sp. (11 %) and Navicula sp. (9 %), and low percentages of other species of
microalgae. A variety of microorganisms, such as foraminifera and tintinnids
(0.7 %), as well as abundant detritus was found. Isostichopus fuscus is mostly
active at night (Hickman 1998; Hearn and Pinillos 2006).
Stichopus horrens
Distribution and Density
Stichopus horrens (Fig. 6.4i) is a large holothurian that can grow to a length of
50 cm (Schoppe 2000). The largest specimen from Galápagos was collected in the
western region with a length of 42 cm (Hearn and Pinillos 2006). This species is
found in shallow waters at depths between 5 and 20 m, mostly occurs on rocky
reef substrates in the central and southern region of Galápagos (Edgar et al.
2002b). Stichopus horrens tends to contract to less than half its length during its
cryptic behavior during the day. It emerges around dusk to form aggregations with
densities exceeding 1–2 ind m
-2 (Hearn and Pinillos 2006).
Growth and Reproduction
Throughout the Galápagos Islands, the population structure of Stichopus horrens
has a uni-modal length frequency distribution ranging from 14 to 42 cm. The mean
length of individuals was around 28 cm at most islands, although smaller individuals occur at Rábida (22 cm) and Wolf (24 cm). No individuals smaller than
12 cm in length were recorded. Nothing is known about the larval biology and
recruitment of this species. Hearn and Pinillos (2006) made preliminary estimates
of the Von Bertalanffy population parameters using size frequency distributions
(L? = 38.8 cm, K = 0.17), which indicated that an individual of 20 cm in length
would correspond to an age of 4 years. Stichopus horrens reproduces asexually by
fission (Kohtsuka et al. 2005), as well as sexually. Hearn and Pinillos (2006) found
individuals greater than 16 cm in length were mature. Fecundity was estimated to
vary greatly between 1 9 10
3 and 1 9 10
6 eggs per individual.
Holothuria theeli
Distribution and Density
Sonnenholzner and Lawrence (2002) and Sonnenholzner (2003) evaluated the
distribution and density by microhabitat preference of Holothuria theeli along the
continental coast of Ecuador. The maximum density was at the lowest tidal level
and there was a progressive decrease in abundance with depth. It was observed on
exposed surfaces at low tide, suggesting a resistance to desiccation. The capacity
to withstand and exploit air-exposed areas during the tidal cycle has been observed
in other species such as Stichopus badionotus (Sloan and Von Bodungen1980),
198
J. Sonnenholzner et al.
microalgae. A variety of microorganisms, such as foraminifera and tintinnids
(0.7 %), as well as abundant detritus was found. Isostichopus fuscus is mostly
active at night (Hickman 1998; Hearn and Pinillos 2006).
Stichopus horrens
Distribution and Density
Stichopus horrens (Fig. 6.4i) is a large holothurian that can grow to a length of
50 cm (Schoppe 2000). The largest specimen from Galápagos was collected in the
western region with a length of 42 cm (Hearn and Pinillos 2006). This species is
found in shallow waters at depths between 5 and 20 m, mostly occurs on rocky
reef substrates in the central and southern region of Galápagos (Edgar et al.
2002b). Stichopus horrens tends to contract to less than half its length during its
cryptic behavior during the day. It emerges around dusk to form aggregations with
densities exceeding 1–2 ind m
-2 (Hearn and Pinillos 2006).
Growth and Reproduction
Throughout the Galápagos Islands, the population structure of Stichopus horrens
has a uni-modal length frequency distribution ranging from 14 to 42 cm. The mean
length of individuals was around 28 cm at most islands, although smaller individuals occur at Rábida (22 cm) and Wolf (24 cm). No individuals smaller than
12 cm in length were recorded. Nothing is known about the larval biology and
recruitment of this species. Hearn and Pinillos (2006) made preliminary estimates
of the Von Bertalanffy population parameters using size frequency distributions
(L? = 38.8 cm, K = 0.17), which indicated that an individual of 20 cm in length
would correspond to an age of 4 years. Stichopus horrens reproduces asexually by
fission (Kohtsuka et al. 2005), as well as sexually. Hearn and Pinillos (2006) found
individuals greater than 16 cm in length were mature. Fecundity was estimated to
vary greatly between 1 9 10
3 and 1 9 10
6 eggs per individual.
Holothuria theeli
Distribution and Density
Sonnenholzner and Lawrence (2002) and Sonnenholzner (2003) evaluated the
distribution and density by microhabitat preference of Holothuria theeli along the
continental coast of Ecuador. The maximum density was at the lowest tidal level
and there was a progressive decrease in abundance with depth. It was observed on
exposed surfaces at low tide, suggesting a resistance to desiccation. The capacity
to withstand and exploit air-exposed areas during the tidal cycle has been observed
in other species such as Stichopus badionotus (Sloan and Von Bodungen1980),
198
J. Sonnenholzner et al.