Resumen. El objetivo de este estudio fue determinar la maduración gonadal, calidad de los huevos y larvas de hembras de Macrobrachium tenellum alimentadas con dietas con diferentes niveles de proteínas y lípidos, utilizando indicadores morfológicos y pruebas de estrés. Se capturaron reproductores de M. tenellum en el río Ameca, Jalisco-Nayarit. Se probaron ocho dietas experimentales con cuatro niveles de proteína (30, 35, 40 y 45% P) y dos niveles de lípidos (4 y 12% L), se evaluó la fecundidad (FC), esfuerzo reproductivo (ER), la tasa de eclosión (TE), índice gonadosomático (IGS), índice hepatosomático (IHS), y pruebas de estrés en larvas: supervivencia en inanición y tolerancia a salinidad alta (45 ups). Los resultados muestran que las interacciones entre proteínas y lípidos tienen efectos diferentes en la calidad de huevos y las pruebas de estrés en larvas. La dieta que presentó el promedio más alto en FC, ER y TE fue P30L12, a su vez, la dieta P30L4 obtuvo los promedios más bajos en dichos parámetros. Los IGS e IHS fueron independientes de los tratamientos dietarios y no se encontraron diferencias haciendo comparaciones entre ambos índices. La dieta P30L4 no es la mejor opción para reproductoras de la especie y se recomienda la dieta P35L4 ya que garantiza una calidad de huevos y larvas similar a la mayoría de las dietas evaluadas.

Abstract. This work aimed to determine the gonadal maturation, egg and larval quality of Macrobrachium tenellum females fed diets with different protein and lipid levels, using morphological indicators and stress tests. M. tenellum broodstock were captured in the Ameca River, Jalisco-Nayarit. Eight experimental diets with four protein levels (30, 35, 40 and 45% P) and two lipid levels (4 and 12% L) were tested. Fecundity (FC), reproductive effort (RE), hatching rate (HT), Gonadosomatic Index (GSI), Hepatosomatic Index (HSI), and larval tests: starvation survival and tolerance to high salinity (45 psu), were evaluated. The results show that protein-lipid interactions have different effects on egg quality and larval stress tests. The diet with the highest mean in FC, RE and HT was P30L12, while the P30L4 diet obtained the lowest averages in these parameters. The GSI and HSI were independent of the dietary treatments and no differences were found when comparing the two indexes. The present study showed that the P30L4 diet is not the best option for broodstock of the species and the P35L4 diet is recommended since it guarantees egg and larval quality similar to most of the diets evaluated.

Resumen: Un pez nativo cada vez más estudiado en Latinoamérica es el Dormitator latifrons, pero se desconoce el efecto de altas densidades de siembra en su fisiología. El objetivo fue determinar el efecto de diferentes densidades de siembra en el crecimiento y parámetros sanguíneos. Se utilizaron organismos silvestres aclimatados al cautiverio, alimentados al 4% de biomasa total durante 60 días. Se registró peso y longitud inicial y final, determinando índices de crecimiento y supervivencia. Al final del experimento se tomó una muestra de sangre al total de organismos para evaluar parámetros sanguíneos No se encontraron diferencias en el crecimiento y supervivencia entre las diferentes densidades. Los parámetros sanguíneos no fueron afectados por la densidad, a excepción del estallido respiratorio, todos se encuentran entre los rangos de referencia de buena salud para peces. La especie no presentó señales de estrés o respuesta inmune adversa asociada al incremento de la densidad de cultivo.

Abstract: The native fish Dormitator latifrons culture technology in Latin America has increased, but the effect of high stocking densities on the physiology of the species is still unknown. The objective of this study was to analyze the effect of different stocking densities on growth and blood parameters. Wild organisms were acclimatized to culture conditions, and fed daily at 4% of total biomass, during 60 days. The weight and length of the organisms were recorded at the beginning and end of the experiment, growth and survival rates were determined. At the end of the experiment, a blood sample was taken from all fish for blood parameters evaluation. No differences in growth and survival were found between the different densities tested. Blood parameters were not affected by stocking density. All blood parameters are within the reference ranges indicating good fish health, except respiratory burst. The fish did not show signs of stress or any negative immune response at all culture densities tested.

