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Nutrition of Corals
Among the majority of corals groups of species could be named which
exhibit a definite preference for the use of one of the two above-mentioned
ways of feeding: the catching of prey with the aid of tentacles armed with
cnidocil, or with the aid of the mucus nets (Yonge 1930b, 1940; Lewis and
Price 1975). The first group includes some corals with small polyps, like
Pocillopora, Stylophora, and Madracis. They do not produce real mucus
nets, but excrete mucus in the form of flakes. Another group of corals,
which have small polyps with very short tentacles and flat colonies with
well-developed septae (Agaricidae), catch prey only with the use of mucus
nets. In corals of this group (Pashyseris) the tentacles are completely
dwarfed and their function in capturing preys is to take the mesenterial
filaments protruding from the mouths of polyps (Yonge 1930b). The most
numerous is the third group of corals, which use both mechanisms of
feeding. These corals are Acropora, Favia, Syderastrea, Mussa, Isophyllia,
Meandrina, Pavona, Hydnophora and many other relative taxa. Most of
them have polyps with a large oral disc and long tentacles. In active state,
their polyps completely emerge from the corallites and expand their
tentacles wide so that uder the net of the so expanded tentacles the colony
remains sometimes unseen. The mouths of polyps are semi-opened, their
rolled edges forming a "lip". From the oral disk out to the side of septae
strong ciliar currents of water pass and from the mouths the stripes of mucus
come out, forming at their ends the mucus nets. In the presence of food
objects, such as little crustaceans, the "food reaction" in their polyps
immediately sets in the polyps open their mouths, the mucus stripes are
pulled in and swallowed. The tentacles are busily moving trying to capture
the prey. The coral Montastrea has special long "sweeper" tentacles, which
energetically "pursue" the preys.
The size of preys which corals can catch and digest actually is not strictly
limited by the size of their polyps. Small polyps have several adaptations
which permit them to manage large preys. In corals with small corallites,
which have a column in the middle, the polyp's body may emerge from the
corallite completely, and so expanded it may swallow large preys. The coral
Pocillopora may swallow preys two to three times larger than its own size.
The polyps of this coral swallow sagittas 10 mm long in 30 s, their own
diameter measuring 1-1.5 mm within the corallite. Polyps of Leptastrea have
corallites 2 mm in diameter. However, in the active state they come out and
expand them 4-5 mm, being there able to swallow large pieces of meat
(Yonge 1930b). Corals in which polyps do not come out in the active state,
have as a rule a spacious corallites with reduced central column (Euphyllia,
Asteropora). Other corals have well-developed long mesenterial filaments.
With the aid of these filaments their polyps may digest large preys outside,
even without swallowing them. When the prey is caught but not yet
swallowed, being attached to the oral disk by mucus nets and by cnidae,
these filamenta, which are actually the powerful digestive organs protruding
from the polyp's mouth or through the wall of the gastral cavity, entwine the
Nutrition of Corals
Among the majority of corals groups of species could be named which
exhibit a definite preference for the use of one of the two above-mentioned
ways of feeding: the catching of prey with the aid of tentacles armed with
cnidocil, or with the aid of the mucus nets (Yonge 1930b, 1940; Lewis and
Price 1975). The first group includes some corals with small polyps, like
Pocillopora, Stylophora, and Madracis. They do not produce real mucus
nets, but excrete mucus in the form of flakes. Another group of corals,
which have small polyps with very short tentacles and flat colonies with
well-developed septae (Agaricidae), catch prey only with the use of mucus
nets. In corals of this group (Pashyseris) the tentacles are completely
dwarfed and their function in capturing preys is to take the mesenterial
filaments protruding from the mouths of polyps (Yonge 1930b). The most
numerous is the third group of corals, which use both mechanisms of
feeding. These corals are Acropora, Favia, Syderastrea, Mussa, Isophyllia,
Meandrina, Pavona, Hydnophora and many other relative taxa. Most of
them have polyps with a large oral disc and long tentacles. In active state,
their polyps completely emerge from the corallites and expand their
tentacles wide so that uder the net of the so expanded tentacles the colony
remains sometimes unseen. The mouths of polyps are semi-opened, their
rolled edges forming a "lip". From the oral disk out to the side of septae
strong ciliar currents of water pass and from the mouths the stripes of mucus
come out, forming at their ends the mucus nets. In the presence of food
objects, such as little crustaceans, the "food reaction" in their polyps
immediately sets in the polyps open their mouths, the mucus stripes are
pulled in and swallowed. The tentacles are busily moving trying to capture
the prey. The coral Montastrea has special long "sweeper" tentacles, which
energetically "pursue" the preys.
The size of preys which corals can catch and digest actually is not strictly
limited by the size of their polyps. Small polyps have several adaptations
which permit them to manage large preys. In corals with small corallites,
which have a column in the middle, the polyp's body may emerge from the
corallite completely, and so expanded it may swallow large preys. The coral
Pocillopora may swallow preys two to three times larger than its own size.
The polyps of this coral swallow sagittas 10 mm long in 30 s, their own
diameter measuring 1-1.5 mm within the corallite. Polyps of Leptastrea have
corallites 2 mm in diameter. However, in the active state they come out and
expand them 4-5 mm, being there able to swallow large pieces of meat
(Yonge 1930b). Corals in which polyps do not come out in the active state,
have as a rule a spacious corallites with reduced central column (Euphyllia,
Asteropora). Other corals have well-developed long mesenterial filaments.
With the aid of these filaments their polyps may digest large preys outside,
even without swallowing them. When the prey is caught but not yet
swallowed, being attached to the oral disk by mucus nets and by cnidae,
these filamenta, which are actually the powerful digestive organs protruding
from the polyp's mouth or through the wall of the gastral cavity, entwine the