Variations in morphology, growth, and toxicity among strains of the Prorocentrum lima species complex isolated from Cuba and Brazil

Abstract

Benthic dinoflagellates belonging to the genus Prorocentrum are known to produce diarrhetic toxins such as okadaic acid (OA) and its analogues, dinophysistoxins (DTXs), as well as prorocentrolides and other unidentified fast-acting toxins. The present study is a comparative analysis focused on the morphology, genetic, growth, toxin production, and toxicity by strains belonging to the Prorocentrum lima species complex, isolated from different regions along the western Atlantic coast. While cell dimensions (38–45 × 24–30 μm) and shape (ovoid) were similar between strains from Cuba and Recife (Northeast Brazil), cells of the strain from the estuarine complex of Paranagua Bay (South Brazil) were shorter (36–41 × 25–28 μm) and oblong to ovate-oblong (elliptical) in shape. This latter strain exhibited similar LSU rDNA and identical ITS1-5.8S rDNA-ITS2 sequences to those of P. cf. lima “morphotype 5,” which is closely related to Prorocentrum caipirignum by LSU, but separated from it by ITS. This southern Brazilian strain attained the highest growth rate (0.34 ± 0.01 div day−1) and cell densities (11.2 × 105 cell mL−1) in batch culture. Intracellular OA concentrations were higher for the other two strains during the late exponential and stationary phase, but similar for all strains (9.50–10.06 pg cell−1) at the early exponential growth phase; consistently lower levels of DTX-1 were produced by two strains, except the one from Recife. Finally, live cells of the strains from Cuba and Recife were more toxic to A. salina metanauplii, whereas the southern Brazilian strain exhibited higher culture medium toxicity. The contrasts in growth and toxicity potential revealed for these morphologically and genetically distinct Prorocentrum strains might be relevant for the local management of diarrhetic poisoning outbreaks in shellfish harvesting and aquaculture sites, including in estuarine areas.