Abstract The relationship of body weight and length with sperm load and spermatophore weight was evaluated in wild males of Macrobrachium tenellum (Smith, 1871). In addition, the influence of a commercial and natural feed on the load and viability of sperm was determined in wild males. In 28 wild males spermatophore extraction was performed by electrostimulation 24 h after capture to analyze the relationship between body length/weight and sperm load and viability, respectively. Spermatophore weight (SW), total number (TS), dead (DS) and abnormal sperm cells (AS) were used as indicators of sperm viability. The results obtained show that there is a positive correlation between TS per spermatophore compared to body length and weight of the male. To study the effect of different diets on sperm load, three diets were employed: Diet A, commercial shrimp feed; Diet B, natural feed (mixture of squid, sardine and clam); and Diet C, combination of natural and commercial diet. To assess the initial reproductive status of the males at the beginning of the experiment, sperm viability was determined in a subsample of specimens after capture. Broodstock were fed ad libitum once a day during 70 days. TS, DS, AS and SW were evaluated. The results of the bioassay did not show differences between treatments in the parameters analyzed, except DS, which was higher in the initial group. In conclusion, the present work suggests that it is feasible to substitute fresh feed for an artificial diet for the maintenance in captivity of male M. tenellum broodstock shrimp.

Abstract Understanding the upstream migration of amphidromous prawns is important to address the impact of anthropomorphic activities in natural freshwater ecosystems. The ability of Macrobrachium tenellum (Smith, 1871) juveniles to overcome an artificial barrier was evaluated, simulating an obstacle in their upstream migration, under an experimental laboratory system. The prawns were collected from a stream located in Puerto Vallarta, Mexico (N = 1000). An experimental recirculation system was used, which consisted of a tank with a capacity of 600 L, a sheet of galvanized steel that acted as an anthropogenic barrier and two submersible electric pumps with flows of 0.12 L/s and 0.40 L/s. In this system, two inclinations of the barrier were tested, 45° and 90° in combination with the two flows. The results show that there are significant differences between the treatments with different inclinations, where a higher stimulation response was observed at the 90° angle. Within this inclination, the flow of 0.40 L/s produced the highest stimulation to climb the barrier in prawns between 30 and 60 mm in length. This study demonstrates the direct relationship between the slope and the effect of water flow of the anthropogenic barriers that hinder the migration process of M. tenellum.

ABSTRACT Dormitator latifrons inhabits a wide range of salinities as a result of its migratory and reproductive cycle. The objective of the study was to evaluate the physiological response time and survival to saline change under laboratory conditions. The basal gill ventilation frequency (GVF) of organisms was recorded at 33 ups (SW) and in freshwater at 0.3 ups (FW). The gill ventilation frequency of organisms that were transferred from FW-SW and inversely from SW-FW (15, 25, and 33 ups) was counted, in triplicate, for 1 minute and 1, 4, 24 and 48 h. Statistical differences (p < 0.05) were found in fish transferred from FW-SW and SW-FW at the first minute with respect to basal GVF. In all treatments the organisms recovered their GVF one hour after being exposed to saline modification. There was 100% survival in all treatments. D. latifrons has a rapid physiological response to sudden changes in salinity.

RESUMEN Dormitator latifrons habita en un amplio intervalo de salinidades producto de su ciclo migratorio y reproductivo. El objetivo del trabajo fue evaluar el tiempo de respuesta fisiológica y la sobrevivencia al cambio salino en condiciones de laboratorio. Se registró la frecuencia ventilatoria branquial (FVB) basal de organismos a 33 ups (AS) y en agua dulce 0.3 ups (AD). Se contabilizó la frecuencia ventilatoria branquial de organismos que fueron transferidos AD-AS e inversamente AS-AD (15, 25, y 33 ups), por triplicado, durante 1 minuto, 1,4, 24 y 48 h. Se encontraron diferencias estadísticas (p < 0.05) en los peces transferidos de AD-AS y AS-AD al primer minuto con respecto a FVB basal. En todos los tratamientos los organismos recuperaron la FVB una hora después de ser expuestos a la modificación salina. Se tuvo un 100% de sobrevivencia en todos los tratamientos, D. latifrons tiene rápida respuesta fisiológica a cambios bruscos de salinidad.

ABSTRACT Our knowledge of the reproductive biology of palaemonid shrimps is an important tool to assess potential candidates for aquaculture as well as being useful to develop adequate strategies for the conservation of the biodiversity. Here we analyzed the fecundity, volume and water content of the eggs, and the reproductive output (RO) of Macrobrachium tenellum in the Ameca River, Jalisco-Nayarit, Mexico. The total length of the females ranged from 26.6 to 67.0 mm (average 44.2 ± 8.8 mm) and fecundity (considering all stages) fluctuated between 253 and 10,384 eggs (average 2,418 ± 2,089 eggs). Females lost on average 26% of the initially produced eggs. The average egg length increased from 0.55 (recently produced eggs) to 0.66 mm (eggs close to hatching). The water content of eggs increased significantly during embryogenesis by 11.4%. The RO was not related to female length and fluctuated between 4.1 and 16.0%, which are values within the range reported for other decapods. The results of the current research contribute to laying the foundations for future studies that help to define strategies for the conservation and sustainable use of this crustacean.

