant on vision, so they’re unlikely to become clumsier or more anxious.
Do Hermit Crabs Eyes Grow Back?
Eye stalks can regenerate if the tissue has been mildly damaged.
The success of the regrowth depends on the extent of the mutilation. If the tip of the eye stalk has been severed, enough tissue should remain for regeneration.
If the eye stalk is hollowed or cut at the nerve, it may not regrow. Hermit crabs replace damaged tissue; they don’t grow new limbs, claws, or eyes.
Biological Bulletin explains how, in theory, eyes can be regrown by transplanting tissue from the claws or limbs into the empty socket.
If you’re wondering, “can hermit crabs go blind and live happily?” the answer is yes. Make life easier for them by providing saline water, which stimulates the sense of smell.
How Long Does it Take for a Hermit Crab to Regenerate Eyes?
Like legs and chelipeds, the lenses within a hermit crab’s eye can regenerate within a single molt. Unfortunately, it can take 2-3 molts to fully restore an eye stalk.
As molts occur every 18 months, it could be years before your hermit crabs regenerate lost eyes. You can speed up the process by keeping your hermit crabs in darker conditions to promote more molts.
Why Do Hermit Crabs Lose Eyes?
As hermit crabs don’t shed eyes naturally, there will always be a reason for an eye stalk to be lost.
Sometimes this is just bad luck caused by a genetic mutation. In most cases, a conspecific or the hermit crab itself has actively severed the eye stalk.
Some hermit crabs are born without the use of their eyes.
In these instances, the hermit crabs will have long adjusted to living without sight. If the eyes are useless, they may begin to droop or be willfully severed.
Fighting with Another Hermit Crab
Most hermit crabs are docile and friendly, enjoying the company of conspecifics in a tank.
Even so, conflict can arise on occasion. While hermit crabs will try to come to a peaceful agreement, you must look out for acts of outright aggression.
Battles between hermit crabs may start with play fighting, such as antennae wrestling and tests of strength. If both animals are willing participants, this is nothing to worry about.
Keep an eye out for shell rapping and rocking, as these actions are associated with attempts to mate or challenges for a superior shell. If the recipient of this attention is unwilling to reciprocate, one or both hermit crabs can become aggressive.
Listen out for loud chirping, which suggests that distress is increasing and a fight may break out.
The two hermit crabs may be able to co-exist if you don’t allow them to cross a line. If hermit crabs are agitated, they can fight to the death. Attempting to sever eye stalks is a common practice.
Some hermit crabs will choose to sever their eye stalks. This is a brutal act of self-mutilation, so never ignore warning signs that a hermit crab is struggling with its eyes.
Hermit crabs have delicate eyes, which can be easily irritated.
As hermit crabs spend much of their day buried under the substrate, sand can get trapped in the eye. If you provide bathing water, hermit crabs may be able to rinse their eyes.
A hermit crab will grow increasingly distressed and frustrated if bathing doesn’t work. If the foreign object doesn’t dislodge itself, the hermit crab may take desperate measures, including severance.
Even more problematic is the potential of mites crawling into a hermit crab’s eye socket. These tiny parasites can drive a hermit crab crazy. Again, they’ll try to eradicate mites by bathing.
If this doesn’t help, hermit crabs will start shedding limbs or eye stalks.
As hermit crabs are nocturnal, dim light is enough to allow vision. Bright, intense light blinds hermit crabs, which is why they prefer to feel their way around using the antennae.
Hermit crabs need a contrast of light and dark to flourish in captivity. While it’s light during daylight hours, they’ll likely hide under the substrate, as this replicates the experience of avoiding the sun in the wild.
Dim the lights in and around an enclosure at dusk when your hermit crabs emerge from under the substrate. If the lights are too intense for your hermit crabs’ comfort, they may sever their eye stalks.
Hermit crabs can behave out of character when stressed or overstimulated. This odd behavior can extend to self-mutilation in extreme cases.
Ensure you keep noise to a minimum, especially deep, rumbling bass. This can distract hermit crabs, as they ‘hear‘ through vibrations detected from the ground.
Too much stimulation of this kind can leave hermit crabs confused and upset.
Monitor the temperature and humidity in the enclosure, meeting all necessary needs and providing enough entertainment to amuse your hermit crabs. This will stave off the stress that could lead to severing the eyes.