Teddy Bear Crab Information

[VickyChaiTea]

Ok so... I have been on a quest. For the past few hours I've been trying to find out everything I can about Teddy Bear Crabs. Specifically, Pilumnus vespertilio. It took me like 45 minutes to find the damn things scientific name, and I soon found out there is very little information about keeping these guys in captivity other than "It's not reef safe, kill it."
 
SO as well as wanting to hear about ANY experience you guys have had with this species I'd like to put out some information I've gathered out there so nobody has to do all the searching I did lol. First off, here are the little boogers. I think the brown and black claw tips are just natural variation between the species.

Source: http/tidechaser.blogspot.com/2009/09/project-semakau-september-transect.html

Source: http/www.meerwasser-lexikon.de/tiere/814_Pilumnus_vespertilio.htm
 
From what I've gathered they are usually hitchhikers on live rock, and an unintentional addition to the aquarium. Some people have kept them temporarily without any "problem" but they are known to feed on zooanthids, fish, and sponges so they are not reef safe. I would say it's best to keep them alone.
 
Their distribution is as follows:

Source: http/species-identification.org/species.php?species_group=crabs_of_japan&id=1392
 
So, pretty much anywhere around the equator. The salinity of their natural distribution ranges anywhere from 30ppt to 41ppt. (Specific gravity 1.023-1.031) and the temperature varies quite a bit but I am assuming it's anywhere between 70-80F. (21-26C) As for the pH level... according to this chart http/en.wikipedia.org/wiki/File:WOA05_GLODAP_pd_pH_AYool.png it varies between 8.0-8.2. Which seems kind of low to me? dGH and KH and other levels... I honestly do not know but I think it's safe to assume those vary as well.
 
Here http/jawch.blogspot.com/2012/07/blog-post_9782.html is the first and only time I found something actually recording their diet in the wild. "Seaweed" (which I narrowed down to brown algae "kelp" in the Laminariales Order... not very specific I know) zooanthids, sponges, fish, nudibranchs, and bristleworms. So pretty much anything it can get it's claws on.
 
Pilumnus vespertilio breeds continuously with high incidence in March and December and a strong decrease from April to July.
 
As far as size goes... I keep seeing them very small. But the specimen I've seen is approximately 3" long from leg to leg.
 
So... am I safe in assuming that a 10 gallon aquarium would be sufficient for one? With some live rock and a 2" sand bed? Fed a well rounded diet of macro algae frozen shrimp and fish?
 
Please, if you've ever kept these guys before feel free to share your experience and photos! The one question I have not found an answer to is how long these guys live. Any clue?
 
Sources:
http/rmbr.nus.edu.sg/dna/organisms/details/69

http/journals.cambridge.org/action/displayAbstract?fromPage=online&aid=315995

http/www.jstor.org/discover/10.2307/20103636?uid=3739888&uid=2129&uid=2&uid=70&uid=4&uid=3739256&sid=21101774458271

http/www.tandfonline.com/doi/abs/10.1080/00222930400010070?journalCode=tnah20#preview

> One with diet included http/jawch.blogspot.com/2012/07/blog-post_9782.html
http/muse.jhu.edu/journals/psc/summary/v056/56.3kyomo.html

> Habitat http/tidechaser.blogspot.com/2009/11/semakau-with-hsbc-volunteers-on-14-nov.html
 
P.S
I have never kept saltwater before. So, uh, please bear with me if I made any mistakes. I'm actually going to *fingers crossed* get one of these guys soon hence my spontaneous obsession. Plus they're gosh darn adorable.

 

[Donya]

From what I've gathered they are usually hitchhikers on live rock, and an unintentional addition to the aquarium.

 
This is true for several Pilumnus species. P. vespertilio is fairly rare for shipments in North America. The gulf species of Pilumnus are far more common due to the abundance of gulf-cultured rock. In fact, I've never actually heard of a person in the United States getting a true P. vespertilio hitchhiker. I'm sure it happens sometimes with rock from other regions, but the vast majority of Pilumnus that show up in the USA are other species.
 

but they are known to feed on zooanthids

 
I am somewhat doubtful of this. There is unfortunately also a lot of misinformation about Pilumnus species on the web. Here, an actual diet study on the species using gut content analysis and observation of feeding behavior mentions nothing of corals and is very much in line with what I have seen from other Pilumnus species (which is to say algae + other scavenged bits, but not corals):
 
http/www.ingentaconnect.com/content/umrsmas/bullmar/1999/00000065/00000002/art00005
 
It is possible for other small Pilumnus species to exist even in small tanks for YEARS undetected, with no symptoms to suggest otherwise. In a large tank, I wouldn't be surprised if one never saw them. A problem that Pilumnus species suffer from in the hobby is the label "gorilla crab," which inspires (often irrational) fear in hobbyists. Basically, people see a hairy crab and freak out - doesn't matter what the crab actually is, and any death or mangled coral problem in the tank is immediately blamed on such an animal, whereas very similar to identical cases get more thorough investigation for environmental issues when a crab isn't known to be present. Similarly, crabs can also become starved in very nutrient-poor tanks that are sparsely fed, and they are omnivores. It wouldn't surprise me at all if some people had a Pilumnus or two eat corals out of desperation (so would many otherwise reef-safe animals if placed in the same position). Such reports get blown out of proportion for pretty much all Crustaceans in the hobby.
 
