194
Reef Zoobenthos
forms a chamber. The crab Cryptocherius makes "homes" in the colonies of
massive corals. His larva kills polyps on settling in a coral colony and the
coral stops growing in this spot. Then gradually, while it grows, a hole forms
here, in which the adult crab will live as in a refuge.
The density of infaunal communities in corals appears to be dependent
upon the abundance of plankton in the reef waters (Abele 1979; Kropp and
Birkeland 1981). It is larger on the barrier reefs than in atoll-dwelling corals.
It might depend also upon the rate of sedimentation, because the suspended
matter settling on corals stimulate the production of mucus, which is a main
food source of the infaunal crustaceans (Odinetz and de Forges 1985).
The biomass of infauna in hard ramose corals attains 5 to 15 g per 1 kg dry
weight of the coral colony (Shirayama and Horikoshi 1982). The bulk of it
compose the boring bivalves and sponges (up to 70%), while 20-50%
comprise the infaunal crustaceans, and 10-20% the polychaetes. The total
number of infaunal organisms in ramose corals collected at the fringing reefs
off Guam Island was found to be 50 to 300 sp. kg- l of coral colony. In an
average coral colony (volume 0.5-3 dm 3 ) the number of specialized infaunal
animals, according to Krasnov et al. (1982), varied within 5-30 sp. per
colony, and their biomass within 0.5-4.5 g. Shannon's index (H') in the
infaunal communities is within same values as found in free-living benthic
fauna: 1.5-2.5. The taxonomic composition of the fauna in different species
of corals is varied, even if the shape of their colonies appears to be similar
(Naumov et al. 1980). But after the coral colony dies, its specialized infauna
is gradually replaced by the opportunistic cryptofaunal species (Coles 1980).
Crustaceans live as symbionts or commensals with many other animals,
exept corals. The crab Anchistus custos is the symbiont of large bivalves. He
cleans their gills scraping off the pseudofeces and feeding on them. The
shrimps Alpheus, Hyppolite, Pericliclimenes, and Pontonia live with
sponges, hydroids, ascidians and even with nudibranchs (Periclimenes
imperator). Several species of the shrimps Periclimenes, Pedersonia, as well
as the shrimps Hyppolyzmata grahami, H. californica, Stenopus hispida are
known as the cleaning symbiomts of fish and actinians (Limbaugh et al.
1961; Bruce 1976).
The rich fauna of benthic crustaceans is an important source of feeding
for reef fish (Vivien 1973; Thomassin 1974). Of great importance as food
source for various reef animals, including corals, are also their pelagic larval
and young stages (d. Sect. 9.2.1).
5.5 Reef Echinoderms
The communities of benthic echinoderms include the sea stars, the brittle
stars (ophiuroides), the feathered stars (crinoids), and the sea cucumbers
Reef Zoobenthos
forms a chamber. The crab Cryptocherius makes "homes" in the colonies of
massive corals. His larva kills polyps on settling in a coral colony and the
coral stops growing in this spot. Then gradually, while it grows, a hole forms
here, in which the adult crab will live as in a refuge.
The density of infaunal communities in corals appears to be dependent
upon the abundance of plankton in the reef waters (Abele 1979; Kropp and
Birkeland 1981). It is larger on the barrier reefs than in atoll-dwelling corals.
It might depend also upon the rate of sedimentation, because the suspended
matter settling on corals stimulate the production of mucus, which is a main
food source of the infaunal crustaceans (Odinetz and de Forges 1985).
The biomass of infauna in hard ramose corals attains 5 to 15 g per 1 kg dry
weight of the coral colony (Shirayama and Horikoshi 1982). The bulk of it
compose the boring bivalves and sponges (up to 70%), while 20-50%
comprise the infaunal crustaceans, and 10-20% the polychaetes. The total
number of infaunal organisms in ramose corals collected at the fringing reefs
off Guam Island was found to be 50 to 300 sp. kg- l of coral colony. In an
average coral colony (volume 0.5-3 dm 3 ) the number of specialized infaunal
animals, according to Krasnov et al. (1982), varied within 5-30 sp. per
colony, and their biomass within 0.5-4.5 g. Shannon's index (H') in the
infaunal communities is within same values as found in free-living benthic
fauna: 1.5-2.5. The taxonomic composition of the fauna in different species
of corals is varied, even if the shape of their colonies appears to be similar
(Naumov et al. 1980). But after the coral colony dies, its specialized infauna
is gradually replaced by the opportunistic cryptofaunal species (Coles 1980).
Crustaceans live as symbionts or commensals with many other animals,
exept corals. The crab Anchistus custos is the symbiont of large bivalves. He
cleans their gills scraping off the pseudofeces and feeding on them. The
shrimps Alpheus, Hyppolite, Pericliclimenes, and Pontonia live with
sponges, hydroids, ascidians and even with nudibranchs (Periclimenes
imperator). Several species of the shrimps Periclimenes, Pedersonia, as well
as the shrimps Hyppolyzmata grahami, H. californica, Stenopus hispida are
known as the cleaning symbiomts of fish and actinians (Limbaugh et al.
1961; Bruce 1976).
The rich fauna of benthic crustaceans is an important source of feeding
for reef fish (Vivien 1973; Thomassin 1974). Of great importance as food
source for various reef animals, including corals, are also their pelagic larval
and young stages (d. Sect. 9.2.1).
5.5 Reef Echinoderms
The communities of benthic echinoderms include the sea stars, the brittle
stars (ophiuroides), the feathered stars (crinoids), and the sea cucumbers