Abstract Nitrogen compounds, particularly ammonium, nitrite and nitrate, are a major problem in shrimp production systems. These compounds can accumulate in the aquatic environment and reach harmful or even lethal levels. Thus, monitoring the levels of nitrogenous compounds such as ammonia and studying their effects on the animals are essential. One tool used for this purpose is acute toxicity testing based on the evaluation of LC50 values. Furthermore, tools that can help improve the performance of aquatic organisms in culture are needed. The present study aimed to evaluate the effect of salinity on the toxicity of total ammonia to postlarvae of the freshwater prawn Macrobrachium rosenbergii. For this purpose, acute toxicity testing (LC50-96h) was performed using 540 postlarvae with a mean weight of 0.13 g and a mean total length of 2.47 cm, divided into 54 experimental units of two liters each. A completely randomized design in a 3×6 factorial scheme was used, combining three salinities (0, 5, and 10 g.L-1) and six total ammonia concentrations (0, 8, 16, 32, 64, and 128 mg.L-1), with three replicates per combination. The LC50 values for M. rosenbergii postlarvae at 24, 48, 72, and 96 h and their respective confidence intervals (95%) were estimated using the trimmed Spearman-Karber method. The results showed that salinities of 5 or 10 g.L-1 did not reduce the acute toxicity of total ammonia. ammonium nitrate systems Thus essential LC LC5 Furthermore needed LC5096h LCh 96h (LC50-96h 013 0 13 0.1 247 2 47 2.4 cm each 36 3 6 3× 0, (0 1 g.L1 gL1 gL g.L L 8 16 32 64 12 mg.L1, mgL1 mgL mg.L , mg mg.L-1) combination M 24 48 72 9 95% 95 (95% SpearmanKarber Spearman Karber method g.L- 01 0. 4 2. ( L1 mg.L1 mg.L-1 7 (95 mg.L- (9

Resumo Compostos nitrogenados, particularmente amônia, nitrito e nitrato, são um grande problema nos sistemas de produção de camarão. Esses compostos podem se acumular no meio aquático e atingir níveis nocivos ou mesmo letais. Assim, monitorar os níveis de compostos nitrogenados como a amônia e estudar seus efeitos nos animais são essenciais. Uma ferramenta utilizada para este fim são os testes de toxicidade aguda baseados na avaliação dos valores de CL50. Além disso, são necessárias ferramentas que possam ajudar a melhorar o desempenho dos organismos aquáticos em cultura. O presente estudo teve como objetivo avaliar o efeito da salinidade na toxicidade da amônia total para pós-larvas do camarão de água doce Macrobrachium rosenbergii. Para tanto, o teste de toxicidade aguda (CL50-96h) foi realizado utilizando-se 540 pós-larvas com peso médio de 0,13 g e comprimento total médio de 2,47 cm, divididas em 54 unidades experimentais de dois litros cada. O delineamento experimental utilizado foi o inteiramente casualizado, em esquema fatorial 3×6, combinando três salinidades (0, 5 e 10 g.L-1) e seis concentrações de amônia total (0, 8, 16, 32, 64 e 128 mg.L-1), com três repetições por combinação. Os valores de CL50 para pós-larvas de M. rosenbergii em 24, 48, 72 e 96 h e seus respectivos intervalos de confiança (95%) foram estimados pelo método de Spearman-Karber aparado. Os resultados mostraram que salinidades de 5 ou 10 g.L-1 não reduziram a toxicidade aguda da amônia total. nitrato letais Assim essenciais CL disso cultura póslarvas pós larvas tanto CL5096h CLh 96h (CL50-96h utilizandose utilizando 013 0 13 0,1 247 2 47 2,4 cm cada casualizado 36 3 6 3×6 0, (0 1 g.L1 gL1 gL g.L L 8 16 32 12 mg.L1, mgL1 mgL mg.L , mg mg.L-1) combinação CL5 M 24 48 7 9 95% 95 (95% SpearmanKarber Spearman Karber aparado g.L- 01 4 2, 3× ( L1 mg.L1 mg.L-1 (95 mg.L- (9

ABSTRACT. The current study evaluates the effect of partial or total replacement of fish meal with Haematococcus pluvialis microalgae, cultivated in an NPK culture medium, on the growth performance of Macrobrachion amazonicum shrimp post-larvae. Four diets were formulated: control (without microalgae), 25, 50 and 100% H. pluvialis replacement. Only crude protein weight gain showed no interaction and was not selected for principal components analysis. The 25% fishmeal replacement in the diet was not effective, being similar to the control. However, the complete replacement of fishmeal with H. pluvialis promoted elevated survivability, length, weight and protein retention, making it the most relevant treatment for M. amazonicum post-larvae. Therefore, it is possible to completely replace fishmeal with the microalgae H. pluvialis in the diet of M. amazonicum shrimp, which improves growth performance. ABSTRACT medium postlarvae. postlarvae post larvae. larvae post-larvae formulated without , microalgae) 25 5 100 H analysis effective However survivability length retention M Therefore 2 10 1

