Coping with exposure to hypoxia: modifications in stress parameters in gilthead seabream (Sparus aurata) fed spirulina (Arthrospira platensis) and brewer's yeast (Saccharomyces cerevisiae).

This study aimed to investigate the stress response of Sparus aurata specimens fed with nutraceutical aquafeed brewer's yeast (Saccharomyces cerevisiae) and spirulina (Arthrospira platensis). For that purpose, 96 (169.0 ± 2.8 g) animals were distributed randomly in 12 tanks (8 fish per tank, 4 replicates) and divided in 3 groups (D1, casein/gelatin, control; D2, brewer's yeast; D3, spirulina) and fed for 30 days. At the end of this period, fish from two replicates of each experimental diet were submitted to air exposure for 60 s while the fish from the other two replicates were maintained undisturbed (control). Afterwards, samples of blood, skin mucus, and head kidney were collected. The results revealed that after air exposure, cortisol, and glucose levels increased in the groups fed D1 (18.5 ± 2.6 mg/mL; 7.3 ± 0.6 mmol/L, respectively) and D2 (20.0 ± 6.2 mg/mL; 7.7 ± 0.6 mmol/L), but glucose not increased in fish fed D3 (13.7 ± 2.6 mg/mL; 5.5 ± 0.3 mmol/L). Lactate levels increased in all stressed groups, but in D1, its levels were significantly higher. After stress procedure, immunoglobulin M (IgM) levels in mucus increased only in fish fed D3 (0.1901 ± 0.0126 U/mL). Furthermore, there was a reduction in the expression of some genes involved in stress response (coxIV, prdx3, csfl-r, ucp1, and sod in fish fed D2 and D3). csf1 decreased only in stressed fish fed D2. However, cat increased in fish fed with D3. In summary, these findings points to the beneficial effects of spirulina and brewer's yeast to improve stress resistance in aquaculture practices of gilthead seabream.

Synchronization to light and mealtime of daily rhythms of locomotor activity, plasma glucose and digestive enzymes in the Nile tilapia (Oreochromis niloticus).

The light-dark cycle and feeding can be the most important factors acting as synchronizers of biological rhythms. In this research we aimed to evaluate synchronization to feeding schedule of daily rhythms of locomotor activity and digestive enzymes of tilapia. For that purpose, 120 tilapias (65.0±0.6g) were distributed in 12 tanks (10 fish per tank) and divided into two groups. One group was fed once a day at 11:00h (zeitgeber time, ZT6) (ML group) and the other group was fed at 23:00h (ZT18) (MD group). The fish were anesthetized to collect samples of blood, stomach and midgut at 4-hour intervals over a period of 24h. Fish fed at ML showed a diurnal locomotor activity (74% of the total daily activity occurring during the light phase) and synchronization to the feeding schedule, as this group showed anticipation to the feeding time. Fish fed at MD showed a disruption in the pattern of locomotor activity and became less diurnal (59%). Alkaline protease activity in the midgut showed daily rhythm with the achrophase at the beginning of the dark phase in both ML and MD groups. Acid protease and amylase did not show significant daily rhythms. Plasma glucose showed a daily rhythm with the achrophase shifted by 12h in the ML and MD groups. These results revealed that the feeding time and light cycle synchronize differently the daily rhythms of behavior, digestive physiology and plasma metabolites in the Nile tilapia, which indicate the plasticity of the circadian system and its synchronizers.

Daily rhythms after vaccination on specific and non-specific responses in Nile tilapia (Oreochromis niloticus).

