Effects of Alexandrium minutum exposure upon physiological and hematological variables of diploid and triploid oysters, Crassostrea gigas

Abstract

minutum compared to control oysters. At the same time, many oysters exposed to the harmful microalgae presented a strong inflammatory response in different tissues of the digestive gland: in intestine as well as in digestive ducts and tubules. Spermatozoa in oysters exposed to A. minutum were morphologically and functionally modified compared to spermatozoa of control oysters. Indeed, spermatozoa were less motile and had lower ATP content in oysters exposed to A. minutum. Meanwhile, spermatozoa produced by control oysters showed higher 2 percentage of mortality and relative DNA content than those produced by A. minutum exposed oysters. Finally, the characteristics of the mitochondria of spermatozoa also appeared to be modified upon A. minutum exposure. The results of this study suggests that an exposure of oysters to A. minutum, reducing energy status and motility of spermatozoa associated to morphological changes at the cellular and sub-cellular levels, can have consequences on spermatozoa fertility and reproduction success.

In vitro interactions between several species of harmful algae and haemocytes of bivalve molluscs

“…Contrastingly, in vivo exposure of C. virginica and C. gigas to A. fundyense and A. minutum, respectively, did not induce immunosuppression nor toxicity (Hégaret et al 2007b;Haberkorn et al 2010b). Temporary cysts of A. fundyense and A. minutum have been observed in the stomach, digestive gland and biodeposits of bivalves (Shumway et al 2006;Galimany et al 2008b;Hégaret et al 2008b;Haberkorn et al 2010b), indicating that the algal cells may transform into cysts as they pass through the digestive system. The release of toxic substances might then be reduced, causing less effect on bivalve tissues and haemocytes during in vivo exposures compared with in vitro experiments.…”

“…Moreover, in vivo exposure of C. gigas to A. minutum resulted in immunostimulation, characterised by inflammatory response (Haberkorn et al 2010a), whereas in vitro exposure did not show significant effects of A. minutum, besides a higher mortality and a decrease of the production of ROS. Such an inhibition of the production of ROS was similarly measured in C. gigas exposed in vivo to A. minutum in May, but the contrary was observed a month before on the same oyster population (Haberkorn et al 2010b). These contradictory results underline the difficulties to extrapolate in vitro effects to in vivo exposure of Alexandrium sp.…”

“…Ford et al (2008), however, reported a decrease of adhesion and phagocytosis of Manila clam and soft-shell clam haemocytes exposed in vitro to a non-PST producing Alexandrium tamarense strain, whereas another PST producing strain did not have any significant effect on these immune functions. Pacific oysters, C. gigas, exposed in vivo to Alexandrium catenella had an increase in percentage of dead haemocytes, which was not the case neither for C. virginica nor for C. gigas, respectively, exposed in vivo to A. fundyense and A. minutum (Hégaret et al 2007b;Haberkorn et al 2010b). Arzul et al (1999) showed haemolytic, allelopathic and toxic activities of Alexandrium sp.…”

Identification and characterisation of an ostreid herpesvirus-1 microvariant (OsHV-1 µ-var) in Crassostrea gigas (Pacific oysters) in Australia

“…Conversely, higher metabolic and haemocyte (phagocytic) activity in triploids could theoretically assist viral trafficking within host tissues. Triploidy in C. gigas has also been shown to result in increased PST accumulation (Haberkorn et al 2010a), which may be relevant in cases where toxic phytoplankton blooms coincide with OsHV-1 mortalities.…”

Exposure of marine mussels Mytilus spp. to polystyrene microplastics: Toxicity and influence on fluoranthene bioaccumulation

“…Hemocyte mortality was assessed according to Haberkorn et al (2010) and expressed as the percentage of dead cells present in each sample. The concentration of circulating hemocytes (all hemocytes, granulocytes and hyalinocytes) was also determined.…”