No Hydra food comes even remotely close to Artemia for ease of culture, and ease of feeding Hydra. However, there may be times when you can’t use Artemia for some reason. What else can you use? Here are the alternatives I’ve tested. There may be others as well.

Moina

Moina is a freshwater crustacean related to Daphnia. Hydra loves Daphnia, but culturing Daphnia in the lab is a pain. Culturing Moina is much easier than Daphnia but not nearly as easy as hatching a bunch of Artemia. The Moina cultures can crash for no obvious reason. One cannot easily produce Moina in the numbers required to feed large Hydra cultures on a regular basis.

Pristina leidyi

This oligochaete worm is very easy to culture in the lab and Hydra will eat it readily. I kept some Hydra going for months on a diet of only Pristina. However Hydra has trouble catching the worms because they stay on the bottom of the dish away from the Hydra’s tentacles. One has to push the worms against the tentacles so that the Hydra can grab them. The worms contain granules that are fluorescent, and these persist in the endoderm of the Hydra that eats the worms. This would be a problem when imaging transgenic animals. The worms are small enough for an adult Hydra but are probably too large for a hatchling. But the worms can be cut into pieces that would be small enough for a hatchling. I can provide a protocol for culturing Pristina to anyone who is interested in culturing them. I got the protocol from Alexa Bely at the University of Maryland.

Mosquito larvae

Hydra will readily eat mosquito larvae. However, one obviously needs a source of the larvae. If a lab on your campus or a neighboring campus works on mosquitos, you can ask them to provide you with pupae, which will quickly hatch into larvae when placed in water. A Hydra that eats mosquito larvae will have a black endoderm from the melanin pigment in the mosquito larva head.

Zebrafish hatchlings

Adult Hydra will readily eat newly hatched zebrafish embryos. However these are too large for hatchlings. After feeding some Hydra with zebrafish hatchlings, I learned that this wasn’t allowed because it involved using a live vertebrate as food for another lab animal. One could, however, probably find a way to get approval to do this.

Copepods

Hydra eats copepods in the wild. I once collected a bunch of wild copepods from a vernal pool in Riverside County. Hydra in the lab ate them readily. There are methods for culturing copepods, but culturing them routinely in large numbers would not be easy. The copepods I collected were bright red, so the Hydra that ate them had a bright red endoderm.

Xenopus embryos

I have fed Hydra with tailbud stage Xenopus embryos. This is somewhat ironic given that my lab worked on Xenopus before we started working on Hydra. Hydra ingested the Xenopus embryos, but later spit them out more or less intact. One has the same regulatory issue with using Xenopus embryos as with zebrafish embryos.