Acute exposure to 17α-ethinylestradiol disrupts audience effect on male–female interactions in Betta splendens

Effects of 17α-ethinylestradiol on the neuroendocrine gonadotropic system and behavior of European sea bass larvae (Dicentrarchus labrax)

The widespread use of 17α-ethinylestradiol (EE2), and other estrogenic endocrine disruptors, results in a continuous release of estrogenic compounds into aquatic environments. Xenoestrogens may interfere with the neuroendocrine system of aquatic organisms and may produce various adverse effects. The aim of the present study was to expose European sea bass larvae (Dicentrarchus labrax) to EE2 (0.5 and 50 nM) for 8 d and determine the expression levels of brain aromatase (cyp19a1b), gonadotropin-releasing hormones (gnrh1, gnrh2, gnrh3), kisspeptins (kiss1, kiss2) and estrogen receptors (esr1, esr2a, esr2b, gpera, gperb). Growth and behavior of larvae as evidenced by locomotor activity and anxiety-like behaviors were measured 8 d after EE2 treatment and a depuration period of 20 d. Exposure to 0.5 nM EE2 induced a significant increase in cyp19a1b expression levels, while upregulation of gnrh2, kiss1, and cyp19a1b expression was noted after 8 d at 50 nM EE2. Standard length at the end of the exposure phase was significantly lower in larvae exposed to 50 nM EE2 than in control; however, this effect was no longer observed after the depuration phase. The upregulation of gnrh2, kiss1, and cyp19a1b expression levels was found in conjunction with elevation in locomotor activity and anxiety-like behaviors in larvae. Behavioral alterations were still detected at the end of the depuration phase. Evidence indicates that the long-lasting effects of EE2 on behavior might impact normal development and subsequent fitness of exposed fish.

Oxytocin reduces the frequency of aggressive behaviours in male betta fish (Betta splendens)

The objective of this study was to evaluate the effect of visual isolation and the influence of oxytocin on the aggressive behaviour of male Betta splendens and produce an ethogram for analyses. In the first stage, the fish (n=6) were kept for 60 days in a recirculation system, maintaining visual contact. After this period, the mirror test was applied. The same procedure was performed with the same individuals after 30 days of visual isolation. Visual isolation did no effect on the aggressive behaviour. Application of oxytocin (2.5µg/g) for 1h (twice) in this first stage was also conducted after the mirror test. The effect of exposure to oxytocin was evaluated by applying the mirror test 24hours after the second exposure. The second stage was conducted with another 10 individuals exposed to oxytocin (7.5µg/g) for 1h, after which the mirror test was performed. Exposure to oxytocin (2.5µg/g) did not effect on combat-related behaviours. However, in the second stage influenced all behaviours related to combat and display, with an increase in the frequency of "rest" behaviour. The results indicate that exposure to a neuropeptide at a dose of 7.5µg/g reduces the frequency of aggressive behaviour of male Betta splendens.

Prozac impacts lateralization of aggression in male Siamese fighting fish

Previous studies have shown that Siamese fighting fish, Betta splendens, preferentially use right-eye during the aggressive displays. However, administration of antidepressant drugs may disrupt eye-use preference in association with a reduction in aggression; a phenomena that has not been explored in fish. The objective of the current study was to examine the effects of exposure to the antidepressant drug, fluoxetine, on lateralization in eye-use during aggressive displays in male Siamese fighting fish. Baseline aggression and lateralization in eye use of thirty fish were assessed toward live conspecifics, following which experimental subjects (n=15) were then exposed to fluoxetine (540ng/L) in a static renewal water system. Behavior was quantified again after 9 days of exposure. All of the subjects preferentially used the right-eye during aggressive responses before the exposure experiments. Fluoxetine exposed subjects showed a reduction in the time spent gill flaring as has previously been reported, indicative of a reduction in the level of aggression. Fluoxetine also had a significant effect on the lateralization in preferred eye-use while looking at their opponent. Fish exposed to fluoxetine switched from a preferential use of the right-eye during aggressive encounters prior to exposure to using their left-eye after exposure to fluoxetine. The results are discussed with regard to asymmetrical distribution of serotonin between the two brain hemispheres.

The toxicological effect of Ruta graveolens extract in Siamese fighting fish: a behavioral and histopathological approach

The effects of pharmacological waste on aquatic ecosystems are increasingly highlighted in ecotoxicology research. Many of these products are designed for human physiology but owing to the conservative nature of vertebrate evolution they also tend to have effects on aquatic organisms and fishes in particular when they find their way into aquatic systems via wastewater effluent. One area of research has focused on reproductive control and the associated hormone treatments. Many of these hormones affect the reproductive physiology of fishes and may cause feminization of male reproductive traits. Alternative medicines have also been widely used particularly in traditional cultures but few of these alternative treatments have been assessed with respect to their potential impact on aquatic ecosystems. Rue (Ruta graveolens) has been used as a male contraceptive in traditional medicines but its effects on fish behavior and reproductive anatomy have yet to be established. Here we show that treating Siamese fighting fish, Betta splendens, with extract of rue has a significant effect on key aggressive/reproductive behaviors and the propensity to explore novel objects (boldness). In all cases the respective behaviors were reduced relative to controls and sham injected fish. Histological analysis of the testes revealed that rue exposure reduced the number of spermatozoa but increased the number of spermatocytes relative to controls.

Efeitos de hormônios esteroides de contraceptivos orais combinados sobre os parâmetros comportamentais de Betta splendens (Regan, 1909)

Os hormônios esteroides presentes em várias gerações de contraceptivos orais combinados (COC) podem se apresentar como disruptores endócrinos, produzindo alterações no comportamento e na fisiologia de peixes. Diante disso, o objetivo deste trabalho foi avaliar os efeitos de hormônios esteroides presentes em COC sobre os parâmetros comportamentais de Betta splendens, um peixe ornamental usado na aquariofilia e bastante agressivo. Machos adultos foram observados pelo método ad libitum para confecção do etograma e divididos em cinco grupos, controle e expostos aos hormônios: 17β-estradiol (E2); levonorgestrel e etinilestradiol (LEA - segunda geração de COC); gestodeno e etinilestradiol (GEA - terceira geração de COC); e drospirenona e etinilestradiol (DEA - quarta geração de COC). Os peixes foram expostos por 30 dias à concentração final de 10ng/L. Foram avaliados os comportamentos pelos métodos de varredura instantânea e animal-focal, bem como o consumo de ração. No método varredura, o comportamento descansar apresentou o maior valor (54,4±10,1%) no grupo E2 (P<0,05). Os comportamentos agressivos de carga (16,1±3,6%) e recuar e carga (16,4±5,1%) apresentaram os maiores valores no grupo controle em relação aos demais grupos (P<0,05). Os animais do grupo E2 apresentaram maior frequência de comportamentos inativos (76,1%) comparados aos de outros grupos. O comportamento atípico natação errática não foi observado no grupo controle, mas foi observado nos grupos experimentais. Os grupos E2, LEA, GEA e DEA apresentaram redução nos comportamentos agressivos (10%) quando comparados ao grupo controle pelo método animal-focal. Não foram observadas diferenças na exibição desses comportamentos ao se compararem os animais expostos às diferentes gerações de contraceptivos e no consumo de ração. Pode-se concluir que 17β-estradiol causou mais efeitos aos peixes e que diferentes gerações de COC apresentaram efeitos tóxicos semelhantes em relação aos comportamentos observados.