We evaluated the daily changes in immunological and hematological factors in tilapia (Oreochromis niloticus) after an immunization period with a subsequent challenge. Experiments were divided into two phases: Phase 1 (immunization): 144 fish were distributed into two groups with 72 fish in six tanks. One group (T1) was immunized, comprising six vaccination time points (ZT schedule = ZT2 h, ZT6 h, ZT10 h, ZT14 h, ZT18 h, ZT22 h). The same schedule was applied to the other group, but with saline solution (non-vaccinated: T2). Both groups remained in the laboratory for 30 days (considered the immunization period). Phase 2 (challenge): on day 30, both vaccinated and non-vaccinated groups were challenged with Streptococcus agalactiae (2.0 × 107 CFU mL-1) following the same ZT schedule to stimulate the immune response without leading to widespread infection and mortality. On day 45, blood and head kidney samples were collected during the same ZT schedule. The variations in time of the following parameters within each group were evaluated: hematology, peroxidase activity, IgM, tnf-α3, tgf-ß1, il-1ß and il-12 gene expression. No significant mortality was observed for the groups or the ZT schedule (p > 0.05). Daily rhythms with diurnal acrophases were found in T2 for il12, tnf-α3 and tgf-ß1 expression gene, while the acrophases of the peroxidase level, hematocrit and thrombocytes were at nighttime (p < 0.05). In contrast, most of the parameters in the vaccinated tilapia showed no daily rhythms (p > 0.05), except IgM. For all the parameters, the interaction effect between time and treatment (vaccinated and non-vaccinated groups) depended on ZT. Our results reveal that the humoral and non-specific immune system displayed a circadian rhythm based on the light-dark cycle, which could be affected by the vaccination procedure in tilapia.

Effects of dietary carbohydrate/lipid ratios on growth, body composition, and nutrient utilization of hybrid catfish (Pseudoplatystoma reticulatum x Leiarius marmoratus) / Efectos de la relación carbohidratos/lípidos en el crecimiento, composición corporal y utilización de nutrientes del bagre hibrido (Pseudoplatystoma reticulatum x Leiarius marmoratus) / Efeitos da relação carboidratos/lipídios sobre o crescimento, composição corporal e utilização de nutrientes do bagre híbrido (Pseudoplatystoma reticulatum x Leiarius marmoratus)

Background: farming of hybrid catfish is relatively recent in Brazil; consequently, it is necessary to develop practical diet formulations for this fish. Objective: to evaluate the influence of different carbohydrate/lipid ratios (CHO:L) on growth performance, body composition and nutrient utilization of hybrid catfish (Pseudoplatystoma reticulatum x Leiarius marmoratus). Methods: four isonitrogenous diets were formulated with increasing lipid levels, using the following CHO:L ratios: 1.3:1 (diet 1); 1.1:1 (diet 2); 0.9:1 (diet 3), and 0.8:1 (diet 4). Fish were fed 5% of BW/day (dry-weight basis) in triplicate groups of 6 fish each (18 ± 1.5 g) for 2 months. Results: though final weight and absolute weight gain decreased with increasing dietary lipid (p<0.05), there was no significant difference in daily feed consumption among treatments (p>0.05). Moreover, viscerosomatic index and hepatosomatic index showed no statistical difference among dietary treatments. Body lipid increase for fish fed diet 4. Lipid and energy efficiency retentions were higher at 0.8:1 CHO:L group. Conclusion: CHO:L ratios around 1.3:1 produced large benefit by best growth performance in the studied hybrid model.

Antecedentes: el cultivo del bagre híbrido es relativamente reciente en Brasil, con lo cual se hace necesario desarrollar dietas prácticas para este pez. Objetivo: evaluar la influencia de la relación carbohidratos/ lípidos (CHO:L) en el crecimiento, composición corporal, y utilización de nutrientes por el bagre híbrido (Pseudoplatystoma reticulatum x Leiarius marmoratus). Métodos: cuatro dietas isonitrogenadas fueron formuladas con niveles incrementales de lípidos, utilizando la siguiente relación CHO/L: 1,3:1 (dieta 1); 1,1:1 (dieta 2); 0,9:1 (dieta 3), y 0,8:1 (dieta 4). Los peces fueron alimentados con 5% de BW/día (en base a peso seco), en triplicado con 6 peces/grupo (18 ± 1,5 g) por grupo, por un tiempo de 2 meses. Resultados: aunque el peso final y la ganancia de peso absoluto disminuyó con el aumento de lípidos en la dieta (p<0,05), no hubo diferencia significativa en el consumo diario de alimento entre los tratamientos (p>0,05). Por otra parte, para el índice viscerosomático e índice hepatosomático no hubo diferencias estadísticas entre los tratamientos. Se ha observado el aumento de los lípidos corporales de peces alimentados con la dieta 4. La eficiencia de retención de lípidos y energética fueron mayores en el grupo 0,8:1 CHO:L. Conclusión: la relación CHO:L alrededor de 1,3:1 produce un gran beneficio al mejorar el crecimiento del modelo del pez híbrido estudiado.

