Feeding experiments of Crassostrea virginica on two forms of Pseudonitzschia pungens: behavior and toxicity

Abstract

Domoic acid (DA) is produced. by some diatom species and has become a problem to the shellfish industry. Pseudonitzschia pungensf'. multiseries, a known DA producer, has been discovered in Galveston Bay, Texas. The region produces a large part of the total national oyster harvest. The threat of contamination or mortality to the oyster fishery due to P. pungensf. multiseries was investigated by performing feeding experiments with Crassostrea virginica using clonal cultures of the diatom. Emphasis was placed on oyster feeding behavior, tissue toxicity, and deputation. Crassostrea virginica readily fed on cell concentrations greater than natural blooms. The calculated filtration rate, ranging from 0.01 to 2.02 liters hr-1, and shell openness were not effected by the cell concentration, cell toxicity, or total toxicity of P. pungensf. multiseries. There were no detrimental effects observed to C. virginica.Whole body analysis showed DA accumulation ranging between 1 and 2 pg g-1. The "gut" had five times the toxicity of the adductor muscle and the gills/mantle/labial pulps tissue fractions. Approximately 70% of the total DA in the oyster resided in the "gut." Oysters showed no correlation between whole body toxicity and whole body weight. Whole body depurafion of DA from C. virginica was slow over a 72 hour period (14%). Domoic acid outbreaks may not be confined to the coasts of North America. Two persons in the USA exhibited signs of Amnesic Shellfish Poisoning (ASP) after eating smoked Korean oysters. Monitoring of several brands of this product was conducted, and domoic acid was not detected.