growing on steep rocky platforms, with Pocillopora species having a different
external morphology in response to the slope of the substrate and the strength of
the currents (Brando et al. 1992).
This ecosystem has 32 species (four asteroids, eight echinoids, 11 ophiuroids,
and nine holothurians). In the Gorgona reef, the area with the greatest richness of
echinoderms is the reef front with species of both intertidal and subtidal habitats.
In this ecosystem occur, from the shallow zones to the outer edge, the sea urchins
A. pulvinata, C. coronatus, D. mexicanum, E. vanbrunti and E. thouarsii, between
the coral colonies and in the cavities eroded by them at the base of coral colonies.
Toxopneustes roseus is found in the sandy patches between corals at different
depths. Under the bases of corals and rocks within the reefs are Ophioderma teres,
O. panamensis, Ophiolepis plateia, O. variegata, O. aethiops, O. alexandri,
Ophiocomella schmitti, Ophionereis annulata, and Ophiostigma tenue. Ophiactis
savigny is associated with the bivalves Pinna rugosa and Pinctada mazatlanica),
and O. spiculata is associated with the bivalve Pinna rugosa.
The Asteroidea of the reef areas are Pentaceraster cumingii and Mithrodia
bradleyi, found in the deeper parts of the reef. Cohen-Rengifo (2007) and Narváez
and Zapata (2010) have reported Acanthaster plancii from the Malpelo reefs, and
some unpublished data record it from Gorgona Island. Finally, in the reefs there
are holothurians: Holothuria (Thymiosycia) arenicola, H. (Platyperona) difficilis,
H. (Stauropora) fuscocinerea, H. (Mertensiothuria) leucospilota, H. (Thymiosycia)
impatiens, H. (Mertensiothuria) hilla, H. (Lessonothuria) pardalis, Labidodemas
maccullochi, H. (Cystipus) inhabilis and Pentamera chierchia. All these species
are found at the base of the colonies or out (at night) in the sandy patches.
Sandy Beaches
Sandy beaches of the Pacific coast of Colombia are intertidal zones formed mainly
by sediments from the discharge of rivers. These beaches have an upper area,
emerged most of the time and covered only at high tides and a lower area that
remains submerged much of the time. These beaches may consist of siliceous
materials of medium size (between 1 and 2 mm) mixed with silt and clay brought
from land or mangrove areas through runoff (Von Prahl et al. 1990). This habitat is
associated with external areas of bays which can be subject to strong wave action.
The nine species found on these beaches are irregular urchins of the family
Mellitidae. Their presence at these beaches is seasonal. Very large numbers of
individuals (between 9 and 20 m
-2 ) are found between September and November
and are almost absent at other times (Cantera 1991). The species involved are
Encope insularis and Mellita longifissa, which migrate from the sublittoral zone
(submerged up to a depth of 16 m) to the upper intertidal zone, in places where
tidal changes maintain wet conditions, such as hydraulic dunes characterized by
presence of ripple marks.
5 Echinoderms of Colombia
171
external morphology in response to the slope of the substrate and the strength of
the currents (Brando et al. 1992).
This ecosystem has 32 species (four asteroids, eight echinoids, 11 ophiuroids,
and nine holothurians). In the Gorgona reef, the area with the greatest richness of
echinoderms is the reef front with species of both intertidal and subtidal habitats.
In this ecosystem occur, from the shallow zones to the outer edge, the sea urchins
A. pulvinata, C. coronatus, D. mexicanum, E. vanbrunti and E. thouarsii, between
the coral colonies and in the cavities eroded by them at the base of coral colonies.
Toxopneustes roseus is found in the sandy patches between corals at different
depths. Under the bases of corals and rocks within the reefs are Ophioderma teres,
O. panamensis, Ophiolepis plateia, O. variegata, O. aethiops, O. alexandri,
Ophiocomella schmitti, Ophionereis annulata, and Ophiostigma tenue. Ophiactis
savigny is associated with the bivalves Pinna rugosa and Pinctada mazatlanica),
and O. spiculata is associated with the bivalve Pinna rugosa.
The Asteroidea of the reef areas are Pentaceraster cumingii and Mithrodia
bradleyi, found in the deeper parts of the reef. Cohen-Rengifo (2007) and Narváez
and Zapata (2010) have reported Acanthaster plancii from the Malpelo reefs, and
some unpublished data record it from Gorgona Island. Finally, in the reefs there
are holothurians: Holothuria (Thymiosycia) arenicola, H. (Platyperona) difficilis,
H. (Stauropora) fuscocinerea, H. (Mertensiothuria) leucospilota, H. (Thymiosycia)
impatiens, H. (Mertensiothuria) hilla, H. (Lessonothuria) pardalis, Labidodemas
maccullochi, H. (Cystipus) inhabilis and Pentamera chierchia. All these species
are found at the base of the colonies or out (at night) in the sandy patches.
Sandy Beaches
Sandy beaches of the Pacific coast of Colombia are intertidal zones formed mainly
by sediments from the discharge of rivers. These beaches have an upper area,
emerged most of the time and covered only at high tides and a lower area that
remains submerged much of the time. These beaches may consist of siliceous
materials of medium size (between 1 and 2 mm) mixed with silt and clay brought
from land or mangrove areas through runoff (Von Prahl et al. 1990). This habitat is
associated with external areas of bays which can be subject to strong wave action.
The nine species found on these beaches are irregular urchins of the family
Mellitidae. Their presence at these beaches is seasonal. Very large numbers of
individuals (between 9 and 20 m
-2 ) are found between September and November
and are almost absent at other times (Cantera 1991). The species involved are
Encope insularis and Mellita longifissa, which migrate from the sublittoral zone
(submerged up to a depth of 16 m) to the upper intertidal zone, in places where
tidal changes maintain wet conditions, such as hydraulic dunes characterized by
presence of ripple marks.
5 Echinoderms of Colombia
171