Resumen de Sexual reproduction in the invasive octocoral Carijoa Riisei in Hawaii
Samuel E. Kahng, Yehuda Benayahu, Daniel Wagner, Nina Rothe
Since its initial discovery on Oahu in 1966, the azooxanthellate octocoral, Carijoa riisei (Duchassaing and Michelotti, 1860), has spread across the main Hawaiian Islands and proliferated in abundance. To help understand the substantial ecological success of C. riisei in Hawaii, its sexual reproduction was examined. Carijoa riisei is gonochoric with a male to female ratio of one. Gametogenesis is asynchronous, continuous, and does not exhibit seasonal or lunar periodicity. Carijoa riisei spawns negatively buoyant eggs which suggests external fertilization and possibly benthic larvae. Under favorable conditions, C. riisei exhibits high polyp fecundity. Asynchronous, continuous spawning of gametes is an unusual mode of reproduction which forgoes the advantages of concentrating gametes in space and time and requires dense aggregations of male and female colonies in close proximity to ensure fertilization success. Other life history traits such as fast growth, vegetative propagation, and superior competitive ability enable C. riisei to form dense, multi-colony aggregations thereby facilitating sexual reproduction. Provided C. riisei can achieve a critical density, this unusual sexual reproductive strategy probably enables it to exploit the ephemeral availability of space across time with a high and continuous production of larvae.
