Giant ephemeral anemones? Rapid growth and high mortality of corkscrew sea anemones Bartholomea annulata (Le Sueur, 1817) under variable conditions

Abstract

In shelter symbioses, the recruitment, growth, and lifespan of host organisms influence the life history characteristics of symbiotic guests. Corkscrew sea anemones Bartholomea annulata (Le Sueur, 1817) host diverse crustacean ectosymbionts in the Tropical Western Atlantic, some of which are cleaner shrimps that attract and clean Caribbean reef fishes. These sea anemones potentially function as short-lived cleaning stations due to their high mortality and short lifespans relative to that of many reef fishes. A combination of methods (field monitoring, population modeling, manipulative field experiments) was applied to quantify variation in rates of recruitment, growth, shrinkage, and mortality of this anemone. Population projections at reef sites on St. Thomas, U. S. Virgin Islands, indicated that the most important contributors to population growth were the recruitment and fate of the smallest individuals. Field experiments revealed that recruitment and growth varied significantly with reef site, but that lifespan did not. Population modeling demonstrated effects of body size and habitat on life history traits, with smaller anemones growing faster than large ones, and both very large and small individuals dying more frequently than medium-sized ones. The combined data reveal that B. annulata is among the shortest-lived sea anemones, with most individuals surviving <12 months, and maximum lifespan of only ~1.5–2 years at all examined sites. Together, these patterns suggest that this anemone exhibits characteristics of a weedy species; individuals grow and reach adult body size rapidly and populations have rapid turnover. Life history and recruitment data for crustacean symbionts of B. annulata indicate that this host may be long-lived enough to mediate multiple generations of crustacean associates, fulfilling the expectations of an evolutionarily stable host. The short lifespan of these anemones relative to those of many reef fishes may cause fishes to search frequently for new cleaning stations on Caribbean coral reefs.