Meeting Abstract
P1.157 Tuesday, Jan. 4 Aggression in the clonal intertidal sea anemone Anthopleura dowii PARISSENTI, L.; PAM, M.; PEARSE, V.*; Hopkins Marine Station of Stanford University, Pacific Grove, CA; Hopkins Marine Station of Stanford University, Pacific Grove, CA; Hopkins Marine Station of Stanford University, Pacific Grove, CA vpearse@gmail.com
The clonal intertidal sea anemone Anthopleura dowii possesses acrorhagi on marginal columnar projections, a defining character of the genus. Although anemones with acrorhagi are presumed capable of aggression, such behavior had not previously been documented in this species. Clonal aggregations of A. dowii on rocky shores in the Gulf of California (Sea of Cortez) were tested for aggressive inter- and intra-clonal behavior and compared to A. elegantissima, a similarly clonal, rocky-shore species whose aggression has been well described from populations on the central coast of California. Tests involved bringing into contact the tentacles of polyps of A. dowii from the same and different clones (each clone marked by distinctive color patterns), to observe any reactions by the anemones, especially tentacle retraction and acrorhagial expansion and extension. Polyps of A. dowii demonstrated aggression only to non-clonemates. The behavior was consistent with the five steps of aggression described for A. elegantissima. This behavior is presumably important in defense of habitable space, facilitating survival and growth of the clone. The disproportionately large size of the acrorhagial projections in the small polyps of A. dowii, compared to those of other Anthopleura species, may reflect the particular scarcity of suitable habitat available in the Gulf of California, given exposure to intense sunlight and extremes of temperature and salinity measured in the shallow intertidal pools that A. dowii inhabits. The pattern of aggression in anemones coinciding with small polyp size, clonal growth mode, and high rocky-shore habitat is especially well exemplified by A. dowii.
