Abstract Abstract: This study assessed the effect of salinity on embryonic development, larval growth and survival of the yellow clam Mesodesma mactroides in laboratory. Embryos and larvae of M. mactroides were submitted and maintained at four different salinities: 20, 25, 30 and 35 ppt, to determine optimal conditions for the species. Through descriptive analysis, the results showed that the embryos tolerate salinities between 25 - 35 ppt, presenting fast metamorphoses at salinities 30 and 35 ppt, during experimental period of 27 hours. The same tolerance pattern was observed in larval stage (25 - 35 ppt), showing a better development in salinity of 35 ppt. This result is verified in biometric analyzes of height and length of the shells and survival rate, with higher averages in treatments with salinity 35 ppt. The experimental period of this stage lasted 27 days, when the larvae were able to settle. These results indicate that embryos and larvae of M. mactroides tolerate salinities between (25-35 ppt), with the best growth and survival on high salinities being recommended to better yields in laboratory.

Abstract The yellow clam Mesodesma mactroides (Reeve, 1854) is a sand mollusc with historical and socioeconomic importance in Brazil, Uruguay and Argentina. A guaranteed form to access a successful reestablishment of the species in their natural environment is directly linked to their reproduction biology. Then, our report introduces the embryonic and larval development of the yellow clam reared in laboratory for such purposes. M. mactroides broodstock were selected as specimens who possess a mean total shell length and weight of 66 ± 3.82 mm and 27.15 ± 4.07 g for an afterwards spawn induction through stripping technique. Regarding the embryonic development, newly fertilized oocytes exhibited a mean diameter of 51.20 ± 6.64 μm. The first polar corpuscle, trochophores and D-veliger appeared at 20 min, 18 and 24 h after fertilization, respectively. Umbonate and pediveliger larvae were noticed on the 8th and 25th day, respectively, with complete metamorphosis occurring only at the 27th day, when all larvae were retained in a 200 μm nylon mesh. Therefore, with that basic understanding of the embryonic and larval development of M. mactroides in the laboratory, forwards studies will focus in establish a technological package for this species.

Resumen Antecedentes: La cianobacteria Arthrospira platensis (Spirulina) puede usarse como substituto potencial de la harina de pescado (HP) por su alto contenido de proteína, sus antioxidantes y sus propiedades inmunoestimulantes. Objetivo: Analizar el efecto de la substitución parcial y total de HP por A. platensis (0, 30, 50, 70 y 100% de substitución) en juveniles de lisa (Mugil liza). Métodos: Juveniles de lisa (n=210) se mantuvieron en un sistema de recirculación con parámetros de calidad de agua en niveles óptimos para la especie. Las lisas se alimentaron con las dietas experimentales durante 80 días. Cada dieta fue evaluada en triplicado. Al final del periodo experimental se midieron los parámetros de crecimiento y se colectaron muestras de sangre, hígado y bazo para evaluación del sistema inmune. Resultados: La substitución total (100%) resultó en deficiente crecimiento y baja sobrevivencia. El remplazo de HP produjo cambios en las proporciones de macrófagos y linfocitos. La substitución de hasta un 50% HP aumentó la expresión de receptores CD3 en linfocitos T del bazo. Por otro lado, la substitución mayor a 50% HP disminuyó la expresión de receptores CD3. La substitución parcial de HP disminuyó el proceso de apoptosis. Conclusiones: Proponemos una substitución de HP del 50% por A. platensis, lo cual mejora el desempeño del sistema inmune no especifico de las lisas.

Abstract Background: Cyanobacterium Athrospira platensis (Spirulina) is a potential fishmeal (FM) substitute in fish diets because of its high protein content, antioxidant and immunostimulant properties. Objective: To evaluate the effects of total and partial substitution of FM with A. platensis (0, 30, 50, 70 and 100% substitution) in juvenile mullet (Mugil liza). Methods: Juvenile mullets (n=210) were maintained in a recirculation system under optimal water parameters for the species. Mullets were fed five experimental diets for 80 days. Each diet was tested in triplicate tanks. At the end of the experimental period growth parameters were measured and samples of blood, liver and spleen were taken to evaluate the immune system. Results: Full replacement (100%) of FM resulted in growth deficits and low survival. The FM replacement induced changes in the proportion of macrophages and lymphocytes. Up to 50% FM replacement increased the expression of CD3 receptors in spleen T lymphocytes (T-Cells), whereas >50% FM replacement decreased the expression of CD3 receptors. We also found that partial FM substitution diminished the apoptotic process. Conclusions: Up to 50% FM substitution with A. platensis can improve performance of non-specific immune system of mullets.

Resumo Antecedentes: A cianobactéria Athrospira platensis (Spirulina) é um potencial substituto da farinha de peixe (FP) pelo seu alto conteúdo de proteína, antioxidantes e características imune estimulantes. Objetivo: Foram avaliados os efeitos da substituição parcial e total da FP por A. platensis (0, 30, 50, 70 e 100% substituição) em juvenis de tainha (Mugil liza). Métodos: Juvenis de tainha (n=210) foram mantidos em um sistema de recirculação com os parâmetros da água sendo mantidos em níveis ótimos para a espécie. As tainhas foram alimentadas com as dietas experimentais por 80 dias, cada dieta foi testada em triplicata, ao final do período experimental foram avaliados os parâmetros de crescimento e amostras de sangue, fígado e baço foram coletadas para a avaliação do sistema imune. Resultados: A substituição total de FP resultou em redução do crescimento e baixa sobrevivência. A avaliação do sistema imune demostrou que a substituição da FP produz alterações nas proporções de macrófagos e linfócitos. Provou-se que até 50% de substituição da FP incrementa a expressão de receptores CD3. Além disso, a substituição parcial da FP diminui o processo de apoptose. Conclusão: Baseado em nossos descobrimentos, se propõe a substituição de até 50% da FP por A. platensis que melhorará o desempenho do sistema imunológico não específico das tainhas.

