than 1 % to the carbon losses of the anthozoans tested (Herndl and Velimirov, in prep.).
Therefore, it is more likely that the coelenteric bacterial population provides trace
elements, vitamins (Sorokin, 1973 a) or antibiotic substances (Burkholder, 1973) which
cannot be synthesized by the host rather than providing carbon and nitrogen for metabolic activities. A similar phenomenon was described by Wilkinson (1978 a, b, c) between
sponges and associated bacteria. He Concludes that the digestion of microbial symbionts
does not yield a significant amount of energy to the host sponge.
The rapid response of coelenteric bacteria to particle feeding in S. giganteum provides
evidence that the digestive activity of the CF on bacteria during phago- and pinocytosis of
food items might well be an effective defense mechanism against microbial, invasion
(Disalvo, 1971 a) and a strategy reducing energy losses by exploiting the bacterial biomass
itself.
On the other hand, the support of bacterial growth —even during starvation periods— by
the CF when the bacterial density is low indicates that these bacteria are either essential
for anthozoans or that it is energetically meaningless to clear the CF of bacteria at low
bacterial concentrations.
For bacteria the coelenteron of anthozoa is an endobiotic habitat (Sieburth, 1979) and of
high nutritive value since the CF is the major pathway of heterotrophic nutrition and
excretion of waste products in anthozoans. This specific situation of a protected microhabitat and the high nutritive value of the CF may also account for the low generation
times of bacteria at low bacterial densities.
Further investigations, however, are required to understand the role of bacteria in the CF
of anthozoa. The use of culture techniques for bacteria will give new insights into the
bacteria -anthozoan association.
ACKNOWLEDGEMENTS
This study was supported by the Hochschuljubiläumsstiftung and the Auslandsstudentendienst of the Republic of Austria. We are grateful to Prof. Abel and Doz. Ott for providing working facilities at
the University of Vienna.
BURKHOLDER P.R., 1973. The ecology of marine antibiotics and coral reefs. In : O.A. Jones et R. Endean(eds),
Biology and geology of coral reefs. 2 Biology. Vol. 1. Academic Press, New York : 117-182.
DISALVO L.H., 1971a. Ingestion and assimilation of bacteria by two skleractinian coral species. In : H.M.
Lenhoff, L. Muscatine, L.V. Davis (eds), Experimental coelenterate biology. University of Hawaï Press,
Honolulu : 129-136.
DISALVO L.H., 1971b. Regenerative functions and microbial ecology of coral reefs : labelled bacteria in a coral
reef microcosm. J. Exp. Mar. Biol. Ecol., 7 : 123-136.
FERGUSSON R.L., P. RUBLEE, 1976. Contribution of bacteria to standing crop of coastal plankton. Limnol
Oceanogr. 21 : 141-145.
FUHRMAN J.A., F. AZAM, 1982. Thymidine incorporation as a measure of heterotrophic bacterioplankton
production in marine surface waters : evaluation and field results. Mar. Biol. 66 : 109-120.
FUHRMAN J. A., J. W. AMMERMAN, F. AZAM, 1980. Bacterioplankton in the coastal euphotic zone : distribution,
activity and possible relationship with phytoplankton. Mar. Biol 60 : 201-207.
HERNDL G.J., B. VELIMIROV, R.E. KRAUSS, 1985. Heterotrophic nutrition and control of bacterial density in the
coelenteron of the giant sea anemone Stoichactis giganteum Forskal. Mar. Ecol. Prog. Ser., 22 : 101-105.
413
Therefore, it is more likely that the coelenteric bacterial population provides trace
elements, vitamins (Sorokin, 1973 a) or antibiotic substances (Burkholder, 1973) which
cannot be synthesized by the host rather than providing carbon and nitrogen for metabolic activities. A similar phenomenon was described by Wilkinson (1978 a, b, c) between
sponges and associated bacteria. He Concludes that the digestion of microbial symbionts
does not yield a significant amount of energy to the host sponge.
The rapid response of coelenteric bacteria to particle feeding in S. giganteum provides
evidence that the digestive activity of the CF on bacteria during phago- and pinocytosis of
food items might well be an effective defense mechanism against microbial, invasion
(Disalvo, 1971 a) and a strategy reducing energy losses by exploiting the bacterial biomass
itself.
On the other hand, the support of bacterial growth —even during starvation periods— by
the CF when the bacterial density is low indicates that these bacteria are either essential
for anthozoans or that it is energetically meaningless to clear the CF of bacteria at low
bacterial concentrations.
For bacteria the coelenteron of anthozoa is an endobiotic habitat (Sieburth, 1979) and of
high nutritive value since the CF is the major pathway of heterotrophic nutrition and
excretion of waste products in anthozoans. This specific situation of a protected microhabitat and the high nutritive value of the CF may also account for the low generation
times of bacteria at low bacterial densities.
Further investigations, however, are required to understand the role of bacteria in the CF
of anthozoa. The use of culture techniques for bacteria will give new insights into the
bacteria -anthozoan association.
ACKNOWLEDGEMENTS
This study was supported by the Hochschuljubiläumsstiftung and the Auslandsstudentendienst of the Republic of Austria. We are grateful to Prof. Abel and Doz. Ott for providing working facilities at
the University of Vienna.
BURKHOLDER P.R., 1973. The ecology of marine antibiotics and coral reefs. In : O.A. Jones et R. Endean(eds),
Biology and geology of coral reefs. 2 Biology. Vol. 1. Academic Press, New York : 117-182.
DISALVO L.H., 1971a. Ingestion and assimilation of bacteria by two skleractinian coral species. In : H.M.
Lenhoff, L. Muscatine, L.V. Davis (eds), Experimental coelenterate biology. University of Hawaï Press,
Honolulu : 129-136.
DISALVO L.H., 1971b. Regenerative functions and microbial ecology of coral reefs : labelled bacteria in a coral
reef microcosm. J. Exp. Mar. Biol. Ecol., 7 : 123-136.
FERGUSSON R.L., P. RUBLEE, 1976. Contribution of bacteria to standing crop of coastal plankton. Limnol
Oceanogr. 21 : 141-145.
FUHRMAN J.A., F. AZAM, 1982. Thymidine incorporation as a measure of heterotrophic bacterioplankton
production in marine surface waters : evaluation and field results. Mar. Biol. 66 : 109-120.
FUHRMAN J. A., J. W. AMMERMAN, F. AZAM, 1980. Bacterioplankton in the coastal euphotic zone : distribution,
activity and possible relationship with phytoplankton. Mar. Biol 60 : 201-207.
HERNDL G.J., B. VELIMIROV, R.E. KRAUSS, 1985. Heterotrophic nutrition and control of bacterial density in the
coelenteron of the giant sea anemone Stoichactis giganteum Forskal. Mar. Ecol. Prog. Ser., 22 : 101-105.
413