HCA: Hermit Crab Association

i was changing the crabs' water today when i came across a bit of a surprise in the salt water dish of my 20L. there were hundreds (perhaps thousands) of tiny zoea floating around. unfortunately they were all already dead and simply floating (not swimming, as i have seen before), so im guessing they had probably been in there for a few days already.

my 20L is filled with teenie/small ruggies, teenie/small Es, and one small blueberry. i have my suspicion about who the mother is, a small ruggie named Houdini. i'm thinking it might have been her because a month or so back she was the victim of what i though was agression my multiple crabs on multiple occasions (i would hear chirping and have to pull another ruggie or an E off of her). they have left her alone recently, though, and i have seen her around the salt water dish.

its not my first time with zoea...probably my fifth or sixth in 7 years of crabbing, but i enjoy it each time as a sign that they must be feeling pretty at home to reproduce

i'm sorry i couldn't get better pics, but they are so itty bitty! i poured the water from the dish into a tuperware and this is a shot of the whole thing. You can see the little white specs floating around:



this is more of a close up, where you can see the individual zoea floating around:



this is the final close up...you can see that the zoea picture has two black dots for eyes. i wish it could be clearer though




annopia

AWESOME!!! Sorry they were dead. But still so awesome! Congrats. You have some happy crabbies.

sweet lovin!!

Am I the only one that gets horribly depressed by zillions of dead babies?

What is the progress on possibly getting them to live? Do we think you'd need, like, oh yeah--the OCEAN--in your tank to help them survive? Or might there ever be any hope of actually getting them to breed and survive domestically, so they can stop stealing them from the wild?

Annopia, did I read that right that it appeared that two DIFFERENT species of males were mating with this ruggie female?

What is your secret?!?! I keep looking and hoping and begging (to which my husband loves to laugh at as the only time words "babies" and "want" appear in the same sentence is when I'm talking to my inverts) and still zilch.

And DragonsFly, they can be raised using filtered sea water, but it is extremely time consuming:
http://si-pddr.si.edu/dspace/bitstream/ ... Harvey.pdf

Ooh! Scientific literature time! My favorite!

Well, actually it has been done successfully in laboratory settings since the 1960's by Anthony Provenzano (he wrote a paper entitled "The Larval Development of the Tropical Land Hermit Coenobita clypeatus in the Laboratory" (http://www.jstor.org/discover/10.2307/2 ... 9033926527). I have a copy of this paper and can email a PDF of it to anyone who's interested, (send me a PM). It's actually got lots of diagrams of the different developmental stages so it's pretty cool. (EDIT: Similar diagrams are also in the Brodie and Harvey paper on C. compressus that both Wodesorel and I posted a link to so you can view them there if you want)

Al-Aidaroos and WIlliamson did a similar study on Coenobita scaevola (closely related to C. rugosus I believe) in 1989 (http://www.tandfonline.com/doi/abs/10.1 ... 71#preview). Alan Harvey studied C. variabilis in 1992 (http://www.jstor.org/discover/10.2307/1 ... 9033926527). And the link Wodesorel posted is Harvey and Brodie's published study of C. compressus in 2001 (http://si-pddr.si.edu/jspui/bitstream/1 ... Harvey.pdf).

Essentially, getting zoea is probably the easiest part, given you don't have to do anything regularly. So essentially the protocol is to check for zoae daily, and separate them out into small, temperature controlled containers. Then raise them on brine shrimp, changing their water after feedings. Offer them shells once they've reached the later stages of development, and give them some land to crawl up on. Once they start becoming terrestrial I presume a small tank with a shoreline setup would be useful, and you could presumably house a bunch in there.

I haven't read through all these articles completely, but I know the Brodie and Harvey paper on C. compressus got them to take on shells, become terrestrial, and successfully molt.

I'm a marine ecology graduate student, and I've actually raised Cassiopea jellyfish larvae using nearly the exact method (4 ml water containers, fed brine shrimp 3 times weekly, water changes 3 times weekly), and it isn't difficult at all. It just ends up being a lot of work, requiring a lot of precision (measuring salinity of SW, not letting algae grow in the individual containers) and a lot of resources (deionized water, temperature controlled room with controlled lighting). I did it all in my laboratory, and I can't imagine being able to do it successfully in my home.

Ultimately, the reason why this isn't a commercial option (as opposed to harvesting wild crabs) is because of the time and money it would cost to pay people to raise them from zoea. Even at minimum wage, you're looking at least $100/week to pay someone to raise your larvae. Multiply that by the 8 weeks it takes to develop from hatched zoae, and you're looking at up to $1000 for 1 batch of crabs, and that's only counting labor, not supplies/resources. I feel like I'm writing a novel here, so I'll stop for now hahahaha

These peeps are doin' it with the b. latros.

http://biodiv.sinica.edu.tw/~coconutcra ... intro.html
http://biodiv.sinica.edu.tw/~coconutcra ... larva.html
http://biodiv.sinica.edu.tw/~coconutcra ... _post.html

frondosa - so cool! (I had a major geek-out moment reading your post. )

Since you've done it with jellies and you've read the papers, is using marine mix sufficient? The studies I've read have all been done with filtered sea water, which to me a huge distinction from the artificial water most of us are stuck with. Since you mentioned distilled water I'm assuming you were mixing your own. Do you think rotifers be a better option than brine shrimp, since the shrimp can grow larger than larvae and potentially eat them?