ABSTRACT Shrimp aquaculture is an industry that uses fishmeal in diets, which is an ingredient difficult to obtain at low cost and increasingly scarce. It is important to find strategies that help shrimp nutrition by using alternative ingredients that replace or complement fishmeal and help develop a more environmentally friendly industry. Yeasts can be added to diets for aquatic organisms and are microbial products generated by biotechnological systems or a by-product from agri-food industries. This study determined the potential use of active yeasts (Candida insectorum, C. parapsilosis, C. sake, C. utilis, Debaryomyces hansenii, Rhodosporidium paludigenum, Saccharomyces cerevisiae, Schizosaccharomyces pombe, and Yarrowia lipolytica) in juvenile and postlarvae shrimp of Litopenaeus schmitt, Fenneropenaeus indicus, and L. vannamei. The results show that active yeasts can be used at different doses, as partial substitute for a fishmeal-soybean meal and incorporated into diets for juvenile shrimp or used directly in diets for postlarvae. However, it is necessary to carry out studies to determine the most efficient strategies for the active yeast to be ingested by shrimp.

RESUMEN La acuacultura de camarón es una industria que usa harina de pescado en las dietas, el cual es un ingrediente difícil de obtener a bajo costo y es cada vez más escaso. Es importante encontrar estrategias que ayuden a la nutrición del camarón mediante el uso de ingredientes alternativos que reemplacen o complementen a la harina de pescado y ayuden a desarrollar una industria más amigable para el medio ambiente. Las levaduras se pueden añadir a las dietas para los organismos acuáticos y son un producto microbiano generado por sistemas biotecnológicos o un subproducto de las industrias agroalimentarias. Este estudio determinó el uso potencial de levaduras activas (Candida insectorum, C. parapsilosis, C. sake, C. utilis, Debaryomyces hansenii, Rhodosporidium paludigenum, Saccharomyces cerevisiae, Schizosaccharomyces pombe, y Yarrowia lipolytica) en camarones juveniles y postlarvas de Litopenaeus schmitt, Fenneropenaeus indicus y L. vannamei. Los resultados muestran que las levaduras activas pueden ser empleadas a diferentes dosis como un sustituto parcial de la harina de pescado y/o harina de soya e incorporarse a dietas de camarones juveniles o usarse directamente en dietas para postlarvas. Sin embargo, es necesario realizar estudios que determinen las estrategias más eficientes para que la levadura activa sea ingerida por el camarón.

ABSTRACT Pyrrhulina brevis is an endemic fish from the Amazon basin that is valued in the ornamental fish market. In larviculture, fish are very sensitive to stressors and have a high mortality rate. Salinized water may provide more energy to overcome stress and feeding frequency is an important strategy to improve productive performance. Therefore, the aim of this study was to evaluate the best feeding frequency and the best level of water salinization for larval development of P. brevis. A total of 360 post-larvae of P. brevis (5.26 ± 1.65 mg, 5.57 ± 0.68 mm) were randomly distributed in 36 aquariums (1 L) in a 3x4 factorial scheme, to evaluate three concentrations of salt in water (0, 1 and 2 g L-1) and four feeding frequencies (once, twice, three and four times a day). We offered 150 Artemia nauplii per day and per post-larvae during 15 days. The fish kept at 1 g L-1 salinized water, and those fed 3 and 4 times a day presented significantly greater final length and weight, weight gain, and specific growth rate for length and weight. An interaction between salinized water and feeding frequency was observed for survival rate. We conclude that, during the initial rearing phase of P. brevis, feeding frequency of three times a day and salinized water at 1 g L-1 is recommended. market larviculture performance Therefore P postlarvae post larvae 5.26 526 5 26 (5.2 165 65 1.6 mg 557 57 5.5 068 0 68 0.6 mm ( L x 3x scheme 0, (0 L1 once, once (once twice day. . day) days L- gain recommended 5.2 52 (5. 16 6 1. 55 5. 06 0. (5

