RESUMO

This study interrogated factors which affect the appearance of secondary sexual characteristics, namely, fin spinelets (rigid dimorphic structure empirically associated with male sexual maturity in characids), in Astyanax altiparanae. Many variables such as the season of the year and several biotic components, including organism length, sex, phase of maturation, and the presence of gonads, were investigated. These factors were then associated with the physiological development of fin spinelets. The development of this trait is related to reproductive strategies but demonstrates considerable population variability as it is found throughout the year in some species but only during specific periods in others. Seventy-five specimens obtained from spontaneous spawn of farmed fish were arbitrarily grouped into small-, medium-, and large-sized groups in both summer and winter. Gonadal histology was performed to confirm each animal's sex and phase of maturation. Diaphanization of the fish was performed to visualize, count, and measure the fin spinelets. Finally, gonadectomization of some males was utilized to investigate the gonadal effect on the presence of fin spinelets. The present results show that the presence of fin spinelets is a secondary sexual characteristic of males which occurs independently of the season and is always present in males longer than 48 mm. However, in the summer, male specimens presented more rays with fin spinelets than during the winter. Furthermore, since fin spinelets were observed on immature males as well as spawning capable males, their presence cannot be directly associated with sexual maturity in male A. altiparanae, as previously supposed. Finally, gonadectomization resulted in an initial reduction in the length of fin spinelets. However, this trend was eventually normalized with time.

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RESUMO

In the present experiment, the effects of mannan-oligosaccharide (MOS) on health and growth of Nile tilapia juveniles were investigated. In addition to the control treatment (without MOS),three levels of MOS were included in Nile tilapia diets (1, 8, and 15 g kg−1), and hematology, reactive oxygen species (ROS) production, lysozyme and productive parameters were analyzed. Fish blood was sampled at day zero (basal sample) and after 60 days of trial, and the productive parameters were evaluated at the end of the experiment. MOS feeding decreased the feed consumption (p = 0.0299) in fish fed with 1 and 8 g kg-1, but without any alteration in weight gain (WG) and feed conversion ratio (FCR). No changes were observed in the hematology due to MOS feeding after 60 days. However, the prebiotic caused changes in the innate immunity of fish, giving rise to ROS production in fish fed with 1 g kg-1 (p<0.0001) and decreasing the serum lysozyme activity of fish fed with 15 g kg-1 (p<0.0001). In conclusion, the authors recommend the inclusion of 1 g kg-1 for Nile tilapia juveniles feeding due to the positive effect in innate immune system.(AU)

No presente experimento, os efeitos do mananoligossacarídeo (MOS) na saúde e no crescimento de tilápias do Nilo foram investigados. Além do tratamento controle (sem adição de MOS), três níveis de MOS foram adicionados na dieta de tilápias do Nilo (1, 8 e 15 g kg-1). Foram analisadas a hematologia, a produção de espécies reativas de oxigênio (EROs), a lisozima e parâmetros produtivos. Os peixes tiveram o sangue colhido no dia zero (amostragem basal) e depois de 60 dias de experimento, juntamente com a avaliação dos parâmetros produtivos. A alimentação com MOS diminuiu de forma significativa o consumo (p = 0.0299) em peixes alimentados com 1 e 8 g kg-1, mas sem quaisquer alterações sobre o ganho de peso (GP) e conversão alimentar (CA). Não foram observadas mudanças nos parâmetros hematológicos devido à alimentação com MOS. No entanto, o prebiótico alterou sua resposta imune, aumentando a produção de EROs nos animais alimentados com 1 g kg-1 (p<0,0001) e diminuindo a atividade de lisozima sérica em peixes alimentados com 15 g kg-1 (p<0,0001). Em conclusão, os autores recomendam a inclusão de 1 g kg-1 de MOS na dieta para tilápias do Nilo juvenis devido ao efeito positivo sobre o sistema imune.(AU)

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RESUMO

In the present experiment, the effects of mannan-oligosaccharide (MOS) on health and growth of Nile tilapia juveniles were investigated. In addition to the control treatment (without MOS),three levels of MOS were included in Nile tilapia diets (1, 8, and 15 g kg−1), and hematology, reactive oxygen species (ROS) production, lysozyme and productive parameters were analyzed. Fish blood was sampled at day zero (basal sample) and after 60 days of trial, and the productive parameters were evaluated at the end of the experiment. MOS feeding decreased the feed consumption (p = 0.0299) in fish fed with 1 and 8 g kg-1, but without any alteration in weight gain (WG) and feed conversion ratio (FCR). No changes were observed in the hematology due to MOS feeding after 60 days. However, the prebiotic caused changes in the innate immunity of fish, giving rise to ROS production in fish fed with 1 g kg-1 (p<0.0001) and decreasing the serum lysozyme activity of fish fed with 15 g kg-1 (p<0.0001). In conclusion, the authors recommend the inclusion of 1 g kg-1 for Nile tilapia juveniles feeding due to the positive effect in innate immune system.