Abstract: The skin of three juvenile Lepidosiren paradoxa specimens was examined. The epidermis was composed of a polystratified epithelium resting on a basement membrane, including mucus-secreting cells, and a cuticle of mucopolysaccharides on the surface. Two types of skin receptors, electroreceptors and mechanoreceptors, were found; the first type was located in the dermoepidermal junction, and the second type was completely intraepiderma. The skin structure of these fish, suggests the possibility of the skin participating in the breath.

Resumo: O objetivo deste trabalho foi avaliar o efeito do sistema de cultivo tradicional em água clara e do em bioflocos sobre os estados antioxidante e imunológico do camarão Litopenaeus vannamei. Amostras (brânquia, hemolinfa e hepatopâncreas) foram coletadas nos dias 15, 30 e 60 do período experimental. Os seguintes parâmetros imunológicos foram analisados a cada tempo amostral: hemócitos granulares e hialinos, proteína total e apoptose. Também foram realizados ensaios da atividade da glutamato-cisteína ligase (GCL) e das concentrações de glutationa reduzida (GSH) e de substâncias reativas ao ácido tiobarbitúrico (TBARS). Os parâmetros imunológicos avaliados não diferiram significativamente entre os tratamentos. Os camarões criados em água clara apresentaram maiores níveis de peroxidação lipídica nas brânquias e de GCL na hemolinfa nos dias 15 e 30. Camarões em bioflocos apresentaram maior taxa de sobrevivência, e a água não precisou ser renovada durante o período experimental. O sistema de bioflocos melhora os níveis de produtividade e promove um ambiente de cultivo mais saudável.

Abstract: The objective of this work was to evaluate the effect of the traditional culture system in clear water and of the one in microbial flocs on the antioxidant and immunological status of Litopenaeus vannamei shrimp. Samples (gill, hemolymph, and hepatopancreas) were collected on days 15, 30, and 60 of the experimental period. The following immunological parameters were analyzed at each evaluation time: granular and hyaline hemocytes, total protein, and apoptosis. Assays on glutamate-cysteine ligase (GCL) activity and on the concentrations of reduced glutathione (GSH) and thiobarbituric acid reactive substances (TBARS) were also performed. The evaluated immunological parameters did not differ significantly between treatments. Shrimp reared in clear water showed higher levels of lipid peroxidation in the gills and of GCL activity in the hemolymph on days 15 and 30. Shrimp in microbial floc had a higher survival rate, and the water did not have to be renewed during the experimental period. The microbial floc system improves production levels and provides a healthier culture environment.

O objetivo deste trabalho foi avaliar o efeito de restrição alimentar sobre o desempenho zootécnico e custo de alimentação em juvenis de tainha (Mugil liza). Foram avaliados cinco taxas de alimentação - 100, 80, 60, 40 e 20% da saciedade, denominados F100%, F80%, F60%, F40% e F20% -, em triplicata. Juvenis com 0,21±0,03 g (n=30) foram distribuídos em 15 tanques de 200 L. A estimativa do custo foi feita quanto à produção de mil juvenis de tainha. A sobrevivência foi superior a 93%, e não houve influência dos tratamentos. A taxa de crescimento específico no tratamento F100% foi de 5,96±0,18% por dia, e o peso final foi aproximadamente seis vezes maior que o inicial. Tainhas do tratamento F20% apresentaram menor índice hepatossomático, hepatócitos e núcleos menores e menor reserva de glicogênio hepático em relação aos demais tratamentos. A redução da taxa de alimentação influenciou negativamente o crescimento de juvenis de tainha. No entanto, uma taxa de alimentação em torno de 72% da saciedade é capaz de promover o melhor aproveitamento do alimento consumido, com 28% de redução do custo da ração.

The objective of this work was to evaluate the effect of restricted feeding on the growth and fed costs of juvenile mullet (Mugil liza). Five feeding levels - 100, 80, 60, 40 e 20% satiation, named as F100%, F80%, F60%, F40% e F20% - were evaluated in triplicate. Juvenile mullets with 0.21±0.03 g (n=30) were randomly distributed in 15 tanks of 200 L. Cost estimation was done for the production of one thousand juvenile mullets. Survival was higher than 93%, and there was no influence of treatments. The specific growth rate of mullet in the F100% treatment was 5.96±0.18% per day, and the final weight was six-fold higher than the initial one. Mullets of the F20% treatment had the smallest liver somatic index, smallest hepatocytes and nuclei, and the smallest hepatic glycogen reserve, in comparison to fish of other treatments. The feeding level reduction hampered the juvenile mullet growth. However, a feeding level of about 72% satiation is capable of promoting a better utilization of the feed consumed, with 28% reduction of feed costs.

In this study, we detected White spot syndrome virus (WSSV) in wild Farfantepenaeus paulensis collected in the Lagoa dos Patos estuary and cultivated Litopenaeus vannamei. This is the first report of WSSV in F. paulensis from Lagoa dos Patos and farmed L. vannamei shrimps in Rio Grande do Sul.