And yes, I would love to take you up on the offer for a copy of the Provenzano paper! I keep hoping that I'll find larvae one of these days, and since it will most likely be the clypeatus I would love to read through it all ahead of time to know what to expect!

And no, getting the zoea is the hardest part. I only know of about a dozen crabbers who were lucky enough to have captive bred zoea, and it's always the same ones over and over. Either they are doing something magical and aren't telling ( ), or only certain crabs are able to adapt enough to captivity to reproduce.

DragonsFly wrote:Am I the only one that gets horribly depressed by zillions of dead babies?

What is the progress on possibly getting them to live? Do we think you'd need, like, oh yeah--the OCEAN--in your tank to help them survive? Or might there ever be any hope of actually getting them to breed and survive domestically, so they can stop stealing them from the wild?

Annopia, did I read that right that it appeared that two DIFFERENT species of males were mating with this ruggie female?

well, when i see dead babies, i have two kinds of thoughts. one is that yes, it is sad that they are dead, that they will never hace the chance to fully develop into adult hermit crabs. but on the other hand, probably 95% of them wouldn't make it in the wild anyway, and just getting the crabs to reproduce seems to mean i'm doing something right.

and yes...you read that right, the ruggie was mating with two different species (that i saw). it was a female ruggie (Houdini) with a male ruggie (Bones) as well as with a male E (El Commandante). i've had a female ruggie (Merangue)/male blueberry (Agate) mating before, though. and just this week i caught a female E being copulated with by a male PP and two male Es (not at the same time, though). so i expect to have some more eggs sometime soon.

annopia

annopia wrote:...i'm thinking it might have been her because a month or so back she was the victim of what i though was agression my multiple crabs on multiple occasions (i would hear chirping and have to pull another ruggie or an E off of her). they have left her alone recently, though, and i have seen her around the salt water dish.

well. certain natural processes aren't always "pretty"

@wodesorel - Instant Ocean in deionized water was fine for the jellies, and in my lab we've also raised coral polyps from larvae using just IO +DI H2O, so my feeling is that it would be fine.

Rotifers would probably be a fine food supplement too (that's what we feed the corals). All the papers I've read have used Artemia (brine shrimp) and seem to have not had any problems, but rotifers would probably work too. I doubt freshly hatched brine shrimp would be big enough to harm the zoae, and since the artemia are filter feeders that mosly feed on algae, they'd have to be pretty big (comparatively) to accidentally munch up any crab larvae. Also, if you keep the larvae in individual containers (10-20mL) and change their water after feeding them for an hour or 2, they're left alone for most of the time, decreasing interaction with the brine shirmp anyway.

And yeah I guess I just meant from a personal time/effort perspective getting the zoae is the easiest. I expect that comes down to a proper combination of those million variables involved in getting crabs in the mating mood hahaha. IIRC the Provenzano paper says they collected females that were already carrying fertilized eggs, put them in terrariums in the lab, and waited for them to spawn (I PM'd you about the paper).

EDIT - @amnopia - Species are mostly defined by the fact that they can't successfully interbreed. Or they can, but the offspring are sterile (such as Ligers, and Mules, and the such). But for the most part (99% of the time), the cellular identification mechanisms prevent sperm from other species from fertilizing the egg. So while members of 2 different species may have tried to "mess around", the zoea were more than likely have been from the 2 mates that were the same species. Not that that really makes any difference, I just wanted to clarify So nobody get your hopes up for PP/Straw hybrids or anything like that hahaha

wodesorel wrote:frondosa - so cool! (I had a major geek-out moment reading your post. )

And no, getting the zoea is the hardest part. I only know of about a dozen crabbers who were lucky enough to have captive bred zoea, and it's always the same ones over and over. Either they are doing something magical and aren't telling ( ), or only certain crabs are able to adapt enough to captivity to reproduce.

i don't think getting zoea is random when the crabs have been with you for awhile. obviously, if you get a new crab and have zoea within a month, they were fertilized in the wild and you can't really consider the conditions. i think it has to do with specific conditions in the tank. i am pretty sure who the "mothers" of all my clutched have been, and they have all been with me for over a year when the mating occurred and they have all had specific conditions. i can tell you what the conditions usually are for mine when it happens, and you may or may not want to try to do them (because some are counter-intuitive). the humidity in the tank is always very high (think 95%), the tank is always nearing overcrowding, the male:female ration is near 1, and the tank is populated by crabs that are all very similar in size.

this year i might have more zoea, too. this week a female E had several copulations, with 3 males: 2 Es and 1 PP. so we'll see what happens!

annopia

oh, and by the way....one of the fathers of the former clutches, my blueberry Agate, is captive bred himself .

annopia

Replicate the rainy season... hmmmm.....

LOVE this thread!! Have at it you guys.