Internal brooding as a beneficial reproductive strategy for sea anemones in the intertidal zone

No abstracts are to be cited without prior reference to the author.

Brooding is an interesting reproductive strategy of sea anemones inhabiting a wide variety of sub‐ and intertidal zones. We focused on the spatial structure of sea anemones forming aggregations in the intertidal zone of the Barents Sea. We found three dominant arctic–boreal species in the study area: Urticina crassicornis, Cribrinopsis similis, and Aulactinia stella. All of these species are internal brooders. The first two species release fully developed young through the mouth, the third one releases juveniles using the tentacles. Although brooding is a reproductive strategy that reduces dispersion, it leads to rapid colonization of the sites occupied by the parents. We found mixed aggregations of three or two studied anemone species. A. stella appeared to be widely distributed around the coast. Although U. crassicornis and C. similis were less widely distributed, when present they formed dense aggregations. They preferred the sites between rocks that are sheltered from waves. The analysis of the distance between juveniles and the reproducing anemones revealed that the smallest young anemones of U. crassicornis were less abundant and settled significantly closer to parents compared with juveniles of A. stella. The strategy of releasing juveniles through the tentacles allows the young A. stella to attach directly to the substratum. It seems to be more beneficial in the littoral zone disturbed by waves compared with the strategy of the Urticina and Cribrinopsis species that release juveniles through mouth.