RESUMO

The trade of aquarium organisms is growing worldwide. This market depends on a continuous supply of healthy and colorful aquatic animals, but this sector has few initiatives. However, in the last decade, there has been a growing interest in researching captive breeding of these animals, aiming to develop a more sustainable aquarium hobby. Larviculture is an important phase in the cultivation process because the larvae are more sensitive to stress and variations in the bulk of variables, such as temperature, salinity, nutritional management, light intensity and spectrum, and environmental background colors. Because background color could be a promoter variable of proper welfare, we tested whether it affects the endocrine response of tomato clownfish Amphiprion frenatus larvae to an acute stress challenge. We show that background color influences the endocrine stress axis responsiveness in tomato clownfish. When fish were subjected to a standard acute stressor of 61 days after hatching, only fish adapted to white walls increased the whole-body cortisol levels. From the results presented herein, we recommend that white tanks be avoided for A. frenatus larviculture. Both, the less stress level and the good welfare condition of larvae reared in colored tanks may have robust, practical applications since almost all clownfish in the ornamental aquarium trade come from captive breeding.

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The false clown anemonefish (Amphiprion ocellaris) is a protandrous hermaphrodite with a distinctive reproductive behavior. This study elucidates the genetic mechanisms and timing of sex changes in captive-bred A. ocellaris by examining the expression of key genes involved in this process, specifically cyp19a1a and cyp19a1b. Gonadal histological analyses and gene expression studies were conducted on subadult fish paired for 0, 1, 2, 3, 4, 5, and 16 months. Our findings reveal that alterations in cyp19 gene expression coincide with a pairing period starting after 3 months. Both cyp19a1a and cyp19a1b expression levels were significantly elevated in paired females compared with their male counterparts and unpaired controls. Histological investigations demonstrated that sex conversion to females occurred during the 3-month pairing period. This study highlights the crucial role of cyp19a1a and cyp19a1b in the sex change process of A. ocellaris and indicates that a minimum of 5 months of pairing is necessary for completing the sex change.

O peixe-palhaço falso (Amphiprion ocellaris) é um hermafrodita protândrico com um comportamento reprodutivo distintivo. Este estudo esclarece os mecanismos genéticos e o período das mudanças de sexo em A. ocellaris criados em cativeiro, examinando a expressão de genes-chave envolvidos nesse processo, especificamente cyp19a1a e cyp19a1b. Análises histológicas gonadais e estudos de expressão gênica foram conduzidos em peixes subadultos emparelhados por 0, 1, 2, 3, 4, 5 e 16 meses. Os resultados revelam que alterações na expressão do gene cyp19 coincidem com um período de emparelhamento a partir de 3 meses. Os níveis de expressão de cyp19a1a e cyp19a1b foram significativamente elevados em fêmeas emparelhadas em comparação com seus homólogos masculinos e controles não-emparelhados. Investigações histológicas demonstraram que a conversão sexual para fêmeas ocorreu durante o período de emparelhamento de 3 meses. Este estudo destaca o papel crucial de cyp19a1a e cyp19a1b no processo de mudança de sexo de A. ocellaris e indica que um mínimo de 5 meses de emparelhamento é necessário para concluir a mudança de sexo.

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The nitrification process in recirculating aquaculture systems can reduce water pH. Fish can also be exposed to water acidification during transport, an important feature in the aquarium industry, as live fish can be kept in a closed environment for more than 24 h during overseas aerial transportation. Therefore, it is important to study the responses of fish to acidic environments. We investigated the impacts of acute exposure to decreasing pH levels in orange clownfish Amphiprion percula juveniles on their survival and oxidative stress status. Fish were exposed to pH 5, 6, 7, and 8 for 96 h. We observed a significant reduction in survival (85%) and protein damage as measured by P-SH (protein thiol) for fish maintained at pH 5. Despite no effects on survival or oxidative damage, fish exposed to pH 6 showed an increase in their antioxidant defense systems, demonstrating this pH level could not be suitable for them as well. Furthermore, there were no negative effects for fish kept at pH 7, compared to those maintained at pH 8 during this short-term evaluation.

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