Effects of Non-Lethal Arsenic Contamination on Manifesting Fin Strokes in Zebrafish (Danio rerio) ^†

Introduction: The locomotion of fish is considered to be crucial in regulating activities such as prey predation and foraging. Understanding the swimming patterns of fishes provides deep insights into the underlying neuroethological and biomechanical mechanisms. The fish locomotion mechanism is predominantly controlled through regulated fin strokes, which involve correlation between the stroking patterns of the fins (pectoral, dorsal, anal, pelvic and caudal). However, geometric morphology and hydrodynamics also play a critical role. The aim of our study is to elucidate whether non-lethal concentrations of arsenic trioxide (As₂O₃) in the aquatic environment can affect the swimming pattern of a freshwater-habitant zebrafish (Danio rerio).

Methods: A population of zebrafish was exposed to a 1/50 LC₅₀ concentration of As₂O₃ for 7 days. A comparative assessment of fin stokes per minute was conducted between fishes from uncontaminated and arsenic trioxide-contaminated water. The stroking frequencies of all the fins were analysed to understand the effect of arsenic on fish locomotion.

Results: Our result demonstrates that fishes in arsenic-contaminated water manifest more frequency of all fin strokes. All of the fins move significantly more in a given time frame due to arsenic trioxide contamination. The alteration of the fin stroke pattern of fishes in a polluted environment is clearly elucidated.

Conclusions: This study clearly indicates that arsenic contamination can be a causative abiotic stressor for the alteration of neuronal activities, which in turn alters the muscular activities responsible for the movements of fins. Danio rerio is a promising model to study the environmental pollution and neurotoxicity of arsenic. It is postulated that enhanced fin activity alters the locomotion pattern as well as the velocity of fish. This study encompasses the three disciplines of behavioural ecotoxicology, neurotoxicology and biomechanics, highlighting locomotory abnormalities in fish due to environmental perturbation.