This is not, however, positive proof that brevetoxin-laced menhaden killed the dolphins. In fact, scientists don't know how much brevetoxin constitutes a lethal dose for dolphins.
Necropsies or post-mortem examinations at the state's Marine Mammal Pathobiology Laboratory in St. Petersburg hinted inconclusively at brevetoxin as the possible killer.
When red tide toxin kills manatees, the animals show specific symptoms, such as runny blood, lungs congested and heavy with thick, ropy, blood-tinged mucous, and enlarged kidneys and livers. The dead Panhandle dolphins didn't show the same set of symptoms, Costidis said.
"There was some pretty runny blood, which seems to be one of the side-effects of brevetoxin," Costidis said. "But that could be something other than brevetoxin. Beyond that, no, there were no similarities."
Tests on dolphin tissue performed at the Armed Forces Institute of Pathology in Washington, D.C., indicate that neither virus nor disease caused the die-off, although more tests are being done.
While red tide is a familiar phenomenon in the Gulf of Mexico, domoic acid is the new toxin on the block.
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