Insect (Locusta migratoria migratorioides) test monitoring the toxicity of cyanobacteria

An insect test was developed to investigate the toxicity of cyanobacteria. The African locust, Locusta migratoria migratorioides R.F. was used as a test animalinstead of mouse. The cyanobacteriatested were Aphanizomenon flos-aque, Anabaenaaphanizomenoides, Cylindrospermopsis raciborskii, Microcystis aeruginosa. The toxicity of authentic microcystin-LR was also tested. Cyanobacteriaproducing toxins killed the animalswhen the homogenized cell suspension was injected into the animals. The locusttest proved to be more sensitive than the mouse test. The LD 50 values of the different cyanobacteriafor locustsand for mice, respectively were the following: 90 μg/ animal(60 mg/kg) and 8000 μg/ animal(320 mg/kg), for Aphanizomenon flos-aquae; 255 μg/ animal(170.2 mg/kg, and 3750 μg/ animal(150 mg/ kg), for Anabaenaaphanizomenoides; 195 μg/ animal(131.4 mg/kg) and 5750 μg/ animal(230 mg/kg), for Cylindrospermopsis raciborskii; 22.5 μg/ animal(15 mg/kg) and 6000 μg/ animal(240 mg/kg), for Microcystis aeruginosa.. In locuststhe LD 50 value for authentic microcystin-LR was 0.2 μg/ animal(130 mg/kg). Since the weight of the mice is 15 to 20 times larger than that of the locusts, hence less toxic cells are needed to kill the locusts. The locusttest is cheaper than the mouse test, large number of animalscan be used in the experiments and the LD 50 values can be estimated more precisely. The toxicity of C. raciborskii was significantly lower when the lyophilized cells were extracted in methanol (LD 50 = 767 mg/ kg), instead of NaCl solution (LD 50 = 131.4 mg/kg).