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FAQs about Horseshoe Crabs, Disease

Related FAQs: Horseshoe Crabs 1Horseshoe Crabs 2, & FAQs on: Horseshoe Crab ID, Horseshoe Crab Behavior, Horseshoe Crab Compatibility, Horseshoe Crab Selection, Horseshoe Crab Systems, Horseshoe Crab Feeding, Horseshoe Crab Reproduction, & Crustaceans 1, Micro-Crustaceans, Amphipods, Copepods, Mysids, Hermit Crabs, Shrimps, Cleaner Shrimps, Banded Coral Shrimp, Mantis Shrimp, Anemone Eating Shrimp

Related Articles: Horseshoe Crabs: Latter Day Trilobites for Some Systems & CrustaceansMicro-Crustaceans, Amphipods, Copepods, Mysids, Isopods, Shrimps, Coral Banded Shrimp, Cleaner ShrimpP. holthuisi Pix, Mantis "Shrimp", Lobsters, Slipper Lobsters, Hermit Crabs, Squat Lobsters, Crabs, Arthropods, Pycnogonids (Sea Spiders),

Horseshoe crab molting     4/5/17
To whom it may concern,
I'm a naturalist and we have a lot of aquariums at my nature center. We've had a resident horseshoe crab (about 5-6" diameter) for some time, but his last molt was unsuccessful and it seems to be in poor health now. It's
limbs an carapace are deformed.
<Mmm; there are a few general "causes" for such: A lack of iodide-ate, imbalance/deficiency in alkaline earth materials (mostly Calcium; to a lesser degree Magnesium), "poor" water quality outright (e.g. too much
organic content); and lack of nutrition. You should look at all these possibilities>
It's been flipping itself upside down repeatedly today with no success in righting itself (I've tried righting it several times by hand). It still eats fine and the water levels are all normal;
<.... data please; not impressions>
everything else in the tank is in fine health (urchins, another horseshoe, etc.).
<Ahh; a good clue>
Is there anything that can be done to help ensure a successful molt?
<The above considerations. Do you have test gear for water parameters? What are you feeding, using for supplements?>
Based on my observations, I think it should've molted again by now but it just hasn't.
Sara Yinger
<Let's keep chatting till this is solved. Bob Fenner>

OUR HORSESHOE CRAB; hlth.       12/4/13
Hi Crew,
Our small, male horseshoe crab, who's in a touch tank, has lost all its pedipalps and "pusher" feet, exposing tissue. We're thinking that constant movement on the rough sides of the tank and digging in the sand has caused this, but that's just a guess. Can you help us?
<Possibly. Most limb losses are due to issues of nutrition or water quality. Do read here re:
and the linked files re Limulus above. Bob Fenner>
Brandis Hartsell, Ph.D
Dept. Chair and Curator
Marine and Earth Sciences
Roper Mountain Science Center
Greenville, SC  29687

Limulus polyphemus questions -- 08/26/09
We have had six horseshoe crabs (Limulus polyphemus) for the past 6 years for our touch tank- two are out for touching, and the other four are held and rotated periodically.
Our largest one (shell is approximately 6 inches across) molted 2 years ago, but the new shell has never reached the normal level of hardness. It seems to be thinner and gives to the touch. Calcium levels in the tank are in the 330 to 360 range. Any ideas on why it has not hardened up?
<Mmm, yes. Best guess is a disproportionality of Magnesium (should be about 3X Ca) and/or low Alkalinity... in the water, though these can be made up in foods>
Our other issue is on another crab in our holding tank has just recently developed loss of color and hardness in portions of the last half of its telson, with the last 2 cm breaking off. Anyone out there have any experience with this sort of problem?
<Mmmm.. is there an excess of nitrogenous wastes, e.g. Nitrate present?>
The crabs are fed either mussels or silversides. Tanks are kept around 14 C degrees, specific gravity 1.020,
<Too low... this may be a factor... I'd raise to 1.025>
Ammonia <.15, Nitrite .02,
<These should be 0.0 ppm>
Nitrate 0, Mg 1290, pH 8.4, Alkalinity 3.6. with algal scrubbers for filtration.
<Likely NO3 issue with this form of filtering>
Thanks for any ideas.
Dave Sobal
CSC Aquaria & Animals
<... Catawba... Bob Fenner>

Horseshoe Crab/Health 2/9/07 I'm hoping you can help me out. <Hope so, Deborah> I have a 90 gallon well-established salt tank that currently houses five yellow-tail damsels, a striped damsel, and a horseshoe crab.  We have had the damsels for almost two years and the horseshoe crab for almost a year now.  We were lucky enough to watch our horseshoe crab molt and got to save the shell (see attachments).  We are currently fixing a poisonous algae problem and I think it has affected the horseshoe crab.  I found her upside down under one of the filters this morning and thought she was dead.  When I netted her and brought her to the surface, her gills were moving but very slowly.  I put her in an isolation/hatching net (see attachments) and saw that she improved quickly.  Her tail is snapped at the end which I realize she will likely regenerate during her next molt.  Finally, I am getting to the point of my letter.  I don't want to release her until this evening when the bulk of the algae is cleaned but, she has other plans.  In her  attempts to free herself from the isolation box, she keeps landing on her back and can't right herself because of the snap in her tail.  I have spent the better part of the morning flipping her back over.  Do you think it's safe to release her?  How long can she stay on her back safely?  Thanks so much, in advance, for any help you can provide.   <I'd leave the crab in isolation until health improves, eating, righting itself.  Having gravel in the isolation tank will help it right itself.  If you have treated the tank with an algae inhibitor, this very well could have affected the crab's health. Read FAQ's here and linked files above.  Learn here from the experiences of other Horseshoe Crab keepers. http://www.wetwebmedia.com/horseshoecrabfaqs.htm  James (Salty Dog)> Deborah

