because it can tolerate at least a 30 % reduction in seawater salinity for 5 days;
however it is not able to maintain large ion gradient, especially of Na
+ and Cl
- , with
respect to external seawater (Freire et al. 2011). On the other hand, L. variegatus is
able to take up Na
+ by active transport, showing selective permeability or ion
regulation, somewhat different from A. lixula. Therefore, L. variegatus was termed
as ‘‘hyper-conformer’’ and A. lixula as ‘‘iso-conformer’’ (Vidolin et al. 2007). In
situ experiments with the holothuroid H. grisea and the asteroid A. stellifera
indicated that these intertidal species may have a mechanism to detect exposure to
air, possibly reducing body wall permeability to avoid intense water loss (Vidolin
et al. 2002).
Studies on the immunological response of sea urchins have been conducted at the
University of São Paulo (e.g., Silva et al. 2001; Shimada-Borges et al. 2005),
described later in this chapter. In addition, research on the ecology and biology of
echinoderms yielded many contributions on the function of reproduction and
development (e.g., Alves et al. 2002; Carvalho and Ventura 2002; MacCord and
Ventura 2004; Tavares and Borzone 2006; Cinelli et al. 2007; Lima et al. 2009;
Vellutini and Migotto 2010; Contins and Ventura 2011). For instance, there is a
significant imbalance in sex ratio in a population of the fissiparous sea star Coscinasterias tenuispina where no females have been found (Alves et al. 2002). Although
fission occurred throughout the year, it was most frequent in the winter (July, August
and September) when the extremely low tides occur during the daytime.
Echinoderms have also been studied in Brazil in the sister-area of physiology,
biochemistry, and are also common subjects of toxicological studies in environmental agencies. The biochemistry of sulfated oligo- and polysaccharides from
echinoderms with anticoagulant and antithrombotic activities (Mourão et al. 1998)
and the reproductive features of these organic substances (e.g., Cinelli et al. 2007,
2010) have been the subject of intensive research for more than two decades at the
Federal University of Rio de Janeiro. The antithrombotic activities of a polysaccharide (a fucosylate, chondroitin-sulfate-like polysaccharide) extracted from the
body wall of the holothuroid Holothuria grisea and its chemically modified
derivatives were tested using a static thrombosis model in rabbits. The native
organic extract has an effective antithrombotic action. It prevents thrombosis
completely at a dose of 1.5 mg kg
-1 after 10 min stasis, and also, in a dosedependent manner, it reduces thrombosis. The anticoagulant or antithrombotic
effects are suppressed by partial defucosylation and desulphation of the polysaccharide (Mourão et al. 1998). The dynamic of polysaccharide sulfated presented in
the jelly egg coats of the sea urchin E. lucunter shows that: (1) a great amount of
sulfated polysaccharide is present in mature oocytes; (2) a disulfated galactans
(2, 6- disulfated galactan) is produced in the ovary firstly and (3) the 6-sulfate ester
is removed when the polysaccharide concentration increases in the egg jelly coat.
In conclusion, the ovary of E. lucunter synthesizes a specific sulfated galactan
isotype composed of two subunits (2, 6-disulfated units), but its egg jelly coat has
only 2-sulfated residues (Cinelli et al. 2010). These compounds (i.e. sulfated
polysaccharides) are important due to their species specificity in inducing the
acrosome reaction in the fertilization process.
9 Echinoderm from Brazil
309
however it is not able to maintain large ion gradient, especially of Na
+ and Cl
- , with
respect to external seawater (Freire et al. 2011). On the other hand, L. variegatus is
able to take up Na
+ by active transport, showing selective permeability or ion
regulation, somewhat different from A. lixula. Therefore, L. variegatus was termed
as ‘‘hyper-conformer’’ and A. lixula as ‘‘iso-conformer’’ (Vidolin et al. 2007). In
situ experiments with the holothuroid H. grisea and the asteroid A. stellifera
indicated that these intertidal species may have a mechanism to detect exposure to
air, possibly reducing body wall permeability to avoid intense water loss (Vidolin
et al. 2002).
Studies on the immunological response of sea urchins have been conducted at the
University of São Paulo (e.g., Silva et al. 2001; Shimada-Borges et al. 2005),
described later in this chapter. In addition, research on the ecology and biology of
echinoderms yielded many contributions on the function of reproduction and
development (e.g., Alves et al. 2002; Carvalho and Ventura 2002; MacCord and
Ventura 2004; Tavares and Borzone 2006; Cinelli et al. 2007; Lima et al. 2009;
Vellutini and Migotto 2010; Contins and Ventura 2011). For instance, there is a
significant imbalance in sex ratio in a population of the fissiparous sea star Coscinasterias tenuispina where no females have been found (Alves et al. 2002). Although
fission occurred throughout the year, it was most frequent in the winter (July, August
and September) when the extremely low tides occur during the daytime.
Echinoderms have also been studied in Brazil in the sister-area of physiology,
biochemistry, and are also common subjects of toxicological studies in environmental agencies. The biochemistry of sulfated oligo- and polysaccharides from
echinoderms with anticoagulant and antithrombotic activities (Mourão et al. 1998)
and the reproductive features of these organic substances (e.g., Cinelli et al. 2007,
2010) have been the subject of intensive research for more than two decades at the
Federal University of Rio de Janeiro. The antithrombotic activities of a polysaccharide (a fucosylate, chondroitin-sulfate-like polysaccharide) extracted from the
body wall of the holothuroid Holothuria grisea and its chemically modified
derivatives were tested using a static thrombosis model in rabbits. The native
organic extract has an effective antithrombotic action. It prevents thrombosis
completely at a dose of 1.5 mg kg
-1 after 10 min stasis, and also, in a dosedependent manner, it reduces thrombosis. The anticoagulant or antithrombotic
effects are suppressed by partial defucosylation and desulphation of the polysaccharide (Mourão et al. 1998). The dynamic of polysaccharide sulfated presented in
the jelly egg coats of the sea urchin E. lucunter shows that: (1) a great amount of
sulfated polysaccharide is present in mature oocytes; (2) a disulfated galactans
(2, 6- disulfated galactan) is produced in the ovary firstly and (3) the 6-sulfate ester
is removed when the polysaccharide concentration increases in the egg jelly coat.
In conclusion, the ovary of E. lucunter synthesizes a specific sulfated galactan
isotype composed of two subunits (2, 6-disulfated units), but its egg jelly coat has
only 2-sulfated residues (Cinelli et al. 2010). These compounds (i.e. sulfated
polysaccharides) are important due to their species specificity in inducing the
acrosome reaction in the fertilization process.
9 Echinoderm from Brazil
309