Coral Communities: Composition and Formation
257
dendrophylliids are ahermatypic (asymbiotic) except the genera Turbinaria
and Heteropsammia, which harbor algal symbionts. Large colonies of
Turbinaria could be met with usually in poorly illuminated biotopes of reef
slopes, on walls of channels and caves, on reefs with turbid waters and low
water transparency situated on coastal reefs of continental coasts. Other
hermatypic genus is Heteropsammia, which includes a single species H.
cochlea, and has, besides the zooxanthellae, another remarkable symbiont -
the sipunculid worm Aspidosiphon, which moves these small (1-3 cm) freeliving solitary corals over the sandy bottom of the lagoon or at the foot of
reef slopes (cf. Sect. 7.3). Their number in such biotopes is often extremely
high, up to hundreds m- 2 (Latypov 1985). The ahermatypic dendrophylliids
Dendrophyllia, Balanophyllia, and Tubastrea are components of the
sciophylous scleractinian fauna in poorly illuminated or even dark biotopes:
in caves, trenches, channels, and in deep zones of the reef (Sheppard 1981b;
Dinesen 1982).
7.1.2 Zoantharians and Octocorals
Zoantharians like scleractinian corals form colonies by the budding of
polyps. Most of them do not have skeletal elements. Only the genus
Palythoa forms hard massive crustose colonies of firm chitin-like material
incrusted with calcareous globules. This group of Anthosoa, though
taxonomically poor, nevertheless is very widespread in shallow reef
biotopes. They form large colonies on rubble, on rock surfaces of flats, on
dead, and even on living, colonies of corals (Goreau 1959; Herberts 1972;
Karlson 1983). The most common reef zoantharians are represented only by
three genera: Zoanthus, Isaurus and Palythoa. They include both in the
Atlantic and in the Indo-Pacific the species Z. sociatus, Z. pacijicus, and Z.
sandwichiensis. On the Atlantic reefs also common are Polythoa
caribaeorum, Isaurus duchassainngi and I. spongiosus, while in the IndoPacific P. tuberculosa, P. caesia and P. vestitus.
The role of octocorals in the formation of coral communities on reefs is
often just as important as those of the scleractinians. By numbers of species,
cover of bottom surface and by their biomass they are comparable on many
reefs. Often the octocorals even dominate over scleractinians. They are
pioneering in the recolonization of reefs which suffered from catastrophic
events: after hurricanes, or after Acanthaster plagues (Nishihira and
Yamazato 1974; Nishihira 1981; Yoshioka and Yoshioka 1989). Octocorals
harbor many different invertebrates - commensals, symbionts, and
parasites. They are also effective producers of biologically active substanses
and calcareous material (Cary 1931; Crossland 1938; Bayer 1961; Velimirov
and King 1979). Nevertheless, in most studies on coral communities they
were most often simply ignored, apart from the fact that the description of
their fauna is rather difficult because of their insufficiently developed
257
dendrophylliids are ahermatypic (asymbiotic) except the genera Turbinaria
and Heteropsammia, which harbor algal symbionts. Large colonies of
Turbinaria could be met with usually in poorly illuminated biotopes of reef
slopes, on walls of channels and caves, on reefs with turbid waters and low
water transparency situated on coastal reefs of continental coasts. Other
hermatypic genus is Heteropsammia, which includes a single species H.
cochlea, and has, besides the zooxanthellae, another remarkable symbiont -
the sipunculid worm Aspidosiphon, which moves these small (1-3 cm) freeliving solitary corals over the sandy bottom of the lagoon or at the foot of
reef slopes (cf. Sect. 7.3). Their number in such biotopes is often extremely
high, up to hundreds m- 2 (Latypov 1985). The ahermatypic dendrophylliids
Dendrophyllia, Balanophyllia, and Tubastrea are components of the
sciophylous scleractinian fauna in poorly illuminated or even dark biotopes:
in caves, trenches, channels, and in deep zones of the reef (Sheppard 1981b;
Dinesen 1982).
7.1.2 Zoantharians and Octocorals
Zoantharians like scleractinian corals form colonies by the budding of
polyps. Most of them do not have skeletal elements. Only the genus
Palythoa forms hard massive crustose colonies of firm chitin-like material
incrusted with calcareous globules. This group of Anthosoa, though
taxonomically poor, nevertheless is very widespread in shallow reef
biotopes. They form large colonies on rubble, on rock surfaces of flats, on
dead, and even on living, colonies of corals (Goreau 1959; Herberts 1972;
Karlson 1983). The most common reef zoantharians are represented only by
three genera: Zoanthus, Isaurus and Palythoa. They include both in the
Atlantic and in the Indo-Pacific the species Z. sociatus, Z. pacijicus, and Z.
sandwichiensis. On the Atlantic reefs also common are Polythoa
caribaeorum, Isaurus duchassainngi and I. spongiosus, while in the IndoPacific P. tuberculosa, P. caesia and P. vestitus.
The role of octocorals in the formation of coral communities on reefs is
often just as important as those of the scleractinians. By numbers of species,
cover of bottom surface and by their biomass they are comparable on many
reefs. Often the octocorals even dominate over scleractinians. They are
pioneering in the recolonization of reefs which suffered from catastrophic
events: after hurricanes, or after Acanthaster plagues (Nishihira and
Yamazato 1974; Nishihira 1981; Yoshioka and Yoshioka 1989). Octocorals
harbor many different invertebrates - commensals, symbionts, and
parasites. They are also effective producers of biologically active substanses
and calcareous material (Cary 1931; Crossland 1938; Bayer 1961; Velimirov
and King 1979). Nevertheless, in most studies on coral communities they
were most often simply ignored, apart from the fact that the description of
their fauna is rather difficult because of their insufficiently developed