Re:  Horseshoe Crab/Health 2/9/07 Thanks so much for sending such a fast response. <You're welcome.> It's nice to know that there are volunteers taking the time to help those of us who need it especially when the same LFS who sell these little guys know nothing about them.  I ended up releasing the crab late last night because the tank bottom was cleaned.  A few months ago we found that our substrate was too thick resulting in not enough aeration and it was causing spots of anaerobic bacteria throughout the tank. <Yes, can/will happen.> We removed a lot of the substrate and the problem slowly subsided.  Harry (the horseshoe crab) <Skinhead would have been a better name:)> also helped with that because she constantly moved the substrate.  Recently, the same bacteria came back with a vengeance and we were concerned that Harry would be affected.  We were told by our LFS that we should replace our lights.  I have been telling my husband this for months.  Now, its just a waiting game.  Harry seems to be holding her own but insists on staying directly beneath one of our filters.  As for your response to my original email, we don't use algae inhibitors because normally our tank produces just enough of the good algae to keep our fish happy. <My concern here is the chemical make-up of some of these products that can affect the health of invertebrates.> I wish I could have put gravel in the isolation tank.  It would have kept me from spending the day flipping Harry over.  Its a net tank and just can't handle the extra weight of any gravel.  I've decided to use my spare 10-gallon tank for all future isolation issues.  You're horseshoe crab FAQ's section has been a lifesaver.  We bought Harry on a whim, like so many others mistakenly do (our first unresearched purchase) along with a hermit crab from our LFS.  We knew nothing and could find no information anywhere.  We even went to two large local aquariums and they could not help us.  After many more long hours searching online, we finally found your website!  What a relief we felt.  Your site has been a constant source of valuable information for to us.  This reply needs no response.  Thanks for all that you do for us. <You're welcome, Deborah, and continue reading/learning.  James (Salty Dog)> Deborah Rowe

Horseshoe Crab Health and Cucumber Fission 4/5/07 Hello! <Hi Susan!> I just recently found your site and have learned a great deal from it already. <Thank you! How may we help you today?>. I have a 30 gallon tank that I have had for about 4 years. I purchased a horseshoe crab, sadly, since I have read your article, 3 years ago. <Wow, considering their specialized needs, 3 yrs in a 30g tank is a long time for one of these guys to survive!> He has seemed to do well until the past week, he has molted twice during the time I have had him. <Depending on his age, he should have molted more than this over a three year period> He now has a dark brown color to his back, his shell is soft and he does not seem to be moving his gills very often.<Did he just molt in the last day? If so, that would be normal. Their shell doesn't harden for around 24 hrs. If not, that combined with the slow gill action sounds like he's in trouble. How is everything else in the tank? What are your water parameters, including calcium? Have you ever tested for Iodine/Iodide? Is he still eating and if so, what do you feed him? Also, how large is he now?> He also is spending a lot of time upside down.<Horseshoe crabs sometimes do odd things but all in all, I'm concerned for the little guy> I do hope I have not starved him or caused him other harm. <If he survives, he really needs to be in a tank more equipped for his needs. Please read the FAQ listed as 'Horseshoe crab Overview 4/14/03' at this link: http://www.wetwebmedia.com/horseshoecrabfaqs.htm > It is a shame that some fish dealers do not have the knowledge to help educate people on purchases. <Agreed. Horseshoe crabs are wonderfully interesting creatures that in the right setting, can be very hardy. Unfortunately, they're not well suited to the warmer, predominantly rock filled reef tanks that most saltwater enthusiasts keep> I will not make another purchase without checking your site first. <Yes, it's a difficult lesson that many of us have learned the hard way, but the good news is that by you writing this, you may be saving another life down the road> I also have a light spotted sea cucumber that recently divided into two sea cucumbers. Both "halves" seem to be doing fine but I have not been able to find any information on this. I would appreciate any help you could give me. <Ha! Thought you were seeing double, didn't you? Actually, "fission", or splitting into two parts in this case, is normal for some species of cucumber. Interestingly enough, these species can reproduce sexually or asexually. What usually happens is the Cuke will disappear for a bit, maybe a week or two, then reappear as two separate entities! How neat is that? Here's a link to our Faq's on Cuke reproduction: http://www.wetwebmedia.com/cukereprofaqs.htm > Thank you for your time and expertise.<You're very welcome, Susan! -Lynn>

Small SW... Horseshoe Crab... No useful info.  -- 06/08/07 Hello, I just recently found your site and have learned a great deal from it already. It is a shame that some fish dealers don't have the knowledge to advise people in their purchases in the beginning. <Such is the nature of experience, reality... "Once you get something wired... your chances are generally long over"> I have a 30 gal tank, have had it for 4 years. I purchased a horseshoe crab <What species? Might be at the end of its lifespan for these circumstances...> three years ago. (sadly, after reading your article). It has seemed to do well until the past week. It has molted twice in the time I have had him. He now seems to be in trouble, hopefully I am not starving him, but he is spending a lot of time upside down, his gills do not seem to be moving very often and his shell is soft and has a brown tint on the back that was not previously there. Any help would be greatly appreciated. <Mmm...> I also have a light spotted sea cucumber that I have had for about a year. <Could be a factor here as well...> It recently divided into two separated cucumbers. Both "ends" seem to be doing well but I have not been able to find any information on this. <Need to identify... Pix?> Thank you again for your time and expertise. I will definitely see your page before any future purchases. <Uhh... need more input... system make-up, maintenance, water quality tests/history, foods/feeding... Bob Fenner>

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