membrane, an osmometric increase of the cells and a decrease of potassium,
sodium and chloride when the cells were treated with the same dilutions of sea
water with distilled water. Jurisic et al. (1983) studied the role of chloride in the
intracellular isosmotic regulation in cells of the respiratory tree of H. glaberrima
exposed to different concentrations of chloride (100, 60 and 24 % of normal),
finding a small decrease in the intracellular potassium content. However, as a
consequence of the 50 % reduction in cell volume, the intracellular concentration
of potassium increased approximately by twofold, while that of sodium decreased
considerably. Respiratory rate of tissues increased with the reduction of external
chloride, which reveals an increase in the metabolic work needed for the sodium
and potassium pump against the ever increasing electrolytic gradient of these ions.
Foglietta (1994) studied the ion-osmotic response to changes in salinity of the
external medium in I. badionotus pre-incubated in 57, 100 and 137 % sea water
and the effect of ouabain in pre-incubated individuals at 100 % sea water. She
found an inverse linear relationship between the relative intracellular space to
incubation concentrations. These results indicate that cells show perfect osmometric behavior. On the other hand, the intracellular concentration of K
+ remained
unchanged, that of Na
+ decreased with external salinity, and that of Cl
- decreased
slightly when incubated above and below 83 % sea water and ouabaine.
Foglietta and Herrera (1996) performed studies similar to those of Foglietta
(1994), without the use of ouabain. They evaluated the ion-osmotic response of the
respiratory tree of I. badionotus pre-incubated in hyper-, iso- and hypo-osmotic sea
water. The cells and tissues of individuals pre-incubated in 20 and 48 % sea water
responded in a similar way to those pre-incubated in 35 % sea water. The intracellular content of potassium was well regulated, remaining constant in spite of
changes in sea water concentration; that of sodium decreased with extracellular
concentration, while that of chloride increased in concentrations above and below
of 29 %. I. badionotus seemed to be more tolerant to hyposaline than to hypersaline sea water, which suggests that normal sea water represents the upper limit of
its salinity range. The osmotic condition of the cell and the response of the tissue
do not seem to be modified by the variation in the concentration of the means in
which it was pre-incubated.
In contrast to the studies just described, Conde et al. (1991) evaluated the
patterns of disintegration of fecal material of H. mexicana and I. badionotus. In
I. badionotus, the feces completely disintegrate around 8 h, suggesting a high
probability of dispersion in comparison with feces of H. mexicana which remain
on the substrate even after 25 h. The authors suggest that bacterial activity and
fungal growth are responsible for the disintegration of the fecal material of
I. badionotus, while the disintegration of the feces of H. mexicana is associated
with the activity of motile marine organisms.
There are few studies at the biochemical level. Urbaneja (1968) determined
steroidal and lipid contents in the sea star Echinaster sentus. Cedeño (1971)
identified the fatty acids of the holothurian, Ludwigothuria mexicana. Salazar et al.
(1994) made histochemical studies of cells of the echinoids, L. variegatus and
E. lucunter. Malavé (1995) characterized and quantified the lipid and fatty acid
246
C. Lodeiros et al.
sodium and chloride when the cells were treated with the same dilutions of sea
water with distilled water. Jurisic et al. (1983) studied the role of chloride in the
intracellular isosmotic regulation in cells of the respiratory tree of H. glaberrima
exposed to different concentrations of chloride (100, 60 and 24 % of normal),
finding a small decrease in the intracellular potassium content. However, as a
consequence of the 50 % reduction in cell volume, the intracellular concentration
of potassium increased approximately by twofold, while that of sodium decreased
considerably. Respiratory rate of tissues increased with the reduction of external
chloride, which reveals an increase in the metabolic work needed for the sodium
and potassium pump against the ever increasing electrolytic gradient of these ions.
Foglietta (1994) studied the ion-osmotic response to changes in salinity of the
external medium in I. badionotus pre-incubated in 57, 100 and 137 % sea water
and the effect of ouabain in pre-incubated individuals at 100 % sea water. She
found an inverse linear relationship between the relative intracellular space to
incubation concentrations. These results indicate that cells show perfect osmometric behavior. On the other hand, the intracellular concentration of K
+ remained
unchanged, that of Na
+ decreased with external salinity, and that of Cl
- decreased
slightly when incubated above and below 83 % sea water and ouabaine.
Foglietta and Herrera (1996) performed studies similar to those of Foglietta
(1994), without the use of ouabain. They evaluated the ion-osmotic response of the
respiratory tree of I. badionotus pre-incubated in hyper-, iso- and hypo-osmotic sea
water. The cells and tissues of individuals pre-incubated in 20 and 48 % sea water
responded in a similar way to those pre-incubated in 35 % sea water. The intracellular content of potassium was well regulated, remaining constant in spite of
changes in sea water concentration; that of sodium decreased with extracellular
concentration, while that of chloride increased in concentrations above and below
of 29 %. I. badionotus seemed to be more tolerant to hyposaline than to hypersaline sea water, which suggests that normal sea water represents the upper limit of
its salinity range. The osmotic condition of the cell and the response of the tissue
do not seem to be modified by the variation in the concentration of the means in
which it was pre-incubated.
In contrast to the studies just described, Conde et al. (1991) evaluated the
patterns of disintegration of fecal material of H. mexicana and I. badionotus. In
I. badionotus, the feces completely disintegrate around 8 h, suggesting a high
probability of dispersion in comparison with feces of H. mexicana which remain
on the substrate even after 25 h. The authors suggest that bacterial activity and
fungal growth are responsible for the disintegration of the fecal material of
I. badionotus, while the disintegration of the feces of H. mexicana is associated
with the activity of motile marine organisms.
There are few studies at the biochemical level. Urbaneja (1968) determined
steroidal and lipid contents in the sea star Echinaster sentus. Cedeño (1971)
identified the fatty acids of the holothurian, Ludwigothuria mexicana. Salazar et al.
(1994) made histochemical studies of cells of the echinoids, L. variegatus and
E. lucunter. Malavé (1995) characterized and quantified the lipid and fatty acid
246
C. Lodeiros et al.