Antecedentes: o cultivo de bagre híbrido com características favoráveis ao crescimento é relativamente recente no Brasil, consequentemente é necessária a formulação de dietas práticas para essa espécie. Objetivo: se avaliou a influência da relação carboidrato/lipídio (CHO:L) no crescimento, composição corporal e utilização de nutrientes pelo bagre híbrido (Pseudoplatystoma reticulatum x Leiarius marmoratus). Métodos: quatro dietas isonitrogenadas foram formuladas com o aumento dos níveis de lipídios na dieta, utilizando a seguinte relação CHO/L: 1,3:1 (dieta 1); 1,1:1 (dieta 2); 0,9:1 (dieta 3), y 0,8:1 (dieta 4). Os peixes foram alimentados a 5% de BW/dia (base de peso seco), sendo triplicatas de 6 peixes (18 ± 1,5 g) por grupo por um período de 2 meses. Resultados: apesar do peso final e do ganho de peso absoluto decrescerem com o aumento da dieta lipídica (p<0,05), não houve diferença significativa no consumo diário de alimento entre os tratamentos (p>0,05). Contudo, os índices viscerossomático e hepatossomático não demonstraram diferença estatística entre os tratamentos. Foi registrado aumento dos lipidios corporais para os peixes alimentados com a dieta 4. A eficiência de retenção de lipídios e a eficiência de retenção energética foram maiores para o grupo 0,8 CHO:L. Conclusão: a relação ao redor de 1,3 produziu grandes benefícios por melhorar o crescimento do modelo de peixe híbrido estudado.

Parâmetros hematológicos e alterações histopatológicas em bijupirá (Rachycentron canadum Linnaeus, 1766) com amyloodiniose / Parameters hematological and histopathologic alterations in cobia (Rachycentron canadum Linnaeus, 1766) com amyloodiniose

O objetivo do trabalho foi descrever os parâmetros hematológicos e as alterações histopatológicas em bijupirás infectados por Amyloodinium ocellatum. Um grupo de 27 peixes foi anestesiado para coleta de amostras de sangue e eutanasiados para coleta de muco e fragmentos de tecido cutâneo e branquial. Foram avaliadas a prevalência e a intensidade parasitária da infecção, assim como os valores de parâmetros hematológicos e alterações histopatológicas. A prevalência parasitária nas brânquias foi de 100% e no muco foi de 80,8% e as intensidades parasitárias médias foram de 683,5 nas brânquias, e 67,1 no muco cutâneo. Os valores médios dos parâmetros hematológicos foram: eritrócitos 4,3x10(6)µL; VG 26%; VGM 64,2fL; proteína plasmática 5,8mg/dL; trombócitos 5,2 x10³/µL e leucócitos 3,6 x10³/µL. Além disso, foram verificadas hiperplasia do epitélio respiratório acompanhada de fusão lamelar, descolamento do epitélio, dilatação do seio venoso, formação de aneurisma, ruptura do epitélio lamelar, hemorragia, necrose, reação inflamatória linfocítica. O parasito foi observado nas lamelas branquiais, o VMA variou do grau discreto ao severo e o IAH foi de 76,8. A pesquisa assume importância por se tratar dos primeiros estudos em Rachycentron canadum, um peixe que se destaca com potencial ao cultivo.

The aim of this study was to describe the hematological parameters and histopathologic alterations in cobia infected by Amyloodinium ocellatum. A group of 27 fish were anesthetized to collect blood samples and euthanatized to collect mucus and tissue fragments of skin and gills. The prevalence and parasitic intensity of the infection, besides hematologic parameters and histopathologic alterations, was measured. Parasite prevalence in the gills was 100% and in the mucus 80.8%, and the average intensity of infection in gills and skin was 683.5 e 67.1 respectively. The mean values of hematological parameters were: erythrocytes 4.3x10(6)μL; PCV 26%, MCV 64.2 fL, plasma protein 5.8mg/dL, thrombocytes 5.2x10³/μL and leukocytes 3.6x10³/μL . Furthermore was found hyperplasia of the respiratory epithelium accompanied by lamellar fusion, detachment of the epithelium, venous sinus dilatation, aneurysm formation and rupture of the lamellar epithelium, hemorrhage, necrosis and lymphocytic inflammatory reaction. The parasite was observed between the gills lamellae, the AMV ranged from mild to severe and AHI values were 76.8. The study assumes importance because it is the first study in Rachycentron canadum, a fish that stands out with potential for growing.