206
Reef Zoobenthos
dollar"), Amphistegina lessoni, Calcarina calcarea, Archais angulatus, and
Spirolina arietina. The symbiotic algae accomplish in foraminifera the same
function as they do in corals. They translocate a larger portion of their
photosynthates to the host foram cells. This was proved by observations of
an active growth of the symbiotic foram Heterostegina depressa, kept in the
light without any food (R6ttger 1972). The symbiotic algae take part also in
the process of calcification in forams, thus helping them to construct their
shells. The curves of dependence on rates of photosynthesis and of
calcification in the symbiotic foram Archais angulata were similar to those in
corals (Duguay and Taylor 1978). This explains why all the gigantic forams
have algal symbionts. A striking peculiarity of foraminiferan symbiosis is the
wide taxonomic diversity of their symbionts. They can belong to different
taxa even within the same foram family (Lee 1980). For example, in
symbiotic forams from the family Soritidae there were found: four species of
symbiotic dinoflagellates (Symbiodinium microadriaticum - zooxanthella,
Gymnodinium vertebralis, G. rotundatum, Amphidinium sp.), two species of
green algae (Chlamydomonas provasolii, C. hedrei) , three species of
diatoms (Amphora sp., Nitzschia sp., Fragillaria sp.), and even the
unicellular red alga Porphiridium. Moreover, even the same foram species,
while living in different regions, may harbor different symbionts. Thus, the
foram Homotrema depressa from the Red Sea reefs has as symbiont the
diatom Nitzschia panduriformis, while the same foram from the Hawaiian
reefs harbor another diatom, Nitzschia valdestrigata (Schmaljohann and
R6ttger 1976; Lee et al. 1979b). In the same foram species Amphistegina
lessoni from different regions there were found diatoms which belong even
to different genera: Nitzschia and Fragillaria. Similarly, the foram
Maginopora vertebralis contains one (out of two) species of dinoflagellates
or Chamidomonas sp. Among forams there are also symbiotic species that
harbor cyanellae - the cells of the small blue-green Chroococcum (Hedley
1964). Most of them live in temperate waters, but some could be met with
also in reef biotopes.
It is just symbiosis which is the main factor in providing for the
appearance of such fantastically sophisticated and large-shelled protozoans,
which, moreover, are able to live in symbiosis with such taxonomically
different species as unicellular algae (Ross 1977). The construction of their
shells is extremely complex and resembles those of a greenhouse. The flat
shell has on its surface hundred and more chambers with very thin walls.
The roof of such a chamber is formed by the needle crystals of calcite. They
are oriented along the light-stream and perform actually the function of light
.conductors. Each chamber harbors 10-20 algal cells. When a part of the
chambers is shadowed, the algae from them migrate to the illuminated ones
(Ross 1972; Lee et al. 1979a). Marginopora has also another kind of
chambers on its surface - the nurseries. In these chambers the young cells
of foram produced parthenogenetically grow. The rate of movement of
Marginopora is 1-3cmh-l.
Reef Zoobenthos
dollar"), Amphistegina lessoni, Calcarina calcarea, Archais angulatus, and
Spirolina arietina. The symbiotic algae accomplish in foraminifera the same
function as they do in corals. They translocate a larger portion of their
photosynthates to the host foram cells. This was proved by observations of
an active growth of the symbiotic foram Heterostegina depressa, kept in the
light without any food (R6ttger 1972). The symbiotic algae take part also in
the process of calcification in forams, thus helping them to construct their
shells. The curves of dependence on rates of photosynthesis and of
calcification in the symbiotic foram Archais angulata were similar to those in
corals (Duguay and Taylor 1978). This explains why all the gigantic forams
have algal symbionts. A striking peculiarity of foraminiferan symbiosis is the
wide taxonomic diversity of their symbionts. They can belong to different
taxa even within the same foram family (Lee 1980). For example, in
symbiotic forams from the family Soritidae there were found: four species of
symbiotic dinoflagellates (Symbiodinium microadriaticum - zooxanthella,
Gymnodinium vertebralis, G. rotundatum, Amphidinium sp.), two species of
green algae (Chlamydomonas provasolii, C. hedrei) , three species of
diatoms (Amphora sp., Nitzschia sp., Fragillaria sp.), and even the
unicellular red alga Porphiridium. Moreover, even the same foram species,
while living in different regions, may harbor different symbionts. Thus, the
foram Homotrema depressa from the Red Sea reefs has as symbiont the
diatom Nitzschia panduriformis, while the same foram from the Hawaiian
reefs harbor another diatom, Nitzschia valdestrigata (Schmaljohann and
R6ttger 1976; Lee et al. 1979b). In the same foram species Amphistegina
lessoni from different regions there were found diatoms which belong even
to different genera: Nitzschia and Fragillaria. Similarly, the foram
Maginopora vertebralis contains one (out of two) species of dinoflagellates
or Chamidomonas sp. Among forams there are also symbiotic species that
harbor cyanellae - the cells of the small blue-green Chroococcum (Hedley
1964). Most of them live in temperate waters, but some could be met with
also in reef biotopes.
It is just symbiosis which is the main factor in providing for the
appearance of such fantastically sophisticated and large-shelled protozoans,
which, moreover, are able to live in symbiosis with such taxonomically
different species as unicellular algae (Ross 1977). The construction of their
shells is extremely complex and resembles those of a greenhouse. The flat
shell has on its surface hundred and more chambers with very thin walls.
The roof of such a chamber is formed by the needle crystals of calcite. They
are oriented along the light-stream and perform actually the function of light
.conductors. Each chamber harbors 10-20 algal cells. When a part of the
chambers is shadowed, the algae from them migrate to the illuminated ones
(Ross 1972; Lee et al. 1979a). Marginopora has also another kind of
chambers on its surface - the nurseries. In these chambers the young cells
of foram produced parthenogenetically grow. The rate of movement of
Marginopora is 1-3cmh-l.