Reef Echinoderms
197
5.5.2 Sea Stars
The fauna of reef sea stars lists over 250 species. Within a particular reef
system 5 to 20 species could be found (Marsh 1974; Clark 1976). The most
common reef asteroids belong to the family Oreasteridae (Budin 1980;
Marsh and Marshall 1983). Among them are the blue star Linkea laevigata,
the small motile Linkea multiflora, the large (over 30cm) massive stars
Culcita coricca, C. schmideliana, C. novaeguineae, the large stars Pentaceraster gracilis, P. regulus and P. australis, and related to this genus,
the spiny large stars Protoreaster nodulosus and P. lincki. Some common
oreasterid stars belong to the families Ophidiaster, Oreaster, Nardoa,
Fromia, and Leiaster. The common asteroids Echinaster, Methrodia,
Valvaster, Asterina, Luidia, Astropecten, Arhaster and well-known corallopage Acanthaster belong to several families of the order Spinulosida.
Most sea stars inhabit the hard bottom biotopes of reef flats, sublittoral
and patch reefs. Some (Oreaster) prefer the lower zones of the outer reef
slope (Budin 1980). Small stars could be found in cryptofaunal habitats
(Ophidiaster gran dis , Asterina burtoni, Diasterina leptalacantha). The
massive large star Culcita lives on sandy shallows on the flat and in the
patch-reef areas, covered with seaweeds and sea grasses.
Most stars are omnivores. When feeding, the star crawls up to the food
object and extrudes its stomach and turns it inside out. The sessile organisms
attached to the ground the star then envelops with its stomach and digests
them on the spot (Thomassin 1976). Detritus and vagile benthic animals,
forams, and gastropods the star also captures with its stomach, takes in it
the food back to its place and digests it while it moves to a new feeding
place. The stars Pteraster and Asterina are predators. They feed on sponges,
hydroids, and ascidians. The star Culcita, being omnivorous, feeds also on
corals prefering young colonies of species with large polyps. The damage
done to corals by this star on some reefs of the Western Pacific can be quite
noticeable (Endean 1971; Goreau et al. 1972). The specialized corallovorous
star Acanthaster planci feeds only on corals. This large asteroid, called also
the "crown of thorns", is armed with long poisonous thorns. These form
large aggregations and cause drastic damage to the reefs. The problem of
Acanthaster will be discussed elsewhere (d. Sect. 11.1). The stars
themselves, and especially their small-sized species, as well as their egg
layings, larvae and young, are important sources of feeding for many fish,
crabs and predatory gastropods.
5.5.3 Brittle Stars
The reef brittle stars, ophiuroids, are nocturnal animals. In the daytime they
are hiding in their refuges: under the stones in trenches or in seagrasses.
Their number in some reef biotopes attains 50 to 70 sp. m- 2 (Finshelson
197
5.5.2 Sea Stars
The fauna of reef sea stars lists over 250 species. Within a particular reef
system 5 to 20 species could be found (Marsh 1974; Clark 1976). The most
common reef asteroids belong to the family Oreasteridae (Budin 1980;
Marsh and Marshall 1983). Among them are the blue star Linkea laevigata,
the small motile Linkea multiflora, the large (over 30cm) massive stars
Culcita coricca, C. schmideliana, C. novaeguineae, the large stars Pentaceraster gracilis, P. regulus and P. australis, and related to this genus,
the spiny large stars Protoreaster nodulosus and P. lincki. Some common
oreasterid stars belong to the families Ophidiaster, Oreaster, Nardoa,
Fromia, and Leiaster. The common asteroids Echinaster, Methrodia,
Valvaster, Asterina, Luidia, Astropecten, Arhaster and well-known corallopage Acanthaster belong to several families of the order Spinulosida.
Most sea stars inhabit the hard bottom biotopes of reef flats, sublittoral
and patch reefs. Some (Oreaster) prefer the lower zones of the outer reef
slope (Budin 1980). Small stars could be found in cryptofaunal habitats
(Ophidiaster gran dis , Asterina burtoni, Diasterina leptalacantha). The
massive large star Culcita lives on sandy shallows on the flat and in the
patch-reef areas, covered with seaweeds and sea grasses.
Most stars are omnivores. When feeding, the star crawls up to the food
object and extrudes its stomach and turns it inside out. The sessile organisms
attached to the ground the star then envelops with its stomach and digests
them on the spot (Thomassin 1976). Detritus and vagile benthic animals,
forams, and gastropods the star also captures with its stomach, takes in it
the food back to its place and digests it while it moves to a new feeding
place. The stars Pteraster and Asterina are predators. They feed on sponges,
hydroids, and ascidians. The star Culcita, being omnivorous, feeds also on
corals prefering young colonies of species with large polyps. The damage
done to corals by this star on some reefs of the Western Pacific can be quite
noticeable (Endean 1971; Goreau et al. 1972). The specialized corallovorous
star Acanthaster planci feeds only on corals. This large asteroid, called also
the "crown of thorns", is armed with long poisonous thorns. These form
large aggregations and cause drastic damage to the reefs. The problem of
Acanthaster will be discussed elsewhere (d. Sect. 11.1). The stars
themselves, and especially their small-sized species, as well as their egg
layings, larvae and young, are important sources of feeding for many fish,
crabs and predatory gastropods.
5.5.3 Brittle Stars
The reef brittle stars, ophiuroids, are nocturnal animals. In the daytime they
are hiding in their refuges: under the stones in trenches or in seagrasses.
Their number in some reef biotopes attains 50 to 70 sp. m- 2 (Finshelson