286
Communities of Corals in Reef Ecosystems
revealed the dominance of hermaphrodites among the corals investigated
(Stimson 1978; Connell 1978). The explanation of these facts came only in
the early 1980s when it was discovered that the viviparous corals, which
breed periodically around the year, and have several cycles of gametogenesis
during this period, are actually rarities in coral communities. On the IndoPacific reefs they comprise less than 5% of all species and in the western
Atlantic less than 10%. The rest, 90-95% of corals, appears to be spawning
hermaphrodites with external fertilization, an annual cycle of multiplication
and a very short period of spawning, which takes only 2 to 6 days (Harrison
et al. 1984; Szamant 1986). No wonder that previous researchers waiting for
the expected monthly appearance of planulae easily missed these short
periods of their annual spawning (Kojis and Quinn 1981).
It is recognized now more clearly that within the coral communities taxa
can be found at levels, of families, genera and even species, with different
types of sexual multiplication, which specifically correspond to their life
strategy.
Among the variety of members of reef coral communities, taxa can be
found with one of the following modes of sexual breeding: spawning
hermaphrodites, spawning bisexuals, vIvIparous hermaprodites and
viviparous bisexuals (Stimson 1978; Fadallah 1983; Harrison 1983, 1985;
Richmond and Jokie! 1984; Babcock 1984; Kojis and Quinn 1982, 1984,
1985; Jokiel 1985; Wyers 1985; Babcock et al. 1986; cf. Table 7.11).
According to present knowledge, some 60% of corals of the Pacific reefs are
spawning hermaphrodites with external fertilization (Harrison et al. 1984).
Among the corals of the western Atlantic reefs, they comprise slightly more
than 50% (Szamant-Froelich et al. 1984; Szamant 1986). In some corals one
further mode of multiplication was discovered - partial parthenogenesis,
when part of the oocytes does not pass through the phase of meiosis. Thus,
the developing larvae are genetic copies of the parent organism. These
planulae are born by polyps together with the normal planulae developed
after fertilization (Stoddart and Black 1985; Ayre and Reising 1986). Among
these species are Pocillopora damicornis and Tubastrea sp.
Sexual maturity in corals can be estimated by the appearance of gonads in
their polyps. It comes in most corals late - at the age of 3-5 years
(Rinkevich and Loya 1979a; Kojis and Quinn 1981, 1985; Harrison 1985).
But the main factor which controls the coming of corals to maturity is the
size of the colony, not just age, though this is also of definite importance. In
massive corals (Montastrea, Cyphastrea) the projective area at this period of
development should be 80-100 cm 2 , and in ramose corals (Acropora) the
length of the branches has to reach 1O-20cm (Szamant 1986). In
experiments, the pieces of old mature colonies of the above-mentioned
massive corals after their acclimatation and the formation of new colonies
lost the ability of sexual breeding, and gonads in their polyps disappeared.
They recover only when new colonies attain the necessary size and number
of polyps (over 30 in M. annularis).
Communities of Corals in Reef Ecosystems
revealed the dominance of hermaphrodites among the corals investigated
(Stimson 1978; Connell 1978). The explanation of these facts came only in
the early 1980s when it was discovered that the viviparous corals, which
breed periodically around the year, and have several cycles of gametogenesis
during this period, are actually rarities in coral communities. On the IndoPacific reefs they comprise less than 5% of all species and in the western
Atlantic less than 10%. The rest, 90-95% of corals, appears to be spawning
hermaphrodites with external fertilization, an annual cycle of multiplication
and a very short period of spawning, which takes only 2 to 6 days (Harrison
et al. 1984; Szamant 1986). No wonder that previous researchers waiting for
the expected monthly appearance of planulae easily missed these short
periods of their annual spawning (Kojis and Quinn 1981).
It is recognized now more clearly that within the coral communities taxa
can be found at levels, of families, genera and even species, with different
types of sexual multiplication, which specifically correspond to their life
strategy.
Among the variety of members of reef coral communities, taxa can be
found with one of the following modes of sexual breeding: spawning
hermaphrodites, spawning bisexuals, vIvIparous hermaprodites and
viviparous bisexuals (Stimson 1978; Fadallah 1983; Harrison 1983, 1985;
Richmond and Jokie! 1984; Babcock 1984; Kojis and Quinn 1982, 1984,
1985; Jokiel 1985; Wyers 1985; Babcock et al. 1986; cf. Table 7.11).
According to present knowledge, some 60% of corals of the Pacific reefs are
spawning hermaphrodites with external fertilization (Harrison et al. 1984).
Among the corals of the western Atlantic reefs, they comprise slightly more
than 50% (Szamant-Froelich et al. 1984; Szamant 1986). In some corals one
further mode of multiplication was discovered - partial parthenogenesis,
when part of the oocytes does not pass through the phase of meiosis. Thus,
the developing larvae are genetic copies of the parent organism. These
planulae are born by polyps together with the normal planulae developed
after fertilization (Stoddart and Black 1985; Ayre and Reising 1986). Among
these species are Pocillopora damicornis and Tubastrea sp.
Sexual maturity in corals can be estimated by the appearance of gonads in
their polyps. It comes in most corals late - at the age of 3-5 years
(Rinkevich and Loya 1979a; Kojis and Quinn 1981, 1985; Harrison 1985).
But the main factor which controls the coming of corals to maturity is the
size of the colony, not just age, though this is also of definite importance. In
massive corals (Montastrea, Cyphastrea) the projective area at this period of
development should be 80-100 cm 2 , and in ramose corals (Acropora) the
length of the branches has to reach 1O-20cm (Szamant 1986). In
experiments, the pieces of old mature colonies of the above-mentioned
massive corals after their acclimatation and the formation of new colonies
lost the ability of sexual breeding, and gonads in their polyps disappeared.
They recover only when new colonies attain the necessary size and number
of polyps (over 30 in M. annularis).