6.3.2 Immune Response
Sea Urchins
It is well known that high temperatures have caused a widespread mortality of key
species, coral bleaching in many regions of the world, a decrease in number,
density and biomass of species with high immigration of predators and a decrease
in number of grazers (Epstein et al. 1998). Considering the ecological role of sea
urchins as key species in shallow coastal and marine rocky environments, and the
paucity of knowledge of their immune response during strong natural disturbances,
Sonnenholzner (2001) documented in detail the immune response of the sea urchin
E. vanbrunti during El Niño episode of 1997–1998 and the cold phase La Niña of
1999–2000. He made observations under laboratory (in vitro) and natural conditions (in vivo, where specimens were collected along a gradient of intertidal rocky
pools at Anconcito, Santa Elena, see Fig. 6.1). Four coelomocyte types were
identified in the perivisceral coelom of E. vanbrunti: (1) the phagocytic
amoebocytes, which were the only phagocytic cells studied in this experiments
(Fig. 6.5a, b); (2) spherule cells, divided into colorless (with intense amoeboid
movements, and colorless cytoplasmic granules, see Fig. 6.5c), and red cells
(similar to colorless spherules, but with red granules, see Fig. 6.5c); and vibratile
cells (flagellated and small rounded cells, see Fig. 6.5d). The effect of three different temperatures: 19 ± 1 °C (low); 24 ± 1 °C (medium); and 29 ± 1 °C
(high) on the immune response of E. vanbrunti was evaluated using the perivisceral coelom fluid and four immune assays: (1) antibacterial activity from the
plasma (clearance efficiency); (2) total hemocytes count (THC); (3) differential
hemocytes count (DHC); and (4) microbicidal activity (oxidative activity by
nitroblue tetrazolium reduction related to phagocytosis generated by stimulated
phagocytes in phorbol 12-myristate 13-acetate) (Sonnenholzner 2001). Both hemograms (THC and DHC) were useful assays related to the microbicidal activity.
At the high temperature in the laboratory conditions and during the mid phase of
the El Niño 1997–1998 warming event, four remarkable aspects of the phagocytes
were observed in natural conditions: (1) phagocytes were very motile cells and
spread rapidly, accompanied by a complete change in morphology (Fig. 6.5a, b);
(2) the aggregation-clotting process was accelerated (1.0 ± 0.5 min) at high
temperature conditions ([24 °C); (3) the oxidative activity increased (‘‘respiratory
burst’’); and (4) production of spheres-cellular masses with formation of microvilli
(Fig. 6.5b). A significant difference in clearance efficiency was observed with
different temperatures. This study showed that hemograms (DHC and THC),
clearance efficiency, and phagocytosis are reduced in E. vanbrunti at high temperature conditions. These data are important because they provide baseline values
for tropical echinoid species in their natural environments that are affected by
strong environmental stress episodes. Thus, it is an excellent opportunity for study
and verifying through these immune indicators the health condition of this
potential bioindicator (as E. vanbrunti). Nonetheless, these findings indicate that
208
J. Sonnenholzner et al.
Sea Urchins
It is well known that high temperatures have caused a widespread mortality of key
species, coral bleaching in many regions of the world, a decrease in number,
density and biomass of species with high immigration of predators and a decrease
in number of grazers (Epstein et al. 1998). Considering the ecological role of sea
urchins as key species in shallow coastal and marine rocky environments, and the
paucity of knowledge of their immune response during strong natural disturbances,
Sonnenholzner (2001) documented in detail the immune response of the sea urchin
E. vanbrunti during El Niño episode of 1997–1998 and the cold phase La Niña of
1999–2000. He made observations under laboratory (in vitro) and natural conditions (in vivo, where specimens were collected along a gradient of intertidal rocky
pools at Anconcito, Santa Elena, see Fig. 6.1). Four coelomocyte types were
identified in the perivisceral coelom of E. vanbrunti: (1) the phagocytic
amoebocytes, which were the only phagocytic cells studied in this experiments
(Fig. 6.5a, b); (2) spherule cells, divided into colorless (with intense amoeboid
movements, and colorless cytoplasmic granules, see Fig. 6.5c), and red cells
(similar to colorless spherules, but with red granules, see Fig. 6.5c); and vibratile
cells (flagellated and small rounded cells, see Fig. 6.5d). The effect of three different temperatures: 19 ± 1 °C (low); 24 ± 1 °C (medium); and 29 ± 1 °C
(high) on the immune response of E. vanbrunti was evaluated using the perivisceral coelom fluid and four immune assays: (1) antibacterial activity from the
plasma (clearance efficiency); (2) total hemocytes count (THC); (3) differential
hemocytes count (DHC); and (4) microbicidal activity (oxidative activity by
nitroblue tetrazolium reduction related to phagocytosis generated by stimulated
phagocytes in phorbol 12-myristate 13-acetate) (Sonnenholzner 2001). Both hemograms (THC and DHC) were useful assays related to the microbicidal activity.
At the high temperature in the laboratory conditions and during the mid phase of
the El Niño 1997–1998 warming event, four remarkable aspects of the phagocytes
were observed in natural conditions: (1) phagocytes were very motile cells and
spread rapidly, accompanied by a complete change in morphology (Fig. 6.5a, b);
(2) the aggregation-clotting process was accelerated (1.0 ± 0.5 min) at high
temperature conditions ([24 °C); (3) the oxidative activity increased (‘‘respiratory
burst’’); and (4) production of spheres-cellular masses with formation of microvilli
(Fig. 6.5b). A significant difference in clearance efficiency was observed with
different temperatures. This study showed that hemograms (DHC and THC),
clearance efficiency, and phagocytosis are reduced in E. vanbrunti at high temperature conditions. These data are important because they provide baseline values
for tropical echinoid species in their natural environments that are affected by
strong environmental stress episodes. Thus, it is an excellent opportunity for study
and verifying through these immune indicators the health condition of this
potential bioindicator (as E. vanbrunti). Nonetheless, these findings indicate that
208
J. Sonnenholzner et al.