Can I Support A Horseshoe Crab?

[Dave Legacy]

As I get deeper into my 200G Paludarium project I can't help but ask myself, "with a tank of this size, what can I get away with"? I've considered trying out a horseshoe crab in the past, but researching other people's past experiences with them brought me to the conclusion that I would be better off not trying. Yet I sit here viewing into a tank with almost 12sq/ft of open sandbed, that will only be occupied by hogchocker sole, and think... why not give a horseshoe a try?

These are the issues I think might pose a problem:

1. Horseshoe Crabs are sand sifters. My plan was to use Silica-Based "Playsand", possibly mixed or layered with Caribsea Araga-Mud Substrate. I don't see where the horseshoe would get it's food with what seems like a baron sandbad. "Live-sand" might solve that problem, but could it survive between 1.010-1.015SG and for how long would the food supply last?

2. Size Matters! I've read that these guys have the potential to reach 24" in length. This would make turing around very difficult and unreasonable. Do all species of horseshoe crab get this large? Is growing to this size common in a home aquarium?

3. Temperature of my tanks are kept at 78-80F. I have read that horseshoe crabs live in temps varying from 57-78F. Are my tanks too hot?

By the time I've finished writing out this thread I've almost completely talked myself out of getting a Horseshoe Crab. However, I'd like to hear some opinions before I write it off completely.

- David

 

[AMS]

1. Live sand wont fix the problem. Limulus polyphemus finds most of its food by scavenging micro crustaceans such as copepods out of the sand, these marine food items wont survive at a SG this low. Supplemental feeding should only form a small part of it's diet, unfortunately many owners of horseshoe crabs dont find this to be important and feed them whatever they like.

Even if it were possibly, live rock would be a better option as it will eventually seed the sand and the rock itself where as the sand doesnt seed the rock.

2. Limulus polyphemus normally wont exceed 16 inches in aquariums. The body reaches 16 inches, but the tail can be just as long! I am not sure how large other species grow to but I assume around the same.

3. Lower temperatures would be much better (around 74 degrees) but it will probably do OK at 78-80.

So if you want to risk it in a tank arguably too small, insufficient foods, and too high temperatures you can try a horseshoe crab. IMHO dont try it until you get a larger tank, marine SG, LOTS of live rock and cooler temperatures.

 

[Dave Legacy]

Then I'll be counting it out for now unless anyone can offer up a better argument. Does anyone have any experience with Sally Light Foot Crabs in a brackish tank? I'll probably try a whole gang of blue-legged hermits as well as the usual fiddler crabs... I guess I'm just on a bit of a crustacean kick right now.

 

[AMS]

Sally lightfoot crab refers to Grapsus grapsus, Grapsus adscensionis, and Percnon gibbesi. The most common in the aquarium trade is Percnon gibbesi followed by Grapsus grapsus. I have not heard of any of these species adapting to less than marine salinity waters, but I could be wrong. I am assuming this paludarium is a mangrove tank, correct?

These crabs would make ideal mangrove inhabitants, whether they are brackish or not. They primarily feed on algaes, especially brown algaes. They hide among rock-work and other crevices, occasionally poking their bodies out of water.

Perhpas nmonks would know whether they are brackish or not.


EDIT: Adapting marine fish to lower than full marine SG's (IE 1.017) has proved successful because the less strain on their kidneys (nmonks correct me if I am wrong). Marine inverts is a different matter. Marine inverts such as corals, urchins, hermit crabs, cleaner shrimp, favor a higher SG than fish, 1.027, while fish like it lower around 1.020. Unless they naturally inhabit brackish waters, chances are (unless they are extremly) hardy any SG under 1.021 means a dead invert.

 

[nmonks]

This is a complicated question. First you have to define "horseshoe crab". A surprise to most people is that there are at least four species in three genera, one North American, and the others South East Asian. Some of the Asian species, incidentally, are valued as food. I have a friend who ate them at a feast in Indonesia, not the actual "crab", but the eggs, scooped out of the "head" part of the animal. Apparently served with such a spicy chilli sauce it brought tears to his eyes!

