Brevetoxins, like ciguatoxins, are potent ichthyotoxic neurotoxins that accumulate in fish

Abstract

Brevetoxins and ciguatoxins are closely related potent marine neurotoxins. Although ciguatoxins accumulate in fish to levels that are dangerous for human consumption, live fish have not been considered as potential sources of brevetoxin exposure in humans. Here we show that, analogous to ciguatoxins, brevetoxins can accumulate in live fish by dietary transfer. We experimentally identify two pathways leading to brevetoxin-contaminated omnivorous and planktivorous fish. Fish fed with toxic shellfish and Karenia brevis cultures remained healthy and accumulated high brevetoxin levels in their tissues (up to 2675 ng g(-1) in viscera and 1540 ng g(-1) in muscle). Repeated collections of fish from St. Joseph Bay in the Florida panhandle reveal that accumulation of brevetoxins in healthy fish occurs in the wild. We observed that levels of brevetoxins in the muscle of fish at all trophic levels rise significantly, but not to dangerous levels, during a K. brevis bloom. Concentrations were highest in fish liver and stomach contents, and increased during and immediately following the bloom. The persistence of brevetoxins in the fish food web was followed for 1 year after the K. brevis bloom.

Fig. 1

Brevetoxin concentrations measured in muscle and viscera of pinfish (L. rhomboides) and croakers (M. undulatus) fed brevetoxin-contaminated clams (day 1–14) followed by noncontaminated clams (day 15–28). Error bars indicate standard deviation between individual fish (n = 3).

Fig. 2

(a) Brevetoxin concentrations in muscle and viscera of juvenile striped mullet after 24 h exposure to K. brevis cell cultures at indicated cell densities, and total and dissolved concentrations of brevetoxins measured in exposure media. (b) Time to the death of juvenile striped mullet exposed to identical densities of lysed K. brevis cells, and total and dissolved concentrations of brevetoxins measured in exposure media. For (a) and (b), error bars indicate standard deviation between individual fish.

Fig. 3

Maximum Karenia brevis cell densities and brevetoxin concentrations measured in seawater samples collected throughout St. Joseph Bay between January 2005 and December 2006.

Fig. 4

Average concentrations of brevetoxins measured in fish (all species) collected throughout St. Joseph Bay between 2004 and 2006. In 2005 and 2006, fish collections were performed during 2–3 day sampling trips. Error bars indicate standard deviation.

Fig. 5

Prevalence of brevetoxin contamination in fish (all species) collected throughout St. Joseph Bay between 2004 and 2006. Prevalence is expressed as the percentage of fish containing detectable levels of brevetoxins (>5–10 ng g⁻¹).

Fig. 6

Potential sources of brevetoxins and trophic transfer pathways in the fish food web.