Attractant preference between NaCl and KCl in wild-type and mutant Caenorhabditis elegans

Mai Berger, Khojesta Hamid, Alice Koh, Monica Leslie, Susan Park


We investigated preferences between the chemical attractants KCl and NaCl in wild-type (strain N2) and mutant-type (strain VC854) Caenorhabditis elegans (C. elegans). As C. elegans relies on its chemosensory system for survival, we attempted to gain further insight into its sensory system with our experiment. The mutant has an affected unc-2 gene, which limits movement and sensory function.  25 wild-type and 25 mutant-type nematodes were subjected to a V-shaped choice maze with a time limit of 1 minute (wild type) and 3 minutes (mutant-type).  One arm of the maze contained 0.103 M NaCl solution and the other arm contained 0.103 M KCl solution. For the wild type, our data revealed a significant attractant response (choice or no movement) with a chi-square value (X2) of 12.56 and a p-value of 0.0004. An X2 value of 0.80 and a p-value of 0.3711 indicated no significant preference for either attractant in the wild type; however, there was a slight trend for KCl preference. The mutant showed a significant no movement response with a X2 value of 7.12 and p-value of 0.0076, and only 3 nematodes displayed an attractant response. Therefore, we reject our null hypothesis Ho1, but failed to reject null hypothesis Ho2 for wild type.  We failed to reject Ho3 for the mutant type, and in turn had insufficient data to reject Ho4 or Ha4. Studies in the literature support a no movement response from the mutant strain due to the affected unc-2 gene. The no-preference result of wild-type C. elegans may be due to initial habituation conditions and attractant toxicity levels. Further studies should test a larger range of chemical attractants to determine a statistically significant preference in both wild and mutant-type C. elegans

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