Info for Raising Mithraculus forceps

Info for Raising Mithraculus forceps

Postby sihaya » Mon Oct 15, 2007 5:10 am

So, it's like 4am and I'm still staring at these crab larvae trying to figure out if they're doing ok or on the brink of death. So far so good though...

Anyway, I thought I'd share some information I've gathered (mostly from literature, but also from staring at them until four in the morning):

1.) The females do store sperm.

2.) The female can release larvae as often as up to every 2-3 weeks (or so it seems).

3.) Several hundred larvae are in each batch (educated guess).

4.) Apparently, you have to start off feeding them rotifers.

5.) Unless you can rock them in your arms (in a goldfish bowl) 24/7, you really do have to have a kreisel of some sort. I tried a lot of alternatives, but they always sink in anything other than the kreisel. And even in the kreisel they need to be directed a bit with a light source.

6.) Even though they don't pass through brine shrimp netting, they do apparently get stuck in it a lot. They seem to do ok with rotifer screening though.

7.) Density of larvae for rearing is best at 60 larvae per Liter.

8.) When they're big enough to eat baby brine shrimp, the optimal food density is 10 artemia nauplii per mL.

9.) The Zoea I lasts only 2 days, Zoea II lasts only 2 days, and Megalopa lasts only 3 to 7 days (if first clutch, 4 to 8 if second clutch).

10.) Sinking seems to be the biggest problem (at least for the first several days). I've seen them collide into each other an awful lot (and into walls and everything else), but they seem to be ok so long as they're still in suspension. It's hard to explain, but it seems like they just can't keep themselves buoyant and that's what kills them. But if you put them in a kreisel (or rock them in a fish bowl), they seem to be fine.

11.) I think they need to be above 75F, but I'm not sure.

So, well, I don't have many left at this point (maybe 60 or so). I had a lot of mishaps. But labs report up to 85% survival rate! Of course, they have a lot of space and resources which hobbyists don't have.

Some sources of info here:
https://www.was.org/Meetings/AbstractDa ... ctId=13707
http://www.cababstractsplus.org/google/ ... 0053164936

Best,
Sara
Last edited by sihaya on Mon Oct 15, 2007 5:29 am, edited 1 time in total.
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Postby sihaya » Mon Oct 15, 2007 5:28 am

Here are some pics of mama crab when she just started releasing the larvae. (She's sitting in the bottom of my kreisel.)

Btw, interestingly, the larvae of these crabs and the emerald crabs are indistinguishable (at least to me). I expected them to be red or orange (not green). But the larvae of these guys are the same color as those of the emerald crabs.

Image
Image
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Postby aantreklik_jared » Tue Oct 16, 2007 12:09 am

Of course, they have a lot of space and resources which hobbyists don't have.


Not sure how much time you spent in research facilities... but if Australia is anything to go by most researchers could only dream of having the fancy setups of hobby aquarists
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Postby sihaya » Tue Oct 16, 2007 5:30 am

Hmm... well, I'm mostly going by what I've read in the "materials and methods" sections of some of these journal articles on the aquaculture of these crabs. The set-ups they describe and diagram are certainly outside the means of most hobbyists I know. Even if these set-ups are relatively inexpensive (which I doubt they are), I don't think most people would have the space for them...
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Postby FuEl » Tue Oct 16, 2007 11:58 am

Hi Sara, this paper should be of help to you.

Rhyne, A.L., Penha-Lopes, G., Lin, J., 2005. Growth, development, and survival of larval Mithraculus sculptus (Lamark) and Mithraculus forceps (A. Milne Edwards) (Decapoda: Brachyura: Majidae): economically important marine ornamental crabs. Aquaculture 245, 183-191.

The larvae can take NHBS straightaway. M. forceps is easier to culture, with survival rates between 74-80%. M. sculptus is harder..between 19-26% survival to juvenile. My friend and I experimented briefly with M. sculptus before, all died during megalopa stage. :(
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Postby sihaya » Tue Oct 16, 2007 12:08 pm

Yes, thank you. I had read that one already. That's why I picked M. forceps to start with (rather than the emerald crabs). The feeding aspect of that study really confused me because it contradicted other papers I read that said you have to feed them rotifers straight away. That and I tried feeding them baby brine and they didn't seem to be eating them. So, I don't know. I'm hoping they're eating the rotifers.

I'm curious to hear what you did though. What did you feed them? And how did you keep them in suspension? Did you use a kreisel or psuedokreisel of some sort?
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Postby sihaya » Wed Oct 17, 2007 12:08 pm

FuEL- btw, was it obvious when they changed from Zoea to Megalopa?
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Postby FuEl » Thu Oct 18, 2007 12:36 pm

Yes Sara, it was very obvious. They basically looked like miniature crabs during megalopa stage. :wink:

Nothing special for me, just newly hatched bbs and rather vigorous aeration in a pail. :)
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Postby sihaya » Thu Oct 18, 2007 1:40 pm

Hmmm... I guess I'll have to give the BBS another try then. :?
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Re:

Postby FuEl » Sat Oct 20, 2007 1:57 am

sihaya wrote:Hmmm... I guess I'll have to give the BBS another try then. :?


Try a lower density. 10 artemia nauplii/ml sounds awfully high. Lysmata larvae feed best between 2-5 artemia nauplii/ml. Beyond 5/ml and they don't do so well, feeding is actually inhibited. That might be the case for the crab larvae? :idea:
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Postby sihaya » Sat Oct 20, 2007 11:13 am

I didn't actually measure the BBS/ml when I fed them. I just mentioned the 10bbs/ml because that's what the article said they used. I really have no idea.

How do you even get these densities to start with? How would I make sure I had 5 or 10 /ml or whatever density I want?

Thanks again :)
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Postby FuEl » Sun Oct 21, 2007 12:34 am

Use a 1ml syringe and count the amount of bbs in 1ml. :)
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Postby sihaya » Sun Oct 21, 2007 1:23 pm

Please tell me you're kidding... lol
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Re:

Postby Luis A M » Sun Oct 21, 2007 5:40 pm

sihaya wrote:Please tell me you're kidding... lol

Not hard 8) To count rots,bbs or pods in larval water,I take a two ml sample with a bulb plastic pipette from mid depth,put it in a well micro slide and count them under the diss.scope.Not big deal,everyday´s routine 8)
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Postby sihaya » Wed Oct 24, 2007 9:03 am

How do count them when they're constantly moving though?
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Postby Luis A M » Wed Oct 24, 2007 10:14 am

no problem,you scan the field in a zig zag pattern.If you see 20,it´s 10/ml
If there are too many,50 or more,well,you know there are too many! :lol:
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