Two hundred and forty-two species of echinoderms that are known to occur in
Galápagos and the Galápagos Ridge, including three crinoids, 67 asteroids, 82
ophiuroids, 43 echinoids, and 47 holothurians. These islands have a high percentage of endemic species relative to other offshore islands of the Central Eastern
Pacific (between 34°30
0 N and 18°00
0 S), because of the high environmental and
spatial heterogeneity of the archipelago, due to its geographic location (Maluf
1988a, 1991). Seventeen percent of echinoderm species in Galápagos (a total of 34
species) are endemic, particularly the asteroids and ophiuroids.
Of these species, 27 species inhabit deep waters between 105 and 925 m (See
Appendix), and 107 inhabit depths between 20 and 100 m (30 species of asteroids,
46 species of ophiuroids, and 31 species of echinoids). Deep sea urchins, such as
Plagiobrissus pacificus, Brissopsis pacifica and Idiobryssus coelus have been
recorded. For intertidal and shallow water environments (\20 m depth), 14 species
of asteroids, 28 species of ophiuroids, 25 species of echinoids, and 17 species of
holothuroids have been reported. Hickman (1998) and Chiriboga et al. (2011)
prepared a list with the most common species of echinoderms along the intertidal
and shallow waters around the Galápagos. Among the holothuroids are Holothuria
arenicola, H. impatiens, H. imitans and H. theeli, and Isostichopus fuscus. The
latter species is common in the cold western region of Galápagos (Fig. 6.3a).
Among the echinoids are Eucidaris galapagensis (Fig. 6.3b), Lytechinus semituberculatus (Fig. 6.3c), Tripneustes depressus (Fig. 6.3d), Diadema mexicanum
(Fig. 6.3e), Toxopneustes roseus (Fig. 6.3f), Astropyga pulvinata (Fig. 6.3g),
Agassizia scrobiculata, and Clypeaster rotundus. Eucidaris galapagensis was
formerly identified as E. thouarsii, but new genetic evidence recognized it as a
species endemic to the Galápagos Islands, Cocos Islands and Clipperton Atoll
(Lessios et al. 1999). Among the asteroids are Pharia pyramidata (Fig. 6.3h),
Phataria unifascialis (Fig. 6.3i–j), Nidorellia armata (Fig. 6.3k), Pentaceraster
cumingi (Fig. 6.3l), and Mithrodia bradleyi (Fig. 6.4a) are the most common,
while Astropecten armatus (Fig. 6.4b), Leiaster teres (Fig. 6.4c), Heliaster cumingi (Fig. 6.4d), and Heliaster solaris are rare. Among the ophiuroids are Ophiactis savignyi, Ophiocoma aethiops, O. alexandri, and Ophioderma teres.
The distribution and diversity of echinoderms in the Galápagos Islands differs
greatly among biogeographic regions (Maluf 1991). Edgar et al. (2004) proposed a
bio-regionalization scheme of five regions within the Galápagos, based on the
scheme proposed by Harris (1969) using a data set from communities and species
richness of reef fish and macro-invertebrates. These bioregions are the ‘Farnorthern’, ‘Northern’, ‘Southeastern’, ‘Western’ and ‘Elizabeth’ (Fig. 6.2). These
authors emphasized that both faunal abundance and species richness indicate that
Galápagos inshore reef ecosystems are divisible into three major regional components: (1) the far-northern islands of Darwin and Wolf; (2) the central, southern
and eastern islands, including the east coast of Isabela; and (3) Fernandina and
western Isabela. Concerning the echinoderm fauna, the following patterns were
identified:
192
J. Sonnenholzner et al.
Galápagos and the Galápagos Ridge, including three crinoids, 67 asteroids, 82
ophiuroids, 43 echinoids, and 47 holothurians. These islands have a high percentage of endemic species relative to other offshore islands of the Central Eastern
Pacific (between 34°30
0 N and 18°00
0 S), because of the high environmental and
spatial heterogeneity of the archipelago, due to its geographic location (Maluf
1988a, 1991). Seventeen percent of echinoderm species in Galápagos (a total of 34
species) are endemic, particularly the asteroids and ophiuroids.
Of these species, 27 species inhabit deep waters between 105 and 925 m (See
Appendix), and 107 inhabit depths between 20 and 100 m (30 species of asteroids,
46 species of ophiuroids, and 31 species of echinoids). Deep sea urchins, such as
Plagiobrissus pacificus, Brissopsis pacifica and Idiobryssus coelus have been
recorded. For intertidal and shallow water environments (\20 m depth), 14 species
of asteroids, 28 species of ophiuroids, 25 species of echinoids, and 17 species of
holothuroids have been reported. Hickman (1998) and Chiriboga et al. (2011)
prepared a list with the most common species of echinoderms along the intertidal
and shallow waters around the Galápagos. Among the holothuroids are Holothuria
arenicola, H. impatiens, H. imitans and H. theeli, and Isostichopus fuscus. The
latter species is common in the cold western region of Galápagos (Fig. 6.3a).
Among the echinoids are Eucidaris galapagensis (Fig. 6.3b), Lytechinus semituberculatus (Fig. 6.3c), Tripneustes depressus (Fig. 6.3d), Diadema mexicanum
(Fig. 6.3e), Toxopneustes roseus (Fig. 6.3f), Astropyga pulvinata (Fig. 6.3g),
Agassizia scrobiculata, and Clypeaster rotundus. Eucidaris galapagensis was
formerly identified as E. thouarsii, but new genetic evidence recognized it as a
species endemic to the Galápagos Islands, Cocos Islands and Clipperton Atoll
(Lessios et al. 1999). Among the asteroids are Pharia pyramidata (Fig. 6.3h),
Phataria unifascialis (Fig. 6.3i–j), Nidorellia armata (Fig. 6.3k), Pentaceraster
cumingi (Fig. 6.3l), and Mithrodia bradleyi (Fig. 6.4a) are the most common,
while Astropecten armatus (Fig. 6.4b), Leiaster teres (Fig. 6.4c), Heliaster cumingi (Fig. 6.4d), and Heliaster solaris are rare. Among the ophiuroids are Ophiactis savignyi, Ophiocoma aethiops, O. alexandri, and Ophioderma teres.
The distribution and diversity of echinoderms in the Galápagos Islands differs
greatly among biogeographic regions (Maluf 1991). Edgar et al. (2004) proposed a
bio-regionalization scheme of five regions within the Galápagos, based on the
scheme proposed by Harris (1969) using a data set from communities and species
richness of reef fish and macro-invertebrates. These bioregions are the ‘Farnorthern’, ‘Northern’, ‘Southeastern’, ‘Western’ and ‘Elizabeth’ (Fig. 6.2). These
authors emphasized that both faunal abundance and species richness indicate that
Galápagos inshore reef ecosystems are divisible into three major regional components: (1) the far-northern islands of Darwin and Wolf; (2) the central, southern
and eastern islands, including the east coast of Isabela; and (3) Fernandina and
western Isabela. Concerning the echinoderm fauna, the following patterns were
identified:
192
J. Sonnenholzner et al.