RESUMO Pyrrhulina brevis é um peixe endêmico da bacia amazônica que apresenta bons valores no mercado de peixes ornamentais. Na larvicultura, os peixes são muito sensíveis aos estressores e apresentam alta taxa de mortalidade. A água salinizada pode fornecer mais energia para superar o estresse e a frequência alimentar é uma estratégia importante para melhorar o desempenho produtivo. Portanto, o objetivo deste trabalho foi avaliar a melhor frequência alimentar e o melhor nível de salinização da água para o desenvolvimento larval de P. brevis. Um total de 360 pós-larvas de P. brevis (5,26 ± 1,65 mg, 5,57 ± 0,68 mm) foram distribuídos aleatoriamente em 36 aquários (1 L) em esquema fatorial 3x4, para avaliar três concentrações de sal na água (0, 1 e 2 g L-1) e quatro frequências de alimentação (uma, duas, três e quatro vezes ao dia). Foram oferecidas 150 náuplios de Artemia por dia e por pós-larva, durante 15 dias. Os peixes mantidos com 1 g L-1 de água salinizada e os alimentados 3 e 4 vezes ao dia apresentaram comprimento e peso finais, ganho de peso e taxa de crescimento específico para comprimento e peso significativamente maiores. Uma interação entre água salinizada e frequência alimentar foi observada para a taxa de sobrevivência. Concluímos que, durante a fase inicial de criação de P. brevis, recomenda-se uma frequência alimentar de três vezes ao dia e água salinizada a 1 g L-1. ornamentais larvicultura mortalidade produtivo Portanto P póslarvas pós larvas 5,26 526 5 26 (5,2 165 65 1,6 mg 557 57 5,5 068 0 68 0,6 mm ( L 3x4 x 0, (0 L1 uma, (uma duas dia. . dia) póslarva, póslarva larva, larva pós-larva dias L- finais maiores sobrevivência recomendase recomenda se L1. 1. 5,2 52 (5, 16 6 1, 55 5, 06 3x (5

ABSTRACT. The present study evaluated the effect of different energy levels (15.07, 15.91, 17.17, 18.00, and 19.68 kJ g−1 of diet) on isoproteic practical diets for Macrobrachium amazonicum during the nursery phase on the zootechnical performance and proximate composition of the whole body. Postlarvae with a mean weight of 0.043 ± 0.01 g were stored in 25 experimental units, at 150 animals per m2, in a completely randomized design with five treatments and five replicates. The post-larvae were evaluated at the end of the experimental period according to the pre-established performance parameters. The analysis of variance for regression (α = 0.05) allowed us to estimate that the maximum final weight was observed in the treatment with 16.74 kJ g−1. In contrast, the lowest apparent feed conversion was observed at the 16.43 kJ g−1 level. The best values were found in 17.29 and 17.50 kJ g−1, respectively, for the energy and protein retention rates. As the best fit of the equation was presented for the energy retention ratio (R2 = 0.63), which approached the treatment of 17.17 kJ g−1, this energy level is recommended in postlarvae diets.

Abstract The objective of the present study was to evaluate the effect of different fasting periods on mortality of Litopenaeus vannamei post-larvae and the time it took to molt or die. The study applied an experimental design using 20-days-old post-larvae (PL), with a control group subjected to continuous feeding (CF) and 9 treatments (S2, S4, S6, S8, S10, S12, S14, S16, S18) with varying fasting periods, followed by continuous feeding. The time at which food deprivation resulted in death was analyzed for 50% of the post-larvae, even when they received food after fasting. Statistical analysis of time to molt identified 3 different groups (P < 0.05): group 1 with continuous feeding, group 2 with fasting periods of 2 and 4 days (S2, S4), and group 3 with fasting periods between 6-18 days (S6-S18). In control group with continuous feeding, the time to molt was estimated at about 3.44 ± 0.68 days. Time to death, showed 2 significantly different treatment groups (P < 0.05). In CF treatment, all PLs survived. The first group consisted of fasting tests for 2 and 4 days (S2, S4). The second group corresponded to fasting periods from S6 to S18 days, resulting in the shortest time to death with 71.43 and 100% of individuals dead. The PNR50 was estimated to be around 3.97 ± 0.31 days, demonstrating that fasting periods affected development and potentially caused death in PL of L. vannamei.

Resumen El objetivo del presente estudio fue evaluar el efecto de diferentes períodos de ayuno sobre la mortalidad de las post-larvas de Litopenaeus vannamei y el tiempo que les tomó mudar o morir. El estudio aplicó un diseño experimental utilizando post-larvas de 20 días de edad, con un grupo control sometido a alimentación continua (CF) y 9 tratamientos (S2, S4, S6, S8, S10, S12, S14, S16, S18) con períodos variables de ayuno, seguidos de alimentación continua. Se analizó el momento en el que la privación de alimentos provocó la muerte del 50% de los individuos, incluso cuando recibieron alimento después del ayuno. El análisis estadístico para el tiempo de muda identificó 3 grupos diferentes (P < 0,05). Grupo 1 con alimentación continua; Grupo 2 con periodos de ayuno de 2 y 4 días; y grupo 3 con periodos de ayuno entre 6-18 días. En el grupo control con alimentación continua se estimó un tiempo de muda de alrededor de 3,44 ± 0,68 días. En el tiempo de muerte hubo 2 grupos de tratamientos significativamente diferentes (P < 0,05). En el tratamiento con alimentación continua sobrevivieron todas las PL. El primer grupo consistió en pruebas de ayuno durante 2 y 4 días (S2 y S4). El segundo grupo correspondió desde los periodos de ayuno de S6 a S18 días, resultando el menor tiempo hasta la muerte con 71,43 y 100% de individuos muertos. El PNR50 se estimó alrededor de 3,97 ( 0,31 días, demostrando que los períodos de ayuno afectaron el desarrollo y potencialmente causan mortalidad en las post-larvas de L. vannamei.

