The toxicity of cyanide to juvenile rainbow trout held in swimming chambers during 20-day growth experiments at 10°C was found to be size related, the larger trout being more adversely affected than the smaller ones.
The results of four experiments on control and cyanide-exposed trout forced to swim against a constant current speed of 12.1 cm/s while being fed restricted rations revealed that cyanide at 0.01 mg/litre hydrogen cyanide (HCN) increased the food maintenance requirement of the large fish, which were growing less rapidly than their respective controls. The smaller fish, however, grew faster than their controls when exposed to cyanide because of a faster accumulation of lipids.
The metabolic rate of fish is related to size, and this relation is described by the allometric formula Y = aXb, where Y is the metabolic rate, X the body size, a the Y-intercept, and b the weight exponent and slope. This formula was applied to the present results, and a log-log plot of dry weight gains against initial wet weights provided a linear relationship describing the metabolic rates of the control and poisoned fish. The slope representing the controls was 1.12, indicating a metabolic rate function of the weight of the fish, whereas the slope representing the cyanide-poisoned group was 0.67, thus describing a metabolism proportional to the surface area of the fish.
This study brings to light the determining influence of factors modifying the metabolic rate, such as exercise and size, on the response of fish to a toxicant.
A procedure for producing axenic cell suspension cultures of Porphyra is described. Bacteria from a gametophytic frond of P. linearis were evaluated for their sensitivity to different antibiotics. The most effective were ampicillin, carbenicillin, erythromycin, kanamycin, neomycin and ticarcillin. Cells derived from P. linearis clonal cell line CMAC-25, which were contaminated with bacteria, were treated in D-ll medium containing a mixture of these antibiotics at a concentration of 2mgmL~I of each. Next, an abalone enzyme mixture was applied to remove the antibiotic-treated cell walls that normally harbour bacteria. After regulating the osmolality of the protoplasts derived from the cells, single protoplasts were isolated and incubated in an antibiotic solution for 24 h before transferring to D-ll medium for propagation. Axenicity was confirmed in sterility testing media. A success rate of 85 -100% was achieved.
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