Viabilidade do uso de espermatozoides criopreservados de Colossoma macropomum, (CUVIER, 1816) expostos a Cipermetrina

Abstract

Cypermethrin is a pesticide compound widely used to combat insects in agricultural and domestic environments, but its indiscriminate use and inadequate disposal of packaging can cause adverse effects on animals living in directly or indirectly affected environments. This work aimed to analyze the feasibility of using atabaque (Colossoma macropomum) sperm in ecotoxicological bioassays with cypermethrin. Seminal samples from sexually mature Tamaqua males were used. Fresh semen was collected eight hours after hormonal induction in graduated glass tubes. After an initial assessment of the absence of prior activation, the experiment was carried out in a factorial scheme, testing five concentrations of cypermethrin (2.5; 25; 125; 250 and 500 mg/L), where motility was evaluated by the subjective method and the data expressed in percentage of motile cells in samples per time in seconds. The lethal dose (LD50) was evaluated from the activation of the gametes until the motility regressed to 50% in the samples; total activity time was recorded to within 10% of motile cells (in seconds) after their initial activation. As a control, activation with 0.9% NaCl solution and motility analysis were used in the same way as described for cypermethrin. In the cryopreservation stage, cryoprotective solutions were prepared, with concentrations of 75% glucose, 10% DMSO, 5% egg yolk. The semen was then placed in microstrips and stored in a dryshipper with nitrogen for up to 20 minutes. After temperature stabilization, the samples were transferred to liquid nitrogen at a temperature of -196°C. For thawing, the samples were removed from liquid nitrogen and placed in a water bath at 60°C for 8 seconds, transferred to plastic tubes and analyzed. Semen analyzes were carried out under an optical microscope and sperm viability was assessed through activation with NaCl solution. After confirming viability through sperm characterization analysis, the samples were activated by cypermethrin concentrations and the subjective motility rate and motility time were established in triplicates, taking into account the Lethal Dose (LD50) for each repetition. Results indicate that in natura samples based on the subjective method presented an average duration of 118±12 seconds (considering up to 10% of sperm motility) and 95±5% according to the percentage of motile cells. The reduction in sperm motility occurred significantly (p<0.05), mainly at the cypermethrin concentration of 500 mg/L. In thawed samples, the average time was 46.9±10 seconds and the motility rate was 73.9±6% for motile cells. The reduction in motility was more intense from the 125mg/L concentration onwards, indicating the cellular limit of tolerance to the insecticide. The tests carried out demonstrate that tambaqui semen is sensitive to the process of exposure to cypermethrin residues and can be used in ecotoxicological bioassays.