Academic journal article The Spanish Journal of Psychology

Effects of Trophic Poisoning with Methylmercury on the Appetitive Elements of the Agonistic Sequence in Fighting-Fish (Betta Splendens)

Academic journal article The Spanish Journal of Psychology

Effects of Trophic Poisoning with Methylmercury on the Appetitive Elements of the Agonistic Sequence in Fighting-Fish (Betta Splendens)

Article excerpt

The aggressive display in Betta splendens is particularly prominent, and vital to its adaptation to the environment. Methylmercury is an organic variation of Hg that presents particularly pronounced neuro-behavioral effects. The present experiments aim to test the effect of acute and chronic poisoning with methylmercury on the display in Bettas. The animals were poisoned by trophic means in both experiments (16 ug/kg in acute poisoning; 16 ug/kg/day for chronic poisoning), and tested in agonistic pairs. The total frequency of the display was recorded, analyzing the topography of the agonistic response. The methylmercury seems to present a dose- and detoxification-dependent effect on these responses, with a more pronounced effect on motivity in acute poisoning and on emotionality in the chronic poisoning. It is possible that this effect could be mediated by alteration in the mono-amino-oxidase systems.

Keywords: methylmercury, aggression, emotional behavior, Betta splendens

El despliegue agresivo en la Betta splendens es especialmente prominente y es vital para su adaptación al medio ambiente. Metil-mercurio es una variación orgánica de Hg que presenta efectos neuro-conductuales especialmente pronunciados. Los experimentos actuales intentan poner aprueba el efecto de envenenamiento agudo y crónico con metil-mercurio sobre el despliegue en Bettas. Los animales fueron envenenados tróficamente en ambos experimentos (16 ug/kg e el envenenamiento agudo) y probados en parejas agonistas. Se registró la frecuencia total del despliegue, analizando la topografía de la respuesta agonista. El metil-mercurio parece presentar un efecto dependiente de la dosis y de la detoxificación sobre estas respuestas, con un efecto más pronunciado sobre la motilidad en el envenenamiento agudo y sobre la emotividad en el envenenamiento crónico. Posiblemente, este efecto podría mediarse por la alteración en los sistemas de mono-amino-oxidasa.

Palabras clave: metil-mercurio, agresión, conducta emocional, Betta splendens

The aggressive display of the Betta splendens (Teleostei, Belontiidae) is very prominent, and Bronstein (1980, 1981a, 1982) suggested that it's reproductive and agonistic strategies are typical of many teleosts that utilize external fertilization in relation to the body of the female of the species. A speciesspecific agonistic sequence may be separated into appetitive, mating, and post-mating components (Klein, Figler, & Peeke, 1976). In the case of Betta splendens, the appetitive component that corresponds to the display has been the most studied. These appetitive components include saturation of body coloration, erection of the opercles, or gill cover, orientation and movement characteristics (Simpson, 1968). The mating-related components include biting, jaw blocking between opponents and striking with the tail (Simpson, 1968). An alteration in one of the appetitive components predictably alters the mating components (Klein, Figler, & Peeke, 1976; Bronstein, 1985).

The response to the display may be elicited by (a) the presentation of a subject of the same species in the same or another aquarium, (b) the presentation of a model, or (c) the presentation of a mirror (Meliska, Meliska, & Peeke, 1980). The vigor with which animals present their display, defined by the duration and frequency of the demonstration, is a reliable predictor of the animal's performance in a real combat situation (Evans, 1985) and in situations in which dominance is established (Baenninger, 1968; Meliska & Meliska, 1976; Meliska et al., 1975, 1980; Simpson, 1968). Rhoad, Kalat, and Lopfer (1975) showed that the agonistic display in Bettas is more vigorous when they are presented with a male of the same species, followed by a mirror image, a moving model, and finally, a stationary model.

In neural terms, the aggressive display of the Betta splendens was studied with ablation techniques and discrete lesions of the telencephalon (Marino-Neto & Sabbatini, 1983a, 1983b) and through the waterborne presentation of neurotransmitters (Baenninger, 1968). …

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