Common salt (NaCl) causes developmental, behavioral, and physiological defects in Drosophila melanogaster

Purpose: The incidence of obesity has surged to pandemic levels in recent decades. Approximately 1.89 million obesity are linked to excessive salt consumption. This study aims to check the toxicity of salt at different concentrations using an invertebrate model organism Drosophila melanogaster.

Methods: Drosophila food was mixed with different salt concentrations (50, 200, 400, 800 µM). The toxicity of salt in third instar larvae was checked via different experiments such as trypan blue assay, crawling assay, and other histological staining was done to check the deposition of lipid droplets and amount of reactive oxygen species. Food intake analysis was performed to check the feeding rate, and body weight was also calculated to check the obesity index. Several behavioral assays are also performed in adult flies.

Results: Most significant abnormalities were seen at 50 and 200 µM concentrations. Feeding rate increased up to 60%, body weight was increased up to 12% in larvae, and 27% in adult at 200 µM concentration. Approximately 60% larvae and 58% adult flies had defective response to extreme heat. 28% larvae and 38% adult flies were not responding to cold temperature. 55% flies had a defective phototaxis behavior and 40% of them showed positive geotaxis at those range. Salt stress leads to the buildup of free radicals, resulting in DNA damage in both the gut and hemolymph.

Findings: Most toxic consequences are observed at the lower concentration range as the feeding rate was higher. Flies show aversive response to feed on the higher concentration of salt.