News / Species Spotlight / Anemones and Anemonefishes (06/01/17)

Anemones and Anemonefishes

Species Spotlight - Anemones and Anemonefishes

Pair of Aquaculutred Amphirion ocellaris

Theres a misconception among aquarists that to keep an anemonefish (AKA clownfish) happy all you need to do is provide it with an anemone. This line of reasoning leads to the notion that any anemone will do. As a result, it misinforms hobbyists to purchase an expensive anemone their fish wont host in. But, just as you cant make a cat do anything it doesnt want to do, you cant make an anemonefish host in an anemone it doesnt like. So how does one know which anemone to choose?

Stichodactyla tapetum

There are dozens of Amphiprion species on the reefs of the Indo-Pacific, but they only make use of a handful of large zooxanthellate anemones. Youll obviously never find Nemo hosting in an Aiptasia anemone, but youll also never see it anywhere near some of the other larger reef-associated species out there, like the Hellfire Anemone (Actinodendron plumosum). And you would certainly never find them in a Condylactis, as those arent to be found anywhere that anemonefishes occur. Same goes for Mini Carpets (Stichodactyla tapetum), though you will occasionally get some willing specimens who will ignore their better instincts and still host in these unnatural choices. Even in the wild youll occasionally see desperate individuals make use of some very unorthodox hosts, such as the Long-tentacle Plate Coral (Heliofungia actiniformis).

To most easily wrap ones head around Amphiprion biodiversity, its best to break them down into smaller subgroups or species complexes. These arent just arbitrary groupings, but, rather, this system of classification reflects the close evolutionary relationships shared by these species. For the most part, the major lineages of Amphiprion occur across the West Pacific, with only a couple exceptions found in the Indian Ocean or the Central and South Pacific.

Hecteractis magnifica

The most popular and familiar members of this genus are A. percula and A. ocellaris. They are generally referred to as clownfishes vs. the more general term anemonefish, or if youre a fan of PIXAR movies, these are Nemo. Through captive breeding, there are an astounding number of ornamental strains. But, even these aquarium-bred specimens can be choosy when it comes to their host anemone. Their cnidarians of choice are either Carpet Anemones (Stichodactyla spp.) or the Magnificent Sea Anemone (Heteractis magnifica). They seem to do equally well in either of these, showing no obvious preference in the wild. Likely what determines which host they end up in is the relative abundance of these anemones and the presence of their arch nemesis, the skunk anemonefishes.

Aquacultured Amphiprion sandaracions

Amphiprion akallopisos

Amphiprion nigripes cf

There are two main types of skunk anemonefishes out there. They can be recognized easily enough by their choice of anemone. The easiest to remember is A. sandaracinos, the Orange Skunk, which is typically only encountered in Carpet Anemones. On the other hand, all the other species in this group occur in H. magnifica. This includes the Indian Ocean A. akallopisos and its Pacific cousin A. perideraion; as well as A. nigripes from the Maldives and a couple other little-known species. All of these are highly territorial and aggressive when it comes to defending their host anemone. They are known to effectively repel species that are much larger than themselves. In a fight between a skunk anemonefish and any other species, it is usually the little skunk that wins the day.

The Bubbletip Anemone (Entacmaea quadricolor) is another popular host species. There are certain groups of anemonefish that have taken this love to another level. For instance, the Maroon Clownfish (Premnas biaculeatus) is not known to host in any other type of anemone. This should always be kept in mind when attempting to recreate their symbiosis in captivity. The same holds true for the diverse Tomato Clownfish lineage, which can often be seen in huge numbers among dense groups of their bubbly host. But what keeps the Maroons and Tomatoes from fighting amongst themselves for this limited resource? This is an interesting question which has not yet been adequately answered. Yet, one observation is that the Maroon Clownfish typically occurs in large, isolated specimens of E. quadricolor, while the Tomato Clownfishes reside in areas containing numerous small clones. Its even been suggested that these may not truly be the same anemone species, but it has yet to be investigated.

Aquacultured Amphiprion polymnus balck

Aquacultured Premnas biaculeatus

Hecteractis crispa

Another interesting group are the Saddleback Anemonefishes, which includes just two species, A. sebae in the Indian Ocean and A. polymnus in much of the Pacific. Rather than being a true reef species, as all other anemonefishes are, these two are generally found in silty lagoons and seagrass meadows. For this reason, there are several anemone species that they simply never encounter in the wild. Those that they do make use of include Haddons Carpet Anemone (S. haddoni) and the Sebae Sea Anemone (Heteractis crispa).

And, finally, we come to the generalists in the genus. These are the species which dont seem to care when it comes to which tentacles they are rubbing against. Odds are, the determining factor for which host anemone one of these species ends up in has more to do with whats around than any innate preferences the anemonefish may have.

The quintessential anemonefish generalist is unquestionably Amphiprion clarkii. This highly variable species occurs from Oman to Japan to Australia. Its known to use every host species in the Amphiprion repertoire. This little masochist even lies down among the strong stinging cells of the Pizza Anemone (Cryptodendrum adhaesivum). Something which none of its relatives have ever been observed to do. When placed with Carpet Anemones, this species develops a black color morph. This is presumably a response to the strong sting of this host, but, as tends to be the case, it hasnt been studied in any detail.

Aquacultured Amphiprion sabae

Stichodactyla sp.

There are several other major groups which likewise adopt a catholic taste in anemones. The only species found across the Central Pacific, the Blue Stripe Anemonefish (Amphiprion chrysopterus), falls into this category. It tends to be associated with outer reefs. Perhaps for this reason, there are a couple hosts which it has yet to be recorded from, but youll find it on most species of Heteractis and Stichodactyla. The same holds true for Amphiprion allardi and its many relatives in the Western Indian Ocean. Though these species tend to be somewhat poorly studied and there are significant gaps in our knowledge. Lastly, theres the Wide-band Anemonefish (Amphiprion latezonatus), which is only known from a few scattered subtropical reefs near Australia. Because of the chilly waters it inhabits, there is not a lot of anemone diversity. So, it has to make due with just two species, E. quadricolor and H. crispa. However, this species was likely far more widespread in the past. Perhaps during the last ice age, when cooler waters were more prevalent, it too might have been seen making use of other species. Its hard to know why anemonefishes choose the anemones they favor. But, if youre trying to recreate this fascinating symbiotic relationship in an aquarium, its a good idea to stick with what works in nature.