324
Morphology and Ecological Physiology of Corals
valuable, medicinal raw material, which is why their main predator in the
near future will be man himself.
The hermatypic scleractinian corals permanently excrete large amounts of
mucus. This excretion might account for over 20% of their total
photosynthetic production. The mucus is excreted also by zoantharians
(Daumas and Thomassin 1977). Less is known about this function in
octocorals. There were opinions that they do not secrete it at all (Lewis
1982). But we have observed some alcyonacean octocorals (Sarcophyton)
using the fine mucus filaments to catch their zooplankton prey (d. Sect.
9.2.2). The formation of mucus has been recorded also in the octocoral
Biareum (Rublee et al. 1980).
Scleractinian corals excrete mucus in the state of a transparent fluid
(Hubbard and Pocock 1972; Schuhmacher 1979; Coffroth 1985). On the
surface of the colony the mucus denaturates and hardens, forming a thin
cover around it (Lewis 1973; Ducklow and Mitchell 1979b). These mucus
covers, which are quickly overgrown by microflora and powdered with the
settling suspended matter, are soon shed by the coral, cleaning so its
surface. The production of mucus by corals increases when they are
damaged or stressed by heating, pollution or siltation (Bak and Elgershulzen
1976; Thompson et al. 1980), exposure, draining or by drops of salinity
(Sumner et al. 1975; Daumas and Thomassin 1977). The mucus covers
preserve corals from microbial fouling, draining and overheating, when they
are exposed. The production of mucus was evaluated as being 2-6mgday-1
of dry weight per colony of 2-3 dm 3 volume (Richman et al. 1975). With
50% cover of the bottom surface by corals these excrete some
50mgm- 2 day-1 of ash-free organic matter as mucus. R. Johannes (1967)
evaluated the excretion rate of mucus by corals at the reef flat of the atoll
Enivetok as 20mgm- 2 dry weight day-I. The most intensive release of
mucus was recorded in acroporids. The coral Acropora acuminata produces
over 300 J.Lg C of mucus per 1 mg of protein of its tissue. Thus this coral
excretes during the day about 30-40% of its total net photosynthetic
production (Crossland et al. 1980). The content of ash in mucus is rather
high - 50-70% dry weight. The caloric equivalent of mucus is 3-5calmg- 1
of dry, ash-free matter (Richman et al. 1975). The mucus contains a
significant amount of protein, so the C/N ratio in it is low: 4-7 (Coles and
Strathmann 1973; Richman et al. 1975). The basic components of mucus are
the mucopolysaccharides (40-50% dry weight), the lipids cetylpalmitates
and triglycerides (30-40%), and proteins and amino acids (10%). The
mucopolysaccharides provide the hydrophilic properties of mucus and are
composed of amino sugar polymers. The amino acids of mucus are
dominated by glycine and alanine. Proteins, peptides, and lipids form in
mucus the glycoprotein and lypoprotein complexes which compose its
structural basis (Benson and Muscatine 1974; Sumner et al. 1975; Daumas
and Thomassin 1977; Corssland et al. 1980). The most important structural
polymer among them is proteoglycan, which has in its complexes the sulfo-
Morphology and Ecological Physiology of Corals
valuable, medicinal raw material, which is why their main predator in the
near future will be man himself.
The hermatypic scleractinian corals permanently excrete large amounts of
mucus. This excretion might account for over 20% of their total
photosynthetic production. The mucus is excreted also by zoantharians
(Daumas and Thomassin 1977). Less is known about this function in
octocorals. There were opinions that they do not secrete it at all (Lewis
1982). But we have observed some alcyonacean octocorals (Sarcophyton)
using the fine mucus filaments to catch their zooplankton prey (d. Sect.
9.2.2). The formation of mucus has been recorded also in the octocoral
Biareum (Rublee et al. 1980).
Scleractinian corals excrete mucus in the state of a transparent fluid
(Hubbard and Pocock 1972; Schuhmacher 1979; Coffroth 1985). On the
surface of the colony the mucus denaturates and hardens, forming a thin
cover around it (Lewis 1973; Ducklow and Mitchell 1979b). These mucus
covers, which are quickly overgrown by microflora and powdered with the
settling suspended matter, are soon shed by the coral, cleaning so its
surface. The production of mucus by corals increases when they are
damaged or stressed by heating, pollution or siltation (Bak and Elgershulzen
1976; Thompson et al. 1980), exposure, draining or by drops of salinity
(Sumner et al. 1975; Daumas and Thomassin 1977). The mucus covers
preserve corals from microbial fouling, draining and overheating, when they
are exposed. The production of mucus was evaluated as being 2-6mgday-1
of dry weight per colony of 2-3 dm 3 volume (Richman et al. 1975). With
50% cover of the bottom surface by corals these excrete some
50mgm- 2 day-1 of ash-free organic matter as mucus. R. Johannes (1967)
evaluated the excretion rate of mucus by corals at the reef flat of the atoll
Enivetok as 20mgm- 2 dry weight day-I. The most intensive release of
mucus was recorded in acroporids. The coral Acropora acuminata produces
over 300 J.Lg C of mucus per 1 mg of protein of its tissue. Thus this coral
excretes during the day about 30-40% of its total net photosynthetic
production (Crossland et al. 1980). The content of ash in mucus is rather
high - 50-70% dry weight. The caloric equivalent of mucus is 3-5calmg- 1
of dry, ash-free matter (Richman et al. 1975). The mucus contains a
significant amount of protein, so the C/N ratio in it is low: 4-7 (Coles and
Strathmann 1973; Richman et al. 1975). The basic components of mucus are
the mucopolysaccharides (40-50% dry weight), the lipids cetylpalmitates
and triglycerides (30-40%), and proteins and amino acids (10%). The
mucopolysaccharides provide the hydrophilic properties of mucus and are
composed of amino sugar polymers. The amino acids of mucus are
dominated by glycine and alanine. Proteins, peptides, and lipids form in
mucus the glycoprotein and lypoprotein complexes which compose its
structural basis (Benson and Muscatine 1974; Sumner et al. 1975; Daumas
and Thomassin 1977; Corssland et al. 1980). The most important structural
polymer among them is proteoglycan, which has in its complexes the sulfo-