Sea anemones--Behavior

Host specificity by Periclimenes pedersoni and P. yucatanicus to three species of sea anemone was investigated. Field associations, initial preferences (within 72 h of collection) in the laboratory, and changes in preference after "conditioning" with an alternate host were compared. Periclimenes pedersoni associated with Bartholomea annulata in the field preferred this same anemone in choice trials. These same shrimp changed preference after 2 to 8 wks of conditioning with a different host species. Periclimenes yucatanicus associated with Stichodactyla helianthus in the field preferred this same anemone in choice trials. Those P. yucatanicus collected from either Condylactis gigantea or B. annulata did not exhibit an initial preference for these respective hosts. Periclimenes yucatanicus initially found on and preferring S. helianthus did not change their preference after conditioning; those found on other hosts chose S. helianthus after conditioning.

The relationship between heterospecific aggression and dispersion in sea anemones is poorly understood. This relationship was elucidated for Bartholomea annulata Leseur and Aiptasia pallida Verrill at a quarry in the Florida Keys. Laboratory experiments indicated that B. annulata was the aggressor. Individuals of both species moved to avoid contact under both laboratory and field conditions. Field assessment of dispersion revealed aggregated patterns, as well as vertical segregation between the species. Bartholomea annulata was most abundant at a depth of 0.75 m, while A. pallida dominated at the surface. Heterospecific aggression may be just one but probably an important one of several factors mediating the spatial distribution of these two sea anemones.