No presente experimento, os efeitos do mananoligossacarídeo (MOS) na saúde e no crescimento de tilápias do Nilo foram investigados. Além do tratamento controle (sem adição de MOS), três níveis de MOS foram adicionados na dieta de tilápias do Nilo (1, 8 e 15 g kg-1). Foram analisadas a hematologia, a produção de espécies reativas de oxigênio (EROs), a lisozima e parâmetros produtivos. Os peixes tiveram o sangue colhido no dia zero (amostragem basal) e depois de 60 dias de experimento, juntamente com a avaliação dos parâmetros produtivos. A alimentação com MOS diminuiu de forma significativa o consumo (p = 0.0299) em peixes alimentados com 1 e 8 g kg-1, mas sem quaisquer alterações sobre o ganho de peso (GP) e conversão alimentar (CA). Não foram observadas mudanças nos parâmetros hematológicos devido à alimentação com MOS. No entanto, o prebiótico alterou sua resposta imune, aumentando a produção de EROs nos animais alimentados com 1 g kg-1 (p<0,0001) e diminuindo a atividade de lisozima sérica em peixes alimentados com 15 g kg-1 (p<0,0001). Em conclusão, os autores recomendam a inclusão de 1 g kg-1 de MOS na dieta para tilápias do Nilo juvenis devido ao efeito positivo sobre o sistema imune.

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SummaryThe aim of this study was to describe the effect of temperature on the fertilization, early developmental stages, and survival rate of two Neotropical catfishes Pimelodus maculatus and Pseudopimelodus mangurus. After fertilization, the eggs were incubated at 22°C, 26°C, and 30°C, which resulted in fertilization rates of 96.95 ± 1.79%, 98.74 ± 0.76%, and 98.44 ± 0.19% for P. maculatus and 96.10 ± 1.58%, 98.00 ± 0.63%, and 94.60 ± 2.09% for P. mangurus, respectively. For P. maculatus, hatching occurred after 22 h 30 min post-fertilization at 22°C, 16 h 30 min at 26°C, and 11 h 20 min at 30°C, and the hatching rates were 43.87 ± 7,46%, 57.57 ± 17.49%, and 53.63 ± 16.27%, respectively. For P. mangurus, hatching occurred after 28 h 30 min post-fertilization at 22°C and 17 h 30 min at 26°C with respective hatching rates of 45.4 ± 21.02% and 68.1 ± 12.67%. For this species, all embryos incubated at 30°C died before hatching. Additionally, for P. maculatus, the larvae from the lower (22°C) and higher temperatures (30°C) presented increased abnormality rates, as observed in the head, tail and yolk regions. The lowest abnormality rate was detected at 26°C, which was considered the optimal incubation temperature for both species. The developed protocol enables the manipulation of embryonic development, which is important for the application of reproductive biotechniques, including chimerism and chromosome-set manipulation. The data obtained here are also important for the surrogate propagation of this species as P. mangurus was recently categorized as an endangered fish species.

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RESUMO

In this experiment, the beneficial effects of mannan-oligosaccharide (MOS) on immunology and intestinal microbiology of Nile tilapia juveniles was demonstrated. Prior to this, three levels of MOS in Nile tilapia diets (1, 8, and 15 g.kg−1) were tested, and hematological parameters, serum lysozyme, and intestinal microbiology were analyzed. The fish blood was sampled at day zero (basal sample) and after 45 days of trial, and the intestinal microbiota was evaluated at the end of the experiment. After 45 days of trial, fish fed 8 and 15 g.kg−1 of MOS presented an increase in both aerobic and lactic acid bacteria numbers in their guts. The MOS feeding also increased the counts of total leukocytes, monocytes, and lymphocytes of fish, but a decrease in neutrophils was also observed. Additionally, the serum lysozyme was higher in all fish fed MOS. The dietary MOS is able to modulate the intestinal microbiota, increasing the number of beneficial bacteria, and immunostimulates the Nile tilapia juvenile, giving rise to white blood cells and serum lysozyme.(AU)

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