Feeding affects phosphate fluxes in the symbiotic sea anemone Aiptasia pallida

Abstract

Phosphate uptake by the anemone Aiptasia pallida occurred only when anemones were starved and was due to the presence of endosymbiotic zooxanthellae. Anemones fed Artemia nauplii released PO sub(4) super(3-) at 0.26 mu M PO sub(4) super(3-), and showed no evidence of uptake at elevated concentrations (0.66 and 1.26 mu M). In contrast, anemones maintained without food for 2 wk to 1 mo took up PO sub(4) super(3-) at both 0.66 and 1.26 mu M. The uptake of PO sub(4) super(3-) by anemones freshly collected from the field ((PO sub(4) super(3-)) = 0.23 mu M) was greater than that of anemones fed daily in the laboratory, but less than that of 2-wk to 1-mo unfed anemones. Replacement of total (host and symbiont) phosphorus (P) solely from uptake of seawater PO sub(4) super(3-) at 0.66 mu M would require 374 d in fed anemones, indicating that this source is insignificant in comparison to ingested food. Corresponding times for 2-wk and 1-mo starved anemones average less than 8 d, while those for field anemones average 50 d.