numerous along the coasts of central and northern Peru, mainly at Foca island in
the middle of the biogeographic transition area. It is very abundant at this locality,
covering most of the rock surfaces. To the north, where echinoderm diversity
increases, this sea urchin is rare. It is also very numerous in the bays of Sechura,
Lobos de Tierra island, Ancash (mainly Samanco) and Pucusana. This species,
which extends north to Colombia, seems to have its higher concentrations not only
in the area of its biogeographic transition but in the northern bays of the Warm
Temperate South Eastern Province. These are all closed and therefore warmer than
the surrounding oceanic waters, environments similar to that found in the transition area.
In deeper areas, usually below 10 m, the sea urchin Arbacia spatuligera
becomes abundant. It prefers organic remains of decomposing algae and deposited
organic matter as food, especially in the interface between rocks and sand bottoms
(Fig. 8.3f). It is also numerous in soft bottoms with organic matter. Loxechinus
albus becomes abundant from Paracas southwards (Fig. 8.3e). It is found mainly in
areas where kelps are present since it feeds on pieces of algae that fall to bottom
and that are picked with the tube feet. Old fishermen of the area affirm that L. albus
used to cover extended areas and gave a reddish color to the bottom where they
lived. When commercial exploitation of the species began, it became scarce in
most of its distribution area, remaining abundant only in remote localities or in
protected places, such as Punta San Juan in Marcona.
The seastar S. striatus prefers the intertidal and wave exposed well oxygenated
shallow waters, while H. helianthus and Luidia magellanica are found in deeper
waters (Fig. 8.3c). The last two species are active, voracious predators. Heliaster
helianthus is an effective biological control of turbinid snails and mussels, as well
as other small animals. Luidia magellanica may also feed on larger prey, including
A. spatuligera and T. niger. Old fishermen say T. niger was not as abundant as it is
today and that now it is out of control, covering large areas areas in some locations. In the 90s T. niger was a major prey of the wrasse Semicossiphus darwini (Y.
Hooker personal observations). This fish is now almost extinct. This may be one of
the causes of the overpopulation of the sea urchin.
Patiria chilensis, a small seastar, occurs along the entire Warm Temperate
South Eastern Province of Peruvian waters (Fig. 8.3a). The ophiuroid Ophiactis
kroeyeri, is a species that inhabits a wide diversity of habitats and depths in high
concentrations. High amounts of organic matter are required to support its vast
aggregations. It is usually found inside colonies of intertidal mussels, below rocks
with accumulations of detritus, inside the exhalant canals of large sponges, and
mainly at depths greater than 60 m because decrease oxygen reduces its abundance. North of Lima to Paita Bay (Ancash), Ophiothrix magnifica dominates
muddy bottoms. This species is a northern element of the Warm Temperate South
Eastern Province as well as the transition zone to the Tropical Province. The sea
cucumber Pseudocnus dubiosus (Fig. 8.3g) dominates muddy, hypoxic, unstable
bottoms, forming large aggregations. It is the most representative member of this
habitat.
8 Echinoderms of Peru
289
the middle of the biogeographic transition area. It is very abundant at this locality,
covering most of the rock surfaces. To the north, where echinoderm diversity
increases, this sea urchin is rare. It is also very numerous in the bays of Sechura,
Lobos de Tierra island, Ancash (mainly Samanco) and Pucusana. This species,
which extends north to Colombia, seems to have its higher concentrations not only
in the area of its biogeographic transition but in the northern bays of the Warm
Temperate South Eastern Province. These are all closed and therefore warmer than
the surrounding oceanic waters, environments similar to that found in the transition area.
In deeper areas, usually below 10 m, the sea urchin Arbacia spatuligera
becomes abundant. It prefers organic remains of decomposing algae and deposited
organic matter as food, especially in the interface between rocks and sand bottoms
(Fig. 8.3f). It is also numerous in soft bottoms with organic matter. Loxechinus
albus becomes abundant from Paracas southwards (Fig. 8.3e). It is found mainly in
areas where kelps are present since it feeds on pieces of algae that fall to bottom
and that are picked with the tube feet. Old fishermen of the area affirm that L. albus
used to cover extended areas and gave a reddish color to the bottom where they
lived. When commercial exploitation of the species began, it became scarce in
most of its distribution area, remaining abundant only in remote localities or in
protected places, such as Punta San Juan in Marcona.
The seastar S. striatus prefers the intertidal and wave exposed well oxygenated
shallow waters, while H. helianthus and Luidia magellanica are found in deeper
waters (Fig. 8.3c). The last two species are active, voracious predators. Heliaster
helianthus is an effective biological control of turbinid snails and mussels, as well
as other small animals. Luidia magellanica may also feed on larger prey, including
A. spatuligera and T. niger. Old fishermen say T. niger was not as abundant as it is
today and that now it is out of control, covering large areas areas in some locations. In the 90s T. niger was a major prey of the wrasse Semicossiphus darwini (Y.
Hooker personal observations). This fish is now almost extinct. This may be one of
the causes of the overpopulation of the sea urchin.
Patiria chilensis, a small seastar, occurs along the entire Warm Temperate
South Eastern Province of Peruvian waters (Fig. 8.3a). The ophiuroid Ophiactis
kroeyeri, is a species that inhabits a wide diversity of habitats and depths in high
concentrations. High amounts of organic matter are required to support its vast
aggregations. It is usually found inside colonies of intertidal mussels, below rocks
with accumulations of detritus, inside the exhalant canals of large sponges, and
mainly at depths greater than 60 m because decrease oxygen reduces its abundance. North of Lima to Paita Bay (Ancash), Ophiothrix magnifica dominates
muddy bottoms. This species is a northern element of the Warm Temperate South
Eastern Province as well as the transition zone to the Tropical Province. The sea
cucumber Pseudocnus dubiosus (Fig. 8.3g) dominates muddy, hypoxic, unstable
bottoms, forming large aggregations. It is the most representative member of this
habitat.
8 Echinoderms of Peru
289