What is a Sponge Crab? – A Resourceful Creature

Are you familiar with sea sponges and how important they are? If you study them you’ll see that they are central to the health of coral reefs, our oceans and, therefore, our world. Well, the reason why they are so important is the fact that they support numerous creatures in the reef. That may be through the redistribution of vital minerals, that would otherwise not be available to other animals; they also offer protection to smaller creatures by allowing them to hide within its nooks and crannies. As many of the animals in the coral reef already know, it’s not wise to go poking through a sea sponge loaded with powerful toxins.

There’s one creature, however, that has a peculiar and ingenious way to make use of our sea sponge. The Sponge Crab exploits many of the sponge’s natural defenses for its own use. You are probably wondering – just what is a sponge crab.

This eccentric crab belongs to the “Domiidaee” family of crabs. What sets this group apart is their unique relationship with sea sponges – one that seems to benefit the crab more than the sponge, however.

You won’t have trouble identifying these crustaceans. That’s because they form a unique bond with sea sponges, where the crab makes an unwilling partner out of the sponge.

The reason for this acquaintance involves the safety and thus survival of the sponge crab – although it is not clear if and how the sponge benefits.

Although, both animals will continue to grow and develop independently of one another. It can be reasonably assumed that the sponge is not in any way harmed, yet, there’s no evidence that it benefits either (National Geographic).

Pick Your Poison

Crabs are one of my favorite creatures. They remind me of armored warriors from a distant past. The sponge crab, however, has a less dramatic, yet effective means of survival. If you are seeking to spot a sponge crab in nature, they maybe hard to identify – that’s because their aim is to hide by use of camouflage. Sponges are naturally sessile animals, but If you happen to see one moving at all, then chances are that you are looking at a sponge crab.

These sly creatures have the know how to go up to a sponge, cut out a piece, shape it and place it on it’s own shell. This is rather funny, to see a crab strolling about with a hat on. It’s not so humorous for any would be predator, when the hat happens to be host of a powerful toxic cocktail.

Back Off

Just, what is a sponge crab doing with a sea sponge on it’s shell. Well, It’s all about survival for our crab. This very resourceful animal has come to “know” that many sea sponges are highly toxic and as a result are off the menu of most other animals. In addition, their skeletons are constructed of hard to swallow spicules, which can be very painful when attempting to swallow.

Since the sponge crab has no intention of consuming the sea sponge, there’s no issue concerning the latter’s powerful toxins and spicules.

You Have My Back

Once the sponge crab has fashioned and planted the sea sponge on it’s shell, it will also benefit from the powerful toxic cocktails the sponge uses to keep would be predators at bay. Crabs, not withstanding their strong shells, have many animals that would eat them. Having a toxic sponge to cover you can be an ingenious solution to being on the menu of many animals on the reef.

Thanks to its regenerative powers the sea sponge will continue to develop while fixed onto the sponge crab’s shell. Which makes me think – who will live longer? I’ll go for the sponge, since some have been known to live for up to thousands of years.

It’s intriguing to wonder what happens to the sponge once the crab dies, since most sponges will outlive the sponge crab.

Now You See Me, Now You Don’t

Sponges can reproduce either sexually or asexually. The latter allows a piece of the sponge to regenerate (grow back) on another spot – such as the shell of a crab. The crab has learned this through millions of years of evolution. In addition to warding of predators, having a sponge on your back is great camouflage – allowing the crab to go undetected.

We are well aware that a multitude of animals use camouflage to improve their chances for survival. Many are born with the camouflage already on as part of their physical make-up; however, others, like our sponge crab, have to resort to other ingenious tactics.

Helping Others Helps Yourself

Sea sponges have little concern when it comes to other animals attacking them, let alone try to eat them. This is due to the potent toxins they use for protection. The sponge crab, however, is not interested in eating, but allying itself with the sponge for its own protection. This resourceful crustacean uses its pincers to cut a portion of the sponge, before it prunes it to the desired shape and attaches it to its shell.

Thanks to filaments on the sponge crab’s domed shell, the sponge becomes affixed to the crab. Now our armored warrior reveals a comical side. It hints at the idea that nature may have a sense of humor.

What’s interesting to consider is that the sponge will continue to feed and grow on top of the crab. Sponges are able to clone themselves and thus can regenerate away from original sponge. This undoubtedly helps the crab, as it needs the live sponge along with its powerful defenses.

The sponge crab also uses the sea sponge for camouflage. This method of defense is widely used by many creatures in the animal kingdom – including us humans.

