Effects of exposure to sediment-associated fipronil on cardiac function of Neotropical armored catfish Hypostomus regani

Abstract

Fipronil is widely used as a broad-spectrum insecticide in agriculture, urban environments, and veterinary medicine. Fipronil can enter aquatic ecosystems and spread to sediment and organic matter, representing a risk to non-target species. This study aimed to evaluate the effects of short-term (96 h) exposure to a low and realistic concentration of sediment-associated fipronil (4.2 µg.kg⁻¹ of Regent® 800 WG) on myocardial contractility of armored catfish Hypostomus regain, a benthic fish species. Fipronil exposure induced increased inotropism and acceleration of contractile kinetics, although no alterations in the relative ventricular mass were observed. This better cardiac function was associated with an elevated expression and/or function of the Na⁺/Ca²⁺ exchanger and its marked contribution to contraction and relaxation, probably due to a stress-induced adrenergic stimulation. Ventricle strips of exposed fish also exhibited a faster relaxation and a higher cardiac pumping capacity, indicating that armored catfish were able to perform cardiac adjustments to face the exposure. However, a high energetic cost to maintain an increased cardiac performance can make fish more susceptible to other stressors, impairing developmental processes and/or survival. These findings highlight the need for regulations of emerging contaminants, such as fipronil, to ensure adequate protection of the aquatic system.

Keywords:

• Insecticide
• fish
• contaminated sediments
• heart
• excitation-contraction coupling
• physiological biomarkers
• contractile force
• Na⁺/Ca²⁺ exchanger
• cardiac pumping capacity
• calcium handling

Data availability

The data that support the findings of this study are openly available in Institutional Repository of the Universidade Federal de São Carlos at https://repositorio.ufscar.br/handle/ufscar/1377.

Additional information

Funding

The authors are thankful to Santa Cândida Fish Farm (Santa Cruz da Conceição, São Paulo, Brazil) which provided the fish. This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brazil (CAPES) - Finance Code 001 (L. A. Ferro Master's Fellowship) and Instituto Nacional de Ciência e Tecnologia da Biodiversidade e Uso Sustentável de Peixes Neotropicais (INCT-Peixes) - Conselho Nacional de Desenvolvimento Científico e Tecnológico – Brazil (CNPq # 405706/2022-7).