distributed in seven orders and 14 families), and Holothuroidea (73 species,
distributed in six orders and 16 families). Only 17 species are found in the
Temperate South Eastern Province, 64 in the Tropical Eastern Pacific, four are
found in both provinces. Seventy eight are deep water species. That means that
20 % of the 84 shallow water species are temperate, 75 % are tropical and 5 % are
both temperate and tropical.
When dealing with biogeography and the distribution of Peruvian echinoderms,
it is very important to use information gathered in normal oceanographic years.
This is because many tropical species widen their geographical distribution
southward in El Niño years (every 7–12 years). The species that extend their
distribution in El Niño years do so only temporarily, generally for less than
2 years, disappearing later from the colonized area. Our information has been
gathered during several years of observations and collections in about 20 localities
on the Peruvian coast.
8.3.1 Temperate South Eastern Pacific
South of Punta Aguja, around the Illescas Peninsula (6°S), shallow water echinoderm
richness is low, with most species belonging to the Warm Temperate South Eastern
Province and endemic to the Peru Current. In this area no differences in species
composition are found in the intertidal zone and abundance variations are not
significant. However, in the sublittoral zone differences do appear in the distribution
of some species, especially those that are mainly Chilean.
Species representative of the rocky intertidal and upper sublittoral are Stichaster
striatus (Fig. 8.3b), Heliaster helianthus (Fig. 8.3d), Tetrapygus niger and Pattalus
mollis. It is common to find juveniles of T. niger in rocky walls exposed to wave
action feeding on calcareous crustose algae. P. mollis occurs inside mussel
colonies. They use their tentacles to capture juvenile mussels, small crustaceans,
and snails detached from their colonies by wave action (Fig. 8.3h). The seastars
S. striatus and H. helianthus feed in the intertidal below the mussel belt where they
are not exposed to air during extended periods of low tide. The brittle star Ophiactis
kroeyeri lives inside mussel colonies by the thousands. A study carried out in Santa
Island, Ancash (Hooker et al. 2011) found an average of 27,000 ind m
-2 inside the
mussel colonies.
The representative species in the sandy intertidal and upper sublittoral is
Athyonidium chilensis. It lives buried in sand. It has a U-shaped body. The tentacles extend out on the sand and the cloaca shows just at the sediment surface.
This species feeds on suspended material from the water column.
In shallow subtidal waters the widely dominant species are the sea urchins
T. niger and Caenocentrus gibbosus (Fig. 8.4b) and Lytechinus semituberculatus
(Fig. 8.5c). Along the Peruvian central coast both species are equally abundant.
Tetrapigyus niger lives in shallower waters, usually over 5 m in depth, while
C. gibbosus is abundant from less than 1 m to about 10 m in depth. This species is
8 Echinoderms of Peru
285
distributed in six orders and 16 families). Only 17 species are found in the
Temperate South Eastern Province, 64 in the Tropical Eastern Pacific, four are
found in both provinces. Seventy eight are deep water species. That means that
20 % of the 84 shallow water species are temperate, 75 % are tropical and 5 % are
both temperate and tropical.
When dealing with biogeography and the distribution of Peruvian echinoderms,
it is very important to use information gathered in normal oceanographic years.
This is because many tropical species widen their geographical distribution
southward in El Niño years (every 7–12 years). The species that extend their
distribution in El Niño years do so only temporarily, generally for less than
2 years, disappearing later from the colonized area. Our information has been
gathered during several years of observations and collections in about 20 localities
on the Peruvian coast.
8.3.1 Temperate South Eastern Pacific
South of Punta Aguja, around the Illescas Peninsula (6°S), shallow water echinoderm
richness is low, with most species belonging to the Warm Temperate South Eastern
Province and endemic to the Peru Current. In this area no differences in species
composition are found in the intertidal zone and abundance variations are not
significant. However, in the sublittoral zone differences do appear in the distribution
of some species, especially those that are mainly Chilean.
Species representative of the rocky intertidal and upper sublittoral are Stichaster
striatus (Fig. 8.3b), Heliaster helianthus (Fig. 8.3d), Tetrapygus niger and Pattalus
mollis. It is common to find juveniles of T. niger in rocky walls exposed to wave
action feeding on calcareous crustose algae. P. mollis occurs inside mussel
colonies. They use their tentacles to capture juvenile mussels, small crustaceans,
and snails detached from their colonies by wave action (Fig. 8.3h). The seastars
S. striatus and H. helianthus feed in the intertidal below the mussel belt where they
are not exposed to air during extended periods of low tide. The brittle star Ophiactis
kroeyeri lives inside mussel colonies by the thousands. A study carried out in Santa
Island, Ancash (Hooker et al. 2011) found an average of 27,000 ind m
-2 inside the
mussel colonies.
The representative species in the sandy intertidal and upper sublittoral is
Athyonidium chilensis. It lives buried in sand. It has a U-shaped body. The tentacles extend out on the sand and the cloaca shows just at the sediment surface.
This species feeds on suspended material from the water column.
In shallow subtidal waters the widely dominant species are the sea urchins
T. niger and Caenocentrus gibbosus (Fig. 8.4b) and Lytechinus semituberculatus
(Fig. 8.5c). Along the Peruvian central coast both species are equally abundant.
Tetrapigyus niger lives in shallower waters, usually over 5 m in depth, while
C. gibbosus is abundant from less than 1 m to about 10 m in depth. This species is
8 Echinoderms of Peru
285