Effects of Mercury Chloride (HgCl₂) on Betta Splendens Aggressive Display

Abstract

Mercury chloride (HgCl2) is a toxic mercury salt and a major pollutant, that can be found in soil, water and air, with influences on behavior, physiology and adaptation to the environment. In this study two experiments were designed to examine interactions and effects of HgCl2 on some behavioral patterns of Siamese fighting fish (Betta splendens). In the first experiment we tested the effect of a progressive dose (five 0.04 mg) on aggressive display with exposure to a mirror, whereas in the second experiment we tested the effect of an acute dose (0.2 mg) on the aggressive display with exposure to a mirror. The experiments were performed on 5 consecutive sessions at intervals of 18 hours between sessions. Differences of performance were shown by subjects in the acute and progressive treatments when compared with a control treatment in the majority of behaviors evaluated, namely Floating, Slow Swimming, Wavy Swimming, Emerging, Bend, Square Move and Motor Display Components. Acute treatment was different from control only on Show Body, while the progressive group differed on Resting, Horizontal Display and Appropriate Display Components. Differences between Correlate Display Components and Total were also shown. Both the acute and progressive contamination with HgCl2 decrease the motor activity in the aggressive display, mirror-image test of Betta splendens, mainly on the progressive dose. This implies an impairment on feeding behavior, predator avoidance, reproductive behavior, mate choice and territoriality. These results suggest that in this fish species, the progressive dose has a greater effect on behavior in general and that both the acute and progressive contamination with mercury chloride affect many other aspects of behavior.

The effects of uncontrollable shocks on the aggressive behavior of the Siamese fighting fish (Betta splendens).

“…To support this hypothesis there are some studies that investigated the effects of some variables on Betta splendens ’ agonistic behavior and there were no differences found regarding the control animals. de Matos Mansur et al (2012) investigated the effects of mercury chloride on the aggressive behavior of the Siamese fighting fish and observed that the typical aggressive responses as gill cover erection, attacks, and vertical display were not changed after the drug treatment. Lynn et al (2007) exposed Betta splendens to fluoxetine treatment at 3 μg/ml for 3 h and didn’t observe significant reduction when compared with the control group, only three responses were measured from all the behaviors comprised in the aggressive behavior, latency of the first response, gill cover erection and display, the only one changed significantly was the display.…”

“…The registered categories of aggressive behavior were twofold: (a) the display (D) and (b) the attack (A); these categories were based on the studies of Bronstein (1984, 1985), de Matos Mansur, Cavalcante, Santos, and Gouveia Jr. (2012), Fantino, Weigele, and Lancy (1972), and Simpson (1968). The category biting described in some of these studies was replaced by attack in this study, for it was considered more appropriate because of the response topography.…”