**10. Toxin-induced damage of target organs and tissues**

depicts colocalization of fluorescent signals.

Figure 8: Cypermethrin (1.5 ppm/ 7 days globosa. a Control 1.5 ppm/ days) induced histopathological damage of heart of mollusc, 4× b 4× Treated For filter feeding aquatic organisms, the gill, heart, digestive gland, mantle and antennae act as major target organs of common environmental xenobiotics (Figure 8). Mollusca bear a welldeveloped gill which serves as an organ of gaseous exchange, filter feeding and immunosur‐ veillance. Molluscan gill is a thin membranous and vascularized organ that is in continuous contact with the environmental toxicants distributed in water. During the process of respira‐ tion and filter feeding, gill is exposed to various toxins of known and unknown chemistry. Exposure of gill to aquatic sodium arsenite, pyrethroid pesticide and washing soda of pond water yields a structural damage of lamellae. Chakraborty et al. (2010a) reported hyperchro‐ matic anaplastic cells in the gills of *L. marginalis* exposed to sublethal concentrations of arsenic [33]. This is often associated with tissue rupture and formation of dense fibrosis. The heart, in general, acts as an organ of body fluid pumping. Exposure of cypermethrin results in severe histopathological damage of heart of mollusc. Similar kind of morphological damage was recorded due to exposure of aquatic mollusc to washing soda, a common pollutant of pond water. Digestive gland of mollusc bears immense physiological significance. The organ acts as an important site of diverse metabolic activities and biochemical detoxification. Exposure of sodium arsenite yields histopathological damage of the digestive gland of *L. marginalis* [34]. Toxin-induced morphological alteration of digestive gland of mollusc includes hyperinfiltra‐ tion of haemocytes, vacuolation and inflammatory lysis.

of hemocytes of pond B. bengalensis

1000×

FITC and propidium iodide (c)

damage mollusc, P.

and (b)

P. globosa.

invertebrates.

induced morphological alteration of digestive gland of mollusc includes hyperinfiltration of

Figure 9. Ecophysiological consequences of environmental immunotoxins on aquatic

Global environment in recent times is characterised by the presence of various xenobiotics of

known, less known and unknown toxicity and chemistry. Information of immunological

attributes of chemical compounds in aquatic invertebrates is limited in the current scientific

literature. Limited but significant reports indicate a substantial impairment of the immunological

status of invertebrates under the exposure of selected ecotoxins (Figure 9). Acute, subchronic and

chronic exposure of common toxins like pesticides, arsenic and alkaline washing soda cause

severe damage in the morphological and functional profiles of haemocytes, the chief

haemocytes, vacuolation and inflammatory lysis.

1.5 days) induced histopathological damage of heart of mollusc,

PAGE 2

Discussion

exposed to sublethal (3000 ppm/ 7 days) concentrations of washing soda. (a) and

b 1000× c

detection apoptosis of hemocytes of pond snail,

to sublethal 7 days) of washing soda. (a) V-FITC and propidium iodide respectively, (c)

Figure 7: Immunofluorescent detection of apoptosis

a 1000×

represent positive staining by Annexin V

Control Treated **Figure 8.** Cypermethrin (1.5 ppm/7 days)-induced histopathological damage of heart of mollusc, *P. globosa*.

**Figure 9.** Ecophysiological consequences of environmental immunotoxins on aquatic invertebrates.

#### **11. Discussion**

Figure 8: Cypermethrin (1.5 ppm/ 7 days

asymmetry. Kiss (2010) reported the translocation of phosphatidylserine from inner leaflet of the plasma membrane to the outer leaftet, which was considered a hallmark of apoptosis [38]. Ray et al. (2013b) reported the apoptotic and necrotic cell deaths of haemocytes of *B. benga‐ lensis* and *L. marginalis* under the sublethal exposures of cypermethrin and fenvalerate, respectively, employing flow cytometry [2]. According to them, cypermethrin and fenvalerate treatment yielded decrease in the percentage of apoptotic and necrotic haemocyte morpho‐ types of *B. bengalensis* and *L. marginalis.* Pyrethroid-induced apoptosis of molluscan haemo‐ cytes is considered as impairment of immunological status of *B. bengalensis* and *L. marginalis.*

exposed to sublethal (3000 ppm/ 7 days) concentrations of washing soda. (a) and

b 1000× c

signals.

