Biology/Natural History: Background color is due in part to zooxanthellae and zoochlorellae living symbiotically in the gastrodermal layer. Both are able to live in the anemone at the same time. They are able to transfer carbon to their host, the anemone. Its possible that the anemone can control the numbers of algal cells that it has by expelling them in a bolus of mucus. The species can handle a high range of temperatures, but the higher temperatures do affect the number of symbiotic algae. Tend to eat barnacle molts, dead debris from plankton, and mussels that have fallen off the overhead rocks. Anemones of this species frequently divide asexually by expanding the base of their column in two directions until they tear in half. Large clusters, or aggregations, of clonally related anemones come to dominate areas of the intertidal in this way. The aggregating anemones have an aggressive behavior towards other anemones that are not clones of themselves, and maintain anemone-free areas between clones. They do sexually reproduce to disperse to new habitats. The verrucae frequently are holding bits of shell or gravel which is thought to provide some protection from ultraviolet light and/or reduce desiccation. Predators include the seastar Dermasterias imbricata, the nudibranch Aeolidia papillosa, and the wentletrap snail Epitonium tinctum. Asexual division is especially common in January to March This anemone may harbor either zooxanthellae or zoochlorellae intracellular symbionts. In California, the zooxanthellae may be either Symbiodinium californium or S. muscatinei. In Oregon and Washington the only zooxanthellae symbionts are S. muscatinei. Anemones with zooxanthellae have been observed from Baja California to SE Alaska, but are more common from Washington south. Anemones with zoochlorellae occur from Cape Blanco, Oregon north at least to Vancouver Island. The zoochlorella has recently been identified as Elliptochloris marina. In areas where both symbionts occur, anemones with zooxanthellae can be found throughout the intertidal but favor the upper levels, while anemones with zoochlorellae are primarily found in the lower intertidal or in shaded areas. This trend persists through the year, even though anemones appear to be able to change symbionts and many anemones contain a mixture of the two symbionts. The most rapid division of the algal symbionts occurred in July and November Anthopleura elegantissima contains these types of cnidae: Spirocysts, atrichs, basitrichs, and microbasic p-mastigophores.