Toxicant Responses and Culturing Characteristics of Long‐Term Laboratory‐Reared and Field Populations of Ceriodaphnia dubia

Abstract

Ceriodaphnia dubia is a standardized test organism for regulatory toxicity testing of surface waters and commercial chemicals because of its simplicity to culture and responsiveness to toxicants. For testing convenience, C. dubia is often cultured for extended periods in the laboratory with little knowledge of the impact on subsequent generations. Extended laboratory rearing could impact how they respond to stressors and decrease the accuracy of test results. This paper investigated if C. dubia cultured for an extended period were representative of three recently‐collected field populations by comparing their culturing characteristics and sensitivities to toxicants. For culturing characteristics, the field cultures were more challenging as they had shorter body lengths, fewer neonates, and higher mortality rates than the laboratory culture. Comparative chronic toxicity tests with sodium chloride (NaCl) and the neonicotinoid insecticide thiamethoxam indicated that the laboratory and field organisms did not differ much in their toxicological responses but did differ in the variability of responses (% coefficient of variation). The differences between the laboratory and field cultures found in this study highlight the challenges of addressing discrepancies between laboratory and field applications in existing standardized methodologies.