corals. Sorokin (1973a) found that corals consume organic phosphorus bound in the cells
of planktonic bacteria more actively than inorganic phosphate at the same concentrations. Reimer (1971), investigating the nutritional mode of the zoanthid Zoanthus sandwichensis, found a large bacterial population within the coloenteron and discussing the
possible sources of nutrients for Zoanthus the author speculated that zoanthids may be
able to farm a bacterial flora within the coelenteron and perhaps feed on them. Quite
recently, first direct evidence has been presented on the existence of a bacteria - anthozoan
association in the giant sea anemone Stoichactis giganteum (Herndler al., 1985). Bacterial density in the coelenteron of S. giganteum was found to be controlled by the
coelenteric fluid. Below a distinct value of coelenteric bacterial density, bacteria are
farmed ; above this threshold bacteria are digested by the coelenteric fluid.
In this paper, evidence is given that the bacteria - anthozoan association observed in S.
giganteum is not restricted to this single species but can be detected in other anthozoans as
well, in both symbiotic and asymbiotic forms.
MATERIAL AND METHODS
Gut samples of the anthozoan species examined were sucked out of the gastral cavity by
means of a syringe following the method described by Porter (1978). Due to the size of S.
giganteum, a P VC-tube with an inner diameter of 1,6 cm was mounted on a syringe with a
capacity of 60 cm
3 . Gut samples of 3 to 4 specimens and one sample of ambient water were
taken per run.
Gastral samples of Leptopsammia pruvoti (Madreporaria) and Parazoanthus axinellae
(Zoantharia) were sucked out using a blunted needle (1 mm inner diameter) mounted on a
20 ml-syringe. 10 polyps of L. pruvoti and 20 polyps of P. axinellae were sucked out per
run. For Anemonia sulcata (Actiniaria), a blunted needle with a 4 mm inner diameter
mounted on a 20 ml-syringe was used. Three specimens were sucked out per run. The
entire sampling procedure was performed using SCUBA. Sampling intervals varied between 2 to 4 h in L. pruvoti, P. axinellae and A. sulcata, while S. giganteum specimens were
sucked out twice a week.
The syringe needle was inserted into the gastrovascular cavity of the polyp through its
mouth and the coelenteric fluid (CF), together with solids, slowly extracted until either
the column wall and the oral disk collapsed over the skeleton (L. pruvoti) or, in the case of
other species tested, until the smooth column collapsed. Within 5 min after collecting the
CF, the samples were fixed with formalin to a final concentration of 5 % and kept at 4°C in
darkness until analysis.
Additional laboratory experiments were performed in order to evaluate the role of the CF
in controlling bacterial density within the coelenteron on P. axinellae, A. sulcata, S.
giganteum and Cladocora cespitosa (Madreporaria).
For sampling the CF in laboratory experiments, a blunted needle (2 mm inner diameter)
mounted on a 10 ml- syringe was used. The sample volume was always 4ml in S.
giganteum and A. sulcata specimens, while in P. axinellae and C. cespitosa the sample
volume varied between 2-5 ml according to the amount of polyps sampled. Between 6-10
polyps of C. cespitosa and P. axinellae were sampled per run in 2 to 4 h intervals.
One half on the CF sucked out in this manner was fixed immediately by adding formalin,
while the remaining CF was incubated in pre-sterilized scintillation vials for 4h at
ambient water temperature and then fixed as mentioned above. The development of
coelenteric bacterial density within the CF could therefore be investigated by comparing
408
of planktonic bacteria more actively than inorganic phosphate at the same concentrations. Reimer (1971), investigating the nutritional mode of the zoanthid Zoanthus sandwichensis, found a large bacterial population within the coloenteron and discussing the
possible sources of nutrients for Zoanthus the author speculated that zoanthids may be
able to farm a bacterial flora within the coelenteron and perhaps feed on them. Quite
recently, first direct evidence has been presented on the existence of a bacteria - anthozoan
association in the giant sea anemone Stoichactis giganteum (Herndler al., 1985). Bacterial density in the coelenteron of S. giganteum was found to be controlled by the
coelenteric fluid. Below a distinct value of coelenteric bacterial density, bacteria are
farmed ; above this threshold bacteria are digested by the coelenteric fluid.
In this paper, evidence is given that the bacteria - anthozoan association observed in S.
giganteum is not restricted to this single species but can be detected in other anthozoans as
well, in both symbiotic and asymbiotic forms.
MATERIAL AND METHODS
Gut samples of the anthozoan species examined were sucked out of the gastral cavity by
means of a syringe following the method described by Porter (1978). Due to the size of S.
giganteum, a P VC-tube with an inner diameter of 1,6 cm was mounted on a syringe with a
capacity of 60 cm
3 . Gut samples of 3 to 4 specimens and one sample of ambient water were
taken per run.
Gastral samples of Leptopsammia pruvoti (Madreporaria) and Parazoanthus axinellae
(Zoantharia) were sucked out using a blunted needle (1 mm inner diameter) mounted on a
20 ml-syringe. 10 polyps of L. pruvoti and 20 polyps of P. axinellae were sucked out per
run. For Anemonia sulcata (Actiniaria), a blunted needle with a 4 mm inner diameter
mounted on a 20 ml-syringe was used. Three specimens were sucked out per run. The
entire sampling procedure was performed using SCUBA. Sampling intervals varied between 2 to 4 h in L. pruvoti, P. axinellae and A. sulcata, while S. giganteum specimens were
sucked out twice a week.
The syringe needle was inserted into the gastrovascular cavity of the polyp through its
mouth and the coelenteric fluid (CF), together with solids, slowly extracted until either
the column wall and the oral disk collapsed over the skeleton (L. pruvoti) or, in the case of
other species tested, until the smooth column collapsed. Within 5 min after collecting the
CF, the samples were fixed with formalin to a final concentration of 5 % and kept at 4°C in
darkness until analysis.
Additional laboratory experiments were performed in order to evaluate the role of the CF
in controlling bacterial density within the coelenteron on P. axinellae, A. sulcata, S.
giganteum and Cladocora cespitosa (Madreporaria).
For sampling the CF in laboratory experiments, a blunted needle (2 mm inner diameter)
mounted on a 10 ml- syringe was used. The sample volume was always 4ml in S.
giganteum and A. sulcata specimens, while in P. axinellae and C. cespitosa the sample
volume varied between 2-5 ml according to the amount of polyps sampled. Between 6-10
polyps of C. cespitosa and P. axinellae were sampled per run in 2 to 4 h intervals.
One half on the CF sucked out in this manner was fixed immediately by adding formalin,
while the remaining CF was incubated in pre-sterilized scintillation vials for 4h at
ambient water temperature and then fixed as mentioned above. The development of
coelenteric bacterial density within the CF could therefore be investigated by comparing
408