ALGAL GENOTYPE AND PHOTOACCLIMATORY RESPONSES OF THE SYMBIOTIC ALGA SYMBIODINIUM IN NATURAL-POPULATIONS OF THE SEA-ANEMONE ANEMONIA-VIRIDIS

As an approach to investigate the impact of solar radiation on an alga -invertebrate symbiosis, the genetic variation and photosynthetic resp onses of the dinoflagellate algal symbiosis in an intertidal and a sub tidal population of the sea anemone Anemonia viridis were explored. Al lozyme analysis of the anemones indicated that the two populations wer e genetically very similar, with a Nei's index of genetic identity (I) of 0.998. The algae in all animals examined were identified as Symbio dinium of clade a by PCR-RFLP analysis of the small subunit ribosomal RNA gene. The symbiosis in the two populations did not differ signific antly in algal population density, chlorophyll a content per algal cel l or any photosynthetic parameter obtained from studies of the relatio nship between photosynthesis and irradiance. We conclude that there is not necessarily genetic variation or photosynthetic plasticity of the symbiotic algae in Anemonia viridis inhabiting environments character ized by the different solar irradiances of the subtidal and intertidal habitats.