INSECT (LOCUSTA-MIGRATORIA MIGRATORIOIDES) TEST MONITORING THE TOXICITY OF CYANOBACTERIA

An insect test was developed to investigate the toxicity of cyanobacte ria. The African locust, Locusta migratoria migratorioides R.F. was us ed as a test animal instead of mouse. The cyanobacteria tested were Ap hanizomenon flos-aque, Anabaena aphanizomenoides, Cylindrospermopsis r aciborskii, Microcystis aeruginosa. The toxicity of authentic microcys tin-LR was also tested. Cyanobacteria producing toxins killed the anim als when the homogenized cell suspension was injected into the animals . The locust test proved to be more sensitive than the mouse test. The LD50 values of the different cyanobacteria for locusts and for mice, respectively were the following: 90 mu g/animal (60 mg/kg) and 8000 mu g/animal (320 mg/kg), for Aphanizomenon flos-aquae; 255 mu g/animal ( 170.2 mg/kg) and 3750 mu g/animal (150 mg/kg), for Anabaena aphanizome noides; 195 mu g/animal (131.4 mg/kg) and 5750 mu g/animal (230 m/kg) for Cylindrospermopsis raciborskii; 22.5 mu g/animal (15 mg/kg) and 60 00 mu g/animal (240 mg/kg), for Microcystis aeruginosa.. In locusts th e LD50 value for authentic microcystin-LR was 0.2 mu g/animal (130 mg/ kg). Since the weight of the mice is 15 to 20 times larger than that o f the locusts, hence less toxic cells are needed to kill the locusts. The locust test is cheaper than the mouse test, large number of animal s can be used in the experiments and the LD50 values can be estimated more precisely. The toxicity of C. raciborskii was significantly lower when the lyophilized cells were extracted in methanol (LD50 = 767 mg/ kg), instead of NaCl solution (LD50 = 131.4 mg/kg). (C) 1998 Inter Pre ss, Inc.