Venezuela. He found that, in general, male:female sex ratio does not deviate
significantly from 1:1 and there were 2 % hermaphrodites. Sexual maturity was
reached at a horizontal diameter above 147 mm (55 g). Individuals with mature
gametes were found during the entire year, which suggests that reproduction is
continuous, although with a greater synchrony in spawning during the period from
September to November when water masses stratify and temperature is higher.
Fecundity is high, with an average number of eggs per individual of 1,417,330 (SD
151,186), but sometimes exceeded 5 million eggs.
7.2.4 Bioerosion and Herbivory
With respect to bioerosion by echinoderms, Weil (1980) evaluated the impact of
D. antillarum on coral reefs at Mochima National Park and Díaz et al. (1982) and
González (2005) evaluated it in Los Roques Archipelago. Losada et al. (1988)
manipulated densities of D. antillarum in the intake channel of Planta Centro
thermal electric plant, located at Punta Morón-Golfo Triste, and reported a significant increment of bare substrate by grazing at densities that varied from
0.170 ind m
-2 and bare space of 102.6 cm
2 to more than 1,000 cm
2 bare space
when the density reached 0.310 ind m
-2 .
Another aspect, though less known, is the effect of grazing by echinoids as
biocontrol agents. Lodeiros and García (2004) described for the first time in the
Gulf of Cariaco, Sucre state, L. variegatus and E. lucunter as control agents of
fouling in culture baskets and bivalve shells in suspended cultivation systems.
L. variegatus produced a 75 % decrease in the fouling of the culture baskets and
71 % that of the shells of Pinctada imbricata, suggesting the usefulness of this
method as a natural control of fouling in these systems.
7.2.5 Physiology and Biochemistry
There are few physiological studies of echinoderms in Venezuela. Studies with
holothurians have focused mainly on the ion-osmotic response to a great variety of
chemical compounds. The first studies were initiated in the 1970s by Zanders
(1970), Madrid (1971), Zanders and Herrera (1974) and Madrid et al. (1976), who
evaluated the effect of the salinity change of sea water upon the coelomic and
intracellular ionic composition of I. badionotus. Zanders (1970) studied the
histology, ionic composition and permeability to sodium of the intestine of
I. badionotus. The results showed that the organisms is isosmotic to sea water, but
levels of different ions in the tissues could differ from the latter, like potassium
which reaches intracellular concentrations 10–30 times higher than in the external
environment. Tissue water represents 80–90 % of the wet weight of the intestine
and 60–80 % of the tissue water corresponds to extracellular liquid. Zanders and
244
C. Lodeiros et al.
significantly from 1:1 and there were 2 % hermaphrodites. Sexual maturity was
reached at a horizontal diameter above 147 mm (55 g). Individuals with mature
gametes were found during the entire year, which suggests that reproduction is
continuous, although with a greater synchrony in spawning during the period from
September to November when water masses stratify and temperature is higher.
Fecundity is high, with an average number of eggs per individual of 1,417,330 (SD
151,186), but sometimes exceeded 5 million eggs.
7.2.4 Bioerosion and Herbivory
With respect to bioerosion by echinoderms, Weil (1980) evaluated the impact of
D. antillarum on coral reefs at Mochima National Park and Díaz et al. (1982) and
González (2005) evaluated it in Los Roques Archipelago. Losada et al. (1988)
manipulated densities of D. antillarum in the intake channel of Planta Centro
thermal electric plant, located at Punta Morón-Golfo Triste, and reported a significant increment of bare substrate by grazing at densities that varied from
0.170 ind m
-2 and bare space of 102.6 cm
2 to more than 1,000 cm
2 bare space
when the density reached 0.310 ind m
-2 .
Another aspect, though less known, is the effect of grazing by echinoids as
biocontrol agents. Lodeiros and García (2004) described for the first time in the
Gulf of Cariaco, Sucre state, L. variegatus and E. lucunter as control agents of
fouling in culture baskets and bivalve shells in suspended cultivation systems.
L. variegatus produced a 75 % decrease in the fouling of the culture baskets and
71 % that of the shells of Pinctada imbricata, suggesting the usefulness of this
method as a natural control of fouling in these systems.
7.2.5 Physiology and Biochemistry
There are few physiological studies of echinoderms in Venezuela. Studies with
holothurians have focused mainly on the ion-osmotic response to a great variety of
chemical compounds. The first studies were initiated in the 1970s by Zanders
(1970), Madrid (1971), Zanders and Herrera (1974) and Madrid et al. (1976), who
evaluated the effect of the salinity change of sea water upon the coelomic and
intracellular ionic composition of I. badionotus. Zanders (1970) studied the
histology, ionic composition and permeability to sodium of the intestine of
I. badionotus. The results showed that the organisms is isosmotic to sea water, but
levels of different ions in the tissues could differ from the latter, like potassium
which reaches intracellular concentrations 10–30 times higher than in the external
environment. Tissue water represents 80–90 % of the wet weight of the intestine
and 60–80 % of the tissue water corresponds to extracellular liquid. Zanders and
244
C. Lodeiros et al.