Introduction: in the last few years, a lot of importance has been given to natural predators against Aedes aegypti. Several organisms have been studied both in lab and in the field so as to find out their capacity to devour mosquito larvae. High densities of Macrobrachium tenellum are found in natural conditions, it is not aggressive and may stand wide ranges of temperature, rates of salinity and oxygen concentrations. Objective: to evaluate the predatory capacity of Macrobrachium tenellum on Aedes aegypti larvae in lab conditions. Methods: very young Macrobrachium tenellum prawns measuring A(3.0-3.5cm) and B(4.5-5 cm) were used. The mosquito larvae were obtained after hatching of egss from adult females kept in entomological cages. Five, ten, fifteen and twenty Aedes aegypti larvae were placed per treatment per rank, whereas the second bioassays adjusted the number of larvae to 30, 40, 50 and 80 larvae per treatment per rank. Results: Macrobrachium tenellum showed high rate of larval consumption for the two ranks and treatments. In the highest density (80 larvae), the consumption was 95% of larvae at 24 hours for rank A and 100% for rank B. Conclusions: Macrobrachium tenellum may be considered as a potential biological control agent, due to its abundant presence in natural conditions, its resistance to different environmental conditions and to its voraciousness seen in this study.

Introducción: en los últimos años se le ha dado gran importancia a los depredadores naturales de Aedes aegypti. Se han investigado, tanto en el campo como en el laboratorio, los distintos organismos con capacidad de devorar larvas de este mosquito. Macrobrachium tenellum se encuentra en altas densidades en condiciones naturales, no es agresivo y puede tolerar un amplio y fluctuante intervalo de temperaturas, salinidades y concentraciones de oxígeno. Objetivo: evaluar la capacidad depredadora de Macrobrachium tenellum sobre larvas de Aedes aegypti en condiciones de laboratorio. Métodos: se utilizaron juveniles de Macrobrachium tenellum con dos rangos de tallas: A (3,0 cm-3,5 cm) y B (4,5 cm-5,0 cm). Las larvas del mosquito se obtuvieron de la eclosión de huevos producidos por hembras adultas mantenidas en una jaula entomológica. En el primer bioensayo se colocaron 5, 10, 15 y 20 larvas de Aedes aegypti por tratamiento por rango. En el segundo bioensayo el número de larvas se ajustó a 30, 40, 50 y 80 larvas por tratamiento por rango. Resultados: Macrobrachium tenellum demostró un alto consumo de larvas para los dos rangos y tratamientos. En la mayor densidad (80 larvas) se obtuvo el consumo de 95 % de larvas a las 24 h para el rango A y 100 % para el rango B. Conclusión: Macrobrachium tenellum puede ser considerado como un potencial agente de control biológico debido a su abundancia en ambientes naturales, su resistencia a diversas condiciones ambientales y a la voracidad presentada en este estudio.

This research aims to collect and classify information on the biology and culture of the prawn Macrobrachium tenellum, in a clear and sequential manner, which would integrate the knowledge to develop new ways in research and sustainable exploitation of this resource. It covers various topics including taxonomy and systematics, geographic distribution, ecology, reproduction, development, pathology, fisheries and aquaculture of this species, taking into account all the information generated by different authors, from four decades to today. We conclude that there are significant knowledge gaps of basic and applied aspects of the biology of the species and this requires a great deal of research for the correct understanding of this native organism to allow for its protection and proper utilization. It is recommended to take special interest in studies to fully know its distribution, the effects of pollution and the loss of its natural habitats. It is necessary to review the regulations for the use and conservation, and to develop and improve aquacultural management techniques.

El presente trabajo tiene como propósito reunir y clasificar la información existente sobre aspectos biológicos y de cultivo del langostino Macrobrachium tenellum, de una forma clara y secuencial, que permita integrar el conocimiento para desarrollar nuevos caminos en la investigación y aprovechamiento sustentable de este recurso. Se abordan diversos temas que incluyen la taxonomía y sistemática, distribución geográfica, ecología, reproducción, desarrollo, patologías, pesca y acuicultura de la especie, tomando en cuenta toda la información generada por diversos autores, desde hace cuatro décadas a la fecha. Se concluye que existen vacíos importantes en el conocimiento de aspectos básicos y aplicados sobre la biología de la especie y que se requiere un gran esfuerzo de investigación para la correcta comprensión de este organismo nativo, que permita su protección y adecuado aprovechamiento. Se recomienda poner especial interés en estudios que permitan conocer completamente su distribución, el efecto de la contaminación y la pérdida de sus hábitats naturales. Es necesario también revisar la normatividad de aprovechamiento y conservación, así como desarrollar y mejorar las técnicas de manejo acuicultural.