GENITIC VARIABILITY IN TOXIN POTENCIES AMONG SEVENTEEN CLONES OF GAMBIERDISCUS TOXICUS (DINOPHYCEAE)1

Abstract

ABSTRACTSeventeen clones of the ciguatera‐causing dinoflagellate Gambierdiscus toxicus Adachi and Fukuyo were acclimated to the same environments over several months. Significant variance components were detected between non‐acclimated and acclimated cultures for cell potencies, yields and reproduction rates. The resultant variance in acclimated potencies among clones was statistically significant (P < 0.0001), indicating that potency can be used for genetic comparisons. However, cell potency differences for a clone of G. toxicus in the acclimated vs. non‐acclimated phases can exceed genetic differences between clones. This stresses the need for a rigorous acclimation process. Caribbean isolates of G. toxicus were inherently more toxic than isolates from other areas. One Caribbean clone yielded 55 × 10−4 mu (mouse units)·cell−1 whereas clones Bermuda, the Bahamas, and Florida ranged from only 1.8 × 10−4 mu·cell−1 to a maximum of 19.8 × 10−4 mu·cell−1. Toxicity decreased with increasing latitude (r =–0.819, P < 0.01), indicating that environmental differences probably influenced the potencies. A comparison of acclimated reproduction rates at four light intensities also indicated that genetic differences among clones existed. The resulting reproduction rate/light slopes overlapped, indicating that the clones may be adapted to specific light regimes.