Meeting Abstract
The sea anemone Anthopleura elegantissima is a prominent member of the intertidal zone on the west coast of North America and can exist in three symbiotic states: a white, brown, or green state where anemones lack symbionts, contain predominantly Breviolum muscatinei, or Elliptochloris marina, respectively. The enzyme carbonic anhydrase (CA) catalyzes the interconversion between CO2 and HCO3-1 and is known to play a dynamic role in delivering CO2 to symbionts embedded deep within host gastroderm. To test the effect of symbiotic state and anemone size on CA activity in hospite, A. elegantissima were collected near Anacortes, WA, flash frozen in the field, and subsequently processed for CA. In addition to activity, corresponding gene expression of several CA isoforms was evaluated using RT-qPCR. Brown anemones displayed significantly higher CA activity than either greens or whites and greens unexpectedly displayed CA activity equal to that of whites. CA activity, when normalized to anemone protein, was highest in small anemones and lowest in large anemones (small > medium > large); furthermore, regression analysis showed a significant inverse correlation between anemone size and CA activity. Breviolum has much greater rates of primary productivity than does Elliptochloris so higher CA activity in brown anemones is expected in order to provide their algae with unrestricted amounts of CO2 to satisfy photosynthetic carbon demand. The negative correlation between anemone size and CA activity is hypothesized to be driven primarily by the surface area to algal density relationship. We propose that small anemones have smaller photosynthetically active surface area yet have similar algal densities to large anemones, necessitating higher CA activity to provide adequate CO2 for photosynthetic activity.
