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 sewage contains toxic chemical compounds that secondary treatment plants do not eliminate, and chlorine is usually added for disinfection before discharge. Chlorine reacts with sewage compounds forming other toxic compounds. The objective of this study was to evaluate the toxicity of treated sewage from a secondary treatment plant using Danio rerio embryos. Three types of treated sewage were tested, one disinfected with chlorine gas (dCl2), another with sodium hypochlorite (dClO), and the plant discharge, which is a mixture of the two sewage disinfection methods (mCl) with a proportion of 70% of dCl2 and 30% of dClO. To estimate the median lethal dilution treated sewage was diluted with dechlorinated tap water at 20, 40, 60, and 80%. Two additional points were made with pure treated sewage and pure dechlorinated tap water. Embryos were exposed 1 h after fertilization (hpf) to 144 hpf. The dCl2 and the mCl were lethal at 60 and 72 hpf, respectively, while the dClO did not show lethality. The embryos exposed to the mCl showed heart failure and slower blood circulation. Those exposed to dCl2 showed teratogenic effects such as pericardial edema and spinal curvature, while those exposed to dClO presented malformations such as incomplete eye development and otolith formation absence.

ABSTRACT In order to provide information on the current knowledge about the native fish Dormitator latifrons and identify the gaps that must be filled to achieve correct resource management, a scientometric study was carried out using different scientific databases. A total of 103 publications were registered between the years 1972 and 2021. Results indicate that the species has been addressed since 2001 with less than one publication per year, with 2008 being the year with the highest number of publications (10). The main topics addressed were ecology, physiology, and parasitology of fish. The available knowledge generated about the species is concentrated in 68 journals, with Mexico as the most productive country, followed by USA and Ecuador, and the most productive research centers about this fish were Mexico’s Instituto Politécnico Nacional and Universidad de Guadalajara. A total of 285 authors were detected contributing knowledge to the species, with Violante-González in the top with ten publications. The co-authorship co-occurrence maps suggest there is no solid collaborative relationship between the scientific community and that the information generated is insufficient for conserving and exploiting this fish. It is essential to increase the study of thematic areas that allow their comprehensive management in the medium term; topics like reproduction in captivity, aquaculture, and nutrition must be addressed in the future to assure a sustainable use of this resource.

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 The development of native fish aquaculture represents an important alternative to mitigate ecological displacement generated by exotic fish. The introduction of native fish in polyculture systems with high commercial value fishes has provided a useful strategy for sustainable aquaculture development. The present study aims to provide information on tilapia, as an exotic species, and Dormitator latifrons, as a native species, in a duo culture not programmed as such. Using juveniles of Pacific fat sleeper D. latifrons leftovers from another experiment, we decide to analyze and report the biological feasibility of a duoculture system with this species and Nile tilapia (Oreochromis niloticus). Two hundred fifty organisms of each species were placed for 90 days in a concrete tank with a capacity of 50 m3 to evaluate the compatibility of these species. The biological variables measured were growth, survival, feed conversion rate, and protein efficiency. The findings suggest a good interaction between species, with adequate growths and a survival rate of 98%. No antagonistic behavior was observed during confinement, suggesting the duoculture of these species may represent a good alternative for tropical sustainable aquaculture.

ABSTRACT The present work is a review of the literature on the native Mexican fish Dormitator latifrons. The aim is to contribute to the integration and systematization of current knowledge to make it easier to identify existing knowledge gaps and breakthroghs Moreover, promote the successful cultivation and protection of this species whose consumption is increasing in Latin America. A review of the articles related to D. latifrons published in international and regional databases was carried out. The articles reviewed focus on taxonomy and systematics, phylogenetic, geographic distribution, ecology, physiology, reproduction, development, pathology, health, and the technologies used to cultivate this fish species. The conclusion is that, even though the cultivation of D. latifrons is of commercial interest in some countries, there are still significant gaps in our knowledge of biology and, consequently, the domestication potential of the species. Filling these gaps will require systematic research efforts on protecting natural populations and improving mass cultivation techniques.

ABSTRACT Macrobrachium tenellum and M. americanum are common freshwater prawns from the Americas’ tropical and subtropical Pacific continental side. They have different biological attributes and are currently threatened by human impact on their ecosystems. Both species provide different quality products for human consumption and are intensively exploited without proper management. This study analyzes, discusses, and compares the available information for both species and their current status as a live resource.

