Sea anemones and their inhabitants: Field surveys and laboratory experiments

Sea anemones host a wide variety of symbiotic inhabitants. The animals that seek shelter in anemones benefit by avoiding predation in the form of a physical camouflage, as well as the defense system offered by the anemone’s nematocysts. Anemones are thought to benefit by being cleaned as the inhabitants feed. This study explored the factors that affect the types and numbers of species and individuals that inhabit sea anemones in Discovery Bay, Jamaica. Field surveys of anemones were carried out in three areas of the bay including mangrove, limestone area; a jetty; and patch reefs bordering the ocean side of the lagoon and continuing into the reef crest. Size and species of anemone, and all inhabitants were recorded. Condylactis gigantaea, giant anemone, had greater species inhabitant diversity and abundance than Rhodactis lucida, knobby anemone. The greatest number of inhabitant species were found in the patch reefs and the least in the mangrove, limestone area. This is likely due to the high diversity of species supported by reef structure. Also, these organisms may avoid predation by escaping to higher ground on mangrove roots or exposed rock. Based on personal observation, more individuals and species were found in larger Condylactis gigantaea than smaller. Ten sea anemones were tagged during the day and revisited at night to observe any changes in inhabitants based on time of day. Some of the inhabitants were removed prior to revisiting to determine if new individuals would move in. There tended to be fewer or no species present in anemones at night than during the day. Organisms may be able to forage at night, protected from predators by the low light. Of the anemones where inhabitants were removed, some were left empty at night and others were filled by new individuals. Of the anemones where inhabitants were not removed, some had the same species at night and some had become occupied by other individuals. Finally, laboratory experiments were carried out to determine the patterns by which common inhabitants disperse among large and small anemones. There does not seem to be a preference for larger anemones by larger, presumably dominant crabs. The banded cling crabs either preferred or outcompeted the green clinging crabs for anemone space. Smaller individuals tended to share anemones more than larger ones. Further study is needed to determine the patterns of species dispersal across anemones based on size, species, and time of day.

Hazel