Anyway, all species are euryhaline, and will tolerate fairly significant changes in salinity. Limulus and Tachypleus are perhaps the least euryhaline, and I don't think go down to less than half-strength sea water. Carcinoscorpius will go into practically fresh water, where they lay their eggs up rivers and in mangroves. I think this is a useful reference: it reports the maximum density of Tachypleus at a salinity of 28 psu but Carcinoscorpius 10 psu. PSU, incidentally, is "practical salinity units", where normal seawater is at 35 psu (=35 g/l).

This is useful, too. It reports Carcinoscorpius being found only in the Rhizophora apiculata zone.

So while I wouldn't keep a Limulus below 1.015, without at least very carefully watching its behaviour and health, I'd be comfortable taking a Carcinoscorpius right down to 1.010. Regardless of the species involved, acclimitasation to a lower salinity should be done carefully, certainly over several hours, if not days. They are inhabitants of estuaries so should tolerate fairly rapid changes in salinity, but with all the other stress factors involved in aquarium life, I wouldn't push that fact too hard.

In the UK at least, Carcinoscorpius seems to be the more widely traded. They can be identified by looking at the tails: on the Asian species, the tails have a circular cross section, while those of Limulus are more triangular. Carcinoscorpius is known as the mangrove horseshoe crab, a reflection of its preferred habitat. Tachypleus species do not seem to be traded.

http/mangrove.nus.edu.sg/guidebooks/text/2076.htm

Re: temperature; I've usually seen Limulus kept as a coldwater beast, while Carcinoscorpius is a genuine tropical.

Cheers,

Neale

Perhpas nmonks would know whether they are brackish or not.

 

[AMS]

This is a complicated question. First you have to define "horseshoe crab". A surprise to most people is that there are at least four species in three genera, one North American, and the others South East Asian. Some of the Asian species, incidentally, are valued as food. I have a friend who ate them at a feast in Indonesia, not the actual "crab", but the eggs, scooped out of the "head" part of the animal. Apparently served with such a spicy chilli sauce it brought tears to his eyes!

Anyway, all species are euryhaline, and will tolerate fairly significant changes in salinity. Limulus and Tachypleus are perhaps the least euryhaline, and I don't think go down to less than half-strength sea water. Carcinoscorpius will go into practically fresh water, where they lay their eggs up rivers and in mangroves. I think this is a useful reference: it reports the maximum density of Tachypleus at a salinity of 28 psu but Carcinoscorpius 10 psu. PSU, incidentally, is "practical salinity units", where normal seawater is at 35 psu (=35 g/l).

This is useful, too. It reports Carcinoscorpius being found only in the Rhizophora apiculata zone.

So while I wouldn't keep a Limulus below 1.015, without at least very carefully watching its behaviour and health, I'd be comfortable taking a Carcinoscorpius right down to 1.010. Regardless of the species involved, acclimitasation to a lower salinity should be done carefully, certainly over several hours, if not days. They are inhabitants of estuaries so should tolerate fairly rapid changes in salinity, but with all the other stress factors involved in aquarium life, I wouldn't push that fact too hard.

In the UK at least, Carcinoscorpius seems to be the more widely traded. They can be identified by looking at the tails: on the Asian species, the tails have a circular cross section, while those of Limulus are more triangular. Carcinoscorpius is known as the mangrove horseshoe crab, a reflection of its preferred habitat. Tachypleus species do not seem to be traded.

http/mangrove.nus.edu.sg/guidebooks/text/2076.htm

Re: temperature; I've usually seen Limulus kept as a coldwater beast, while Carcinoscorpius is a genuine tropical.

Cheers,

Neale

QUOTE(AMS @ May 21 2006, 08:45 PM) *

LOL I was asking whether the Sally lightfoot crabs were brackish =)

 

[Dave Legacy]

This is excellent information, I'll go through all of the links when I get home from work tonight. Ultimately the deciding factor will be which species I can find and if I'll be able to supply enough food for it. If I can't keep copepods which are essential for it's survival there's really no point in going much futher. The sizing is also a major factor.

I'll do more research and report back with more questions if I have any. I would like more info on Sally Lightfoot Crabs if possible.