Herrera (1974) evaluated the distribution and ion flow in cells of the intestine and
stomach muscle of I. badionotus. They found that potassium concentration in
intestinal cells was 240 l-equiv g
-1 cell and 252 l-equiv g
-1 cell in those of the
stomach; sodium was 246 and 296 l-equiv g
-1 cell, while chloride was 223 and
302 l-equiv g
-1 cell, respectively. In muscle cells, potassium, sodium and chloride concentrations were 348, 119 and 127 l-equiv g
-1 cell, respectively. Madrid
et al. (1976) found that intracellular ionic concentrations increase in direct relation
to the concentration of the external environment and the ionic concentrations of
the coelomic liquid of I. badionotus equilibrates with 80 and 120 % sea water
between 4 and 6 h.
Studies made by Herrera and Plaza (1981a, b), Jurisic (1982), Herrera and
López (1983), Jurisic et al. (1983), Sambrano et al. (1990), Conde et al. (1991),
Egea et al. (1991), Herrera (1991), Foglietta (1994), Foglietta and Herrera (1996),
Herrera and Foglietta (1998) and Herrera et al. (2000) focused their research on the
ion-osmotic response of the respiratory structures of I. badionotus and Holothuria
glaberrima. Herrera and Plaza (1981b), found that the respiratory tree and muscles
of H. glaberrima respire at a rate of 635.5 ± 10 l l O 2 /h 9 g dw and 137.4 ± 6.3
l l O 2 /h 9 g dw, respectively, in response to the concentration of sodium in
artificial sea water. They indicate that the substitution of sodium by chlorine,
lithium or Tris (pH 8.0) does not modify the oxygen consumption of the respiratory trees structures. The low respiratory rate of muscles could be due to limitations of oxygen diffusion in the tissue. Metabolic conditions could be involved in
the respiratory response of tissues to pH. Herrera and López (1983) evaluated the
effect of sodium concentration in the external medium and the intracellular
osmotic condition of the respiratory tree of H. glaberrima. They subjected the cells
of the respiratory trees to sodium concentrations reduced isosmotically (60, 30, 15,
6 and 0 % of normal sea water). The analyses showed an increasing loss of
sodium, potassium and chloride while maintaining the cytoplasm isosmotic with
the external medium. This indicates that the maintenance of isosmoticity with the
external medium assures the constancy of intracellular volume. The intracellular
concentration of potassium was regulated within relatively narrow limits in spite of
the changes in cell volume. In sea water with 6 and 30 % sodium, intracellular
sodium concentration changed only by 1.5 times which suggests a certain degree
of regulation. Herrera and Foglietta (1998) evaluated the effect of ouabain (which
blocks the Na–K pump) on the ion-osmotic properties of cells of the respiratory
trees of I. badionotus. Individuals were exposed to five concentrations of sea
water: 17.5, 21.0, 26.25, 35.0 and 42 % in the presence or absence of ouabain.
They found that control and ouabain-treated cells responded as perfect osmometers
to variations in sea water concentration implying that intracellular organic
osmolyte content also remained unchanged despite changes in sea water concentration. In order to test if cells of marine stenohaline invertebrates can increase in
volume, Herrera et al. (2000) evaluated the effect of five different solutions of
artificial sea water with isosmotic sodium and KCl (100, 83, 71, 60 and 50 %),
with and without ouabain, in fragments of the respiratory tree of I. badionotus.
They found immobilization of extracellular sodium, depolarization of the
7 Echinoderms from Venezuela
245
stomach muscle of I. badionotus. They found that potassium concentration in
intestinal cells was 240 l-equiv g
-1 cell and 252 l-equiv g
-1 cell in those of the
stomach; sodium was 246 and 296 l-equiv g
-1 cell, while chloride was 223 and
302 l-equiv g
-1 cell, respectively. In muscle cells, potassium, sodium and chloride concentrations were 348, 119 and 127 l-equiv g
-1 cell, respectively. Madrid
et al. (1976) found that intracellular ionic concentrations increase in direct relation
to the concentration of the external environment and the ionic concentrations of
the coelomic liquid of I. badionotus equilibrates with 80 and 120 % sea water
between 4 and 6 h.
Studies made by Herrera and Plaza (1981a, b), Jurisic (1982), Herrera and
López (1983), Jurisic et al. (1983), Sambrano et al. (1990), Conde et al. (1991),
Egea et al. (1991), Herrera (1991), Foglietta (1994), Foglietta and Herrera (1996),
Herrera and Foglietta (1998) and Herrera et al. (2000) focused their research on the
ion-osmotic response of the respiratory structures of I. badionotus and Holothuria
glaberrima. Herrera and Plaza (1981b), found that the respiratory tree and muscles
of H. glaberrima respire at a rate of 635.5 ± 10 l l O 2 /h 9 g dw and 137.4 ± 6.3
l l O 2 /h 9 g dw, respectively, in response to the concentration of sodium in
artificial sea water. They indicate that the substitution of sodium by chlorine,
lithium or Tris (pH 8.0) does not modify the oxygen consumption of the respiratory trees structures. The low respiratory rate of muscles could be due to limitations of oxygen diffusion in the tissue. Metabolic conditions could be involved in
the respiratory response of tissues to pH. Herrera and López (1983) evaluated the
effect of sodium concentration in the external medium and the intracellular
osmotic condition of the respiratory tree of H. glaberrima. They subjected the cells
of the respiratory trees to sodium concentrations reduced isosmotically (60, 30, 15,
6 and 0 % of normal sea water). The analyses showed an increasing loss of
sodium, potassium and chloride while maintaining the cytoplasm isosmotic with
the external medium. This indicates that the maintenance of isosmoticity with the
external medium assures the constancy of intracellular volume. The intracellular
concentration of potassium was regulated within relatively narrow limits in spite of
the changes in cell volume. In sea water with 6 and 30 % sodium, intracellular
sodium concentration changed only by 1.5 times which suggests a certain degree
of regulation. Herrera and Foglietta (1998) evaluated the effect of ouabain (which
blocks the Na–K pump) on the ion-osmotic properties of cells of the respiratory
trees of I. badionotus. Individuals were exposed to five concentrations of sea
water: 17.5, 21.0, 26.25, 35.0 and 42 % in the presence or absence of ouabain.
They found that control and ouabain-treated cells responded as perfect osmometers
to variations in sea water concentration implying that intracellular organic
osmolyte content also remained unchanged despite changes in sea water concentration. In order to test if cells of marine stenohaline invertebrates can increase in
volume, Herrera et al. (2000) evaluated the effect of five different solutions of
artificial sea water with isosmotic sodium and KCl (100, 83, 71, 60 and 50 %),
with and without ouabain, in fragments of the respiratory tree of I. badionotus.
They found immobilization of extracellular sodium, depolarization of the
7 Echinoderms from Venezuela
245