Various episodes, reported since '80s, witness for toxicity of phycotoxins to marine mammals and their transfer along food chains. Saxitoxins have been implicated in a mass mortality episode of humpback whales which occurred during late 1987-beginning of 1988 in Massachusetts. During an A. tamarense bloom, whales were forced to feed on mackerels, as their natural preys, sand lance, was largely absent from the affected area. Mackerels fed on A. tamarense and were found to contain a mean concentration of 80 μg/100 g tissue, which were deadly toxic for whales. Indeed, short after feeding on fish, humpback whales were found dead, without any sign of emaciation (blubber was abundant) or starvation (stomachs contained digested fish). Estimated dose absorbed by whales was 3.2 μg/kg b.w., well below toxic threshold defined for humans. Two possible mechanisms have been considered as responsible for apparent higher sensitivity of cetaceans to saxitoxins: 1) approximately 30% of the whales body weight is blubber, into which the water-soluble STXs would not partition, thus being more highly concentrated in metabolically sensitive tissues; 2) the diving physiology of whales concentrates blood to the heart and brain and away from those organs required for detoxification, further concentrating neurotoxins in sensitive tissues. Brevetoxins were considered as responsible agent in many poisoning of cetaceans, like manatees and bottlenose dolphin but also of sea turtles. Die-off on manatees have been linked to NSP since 1965 in Florida, but various episodes have occurred in following years (1982 and 1996) in the same area. Timing of mortality events coincided with the presence of K brevis blooms and was often associated with fish and seabirds die-off. Affected animals showed disorientation, inability to submerge or to maintain horizontal position, listlessness, flexing of the back, lip flaring and labored breathing. The only histological lesions observed were cerebral ones, while no other lesion was observed. The analysis of stomachs content showed a high amount of seagrasses and filter feeding tunicates; no measurable PbTX levels were found in tunicates. Domoic acid has been identified as causative agent in pelicans and cormorants mass mortality in California in 1991 and in various and extensive die-offs of sea lions in the same region in 1998, 2000, 2006 and 2007. Affected birds exhibited neurological symptoms similar to those reported in experimental animals, i.e. scratching and head weaving. In all instances the vector for toxins transfer was anchovy.

, 2008. Algal toxins, health and conservation issues in marine megavertebrates

ZACCARONI, ANNALISA;SCARAVELLI, DINO
2008

Abstract

Various episodes, reported since '80s, witness for toxicity of phycotoxins to marine mammals and their transfer along food chains. Saxitoxins have been implicated in a mass mortality episode of humpback whales which occurred during late 1987-beginning of 1988 in Massachusetts. During an A. tamarense bloom, whales were forced to feed on mackerels, as their natural preys, sand lance, was largely absent from the affected area. Mackerels fed on A. tamarense and were found to contain a mean concentration of 80 μg/100 g tissue, which were deadly toxic for whales. Indeed, short after feeding on fish, humpback whales were found dead, without any sign of emaciation (blubber was abundant) or starvation (stomachs contained digested fish). Estimated dose absorbed by whales was 3.2 μg/kg b.w., well below toxic threshold defined for humans. Two possible mechanisms have been considered as responsible for apparent higher sensitivity of cetaceans to saxitoxins: 1) approximately 30% of the whales body weight is blubber, into which the water-soluble STXs would not partition, thus being more highly concentrated in metabolically sensitive tissues; 2) the diving physiology of whales concentrates blood to the heart and brain and away from those organs required for detoxification, further concentrating neurotoxins in sensitive tissues. Brevetoxins were considered as responsible agent in many poisoning of cetaceans, like manatees and bottlenose dolphin but also of sea turtles. Die-off on manatees have been linked to NSP since 1965 in Florida, but various episodes have occurred in following years (1982 and 1996) in the same area. Timing of mortality events coincided with the presence of K brevis blooms and was often associated with fish and seabirds die-off. Affected animals showed disorientation, inability to submerge or to maintain horizontal position, listlessness, flexing of the back, lip flaring and labored breathing. The only histological lesions observed were cerebral ones, while no other lesion was observed. The analysis of stomachs content showed a high amount of seagrasses and filter feeding tunicates; no measurable PbTX levels were found in tunicates. Domoic acid has been identified as causative agent in pelicans and cormorants mass mortality in California in 1991 and in various and extensive die-offs of sea lions in the same region in 1998, 2000, 2006 and 2007. Affected birds exhibited neurological symptoms similar to those reported in experimental animals, i.e. scratching and head weaving. In all instances the vector for toxins transfer was anchovy.
Abstract of the workshop “Contaminants and pathology in marine megavertebrate as environmental assessment tools”
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Zaccaroni A.; D. Scaravelli
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11585/60896
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