Horseshoe crabs (Limulus polyphemus) feeding tips

[Gaufl]

Hey everyone!
I just purchased a few juvenile Limulus that I would like to raise.
The tank is setup with minimal scape and a large area of fine sand. Temp is at 21°C.

My question is about feeding these guys. They are always completely burried in the sand. So how do I feed them?

I tried placing mussel meat or shrimp pellets on top of the sandbed to no avail. I think digging them out stresses them so they will not conume any food.

At the moment, I have a healthy population of worms in the sandbed so I am not too worried but I would like to plan in advance.

Any tips are welcome!

Greetings,
Flo

 

[Gaufl]

So ive done a little reading and one paper recommended using slow leaching food pellets as the Limulus usually take a long time to find the food. Also food size and the time of feeding seems really important.
So here is what I am going to try:
The problem is that I cant just place the food pellets on the sand as my other inverts would steal the food.

I will try cutting slow leaching pellets and burrying them in the sand at night. This way the "crabs" should have enough time to feed on them.


I will keep you updated. Any tips welcome

 

[ISpeakForTheSeas]

Feeding them with other inverts in the tank may be a bit of a challenge, and I'm not sure what to suggest for that at the moment, but I do have some general advice.

For feeding/care:

It seems to just be the diet/feeding.

Horseshoe crabs are actually aquacultured by a few biomedical companies, and they seem to be basically bulletproof as far as water parameters go (they thrive in conditions that would likely kill half the stuff in our tanks), but they do have a reputation for being impossible to keep the hobby, and it’s speculated to be a nutrition deficiency- from what I’ve seen it’s probably a mix of both too little food (the groups culturing them feed like 5% of the crab’s body weight per day, IIRC, so these things eat a ton) and food that doesn’t meet their nutritional needs.

Edit: It was 3% of the body weight per day.

Honestly, I’m not sure - one of the groups listed what specific feed they were using, but it’s a commercial feed from a company (Skretting) in Utah that doesn’t list their ingredients. From what I’ve been able to find, though, it seems to just be a relatively standard, high quality aquaculture feed (good protein and fat contents, a wide range of food items in it to ensure a good spectrum nutritionally, etc.), so I’d assume pretty much any good feed (like LRS, Hikari Mega Marine, or Rod’s, for frozen examples; TDO Chromaboost & NLS Marine or Otohime & NLS Marine for pellet examples) should work.

The gelatin was to keep the food (the Skretting aquaculture feed I mentioned) stable in the water. Some of them have been successful with the larval rearing, and more research has been/is being done to make egg production in captivity more efficient (to the point where it is seen as a viable method of collecting the blood needed):

https://horseshoecrab.org/research/sites/default/files/DONE%20Schreibman%20and%20Zarnoch.pdf

FA254/FA254: Candidate Species for Florida Aquaculture: American Horseshoe Crab Limulus polyphemus

The American horseshoe crab, Limulus polyphemus, is a member of the phylum Arthropoda, subphylum Chelicerata, and class Merostomata. Although there are four horseshoe crab species worldwide, the American horseshoe crab is primarily found in the Atlantic Ocean along the East Coast of North...

edis.ifas.ufl.edu

Evaluation of Indoor and Outdoor Aquaculture Systems as Alternatives to Harvesting Hemolymph From Random Wild Capture of Horseshoe Crabs

This study evaluated two approaches to the aquaculture of Limulus polyphemus with the ultimate goal of harvesting Limulus amebocyte lysate (LAL) at an industrial scale. To monitor Horseshoe crabs (HSCs), a combination of physical, biochemical and cellular components were examined for HSC cohorts...

www.frontiersin.org

With regards to the parameters (in case the studies already listed aren't proof enough that these things are basically bullet proof):

https://www.journals.uchicago.edu/doi/10.2307/1543539

Also, the Skretting feed used in one of the studies:

Classic Brood - Skretting

Specifically made for Broodstock

www.skretting.com

Expected growth rates:

Fair question- looking at it, they are slow growers (the PDF with a graph detailing average growth per year in mm won’t let me select the graph, but I’ll link it below). They take ~9-11 years to reach maturity, and they molt ~16-17 times over that timeframe (molting less frequently the larger they get). They hit ~2 inches wide at 4 years old, ~6 inches wide by 9 years, ~9” by 15 years, and - for the females, which grow larger - ~12” by 18 years (though their growth does vary depending on their location), so, OP, you may have a lot more time I would have guessed.

https://www.int-res.com/articles/meps2003/246/m246p225.pdf

Random fact that explains why we've learned to aquaculture these:

The blue blood is factual, and their blood - as mentioned - is used to make tests to determine if things like batches of vaccines are clean or contaminated (contaminated vaccines could be lethal, so it’s pretty important to have).

 

[Gaufl]

Thanks a lot for the useful information!

 

[Gaufl]

Hey everyone!
Just wanted to give a little update on how things are going.

After about two weeks, the HSC started to cruise around the tank a lot more. For feeding, I turn off the wavemakers and place a good amount of thawed bloodworms (to mimic their natural diet as juveniles) mixed with small pellets on the sandbed.

I then place the Limulus directly on the food.

So far this has worked well for me. I will keep this post up to update on any observations I may find in the future.

I might also add that I am dosing Iodine three times a week.

Greetings,
Flo