ABSTRACT Objetive. The effect of traditional diets (Thalassiosira weissflogii and Artemia nauplii) and two other alternatives (not traditional) based on microalgae with rotifers were evaluated on the survival, development and growth from nauplii V (NV) larvae until postlarvae (PL1) of Penaeus vannamei. Materials and methods. Sixteen replicates (experimental units) were applied for each of the three diets used. The larvae were placed in 12 L containers at 35 psu, 30°C and a density of 200larvae/L. At the beginning, every 24 h and the end of the experiment (PL1: day 8), samples of larvae were obtained to determine survival, development and growth (length and weight). A one-way ANOVA was applied to the data obtained. Results. Diet had no influence (p>0.05) on survival and weight. Survival ranged from 30.4% (alternative diet B) to 28.5% (traditional diet A). The lowest development, length and weight at PL1 was found with the traditional diet (6.71; 3.53 mm; 58.37 μg/organism) compared with the alternative diets supplied B and C (6.86-6.76; 3.79-3.82 mm; 60.7-65.0 μg/organism. Conclusions. Non-traditional alternative diet (B and C) composed of rotifers was the best diet for larval survival, development and growth.

RESUMEN Objetivo. Evaluar el efecto de dietas tradicionales (Thalassiosira weissflogii y nauplios de Artemia) y otras dos alternativas (no tradicionales) a base de microalgas y rotíferos sobre la supervivencia, el desarrollo y crecimiento de larvas nauplio V (NV) hasta el día de cambio a postlarvas (PL1) de camarón Penaeus vannamei. Materiales y Métodos. Se realizaron dieciséis réplicas (unidades experimentales) para cada una de las tres dietas utilizadas. Las larvas se colocaron en contenedores de 12 L a 35 ups, 30°C y una densidad de 200 larvas/L. La supervivencia, etapa del desarrollo y el crecimiento se determinaron al inicio, cada 24 h y al final del experimento (PL1: día 8). A los datos obtenidos se les aplicó un ANAVA de una vía. Resultados. La dieta no tuvo influencia (p>0.05) sobre supervivencia y el peso. La supervivencia osciló entre 30.4% (dieta alternativa B) y 28.5% (dieta tradicional A). El desarrollo, longitud y peso más bajo a PL1 fue encontrado con la dieta tradicional (6.71; 3.53 mm; 58.37 μg/organismo) en comparación con las dietas alternativas suministradas B y C (6.86-6.76; 3.79-3.82 mm; 60.7-65.0 μg/organismo). Conclusiones. La alimentación más adecuada para la supervivencia, desarrollo y crecimiento larval se obtuvieron con las dietas alternativas no tradicionales (B y C) compuestas de rotíferos.

ABSTRACT A 70-day experimental trial was performed to evaluate the contribution of biofloc to the nutrition of Macrobrachium rosenbergii 15 days old postlarvae (PL) (average 82.00 ± 19.71 mg) fed different crude protein (P) and lipids (L) levels in zero-water exchange culture tanks. Six biofloc treatments (BFT) as experimental diets with 15, 20, or 25% P levels and 5 or 8% L levels were managed: BFT-15/5; BFT-15/8; BFT-20/5; BFT-20/8; BFT-25/5; BFT-25/8, and a clear-water control without biofloc fed with 25% P and 8% L (CW-25/8). The experiment was done in triplicate in 21-60 L plastic tanks containing 10 prawns tank−1. At the end of the experiment, survival of prawns was above 66%, with no significant differences among experimental groups (P > 0.05). The best growth performance was observed in the experimental prawns maintained in BFT-20/5, BFT-20/8, BF-25/5, and BFT-25/8 compared to the control (P < 0.001). The feed conversion rate of the prawns in BFT-20/5 was significantly lower than that in control (P < 0.001); the best P efficiency ratio and productive P value were observed in all BFT compared to control prawns (P < 0.001). Results showed that it is feasible to use low concentrations of P (20%) and L (5%) in diets to grow giant freshwater prawn PL in a biofloc system. Results also demonstrated that biofloc contributes to the P and L requirements of cultured freshwater prawn PL, as indicated by improved feed utilization, P retention, and growth performance.