**Figure 7.** Immunofluorescent detection of apoptosis of haemocytes of pond snail, *B. bengalensis* exposed to sublethal (3000 ppm/7 days) concentrations of washing soda. (a) and (b) represent positive staining by Annexin V-FITC and pro‐

For filter feeding aquatic organisms, the gill, heart, digestive gland, mantle and antennae act as major target organs of common environmental xenobiotics (Figure 8). Mollusca bear a welldeveloped gill which serves as an organ of gaseous exchange, filter feeding and immunosur‐ veillance. Molluscan gill is a thin membranous and vascularized organ that is in continuous contact with the environmental toxicants distributed in water. During the process of respira‐ tion and filter feeding, gill is exposed to various toxins of known and unknown chemistry. Exposure of gill to aquatic sodium arsenite, pyrethroid pesticide and washing soda of pond water yields a structural damage of lamellae. Chakraborty et al. (2010a) reported hyperchro‐ matic anaplastic cells in the gills of *L. marginalis* exposed to sublethal concentrations of arsenic [33]. This is often associated with tissue rupture and formation of dense fibrosis. The heart, in general, acts as an organ of body fluid pumping. Exposure of cypermethrin results in severe histopathological damage of heart of mollusc. Similar kind of morphological damage was recorded due to exposure of aquatic mollusc to washing soda, a common pollutant of pond water. Digestive gland of mollusc bears immense physiological significance. The organ acts as an important site of diverse metabolic activities and biochemical detoxification. Exposure of sodium arsenite yields histopathological damage of the digestive gland of *L. marginalis* [34]. Toxin-induced morphological alteration of digestive gland of mollusc includes hyperinfiltra‐

detection apoptosis of hemocytes of pond snail,

to sublethal days) by Annexin V-FITC and propidium iodide respectively, (c)

FITC and propidium

of snail, B. bengalensis

1000×

histopathological heart P.

and (b)

1.5 ppm/ 7 days) induced histopathological damage of heart of mollusc,

Treated

4× b 4×

Figure 7: Immunofluorescent detection of apoptosis

a 1000×

Figure 8: Cypermethrin (1.5 ppm/ 7 days

Control

tion of haemocytes, vacuolation and inflammatory lysis.

a

globosa.

represent positive staining by Annexin V depicts colocalization of fluorescent signals.

162 Emerging Pollutants in the Environment - Current and Further Implications

pidium iodide, respectively; (c) depicts co-localization of fluorescent signals.

**10. Toxin-induced damage of target organs and tissues**

Global environment in recent times is characterised by the presence of various xenobiotics of known, less known and unknown toxicity and chemistry. Information of immunological attributes of chemical compounds in aquatic invertebrates is limited in the current scientific literature. Limited but significant reports indicate a substantial impairment of the immuno‐ logical status of invertebrates under the exposure of selected ecotoxins (Figure 9). Acute, subchronic and chronic exposure of common toxins like pesticides, arsenic and alkaline washing soda cause severe damage in the morphological and functional profiles of haemo‐ cytes, the chief immunoeffector cells of invertebrates and other organs and tissues. Sponges, in general, are devoid of well-developed organ system. A variety of specialized cells of sponges are functionally involved in various immunological activities. Exposure of immunotoxins like washing soda largely affected the density dynamics of sponge cells as well as the cytotoxic and phagocytic status in freshwater sponge. Invertebrates of freshwater ecosystem act as important economical resource for developed and developing countries. A thorough toxico‐ logical analysis of the functional performance of target cells and tissues of invertebrates needs to be carried out for the purpose of conservation and culture of this species in their natural environment.
