Meeting Abstract

P2-135   -   Light or Flight: Effect of light intensity on settlement behaviors of sea anemones Kwan, MG*; Chan, KYK; Swarthmore College mkwan1@swarthmore.edu

Symbiotic relationships between cnidarians and their photosynthetic symbionts provide vital ecosystem services. To date, many studies have focused on the photobiology of corals. Earlier works have illustrated that light intensity and spectral property affects settlement of coral larvae. Here, we investigate if a similar pattern occurs in adults of aposymbiotic (Actinia equina) and symbiotic (Exaiptasia pallida or Aiptasia) anemones. By manipulating the light intensity, we tested if the presence of symbionts affects the anemones’ movement. Time-lapse videography revealed that on average, A. equina did not respond to low light intensity (~5.33 µmol m^-2 s^-1 and ~12.33 µmol m^-2 s^-1), i.e., remained stationery. They exhibited shade seeking behavior in moderate light intensity (~22.67 µmol m^-2 s^-1) and remained mostly sessile with tentacles fully retracted in high light intensity (~33.67 µmol m^-2 s^-1 and ~39.33 µmol m^-2 s^-1). In contrast to A. equina, Aiptasia generally tolerated high lighting cues: individuals exhibited shade-seeking behavior at light intensity as high as 43.33 µmol m^-2 s^-1. The response of Aiptasia significantly differed between individuals with high quantum yield (Fv/Fm (> 0.7) and those beneath the threshold (≦0.7). This difference suggests that abundance of photosymbionts influences light response behavior. This close association between symbiont and host behaviors supports the use of Aiptasia as an ideal surrogate to study photobiology of coral. The intraspecific variations observed could account for difference in the spatial distribution of Aiptasia and Actinia equina in the field.