Abstract The objective of the study is to identify the production costs of shrimp microproducers in the region of Tibau do Sul, in the state of Rio Grande do Norte, as well as to evaluate the economic/operational viability of the activity. The collected data were separated into three groups, according to the annual production volume and the costs were classified as direct and indirect, fixed and variable. The averages of the total costs of production of the shrimp farmers by group, the averages of the cost of shrimp per kilo, billing, operating result, and the average of the contribution margin were calculated. The results show that the highest costs in production are with direct materials. Variable costs are the most representative, with emphasis on labor, feed, and stocking (post-larvae). About fixed costs, maintenance cost was the most relevant. Regarding the cost of shrimp, it was possible to identify that it is influenced by the area of the ponds and the volume of production, with the cost per kilo being higher for producers with low production capacity. It was found that the activity is profitable and viable, even in periods when the sale price is low. JEL: M410.

Resumo O objetivo do estudo é identificar os custos de produção dos microprodutores de camarão da região de Tibau do Sul, no estado do Rio Grande do Norte, bem como, avaliar a viabilidade econômica/operacional da atividade. Os dados coletados foram separados em três grupos, de acordo com o volume de produção anual e os custos foram classificados em diretos e indiretos, fixos e variáveis. Foram calculadas as médias dos custos totais de produção dos carcinicultores por grupo, as médias do custo de camarão por quilo, faturamento, resultado operacional e a média da margem de contribuição. Os resultados evidenciam que os maiores custos na produção são com materiais diretos. Os custos variáveis são os mais representativos, com destaque para a mão de obra, ração e povoamento (pós-larvas). No que se refere aos custos fixos, o custo com manutenção se apresentou como mais relevante. Com relação ao custo do camarão, foi possível identificar que ele é influenciado pela área dos viveiros e pelo volume de produção, sendo o custo do quilo maior para os produtores com baixa capacidade produtiva. Verificou-se que a atividade é lucrativa e viável, inclusive em períodos em que o preço de venda é baixo. JEL: M410.

Resumen El objetivo del estudio es identificar los costos de producción de microproductores de camarón en la región de Tibau do Sul, en el estado de Rio Grande do Norte, así como evaluar la viabilidad económica/operacional de la actividad. Los datos recopilados se separaron en tres grupos, según el volumen de producción anual y los costos se clasificaron en directos e indirectos, fijos y variables. Se calcularon los promedios de los costos totales de producción de los camaroneros por grupo, los promedios del costo de camarón por kilogramo, la facturación, el resultado operativo y el promedio del margen de contribución. Los resultados muestran que los mayores costos en producción son con materiales directos. Los costos variables son los más representativas, con énfasis en mano de obra, alimentación y repoblamiento (postlarvas). Con respecto a los costos fijos, el costo de mantenimiento fue el más relevante. En cuanto al costo del camarón, se pudo identificar que está influenciado por el área de los estanques y el volumen de producción, siendo el costo por kilogramo mayor para los productores con baja capacidad de producción. Se constató que la actividad es rentable y viable, incluso en períodos en que el precio de venta es bajo. JEL: M410.

Résumé Le but de l’étude est d’itentifier les coûts de production des microproducteurs de crevettes dans la región de Tibau do Sul, dans l’état de Río Grande do Norte, ainsi que d’évaluer la viabilité économique/opérationnelle de l’activité. Les données recueillies sont considerées en trois groupes, selon le volume de production annuelle et les coûts se sont classés en directs et indirects, fixes et variables. Les moyennes des coûts totaux de production des éleveurs de crevettes ont été calculées par groupe, les moyennes du coût des crevettes par kilo, la facturation, le résultat opérationnel et la moyenne de la marge de contribution. Les résultats montrent que les plus forts coûts de production proviennent des matériaux directs. Les coûts variables sont les plus représentatifs, avec l’accent sur la main d’oeuvre, la nourriture et le repeuplement (post-larves). En ce qui concerne les coûts fixes, le coût de l’entretien s’est avéré le plus élevé.Par rapport au coût de la crevette, celui-ci est influencé para l’aire des bacs et le volume de production, étant donc le coût de production par kilo supérieur pour les producteurs ayant une faible capacité de production. Il est prouvé que l’activité est rentable et viable, tout en considérant les périodes où le prix de vente est bas. JEL: M410.

