Aquaculture America 2020

February 9 - 12, 2020

Honolulu, Hawaii

METABOLISM OF BREVETOXINS IN Mercenaria campechiensis

Katherine Baltzer*1, Kathleen El Said1, Sarah May1, Leanne J. Flewelling2, Ann Abraham1
 Affiliations:
1 FDA, Division of Seafood Science and Technology, Gulf Coast Seafood Laboratory, Dauphin Island, AL 36528, USA; 2 Florida Fish and Wildlife Conservation Commission, Fish and Wildlife Research Institute, St. Petersburg, FL 33701, USA
 

Brevetoxins, the causative agent of neurotoxic shellfish poisoning (NSP) produced by the marine dinofla gellate Karenia brevis, are a  significant  concern in seafood safety due to the increasing number and severity of red tide events in the coastal southeastern United States. The commercial shellfish industry is particularly vulnerable to these events as a result of the sessile , filter-feeding life cycle of clams and oysters .  To prevent NSP, shellfish harvest areas are closed when K. brevis density exceeds 5,000 cells/L and re-opened when the shellfish toxicity assessed by mouse bioassay (MBA) is < 20 MU/100g.  Until recently, t he NSP MBA has been the only National Shellfish Sanitation Program (NSSP) approved method for regulatory NSP testing. An ELISA that determines the composite B-type brevetoxins has been approved recently as a limited use method for NSP testing in Eastern oyster (Crassostrea virginica) , sunray venus clams (Macrocallista nimbosa), and hard clams (Mercenaria mercenaria).  Brevetoxins are extensively metabolized  in hard clams and Eastern oysters.  The most persistent and abundant metabolites  contributing to overall toxicity are identified as cysteine and taurine conjugates of B-type brevetoxin. These metabolites ,  BTX-B1, BTX-B2, and S-desoxy BTX-B2, have been identified as biomarkers of brevetoxin exposure in oyster and hard clam and correlate well with  the  composite toxin measurements by ELISA. In this study,  metabolism of brevetoxin in K. brevis bloom-exposed southern hard clams (Mercenaria campechiensis), a  species of  growing  commercial interest, was examined by N2a cytotoxicity assay, ELISA, and LC-MS. Brevetoxins are metabolized in  M. campechiensis and the major metabolites are cysteine and taurine conjugates of brevetoxin. R esults suggest  that  M. campechiensis  and  M. mercenaria  metabolize brevetoxins similarly and  BTX-B1, BTX-B2, and S-desoxy BTX-B2 could  serve as biomarkers of  brevetoxin  exposure in M. campechiensis for confirmation by LC-MS.