Anthozoan host factors are components of host animal homogenates which elic
it the release of newly fixed carbon by symbiotic dinoflagellates in vitro.
The host factor active component of an homogenate of the reef coral Pocill
opora damicornis has recently been isolated and identified as a mixture of
free amino acids. A synthetic host factor (SHF) based on the measured free
amino acid pool of P. damicornis elicits an identical response in symbiotic
dinoflagellates in vitro as does the crude host factor. SHF was used as a
tool with which to investigate the impact of anthozoan host factor on other
aspects of symbiotic dinoflagellate metabolism. Here we demonstrate that d
inoflagellates isolated from the tropical sea anemone Aiptasia pulchella (C
arlgren) incubated in SHF, in addition to releasing fixed carbon, also exhi
bit higher photosynthetic carbon fixation, heterotrophic carbon fixation, p
hotosynthetic oxygen production, respiration rates, and cell specific conce
ntrations of chlorophyll a as compared to dinoflagellates incubated in sea
water in vitro. Thus, the performance of symbiotic dinoflagellates in vitro
appears to be sustained in an amino acid rich environment, but compromised
in sea water. This observation raises the possibility that in nature symbi
otic dinoflagellates released from anthozoan hosts may survive in amino aci
d rich environments such as fish guts and "intermediate hosts". (C) 1999 El
sevier Science B.V. All rights reserved.