Anemone-Eating Nudibranchs: Berghia

Yesterday morning, I received a FedEx shipment from a nudibranch breeder in Florida containing a tiny colony of some very special creatures.

15J30 Berghia hunting

The Berghia Nudibranch (Berghia stephanieae) is a sea slug from the super-family Aeolidioidea, which includes a wide variety of gastropod molluscs.

Although nudibranchs come in a wide variety of delightful colors and patterns, the berghia nudibranch is white–or brown–depending on how recently it ate.

Berghia are plentiful in the wild, but rare in home aquariums because they’re an obligate predator of aiptasia anemones, meaning that without enough aiptasia to eat, the berghia starve. (The term “obligate predator” refers to a species that eats only a certain food or foods, and cannot survive on anything else.) Breeders raise berghia in captivity and sell them to aquarium hobbyists for elimination of aiptasia infestations. Sadly, most of these berghia starve to death when the job is done.

I grew interested in berghia because, despite best efforts, I’ve acquired a couple of irritating hitchhiker aiptasia in my reef, and my peppermint shrimp (who eat aiptasia in the wild) prefer eating leftovers from the daily seahorse buffets to eradicating stinging aiptasia anemones. Can’t say that I blame them.

Enter the berghia.

15J30 Berghia on powerhead

Unfortunately, peppermint shrimp will also eat berghia nudibranchs, given the opportunity.

As a result, and because the berghia are actually fairly adorable (if you’re into slugs), I’ve set up a separate tank to try and get a colony breeding before I put any nudibranchs into the reef. (We’ll see how this works out in the weeks to come.)

Yesterday afternoon, I added the first aiptasia anemones to the little tank with the berghia. I only wish I’d been recording it on video at the time. The little nudibranchs (which measure 1/2″-3/4″ in length) attacked the anemone as a group and devoured it in minutes.

15J30 attacking anemone

After eating, the nudibranchs turned creamy brown in color–partially because of the food in their bodies and partially because the berghia nudibranch can actually incorporate its prey’s stinging cells into the nudibranch’s own tendrils.

15J30 Berghia after eating

As of this morning, they’re white again, and though they haven’t yet consumed the last of the anemones, they’re hunting again, so I’m sure it won’t be long.

15J30 Berghia 2

The diversity within the aquatic world never ceases to fascinate me. It’s one of the reasons I keep a reef. I love to visit well-kept public aquariums, but it’s difficult to really “see” the creatures, and their behaviors, in the span of a single afternoon. By keeping them at home, learning about and trying to meet their needs, I’ve discovered that their lives and world are far more complex than I ever gave credit for.

Here’s hoping I can manage to keep these little guys fed and happy.

Have you ever seen nudibranchs? What do you think about keeping slugs as pets?