As its name suggests, the sponge crab has established a beneficial relationship with the sea sponge. The sponge, however, is neither benefited nor harmed – as far as we can tell. But like many things in nature, the impact of helping the crab is very likely to help our sponge indirectly. One way can be simply by helping the sponge to spread to other parts of the reef.

Another way to look at it is to see that the sea sponge does not need any direct help from the sponge crab. But, because the coral reef is a web of sorts, where the actions of any animal have a ripple effect throughout the community, the sponge is very likely helping itself by being of help to it’s neighbor the snow crab.

What do you think of our amazing Sponge Crab? Do you agree they are hilarious? Do you happen to own a sponge crab? Tell us about in the comments  below.



Thank you fro stopping by,






  1. Hey I’ve just view your website, how interesting it is to see something different. My question to you is can you eat those kinds of crabs? Just curious. Hope you reach to the bottom of the ocean with this and share it with the rest of crabs.

    Good luck with it bro, success be with you always. Never Give up your dream 🙂 

    • Hello Union, I am glad you appreciate my website. Yes It’s different and I think That’s part of the appeal. I will do some research before deciding to eat a sponge crab. That are scavengers and anything they eat you will as well. You will want to remove the sponge first as it may be highly toxic.

      Thank you for your comment,


  2. Oh my gosh the sponge crab is so adorable. Do we have on in the States? To be honest this is the first time I heard about it. I don’t think that I ever seen one at the aquarium. Maybe it is like you said that I might be looking at the sponge crab and did not know it was there because they camouflage themselves so well. Do they have a predictor that can attack them and eat them? Maybe like a sea turtle?

    • Hello Nuttanee, I see when you say the sponge crab is adorable. They are in fact very resourceful. They understand that the sea sponge is highly toxic ( they have very few predators like the  Hawkbill Sea turtle, sea spider and Angel fish) and they can exploit this.

      This hilarious crab lives on coral and rock reefs in the Indo-Pacific Ocean.

      I appreciate your comment..


  3. This is a wonderful review. Sea animals like the sponge crab as the pedigree of using various means to continue to be in existence as well as survive to reproduce and multiply. Mother nature has taught many creatures to fend for themselves and continue to evolute. 

    All animals are born to learn survival and reproduction in form of feeding, protection and reproduction. I love sea animals and we human must learn from the in every aspects.

    • Hello, nature is resourceful by nature. Our friend the sponge crab makes this evidently clear. I, too, lovers sea and all its citizens – how we treat the ocean we do to ourselves and the future.

      Thank you for your comment,


  4. Great post and good info.

    I was reading some things about them and the benefits they give. Now I’m happy to read a whole post about this, and I really hope lots of others also do it. This is an amazing creature, like many others, and this can’t dissappear because our interfere with nature. 

    Thanks a lot for sharing this with us! 

    • Hello Emmanuel, I’m looking forward to have many people read my posts – in addition to the one you read, there are many more having to do with sea sponges. They are simply amazing creature, that many people need to know about. 

      You’re right! We need to be more conscious about our human impact on our world. These animals that can be in danger because of our carelessness could be of great help to us – if only we take care of this planet. 

      Thank you for your great comment


  5. It is such a delight to have this platform in which to extend new information. I have never before heard of a Spong Crab. I would imagine this would add tremendously interest and education for a young child interested in having an aquarium at home. Adding the video to this post was brilliant it farther highlighted the post. Thank you for doing this post and I am glad it has come across my view. now know more about the world in which I live. Perhaps you will do a post blog on where to get and or learn more. Is this an ongoing interest and or study for you? I hope schools are including this in some way. Yes I think you could write or show more on this 

    • Hello Sheree, I am delighted that you found my post appealing. Sponge crab are very funny and resourceful creature. Millions of years of evolution has taught them about the sea sponges defenses and how they can exploit them. 

      Thank you for your words of encouragement. I write mainly about sea sponges – that’s how the sponge crab was added to my posts. 

      I hope that kids can use my website to learn about sea sponges and see how simply amazing they really are. 

      Thanks for your great comment!


  6. Hello Jose,

    I know this may be silly, but the first thing I thought when reading the title was SpongeBob Squarepants. And in the image, it has this kind of yellowish sponge in its back. It amazes me how important and signficant they are, but people are unaware of it. That’s why every single living being is important for this world.

    Thank you for letting us know about the importance of sponge crabs!

    • Hello Mariana, I understand how you could think my post is about Sponge bob square pants. I think the silly looking crab had something to do with it too. 

      Sponge crabs are a very resourceful creature. They have evolved to recognize the usefulness of a piece of sponge. It shows how beneficial sea sponges are to many of the coral reefs animals. 

      Thank you for your comment


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