I have Pilumnus species (although not P. vespertilio) in probably all of my larger-than-pico tanks right now. They are in both reef and non-reef tanks and I don't know how many I have in total. I believe I counted give in one of my 20gal tanks at one point. The only thing I have found them to be guilty of is that they sometimes steal already detached polyps and mushrooms - not to eat, but they "hug" them and try to line their burrows with them. The polyps are eventually hugged to death or die from lack of light after bleaching unless retrieved. I've never been sure what this behavior is about, but in a tank where everything is glued down I have seen no symptoms of crab presence aside from the burrows, which can often only be seen by dismantling the rocks.

 

[VickyChaiTea]

Thank you so much for the response!
 
I am almost 100% certain this is a P. vespertilio. I have photos of it I'll post tonight, and it looks identical to the second crab photo I posted. (the one with black claw tips). So unless that crab isn't a vespertilio or I'm missing something I'm pretty sure he is. I did notice how many people did not have a Pilumnus species in their tank and called it "teddy bear crab", though.
 
Thank you sooooooo much for the information on diet. I think you're probably right, they seem to be extremely opportunistic feeders who will eat whatever they can get their claws on. But you don't think they have a preference for corals? I've read reports of them eating zooanthids in aquariums but maybe, like you said, it was out of desperation.
 
Perhaps after a while I can introduce some to his tank and see if he munches on them! That would at least give us some idea of whether he prefers them or not.
 
That is really interesting behavior, the coral hoarding. Maybe... hmmm... don't zoos release a poison when they're disturbed? Maybe it's kind of like a defense thing?
 
Well, I am off to fetch the little guy! I'll post more when I get home.

 

[Donya]

I think you're probably right, they seem to be extremely opportunistic feeders who will eat whatever they can get their claws on. But you don't think they have a preference for corals?

 
"Opportunistic" is another thing blown out of proportion with Crustaceans in the hobby. Very few crabs found in the hobby are so aggressive that will literally destroy something just because they got a claw on it. When food is abundant and of the right composition, the need for opportunism isn't really there and it just comes down to dietary preference and how aggressive the species is. I have really seen no evidence of predation from my Pilumnus crabs. It's possible that they could periodically eat some of the small Asterina and micro brittle stars that are abundantly available, but, if they do, they don't do it enough to make a serious impact on the populations. Anything larger than that is left alone due to the fact that I ensure sufficient meaty food availability. 
 
If you want to experiment with the diet of a P. vespertilio, be cautious about how you set it up. Definitely don't do it straight away when you get the crab. Crustaceans in general are often at the behavioral worst when first acquired due to having been stressed and poorly fed for a while. Make sure it has access to seaweed and raw meats daily or every other day (also depends where it is in the molt cycle; they won't eat for a bit leading up to that) for at least a couple of weeks before checking for preferences. After that, also make sure you offer the experimental food in conjunction with other food sources to test for actual preference. The flipside of keeping crabs well-fed in captivity is that they may try to eat bizarre things simply due to expecting something edible every time the tank being disturbed and going for the first new thing in the environment. For example, I have had more than one large crab steal and try to eat a pair of metal forceps that I use for both tank maintenance and feeding, even after the metal has been cleaned and disinfected such that it can't possibly smell of food anymore.

 

[VickyChaiTea]

I think you're probably right, they seem to be extremely opportunistic feeders who will eat whatever they can get their claws on. But you don't think they have a preference for corals?

 
"Opportunistic" is another thing blown out of proportion with Crustaceans in the hobby. Very few crabs found in the hobby are so aggressive that will literally destroy something just because they got a claw on it. When food is abundant and of the right composition, the need for opportunism isn't really there and it just comes down to dietary preference and how aggressive the species is. I have really seen no evidence of predation from my Pilumnus crabs. It's possible that they could periodically eat some of the small Asterina and micro brittle stars that are abundantly available, but, if they do, they don't do it enough to make a serious impact on the populations. Anything larger than that is left alone due to the fact that I ensure sufficient meaty food availability. 
 
If you want to experiment with the diet of a P. vespertilio, be cautious about how you set it up. Definitely don't do it straight away when you get the crab. Crustaceans in general are often at the behavioral worst when first acquired due to having been stressed and poorly fed for a while. Make sure it has access to seaweed and raw meats daily or every other day (also depends where it is in the molt cycle; they won't eat for a bit leading up to that) for at least a couple of weeks before checking for preferences. After that, also make sure you offer the experimental food in conjunction with other food sources to test for actual preference. The flipside of keeping crabs well-fed in captivity is that they may try to eat bizarre things simply due to expecting something edible every time the tank being disturbed and going for the first new thing in the environment. For example, I have had more than one large crab steal and try to eat a pair of metal forceps that I use for both tank maintenance and feeding, even after the metal has been cleaned and disinfected such that it can't possibly smell of food anymore.

Yes, I figured I would have to go about it like that. I assumed they were opportunistic because of one report of a wild vespertilio eating a fish which was still alive and forum members claiming to captured and consumed their ornamental fish as well. I think you're absolutely right, though, we probably don't see them at their best because at the store they're probably more or less starving. Especially the guy I'm getting, he hitch hiked in some live rock. As far as food goes I'm thinking about rotating between frozen mysis, frozen silversides, frozen krill (like this, not sure what species it is http/www.petsolutions.com/C/Frozen-Fish-Food/I/San-Francisco-Bay-Frozen-Krill.aspx?utm_source=nextag&utm_medium=comparison&utm_term=10988072&utm_campaign=nextag ) dried brown seaweed, high quality flakes, annnnnnd anything else you'd suggest.
 
Also, I lied. Not getting him today. Getting him in several days.
 
Also also, does anyone have any information on their life span?