ABSTRACT The freshwater prawn Macrobrachium acanthurus represents a valuable resource for fishermen's communities in Mexico, although the information of its culture conditions and nutrition is still scarce. Prebiotics are defined as non-digestible components that are metabolized by specific health-promoting bacteria in the host's digestive system, improving the health status and growth performance of cultured aquatic organisms. Fructooligosaccharides (FOS) and mannan oligosaccharides (MOS) are among the most used prebiotics in aquaculture. The present work aimed to determine the effects of dietary FOS and MOS in the growth performance, immune responses, and sexual maturity of juvenile freshwater prawn Macrobrachium acanthurus. Juveniles (0.06 ± 0.001 g) were fed with diets supplemented with a 3 g kg−1 diet of commercial FOS and MOS for 80 days. At the end of the feeding trial, the following indices were calculated: weight gain, specific growth rate, and feed conversion efficiency, as well as superoxide dismutase and lysozyme activities in hepatopancreas tissue. The growth performance, survival, juveniles’ protein contents did no show significant differences among the groups. No differences were detected in superoxide dismutase and lysozyme activities among experimental groups. Around day 60 of the feeding trial, the females fed with the prebiotics maturated, and by the end of the trial, several of them were carrying eggs. It seems that prebiotics might have a role in sexual maturation, but further research is necessary to establish if prebiotics influences the early maturation of M. acanthurus.

ABSTRACT Groups of Dormitator latifrons in triplicate (4.1 ± 2.0 g and 6.2 ± 1.0 cm) were fed experimental diets containing four levels of substitution of fishmeal (FM) by soybean meal (SM) (0, 40, 70, and 100%, respectively). The diets were formulated to be isoproteic (35% crude protein) and isolipidic (8.0% crude lipids). The effect of each treatment on growth was evaluated and its implications on the cost of feeding. After 60 days of feeding, there were no significant differences in the fish’s proximate composition (P < 0.05). There were no significant differences between the diets (P < 0.05) in the evaluated biological indices: total growth increase (TGI), specific growth rate (SGR), thermal growth coefficient (TGC), and survival (%). Feeding costs decreased significantly as the proportion of soybean meal in the diet increased. The results indicated that substituting FM by up to 100% of SM can promote adequate growth in D. latifrons without affecting body composition and survival while also reducing operative costs during the fattening process.

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 is an amphidromous fish species distributed on the Pacific coastal region from California to Peru. It has a high potential to be cultured in Mexico. However, there is very little information about its biology, physiology and culture. This research study is a contribution to the hematology and blood chemistry of this native species. Results show hematocrit values of 28%, erythrocytes 2.075×106 mm3, leukocytes 35.035×103 mm3, mean corpuscular volume 161.547 fL, NBT 0.39, glucose 51.467 mg dL−1, protein 3.936 g dL−1, albumin 1.906 g dL−1, globulin 2.391 g dL−1 and albumin/globulin ratio 0.686.

ABSTRACT The objective of this work was to assess the acceptance of live and inert food by Macrobrachium tenellum during the early larval stages. The larvae were obtained by collecting wild ovigerous females in the Ameca River in the State of Jalisco, Mexico. Eight treatments (diets) were used to feed the larvae: D1, control (fasting); D2, micro-pulverized food (Purina®); D3, living, newly hatched nauplii of Artemia franciscana (INVE®, Salt Lake City, Utah, USA); D4, commercial paste containing microalgae (Instant Algae Rotifer Diet®); D5, water extracted from a biofloc system; D6, cooked egg yolk; D7, newly hatched and frozen nauplii of A. franciscana (INVE®, Salt Lake City, Utah, USA); D8, nutritional supplement for shrimp larvae (Epifeed LH1®). Treatments D2, D5, D6 and D8 showed traces of food in the digestive system. The larvae did not consume D3 and D7 treatments. The diets that had more acceptance were micro-pulverized food, a nutritional supplement for shrimp larvae Epifeed® LH1, cooked egg yolk, and biofloc water.

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 This study assessed the effect of protein level in diet and feeding schedule on the digestive enzymatic activity of Macrobrachium tenellum juveniles. Freshwater prawn juveniles (0.31 ± 0.004 g and 32.48 ± 0.27 mm) were fed diets with 20, 25, 30, 35 and 40% crude protein (CP) (p/p). In a second experiment, feeding schedules were assessed at 08:00, 14:00 and 20:00 h with feed at 30% CP with juveniles of 0.22 ± 0.002 g and 29.36 ± 0.28 mm. In both experiments, five organisms were sampled after 60 days of treatment in a time-lapse of one hour (08:00 to 09:00 h) per experimental tank and treatment. The enzymatic extract was obtained from the complete organisms to determine specific general protease, trypsin, chymotrypsin, amylase and lipase activities. Greater general protease, trypsin and lipase activities were observed in feed at 40% CP. The feeding schedules with greater general protease, trypsin, lipase and amylase activities were found at 14:00 and 20:00 h. Chymotrypsin did not show differences among treatments at CP levels or feeding schedules. Protein level in diets for M. tenellum modified basal digestive enzymatic activity and increased proteolytic and lipolytic activities, while it decreased amylolytic activity as the inclusion of CP level increased in the diet; likewise, the activity was modified by feeding schedule, showing a direct correlation between the increase in digestive enzymatic activity and food offering at the end of the day.