ABSTRACT The objective of this work was to evaluate the acute toxicity of the commercial herbicides Karmex® (diuron: DCMU 3-(3,4-dichlorophenyl)-1,1-dimethylurea) and Herbipol® (glyphosate: N-(phosphonomethyl) glycine) on the megalopae of Callinectes sapidus and measure their relative abundance in the association of larval and postlarval species of crustaceans from the estuary of the Jamapa River, Veracruz. Collections were made overnight using white light traps. Likewise, dissolved oxygen, pH, temperature, total dissolved solids, and salinity were measured in situ. It was found that the association of larvae and postlarvae consisted of Macrobrachium acanthurus, M. olfersii, Potimirim mexicana, megalopae of C. sapidus and Armases ricordi, and zoeas of Brachyura. In total, 559 and 1057 C. sapidus megalopae were collected in November and March 2019, respectively. Dissolved oxygen was 6 and 7 mg L−1, pH was 7 and 8, the temperature was 26 and 27°C, total dissolved solids were 700 and 1500 ppm, and salinity was 0.70 and 16 in November and March, respectively. Using Probit analysis, a 96 h LC50 of diuron (Karmex®) was 7.69 ± 1.07 mg L−1 in March and 6.64 ± 0.93 mg L−1 in November. The LC50 for glyphosate (Herbipol®) was 247.83 ± 34.54 mg L−1 in March and 288.18 ± 38.66 3 mg L−1 in November. The blue crab C. sapidus is tolerant to a wide range of physicochemical factors; however, it is sensitive in the postlarval stages, like other species of crustaceans, to the herbicides diuron and glyphosate, for which the megalopae can be used in ecotoxicological studies.

ABSTRACT Farmers have increased the production of food by using chemical substances such as diuron; however, these components affect the water quality and the species found in these ecosystems. Macrobrachium acanthurus and M. olfersii postlarvae present in the estuary of Río Jamapa, Veracruz were collected to measure the LC50 and LD50 using the herbicide Karmex (diuron: (3-(3,4-dichlorophenyl)-1,1-dimethylurea [DCMU]). The captures of the prawns were made with light traps. Acute toxicity bioassays were carried out at 96 h to determine the mean lethal concentration (LC50). In the experimental design, a geometric series was used considering the control and five concentrations of the herbicide (1.75, 3.5, 6.99, 14, and 28 mg/L). The data analysis was carried out with the Probit method. A maximum LC50 of 10.233 mg/L and LD50 of 8.221 mg/L of Karmex were obtained for M. acanthurus and a maximum LC50 of 9.242 mg/L and LD50 of 7.504 mg/L of Karmex were obtained for M. olfersii. The average lethal concentration was consistent with those of other crustaceans, such as Artemia salina and Daphnia. Based on the response in the bioassays, Macrobrachium acanthurus and M. olfersii postlarvae can be used in toxicology studies.

RESUMEN Los agricultores han aumentado la producción de alimentos mediante el uso de sustancias químicas como el Diurón; sin embargo, estos componentes afectan la calidad del agua y las especies que se encuentran en estos ecosistemas. Se recolectaron postlarvas de Macrobrachium acanthurus y M. olfersii presentes en el estuario del Río Jamapa, Veracruz para medir la CL50 y DL50 utilizando el herbicida Karmex (diuron: DCMU (3-(3,4-diclorofenil)-1,1-dimetilurea). Se realizaron las capturas de los langostinos con trampas de luz. Los bioensayos de toxicidad aguda se midieron a las 96 h para determinar la concentración letal media (CL50). En el diseño experimental se utilizó una serie geométrica considerando el testigo y cinco concentraciones del herbicida (1.75, 3.5, 6.99, 14 y 28 mg/L). El análisis de datos se realizó con el método Probit. Se obtuvo una CL50 máxima de 10.233 mg/L y una DL50 de 8.221 mg/L de Karmex para M. acanthurus y una CL50 máxima de 9.242 mg/L y DL50 de 7.504 mg/L de Karmex para M. olfersii. La concentración letal promedio fue consistente con la de otros crustáceos, como Artemia salina y Daphnia. Con base en la respuesta en los bioensayos, se pueden utilizar postlarvas de Macrobrachium acanthurus y M. olfersii en estudios de toxicología.

ABSTRACT Experiments were carried out to study the effects of ammonia and nitrite on food consumption of Macrobrachium amazonicum postlarvae. Postlarvae (average weight of 0.0625 g) were exposed during 21 days to four concentrations of total ammonia (0, 1.05, 2.1 and 4.2 mg. NH3+NH4+ L-1) and four concentrations of nitrite (0, 0.075, 0.15 and 0.30 mg N-NO2- L-1). After the exposure period, six prawns per treatment were maintained individually in 250 mL experimental units to analyze the food consumption as a function of the amount of food offered and the leftovers during a 24 h period. The food consumption presented significant alterations for prawns exposed to all nitrite concentrations and at concentrations of twice the recommended safety level for total ammonia. According to the results obtained, high concentrations of total ammonia and nitrite affect the food consumption of M. amazonicum adversely, influencing the species performance in culture systems.

