Nitrate acute toxicity to post larvae and juveniles of Macrobrachium amazonicum (Heller, 1862).

The objective was to determine the median lethal concentration (LC50) of nitrate for post-larvae and juveniles of Macrobrachium amazonicum exposed for 96 h, and to identify histopathological alterations in the gills of juveniles exposed to nitrate. Post-larvae and juveniles of M. amazonicum were exposed to seven different concentrations of nitrate (0, 50, 100, 500, 1000, 1500 and 2000 mg.L-1) with four replicates (n = 10 prawn/experimental unit). The degree of damage to the branchial structure of juveniles was evaluated using standard histological processing with hematoxylin and eosin (H&E), subjected to the Organ Index (Iorg). LC50 values at 24, 48, 72 were estimated by the Trimmed Spearman Karber Method software and were respectively 1574, 638, 237, and 194 mg.L-1 for post-larvae and 1070, 286, 185 and 155 mg.L-1 for juveniles, respectively. From these results, the safety level of nitrate was estimated at 157, 64, 24 and 19 mg.L-1 for post-larvae and 107; 27; 18 and 16 mg.L-1 for juveniles, respectively for 24 h, 48 h, 72 h and 96 h. Damage to the gills in treatments with 100% mortality for nitrate corresponded to the high occurrence of progressive, regressive, circulatory and inflammatory damages. The other treatments, which caused lower mortality, mainly resulted in inflammation and regressive damage, whose occurrence increased with increasing concentration of nitrate. However, in closed systems, the use of anaerobic denitrifying filters or aquatic macrophytes is necessary to provide suitable water quality for the best productive performance, avoiding the negative influence of the accumulated nitrate.

Histological alterations in gills of Macrobrachium amazonicum juveniles exposed to ammonia and nitrite.

Aquaculture has shown great growth in the last decades. Due to the restrictions on water use, production systems are becoming increasingly more intensive, raising concerns about the production water quality. Macrobrachium amazonicum is among the freshwater prawn species with favorable characteristics for production and possibility of intensification. Nitrogen compounds such as ammonia and nitrite affect the health of aquatic organisms since they quickly reach toxic concentrations. These compounds can also cause damage to the gill structure, leading to hypoxia in tissues, affecting acid-base balance, osmoregulation (salt absorption) and ammonia excretion, decreasing the immune capacity of the animal and, in extreme cases, cause death. The aim of this study was to assess histological changes in the gills of Macrobrachium amazonicum juveniles subjected to different concentrations of total ammonia and nitrite. The prawns were subjected to different concentrations of those compounds and their gills were removed and preserved for histological analysis. The gills were assessed for changes according to the Organ Index (Iorg) and, for each change, an importance factor (w) was attributed according to the degree of reversibility and applied according to the degree of extension or frequency of the damage. The damage to the gills in the treatments with 100% mortality, both for ammonia and nitrite, corresponded to the high occurrence of progressive, regressive, circulatory, and inflammation damages. The other treatments (which caused less mortality) had mainly inflammation and regressive damages, whose occurrence increased according to the increase in ammonia and nitrite concentration. The histological analysis confirmed that the higher the total ammonia and nitrite concentrations, the larger the damages caused to the gill structure and that lower nitrite concentrations caused similar damages to those caused by higher total ammonia concentrations, which reflects the lower capacity M. amazonicum has to tolerate nitrite.

Acute Toxicity of Nitrite to Various Life Stages of the Amazon River Prawn, Macrobrachium amazonicum, Heller, 1862.

This study determined the effects of nitrite on different life stages of the Amazon river prawn Macrobrachium amazonicum. Prawns of each life stage (postlarvae, juveniles and adults) were stocked in 24 experimental units (n = 10 prawns), under a complete randomized design. Individuals were exposed to nitrite (0, 1, 2, 4, 8 and 16 mg L-1). The median lethal concentration after 96 h (96 h LC50) was calculated through the Weibull I. The mortality results showed that M. amazonicum is slightly less tolerant to nitrite than other species of Macrobrachium. The 96 h LC50 for postlarvae, juveniles and adults of M. amazonicum were of 1.49, 2.36 and 2.34 mg nitrite/L, respectively. Nitrite intoxication risk quotient suggest moderated risk to low risk to the species. Usually in production systems nitrite values are lower than safe levels suggested in this study (0.1 mg L-1 to postlarvae and 0.2 mg L-1 nitrite to juvenile and adults), which makes our results appropriate for the production of this species.

Disponibilidade do fósforo em alimentos de origem vegetal: atuação na nutrição de peixes / Phosphorus availability in food from vegetable origin: performance in fish nutrition / Disponibilidad del fósforo en alimentos de origen vegetal: actuación en la nutrición de peces

O trabalho aborda a utilização do fósforo na nutrição de peixes e em dietas formuladas com ingredientes de origem vegetal. Nestes ingredientes, o fósforo encontra-se de forma indisponível para animais monogástricos, devido à carência da enzima fitase. A suplementação de enzimas exógenas (fitase) em ração tem por objetivo aumentar a capacidade de absorção do fósforo em dietas contendo ingredientes de origem vegetal, reduzindo a perda por excreção deste nutriente para o ambiente aquático. A enzima atua hidrolisando o fitato, tornando-o disponível para o organismo. Devido à importância do fósforo na nutrição de peixes, esta revisão apresenta alguns aspectos, sobre a importância na nutrição bem como sobre os fatores antinutricional e os benefícios causados pela inclusão da enzima em dietas balanceadas para peixes.

