Search

Ocean surgeons Acanthurus bahianusand doctorfish A. chirurgusdisplayed no preference between food items containing toxic dinoflagellates associated with ciguatera poisoning and nontoxic food when given a choice for up to 42 consecutive days. Two clones of laboratorycultured dinoflagellates Gambierdiscus toxicusand one clone of Prorocentrum concavumwere used in separate trials. Gambierdiscus toxicusclone SIU-350 was toxic to both fish species after 5–8 d at a daily ration of 2.5 mg of cells per food item. Clinical signs were similar to those previously reported for blueheads Thalassoma bifasciatumfed the same clone, Clinical signs became less pronounced with time, but recurred with equal intensity when the ration was doubled. No difference in food consumption between toxic and nontoxic food types was observed. Fish fed G. toxicusSIU-175, previously shown to be considerably more toxic to mice Mussp. and brine shrimp Artemiasp. than to G. toxicusSIU-350, remained asymptomatic at daily rations as high as 7.5 mg of cells per food item. No signs of toxicity were observed in adult brine shrimp that consumed ground muscle and liver tissue from fish fed either G. toxicusclone, indicating that ciguatoxicity had not been induced. Results suggest that herbivorous fish may acclimate to, rather than avoid, macroalgae harboring epiphytic toxic dinoflagellates. Attempts to directly relate these findings to nature should be made cautiously because differences in toxic properties between cultured and wild dinoflagellate cells cannot be discounted.

Four species of piscivorous fishes (coney Epinephelus fulvus; schoolmaster Lutjanus apodus; mahogany snapper L. mahogoni; and largemouth bass Micropterus salmoides) displayed distinct behavioral abnormalities after consumption of a ciguatoxic great barracuda Sphyraena barracuda. Samples of the great barracuda were fed to experimental fishes as ether-soluble extracts or as ground flesh. Largemouth bass were also fed freeze-dried cells of the dinoflagellate Gambierdiscus toxicusin a separate experiment and displayed a similar response, Signs of intoxication included skin color variations, inactivity, loss of equilibrium, erratic swimming, jerky feeding movements, and loss of orientation – and death, in the case of largemouth bass fed 1.0 g or more of great barracuda flesh or 7.1 mg·g–1or more of great barracuda extract. These abnormalities usually were observed within 24 h after the feeding of toxic materials, and were apparent in some cases for as long as 76 d.

Distinct behavioral abnormalities were displayed by blueheads Thalassoma bifasciatum (wrasse: Labridae) after consumption of a dinoflagellate responsible for producing ciguatera toxins. The symptoms, including skin color variations, inactivity, loss of equilibrium, erratic swimming, jerky feeding movements, loss of orientation, and loss of net avoidance ability, appeared after oral treatments ranging from 0.26 to 4.88 mg?g-1of freeze-dried Gambierdiscus toxicus cells. Results suggest that the adverse effects of toxins on blueheads would increase their susceptibility to predation, subsequently increasing the rate of transference within the food chain.

The intracellular ion content of the halophilic blue-green alga, Aphanothece halophytica was studied as a function of age, external sodium and external potassium concentration. Intracellular Na+ was found to be about 0.38 millimoles/g dry mass. Intracellular K+ concentrations were as high as 1 M and varied directly with external salinity. Intracellular Ca++ and Mg++ were in the range previously reported for fresh water blue-green algae despite their extremely high extracellular concentrations. Average cell size is consistent at room temperature with two exceptions. When the outside K+ is lower than 6.5 mM the cells tend to be smaller with less intracellular K+ and high Ca++. In stationary phase cultures the cells are larger with high intracellular Mg++ and low K+.

Cytological observations were made on material from 35 collections taken from 21 populations representing 10 species and 2 genera. Haploid chromosome numbers observed in Nitellawere 9, 12, 18, 18, 18, and 18 + 36. Those observed in Charawere 14, 28, 28, and 42. Several data indicate that Nitella transilisis an established polyploid of N. tenuissima.The evaluation of chromosome numbers in respect to hybridization, polyploidy, and sexuality in haplobiontic plants is discussed.