demipyramids of a lantern of sea urchins increase their capacity to feed.
Nonetheless, Lawrence et al. (2010) determined that the Aristotle’s lantern of sea
urchins can show an allometric relation with body size and that it varies intra- and
inter-specifically. The reasons for this have not been well established, but these
results should be considered for well-focused ecological studies along the
Galápagos Islands, concerning growth and reproduction of this abundant species.
Because ingestion is the largest term in the balanced growth equation, the feeding
apparatus of animals is of particular interest in scaling (Peters 1983).
Diet and Feeding Habits
Hickman (1998) reported L. semituberculatus feeds on algae and debris in the
Galápagos Islands. It is commonly covered by pieces of seaweed or shells, which
would probably be a protection from ultraviolet radiation (UVR). In this sense,
Sharp and Gray (1962) provided some of the first evidence that artificial UVR can
induce covering in L. variegatus.
Tripneustes depressus
Distribution and Density
Idrovo and Sonnenholzner (1994) studied the distribution and abundance of
T. depressus (Fig. 6.3d) at Punta Los Frailes, Machalilla National Park (Fig. 6.1)
along the coast of mainland Ecuador. This species had an aggregated distribution
(Morisita index 2.9–1.6), with a density between 1.5 and 1.8 ind m
-2 .
Luna (2000) conducted density surveys of T. depressus at 35 sites around the
Galápagos Islands from 1996 to 1997. Density fluctuated from 0 to 1.5 ind m
-2
with an average value of 0.3 ± 0.4 ind m
-2 . Higher densities were found in the
central region of Galápagos: Rocas Gordon (1.5 ind m
-2 ), Caleta Bucanero
(1.2 ind m
-2 ) and Cabo Marshall (0.8 ind m
-2 ), whereas consistent lower densities (mostly no individuals) were found in the western islands (Cabo Berkeley,
Bahía Urbina, Bahía Elizabeth, Punta Moreno, Cabo Rosa, Punta Espinoza and
Cabo Douglas), with the exception of Caleta Iguana which had densities of
0.2 ind m
-2 . Luna (2000) also conducted monthly surveys (from October 1996 to
April 1997) at one site, Playa Ratonera, Santa Cruz Island. The density of
T. depressus decreased from 0.5 to 0.1 ind m
-2 over this period.
To understand spatial and temporal patterns of abundance of T. depressus,
Guarderas (2000) conducted monthly population surveys (from September 1998 to
September 1999) in intertidal and subtidal habitats in Santa Cruz Island. In this
study, this species had an aggregated distribution (the ratio variance to average
was higher than 1) with high temporal and spatial variation in abundance within
sites. Populations in subtidal sites had higher densities and were more stable and
more spatially homogenous than in intertidal sites, although there were no statistical differences among habitats. On average, El Barranco had significantly
6 Echinoderms of Ecuador
203
Nonetheless, Lawrence et al. (2010) determined that the Aristotle’s lantern of sea
urchins can show an allometric relation with body size and that it varies intra- and
inter-specifically. The reasons for this have not been well established, but these
results should be considered for well-focused ecological studies along the
Galápagos Islands, concerning growth and reproduction of this abundant species.
Because ingestion is the largest term in the balanced growth equation, the feeding
apparatus of animals is of particular interest in scaling (Peters 1983).
Diet and Feeding Habits
Hickman (1998) reported L. semituberculatus feeds on algae and debris in the
Galápagos Islands. It is commonly covered by pieces of seaweed or shells, which
would probably be a protection from ultraviolet radiation (UVR). In this sense,
Sharp and Gray (1962) provided some of the first evidence that artificial UVR can
induce covering in L. variegatus.
Tripneustes depressus
Distribution and Density
Idrovo and Sonnenholzner (1994) studied the distribution and abundance of
T. depressus (Fig. 6.3d) at Punta Los Frailes, Machalilla National Park (Fig. 6.1)
along the coast of mainland Ecuador. This species had an aggregated distribution
(Morisita index 2.9–1.6), with a density between 1.5 and 1.8 ind m
-2 .
Luna (2000) conducted density surveys of T. depressus at 35 sites around the
Galápagos Islands from 1996 to 1997. Density fluctuated from 0 to 1.5 ind m
-2
with an average value of 0.3 ± 0.4 ind m
-2 . Higher densities were found in the
central region of Galápagos: Rocas Gordon (1.5 ind m
-2 ), Caleta Bucanero
(1.2 ind m
-2 ) and Cabo Marshall (0.8 ind m
-2 ), whereas consistent lower densities (mostly no individuals) were found in the western islands (Cabo Berkeley,
Bahía Urbina, Bahía Elizabeth, Punta Moreno, Cabo Rosa, Punta Espinoza and
Cabo Douglas), with the exception of Caleta Iguana which had densities of
0.2 ind m
-2 . Luna (2000) also conducted monthly surveys (from October 1996 to
April 1997) at one site, Playa Ratonera, Santa Cruz Island. The density of
T. depressus decreased from 0.5 to 0.1 ind m
-2 over this period.
To understand spatial and temporal patterns of abundance of T. depressus,
Guarderas (2000) conducted monthly population surveys (from September 1998 to
September 1999) in intertidal and subtidal habitats in Santa Cruz Island. In this
study, this species had an aggregated distribution (the ratio variance to average
was higher than 1) with high temporal and spatial variation in abundance within
sites. Populations in subtidal sites had higher densities and were more stable and
more spatially homogenous than in intertidal sites, although there were no statistical differences among habitats. On average, El Barranco had significantly
6 Echinoderms of Ecuador
203