This paper discusses the use of phosphorus in fish nutrition and diets formulated with ingredients from vegetable origin. These ingredients from, phosphorus is unavailable for monogastric animals, due to the lack of the phytase enzyme. The supplementation of exogenous enzymes (phytase) in feed is intended to increase the phosphorus absorption capacity in diets containing ingredients from vegetable origin, reducing the loss of such nutrient by excretion into the aquatic environment. The enzyme acts hydrolyzing phytate, making it available to the body. Due to the importance of phosphorus in fish nutrition, this review presents some aspects importance, and anti-nutritional factor and benefits caused by the inclusion of the enzyme in fish balanced diets.

En este trabajo se aborda el uso de fósforo en la nutrición de peces y en dietas formuladas con ingredientes de origen vegetal. Estos ingredientes, el fósforo se encuentra de forma indisponible para animales monogástricos, debido a la falta de la enzima fitasa. La suplementación de enzimas exógenas (fitasa) en la ración tiene por objetivo aumentar la capacidad de absorción del fósforo en dietas que contienen ingredientes de origen vegetal, reduciendo la pérdida por excreción de este nutriente para el ambiente acuático. La enzima actúa hidrolizando el fitato, haciéndolo disponible para el cuerpo. Debido la importancia del fósforo en la alimentación de peces, esta revisión presenta algunos aspectos, tales como la importancia en la nutrición de peces, como el factor anti nutricional y los beneficios causados por la inclusión de la enzima en dietas balanceadas.

Suscetibilidade dos estágios ontogenéticos: padrão osmorregulatório em camarões peneídeos e palemonídeos / Susceptibility of ontogenetic stages: osmoregulatory standard in penaeid and palaemonid shrimps / Susceptibilidad de etapas ontogenéticas: estándar osmorregulatorio en camarones peneídeos y palemonídeos

A invasão da água doce por crustáceos ocorreu repetidamente ao longo dos anos, pressionando um ajuste em seus processos fisiológicos. A habilidade de sobreviver aos diferentes ambientes foi encontrada em traços osmorregulatórios, e estão relacionadas à capacidade de regular o fluido extracelular. Portanto, o objetivo deste manuscrito é explorar os processos osmorregulatórios de camarões palemonídeos e peneídeos, visualizando um padrão na capacidade osmorregulatória em ambas as famílias e, em particular, tratar de assuntos pertinentes aos efeito no ciclo ontogenético e o efeito ocasionado pelo nitrito na hemolinfa de crustáceos. Comparando palemonídeos e peneídeos, percebe-se que o sucesso da conquista do ambiente dulcícola, e a não necessidade de hiporregulação, levou à perda dessa capacidade na maioria dos palemonídeos. Dessa forma, se supõem um ancestral com capacidade hiporregulatória, uma vez que invertebrados marinhos são, parcimoniosamente, osmoconformadores. Compara-se também que o nitrito apresenta efeito nas proteínas presentes na hemolinfa dos crustáceos quando submetidos à exposição natural ou induzida deste composto, e que a capacidade osmorregulatória é, portanto, variada de acordo com seus estágios...

The invasion of freshwater by crustaceans has occurred repeatedly over the years, pressing for an adjustment in their physiological processes. The ability to survive in different environments was found in osmoregulatory traits and is related to the ability to regulate the extracellular fluid. Therefore, the purpose of this manuscript is to explore the osmoregulatory processes in palaemonid and penaeid shrimps, which display a pattern of osmoregulatory capacity in both families and, in particular, to deal with matters related to the effects on ontogenetic cycle and the effect raised by nitrite in crustacean hemolymph. By comparing palaemonid and peneid shrimps, it is possible to note the success of conquering freshwater environment, and not the need for hypo-regulation, has led to the loss of this capability in most palaemonids. Thus, it is assumed that they share an ancestor with hypo-regulatory capacity, since marine invertebrates are sparsely osmoconformers. The article also compares that nitrite has effect on proteins present in the hemolymph of crustaceans when subjected to natural or induced exposure to these compound, and osmoregulatory capacity is therefore varied according to their stages...

La invasión del agua dulce por crustáceos ocurre repetidamente a lo largo de los años, pulsando un ajuste en sus procesos fisiológicos. La capacidad de sobrevivir en diferentes ambientes se ha encontrado en rasgos osmorregulatorios y están relacionados a la capacidad de regular el fluido extracelular. Por lo tanto, el objetivo de este manuscrito es el de explotar los procesos osmorregulatorios de camarones palemonídeos y peneídeos, se muestra un estándar en la capacidad osmorregulatoria en ambas las familias y, en especial, trata de cuestiones relativas a los efectos sobre los ciclo ontogenético y el efecto causado por nitrito en la hemolinfa de crustáceos. Comparando palemonídeos y peneídeos, se da cuenta de que el éxito de la conquista del ambiente dulcícola, y sin necesidad de hipo regulación, condujo a la pérdida de esa capacidad en la mayoría de los palemonídeos. Así, se supone un ancestral con capacidad hipo regulatoria, una vez que los invertebrados marinos son, parsimoniosamente, osmoconformadores. Se compara también que el nitrito presenta efectos en las proteínas presentes en la hemolinfa de los crustáceos cuando sometidos a la exposición natural o inducida por estes compuesto, y que la capacidad osmorregulatoria es, por lo tanto, variada de acuerdo con sus etapas...