Abstract Fipronil and imidacloprid currently represent approximately one third of the global insecticide market. In the present study, the environmental risk (ERA) of fipronil and imidacloprid in the postlarvae of the river shrimp (Cryphiops caementarius, Molina 1782) was evaluated. Short-term toxicity bioassays were performed based on LC50 (mean lethal concentration) (mortality) and EC50 (mean effective concentration) (swimming hypoactivity). PNEC (Predicted Concentration with No Known Effect) and available environmental standards for PEC (Expected Environmental Concentration) were calculated for fipronil and imidacloprid to determine risk quotient (RQ). Imidacloprid was more at risk for the aquatic environment than fipronil for the lethal response (mortality) and sublethal response (swimming hypoactivity). The observed risk difference between the two insecticides could be due to their different modes of action. C. caementarius should be considered as a sensitive species when defining an environmental quality standard for the conservation of the aquatic environment. Therefore, it is recommended to continue monitoring the presence of these insecticides in coastal freshwater bodies, and to reduce the use of fipronil and imidacloprid in the agricultural crops that use them.

Resumen En la actualidad, el fipronil y el imidacloprid representan aproximadamente un tercio del mercado mundial de insecticidas. En el presente estudio se evaluó el riesgo ambiental (ERA) del fipronil e imidacloprid en las postlarvas del camarón de río (Cryphiops caementarius, Molina 1782). Se realizaron bioensayos de toxicidad de corta duración en base a la CL50 (Concentración letal media) (mortalidad) y CE50 (Concentración efectiva media) (hipoactividad natatoria). Se calculó la PNEC (Concentración prevista sin efecto conocido) y los estándares ambientales disponibles para la PEC (Concentración ambiental esperada) para el fipronil y el imidacloprid para determinar los cocientes de riesgo (CR). El imidacloprid resultó con mayor riesgo para el ambiente acuático que el fipronil para la respuesta letal (mortalidad) y subletal (hipoactividad natatoria). La diferencia del riesgo observada entre ambos insecticidas pudiera deberse a sus diferentes modos de acción. C. caementarius debería ser considerado como una especie sensible al momento de definir un estándar de calidad ambiental para la conservación del ambiente acuático. Por ende, es recomendable continuar el monitoreo para observar la presencia de estos insecticidas en los ecosistemas dulceacuícolas costeros, y reducir el uso del fipronil y del imidacloprid en los cultivos agrícolas que los emplean.

RESUMEN El Paraquat es un herbicida utilizado en la actividad agropecuaria para controlar hierbas, su modo de acción es por medio de contacto y no selectivo. Debido a su alta solubilidad en agua y baja volatilidad representa un riesgo potencial para organismos acuáticos, principalmente los que son cultivados con aguas superficiales que reciben impacto de la actividad agrícola. La tilapia Oreochromis niloticus y el langostino Macrobrachium olfersii son organismos de importancia comercial para la industria acuícola del estado de Veracruz, México. El objetivo de este estudio fue determinar la Concentración Letal Media (CL50) del herbicida Dasurquat® (ingrediente activo Paraquat) a través de un bioensayo de toxicidad aguda (96 horas). Se utilizaron como especímenes de prueba a juveniles de tilapia O. niloticus (peso promedio = 10 mg, longitud total= 8,75 mm) y otro el ensayo fue con poslarvas de langostino M. olfersii (peso promedio = 5 mg, longitud total= 5,72 mm). Se emplearon cinco concentraciones (5, 10, 20, 40 y 80 μL-1 para el bioensayo con juveniles de tilapia; para el bioensayo con poslarvas de langostino las concentraciones fueron 0,1, 0,2, 0,5, 0,7 y 1 μL-1). El diseño experimental consideró un control negativo, con dos repeticiones y dos réplicas por cada tratamiento. El análisis de datos se realizó con el método Probit para determinar la CL50 a 96 horas, se obtuvo un valor para juveniles de O. niloticus de 17,49 μL-1 con intervalo de confianza (95 %) con límite inferior de 13,75 μL-1 y límite superior 22,25 μL-1, para las larvas de M. olfersii se obtuvo un valor de 0,31 μL-1 con intervalo de confianza (95 %) con límite inferior de 0,26 μL-1 y límite superior 0,35 μL-1. El análisis de varianza demostró que no existió diferencia estadística significativa (p > 0.05) entre las réplicas de los tratamientos. Se concluye que es necesario continuar con estudios para evaluar su toxicidad en organismos acuáticos debido al amplio uso de este herbicida en la actividad agropecuaria, y determinar su riesgo para otras actividades productivas además de la acuicola.

