Alterações comportamentais no nado livre de camarões Macrobrachium spp. expostos agudamente a estímulo tátil ameaçador que restringe o nado livre: experimento piloto

Abstract

Aversive events often elicit behaviors associated with anxiety, and the learning and memory processes tied to such events are critical for animal survival. In this study, we investigated the formation of aversive memory and behavioral changes related to fear and anxiety in shrimp of the genus Macrobrachium subjected to or exempt from a threatening tactile stimulus that restricted free swimming. During the conditioning session, shrimp in the experimental group (n = 14) were exposed to aversive tactile stimuli upon entering the frontal quadrant of a device divided into three sections: frontal, central, and posterior. The posterior quadrant was characterized by an environmental cue. The control group (n = 12) was placed in the same apparatus but was not exposed to the aversive stimulus. Following 20 minutes of conditioning, behavior was recorded for an additional 10 minutes without stimuli, assessing the time spent and mobility in each quadrant at intervals of 1, 3, and 10 minutes. In the test session, conducted 24 hours later, the shrimp were reintroduced to the same apparatus, and their behavior was reassessed. Subsequently, the animals were transferred to an open field, where additional parameters were evaluated, including the time spent in the central area, latency to leave the center, proximity to the apparatus walls, immobility duration near the walls, and the number of quadrant crossings. Shelter-seeking behavior and escape responses to tactile stimulation on the dorsal region were also assessed. Shrimp exposed to the aversive stimulus spent significantly more time in the quadrant opposite to where the stressor was applied (i.e., the posterior quadrant) and less time in the frontal section during the third minute of evaluation. Increased thigmotaxis was observed in the experimental shrimp, which remained closer to the apparatus walls where it exhibited greater immobility compared to the control group. However, exposure to the aversive stimulus did not result in significant changes in shelter-seeking or escape behaviors. These findings suggest that Macrobrachium ssp. perceived the stimulus as a threat, displaying behaviors analogous to anxiety observed in vertebrates. While behavioral changes persisted for 24 hours post-exposure, aversive memory retention was limited to a very short term (3 minutes).