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Understanding Anemones
by Jim McNulty

Somebody Salt Me
July 1999 newsletter - The Tropical Fish Society of R.I.

Hey Fishheads,

Welcome to the July installment of Sombody Salt Me! This month, I thought we would take a look at Anemones. Just what is an Anemone? Most people associate them with corals or think that they are plants. This is not so. Actually, they are more closely related to the Jellyfishes than to corals though they are considered a distant cousin. Anemones are of the group known as invertebrates. They get their name from their marked resemblance to flowers. Most Anemones are predatory and actively hunt for food. They are an interesting and misunderstood group of animals. There are approximately 1000 species of Anemones known to exist. Probably many more yet to be discovered. They range in habitat from the intertidal zone to at least 30,000 feet in depth.

Lets start by looking at some basic anatomy. They have three major parts: 1) The Oral Disk 2) The Column 3) The Base/Pedal Disk. While they are animals, their rather primitive anatomy sets them relatively low on the evolutionary scale of development. A predominant external feature of these animals is their radial symmetry. The Oral disk comprises the mouth and the tentacles. Tentacles serve for collecting food and protection. Each tentacle is equipped with a stinging cell known as a Nematocyst. These stinging cells produce the most complicated secretion known in the animal kingdom. Surprising considering their primitive development. Depending on the species, tentacles can number from six to over a thousand. They seem to occur in multiples of six. They serve for capturing food and moving that food to the oral disk for ingestion.

The Column of the animal is the cylindrical part of the body, where digestion as well as respiration takes place here. The animal only has one external orifice so food goes in and waist is removed via the Oral Disk. Depending on the species, the column wall varies from a thick, leathery constancy to a thin, transparent material. The transparency of the thin walled varieties helps to confuse them with their Jelly cousins. At the point where the column meets the oral disk, is a sphincter that allows the animal to close off it's body cavity from it's crown in times of low tide or when attacked by a predator. The column wall may be smooth or covered with small structural protuberances and tiny projections. These are usually adhesive and allow the animal to affix gravel, shell fragments and sand grains to itself for camouflage and protective cover. The column wall also contains many small pores through which water can be ejected when the animal contracts suddenly. These animals can expand and contract at will to many times their original size.

The Base Pedal is the final structure. The animal can attach itself to a firm substrate or walk around to find a better spot. Most species do move about. Others prefer to bury themselves in the mud on the bottom. A strong suction is achieved and they are sometimes a challenge to remove one from its perch. The best way is to work your finger underneath the foot and apply firm steady pealing action until the entire foot has released. The base is also the site of laceration when performing a cloning procedure on them.

The feeding of these fascinating creatures is relatively straightforward. Most all Anemones are predatory and must hunt for and capture food. Some do enjoy the unique symbiotic relationship with zooxanthellae algae but only a handful of species. Most just extend their tentacles and wait patiently for a morsel of food to float by or for an unsuspecting fish or crab to stray to close to their Nematocysts. Another type of interesting symbiosis occurs with these animals; they share a relationship with a group of fishes where the host Anemone affords the fish protection and in return the fish brings it's host food and drives off intruders. These fish, known as Anemone fish have evolved to secrete a type of compound that affords them immunity to the sting and sticky secretions of it's host. These fish belong to the genus Amphiprion and are commonly called clownish in the trade. In the home aquarium, Anemones can be hand fed pieces of fish or other frozen foods. The animal will close its oral disk around the food and swallow it. This is a handy trick at glass cleaning time so you don't get stung. Repeated or strong stings on the inner forearm can cause some mild discomfort to the hobbyist.

The reproduction of these animals is another interesting facet of these diverse animals. Many of them are hermaphroditic and can produce offspring without contact with another specimen. Others have sexual organs and actually inseminate a female. Some species are livebearing while others release eggs or sperm into the water. All of these animals can be cloned by performing a pedal laceration procedure. They truly are an odd group of creatures. Sometimes, certain species can reproduce out of control in the aquarium and threaten your other non-mobile inverts. The genus Aiptasia is one such pest. My aquarium is currently experiencing an infestation of these. They are quite attractive and make an interesting display but damage can occur from their constant stinging to the other specimens. There are several prescribed procedures for their eradication. None of them seem to be completely effective but in combination, can keep them manageable.

Besides their feeding and tankmate selection, water quality is of great importance as with any marine life. Water quality parameters need to be maintained at the highest level possible to have them thrive and reproduce. If these basic needs are meet, even the beginner can enjoy success with these unique creatures. Join me again next month as we continue our exploration of the world's diverse marine life and try to recreate a slice of it right in our homes.

Jim Mcnulty