ABSTRACT Paraquat is an herbicide used in the agricultural industry for weed and undergrowth control, its mode of action is by contact and nonselective. Due to its high-water solubility and low volatility, it represents a potential risk for non-target organisms. Oreochromis niloticus tilapia and the prawn Macrobrachium olfersii are important commercial species for Veracruz's aquaculture industry. The objective of this study was to determine the Mean Lethal Concentration (LC50) of the herbicide Dasurquat® (active ingredient Paraquat) through an acute toxicity bioassay (96 hours). Juvenile O. niloticus (average weight = 10 mg, total length = 8.75 mm) and juvenile M. olfersii postlarvae (average weight = 5 mg, total length = 5.72mm) were used as test specimens. Five herbicide concentrations (5, 10, 20, 40 and 80 μL-1 for tilapia and 0.1, 0.2, 0.5, 0.7 y 1 μL-1 for prawn) were applied. The experimental design considered a negative control, with two replications and two replicates for each treatment. Probit analysis determined that the LC50 at 96 hours for O. niloticus was 17.49 μL-1, with a lower 95 % confidence limit of 13.75 μL-1 and an upper limit of 22.25 μL-1, whereas for M. olfersii the LC50 at 96 hours was 0.31 μL-1, with a lower 95 % confidence limit of 0.26 μL-1 and an upper limit of 0.35 μL-1. The analysis of variance showed that there was no significant statistical difference (p > 0.05) between the replicates of the treatments. It is concluded that it is necessary to continue evaluating its toxicity in aquatic organisms due to the wide use of this herbicide in Veracruz's agricultural activity, to determine its potential risk to other activities.

ABSTRACT Background: The southern zone of the estuary of the Jamapa River, Veracruz, is a place of transition between the river and the marine environment to which sediments, compounds, and species of crustaceans are transported to the neritic zone where is the Parque Nacional Sistema Arrecifal Veracruzano. Objective: The responses of exposure of Potimirim mexicana postlarvae to diuron, glyphosate, and paraquat, as well as the relative abundance, diversity of the association of crustaceans, and values of temperature, salinity, oxygen, pH, and dissolved solids in the estuary were evaluated. Methods: Sampling was carried out with white light traps in November and March. Living Potimirim mexicana postlarvae were obtained from the samples to carry out the bioassays; the remaining individuals of the association were fixed in 70% alcohol for identification and quantification. The environmental factors were measured using a multiparameter Hanna HI 9828. Results: Dissolved oxygen was of 6-7 mgL-1, pH of 8-9, temperature of 26-27° C, total dissolved solids of 700-1,500 ppm and salinity of 0.70-16 ups. Environmental conditions permit the presence of Potimirim mexicana postlarvae. Six taxa were found: postlarvae of Macrobrachium acanthurus, M. olfersii and Potimirim mexicana, megalopae of Callinectes sapidus and Armases ricordi, and zoeae of Brachyura. Diversity ranged from 1.55 to 1.77 bits*individual-1, indicating an intermediate stability of the estuary. A total of 12,827 postlarvae of P. mexicana were obtained. The LC50 values of diuron, paraquat, and glyphosate were 5.94, 1.51, and 221.05 mgL-1, respectively. Conclusions: The values found here are consistent with those obtained by other authors for different species of crustaceans. Due to the important ecological in the food web of P. mexicana, its postlarvae can be used as sensitive test organisms in ecotoxicological studies.

RESUMEN Antecedentes: La zona sur del estuario del río Jamapa, Veracruz, es un lugar de transición entre el río y el medio marino al que se transportan sedimentos, compuestos y especies de crustáceos hasta la zona nerítica donde se encuentra el Parque Nacional Sistema Arrecifal Veracruzano. Objetivo: Se evaluaron las respuestas de exposición de las postlarvas de Potimirim mexicana a diurón, glifosato y paraquat, así como la abundancia relativa, diversidad de asociación de crustáceos y valores de temperatura, salinidad, oxígeno, pH y sólidos disueltos en el estuario. Métodos: El muestreo se realizó con trampas de luz blanca en noviembre y marzo. De las muestras se obtuvieron postlarvas vivas de Potimirim mexicana para realizar los bioensayos; los restantes individuos de la asociación se fijaron en alcohol al 70% para su identificación y cuantificación. Los factores ambientales se midieron utilizando un multiparamétrico Hanna HI 9828. Resultados: El oxígeno disuelto fue de 6-7 mgL-1, pH de 8-9, temperatura de 26-27 ° C, sólidos disueltos totales de 700-1,500 ppm y salinidad de 0,70-16 ups. Las condiciones ambientales permiten la presencia de postlarvas de Potimirim mexicana. Se encontraron seis taxones: postlarvas de Macrobrachium acanthurus, M. olfersii y Potimirim mexicana, megalopas de Callinectes sapidus y Armases ricordi y zoeas de Brachyura. La diversidad osciló entre 1,55 y 1,77 bits*individuo-1, lo que indica una estabilidad intermedia del estuario. Se obtuvieron un total de 12,827 postlarvas de P. mexicana. Los valores de LC50 de diurón, paraquat y glifosato fueron 5.94, 1.51 y 221.05 mgL-1, respectivamente. Conclusiones: Los valores aquí encontrados son consistentes con los obtenidos por otros autores para diferentes especies de crustáceos. Debido a la importancia ecológica en la trama trófica de P. mexicana, sus postlarvas pueden usarse como organismos de prueba sensibles en estudios ecotoxicológicos.