192
Reef Zoobenthos
The real crabs Brachyura are the most important crustacean group in the
reef macrobenthos. It lists several tens of genera and hundreds of species.
Most of them are free-living crabs. They inhabit biotopes of sand and
rubble, reef shallows, sandy and rock littoral zones, criptofaunal habitats in
trenches and in holes of lime rocks (Taylor and Lewis 1970; Serene 1972;
Thomassin 1974; Tsareva 1980; Peyrot-Clausade 1981; Jones 1984). Many
brachyuran crabs are commensals, parasites, or symbionts of corals and
other benthic animals. The most numerous among them are the Xanthidae.
This family lists over a hundred species of reef crabs, which live mostly in
cavities and trenches of reef flats, being one of the main components of the
cryptofauna. Xanthid crabs feed on periphyton, on detritus and on
meiobenthos. The common xanthid genera are: Actaea, Paractaea, Eriphia,
Leptodius, Euxanthus, Dairia, A tergatus , Pilumnus, Cymo, Chlorodiella,
Domecia, Liomera, Caprilius, Xanthias. The common commensal xanthids
belong to the genera Trapezia, Tetralia, and Phymodius.
The spider crabs from the family Majidae inhabit mostly biotopes of flats
and outer slope. Their common genera are: Camposcia, Micippa, Tiarina,
Huenia, Oncinopus, and Hyastenus. They have a round spiny carapace
camouflaged with pieces of sponges or with seaweeds. The same is done by
crabs from the family Dromiidae. Their hind legs are modified, being
adapted to preserving permanently the camouflage - with the colony of
sponges or ascidians on their backs. The family of Portunidae includes the
large swimming crabs, which are common in reef shallow biotopes. Most
usual among them belong to the genera Portunus, Thalamita, Thalamitoides,
and Lissocarcinus. Several species of small portunid crabs are the
commensals of holothurians and alcyonaceans. The large grapsid crabs
(family Grapsidae) and the box crabs from the family Calappidae (genera
Calappa and Matuta) are predators and feed mainly on gastropeds. The
former live under stones on reef flats, while the second prefers sand
shallows, digging in during the daytime (Gibbs 1978). The same habit have
the pebble crabs Phylura (family Lencosiidae). In the upper littoral zone the
ghost crabs (family Ocypode) are usually numerous. They are voracious
predators hunting at night on fish and shrimps and even on newly hatched
young turtles. They can run at high speed and on being persued - instantly
disappear, digging into the sand. Other reef crabs from the families
Hapalocarcinidae, Eumedonidae, and Pinnotheridae are mostly commensals
of larger benthic animals.
5.4.2 Symbiosis in Reef Crustaceans
As it was pointed out above, many crustaceans are commensals or
symbionts of various reef animals. The same crustaceans are the main
infaunal symbionts and parasites of corals (Mc Closkey 1970; Patton 1976;
Bruce 1976; Naumov et al. 1980; Odinetz and de Forges 1985). In fact, each
Reef Zoobenthos
The real crabs Brachyura are the most important crustacean group in the
reef macrobenthos. It lists several tens of genera and hundreds of species.
Most of them are free-living crabs. They inhabit biotopes of sand and
rubble, reef shallows, sandy and rock littoral zones, criptofaunal habitats in
trenches and in holes of lime rocks (Taylor and Lewis 1970; Serene 1972;
Thomassin 1974; Tsareva 1980; Peyrot-Clausade 1981; Jones 1984). Many
brachyuran crabs are commensals, parasites, or symbionts of corals and
other benthic animals. The most numerous among them are the Xanthidae.
This family lists over a hundred species of reef crabs, which live mostly in
cavities and trenches of reef flats, being one of the main components of the
cryptofauna. Xanthid crabs feed on periphyton, on detritus and on
meiobenthos. The common xanthid genera are: Actaea, Paractaea, Eriphia,
Leptodius, Euxanthus, Dairia, A tergatus , Pilumnus, Cymo, Chlorodiella,
Domecia, Liomera, Caprilius, Xanthias. The common commensal xanthids
belong to the genera Trapezia, Tetralia, and Phymodius.
The spider crabs from the family Majidae inhabit mostly biotopes of flats
and outer slope. Their common genera are: Camposcia, Micippa, Tiarina,
Huenia, Oncinopus, and Hyastenus. They have a round spiny carapace
camouflaged with pieces of sponges or with seaweeds. The same is done by
crabs from the family Dromiidae. Their hind legs are modified, being
adapted to preserving permanently the camouflage - with the colony of
sponges or ascidians on their backs. The family of Portunidae includes the
large swimming crabs, which are common in reef shallow biotopes. Most
usual among them belong to the genera Portunus, Thalamita, Thalamitoides,
and Lissocarcinus. Several species of small portunid crabs are the
commensals of holothurians and alcyonaceans. The large grapsid crabs
(family Grapsidae) and the box crabs from the family Calappidae (genera
Calappa and Matuta) are predators and feed mainly on gastropeds. The
former live under stones on reef flats, while the second prefers sand
shallows, digging in during the daytime (Gibbs 1978). The same habit have
the pebble crabs Phylura (family Lencosiidae). In the upper littoral zone the
ghost crabs (family Ocypode) are usually numerous. They are voracious
predators hunting at night on fish and shrimps and even on newly hatched
young turtles. They can run at high speed and on being persued - instantly
disappear, digging into the sand. Other reef crabs from the families
Hapalocarcinidae, Eumedonidae, and Pinnotheridae are mostly commensals
of larger benthic animals.
5.4.2 Symbiosis in Reef Crustaceans
As it was pointed out above, many crustaceans are commensals or
symbionts of various reef animals. The same crustaceans are the main
infaunal symbionts and parasites of corals (Mc Closkey 1970; Patton 1976;
Bruce 1976; Naumov et al. 1980; Odinetz and de Forges 1985). In fact, each