Reef Echinoderms
199
5.5.4 Crinoids
The reef comatulid crinoids are also a component of its biofilter. Their
numbers in biotopes of the outer slope could be very high - up to 50 sp.m- 2
(Macurda and Meyer 1977). They are free-living mainly nocturnal animals.
During daytime they hide in their refuges in trenches and in caves. At night,
crinoids crawl out and, swimming in the water column with the aid of their
mobile feathered arms, settle on some protruding element of the bottom,
like colonies of ramose coral or gorgonian, or the high sponge, selecting in
this way a position convenient for feeding by filtration. On being settled, the
crinoid spreads its arms to form the fan or the cap, oriented across the
incoming current. Some of them may turn their arms around the axis so as
to adjust their ambulacral feet in position for meeting the current. With the
aid of their arms they catch the detritus particles and plankton out from the
passing water stream. The food particles caught are then quickly transferred
along the arms to the mouth via axial ambulacral grooves (Meyer 1973b;
Zmarzly and Holland 1981; Liddell 1982). Crinoids which live in areas
where the current is weak, being unable to filter-feed, are adapted to
collecting settling suspended matter. When feeding they spread their arms
horizontally, forming a cap. The efficiency of their nocturnal feeding is
enhanced by vertical zooplankton migration at night. The same manner of
feeding is used by the stalked sessile deep-sea crinoids (Macurda and Meyer
1974). The number of arms in particular species of comatulid crinoids varies
from 10 (Comanthus, Tropiometra, Oligometra) up to 200 (Comanthus
lenneti); most of them have 20 to 40.
The number of species of crinoids in the coral-reef benthic communities
of the Caribbean reefs is only eight, while in reefs of the Indo-Pacific 280. In
particular reef areas of the Western Atlantic it is usually 4-5 species (Meyer
1973b; Macurda and Meyer 1977; Macurda 1982), on the Red Sea reefs up
to 14, and up to 25-35 species on reefs of the GBR or of the Philippines
(Marsh and Marshall 1983; Rowe et al. 1986). Most widespread are crinoids
from the genera Comanthus, Capillaster, Nemataster, Comaster, Comactima
(family Comasteridae), Lamprometra, Heterometra, Oxymetra, Decametra
Family Mariametridae), Toxometra, and Iridometra (family Antedonidae).
Thus at the western Atlantic reefs the common species are: Nemataster
rubiginosa, N. disco idea , N. grandis, Comactinia echinoidea and also Ctenatendon kinze (Meyer et al. 1978). In the Indo-Pacific they are: Lamprometra
klunzingeri, L. palmata, Oxymetra finschi, Heterometra savignyi, Capillaster
multiradiatus, Comanthus benneti, C. suavia, C. mirabilis, Tropiometra
carinata, and Oligometra sirripinna. Within the crinoid communities a
definite zonal distribution was observed (Finshelson 1974). Thus, in the Red
Sea reefs the shallow biotopes of flats are inhabited by the mass crinoids
Lampromera and Capillaster, while at the outer slope Oligometra, Comataster, and Colobometra dwell. The crinoids usually form an important
component of macrobenthos in these biotopes. Being an element of reef
199
5.5.4 Crinoids
The reef comatulid crinoids are also a component of its biofilter. Their
numbers in biotopes of the outer slope could be very high - up to 50 sp.m- 2
(Macurda and Meyer 1977). They are free-living mainly nocturnal animals.
During daytime they hide in their refuges in trenches and in caves. At night,
crinoids crawl out and, swimming in the water column with the aid of their
mobile feathered arms, settle on some protruding element of the bottom,
like colonies of ramose coral or gorgonian, or the high sponge, selecting in
this way a position convenient for feeding by filtration. On being settled, the
crinoid spreads its arms to form the fan or the cap, oriented across the
incoming current. Some of them may turn their arms around the axis so as
to adjust their ambulacral feet in position for meeting the current. With the
aid of their arms they catch the detritus particles and plankton out from the
passing water stream. The food particles caught are then quickly transferred
along the arms to the mouth via axial ambulacral grooves (Meyer 1973b;
Zmarzly and Holland 1981; Liddell 1982). Crinoids which live in areas
where the current is weak, being unable to filter-feed, are adapted to
collecting settling suspended matter. When feeding they spread their arms
horizontally, forming a cap. The efficiency of their nocturnal feeding is
enhanced by vertical zooplankton migration at night. The same manner of
feeding is used by the stalked sessile deep-sea crinoids (Macurda and Meyer
1974). The number of arms in particular species of comatulid crinoids varies
from 10 (Comanthus, Tropiometra, Oligometra) up to 200 (Comanthus
lenneti); most of them have 20 to 40.
The number of species of crinoids in the coral-reef benthic communities
of the Caribbean reefs is only eight, while in reefs of the Indo-Pacific 280. In
particular reef areas of the Western Atlantic it is usually 4-5 species (Meyer
1973b; Macurda and Meyer 1977; Macurda 1982), on the Red Sea reefs up
to 14, and up to 25-35 species on reefs of the GBR or of the Philippines
(Marsh and Marshall 1983; Rowe et al. 1986). Most widespread are crinoids
from the genera Comanthus, Capillaster, Nemataster, Comaster, Comactima
(family Comasteridae), Lamprometra, Heterometra, Oxymetra, Decametra
Family Mariametridae), Toxometra, and Iridometra (family Antedonidae).
Thus at the western Atlantic reefs the common species are: Nemataster
rubiginosa, N. disco idea , N. grandis, Comactinia echinoidea and also Ctenatendon kinze (Meyer et al. 1978). In the Indo-Pacific they are: Lamprometra
klunzingeri, L. palmata, Oxymetra finschi, Heterometra savignyi, Capillaster
multiradiatus, Comanthus benneti, C. suavia, C. mirabilis, Tropiometra
carinata, and Oligometra sirripinna. Within the crinoid communities a
definite zonal distribution was observed (Finshelson 1974). Thus, in the Red
Sea reefs the shallow biotopes of flats are inhabited by the mass crinoids
Lampromera and Capillaster, while at the outer slope Oligometra, Comataster, and Colobometra dwell. The crinoids usually form an important
component of macrobenthos in these biotopes. Being an element of reef