Salamander Skin Toxins 77 



Table 1. Bioassay results of white mice injected i.p. with crude skin extracts 

 from two specimens of Necturus lewisi. 



Dosage (mg/ kg) Result 



Animal 1 





(98mmsvl, 12.7 g) 





300 



moderately strong symptoms 



900 



strong symptoms 



2655 



very strong symptoms 



7765 



very strong symptoms; dead in 2 hr. 20 min. 



Animal 2 





(123mmsvl, 24.2 g) 





996 



very weak symptoms 



4671 



moderately strong symptoms 



9342 



strong symptoms 



12456 



strong symptoms 



to a granular powder with a mortar and pestle. The ground sample was 

 slurried in 4-5 ml distilled water for 5 minutes to extract the toxins, then 

 centrifuged for 2 minutes at 3600 rpm, and the supernatant decanted 

 into a sterile centrifuge tube. The residue was rinsed twice with 1-ml 

 portions of distilled water and the supernatant decanted, after centrifu- 

 gation, into the sterile centrifuge tube. The exact volume was recorded 

 for calculation of dose levels. The sample was kept chilled in ice water 

 at all times except when centrifuged. For all quantitative studies the 

 extract was either tested immediately, or frozen in an ultra-refrigerator 

 (-70 ° C) and lyophilized in a Virtis freezedrier for storage. Lyophilized 

 samples from other salamanders were kept at -15 °C in the freezing 

 compartment of a refrigerator and showed no detectable deterioration 

 over time. 



Crude extracts were injected i.p. into bioassay mice (Cox Standard 

 Outbred) weighing 18-25 g, in mg of sample per kg bodyweight dosages. 

 Mice were also injected with distilled water, Ringer's solution, and skin 

 extracts of Desmognathus monticola as controls; none of these caused 

 symptons. Crude extracts were not toxic enough to yield LD 5 o data but 

 were bioassayed in mice as completely as possible until the sample was 

 expended. Detailed notes were kept of symptoms in bioassay mice to all 

 dosages of crude skin extract. 



RESULTS 

 Following injection of a lethal i.p. dosage of skin extract into a 

 mouse, symptoms appeared within a few minutes and consisted of hind 

 leg stretches (repeated hyperextension of legs and lower back), abdomi- 

 nal compression, occasional hind leg kicks, and wobbly gaint, followed 

 by extreme irritability, then quiescence. The irritability was elicited by 

 contact or impending contact with other mice, a blunt instrument, 



