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Piracanjuba (Brycon orbignyanus) is a species with great productive potential, and during its larval phase, it presents intense cannibal activity. The photoperiod and diet are primary feed behaviour and cannibalism modulators to fishes. This experiment aimed to verify the effect of different photoperiods and diets in Piracanjuba larviculture. Larvae were kept under different photoperiods - 12 h light: 12 h dark (12 L: 12D); 24 h light:00 h dark (24hL: 00D) - Larvae were fed with Artemia nauplii and a formulated micro-diet in a factorial scheme for 10 days, and at the end of the experimental period, the influences of the treatments on performance and quantitative expression of mLeptin and mBmall1 were evaluated. In order to quantify the expression of mLeptin and mBmall1, qPCR adopting β-actin and Elongation Factor 1 as endogenous genes was used. The primers for all the analysed transcripts were obtained through multiple sequences alignments of different fish species. It was observed that the diet and photoperiod influence the performance of Piracanjuba (B. orbignyanus) larvae in the initial phase of larviculture. Feeding with artemia nauplii and the photoperiod of 24 L:00D reduce cannibalism rates in intensive Piracanjuba larviculture. The results on the rate of cannibalism, rate of survival and the relative expression of mLeptin are related to the survival rate of the larvae, and it is inversely proportional to the cannibalism rate. The expression levels of mBmall1 showed a correlation with the final weight of the larvae. Piracanjuba Larvae under a photoperiod of 24 light and fed Artemia nauplii showed more significant levels of mLeptin expression.

Teleost fish are the most diverse group of extant vertebrates and have varied digestive anatomical structures and strategies, suggesting they also possess an array of different host-microbiota interactions. Differences in fish gut microbiota have been shown to affect host development, the process of gut colonization, and the outcomes of gene-environment or immune system-microbiota interactions. There is generally a lack of studies on the digestive mechanisms and microbiota of agastric short-intestine fish however, meaning that we do not understand how changes in gut microbial diversity might influence the health of these types of fish. To help fill these gaps in knowledge, we decided to study the Mexican pike silverside (

Continuous illumination has been known to exert positive effects by stimulating growth and delaying unwanted maturation in seasonal-temperate farmed fish species like salmonids. However, in tropical fish like Nile tilapia ( Oreochromis niloticus ), some studies exist showing inconsistent results and even fewer data is available regarding the effects of light intensity. To clarify some of the inconsistent results in literature and evaluate the effect of different light intensity levels on growth and sexual maturation in Nile tilapia ( Oreochromis niloticus ), we reared twenty days post-hatch Nile tilapia larvae under continuous illumination at three different light intensities and compared against a control photoperiod (12L:12D) up to 118 days post-hatch. A total of 600 fry were used using 75 fry per experimental unit in a previously tested experimental aquarium setup. Fish exposed to high and medium intensity continuous illumination treatments were significantly heavier (13-20%) and longer (6-8%) than fish exposed to the control photoperiod. Importantly, however, the degree of growth enhancement did not vary significantly according to the light intensity used. Feed intake was also higher in all continuous illumination treatments than in the control photoperiod, suggesting that growth benefits might be due to an increase in feed intake, which is not affected by the light intensities used. Gonadal development on the other hand, presented differences between sexes with a delay in spermatogenesis, while an advancement towards ovarian maturation occurred compared with the control fish. These results suggest that continuous illumination can influence both growth and gonadal development in Nile tilapia with no apparent differences between the light intensities tested in this study.

An experiment was carried out to evaluate the effect of the use of a fish hydrolysate, CPSP Special-G™ (FH) and a soy protein isolate, SUPRO-590™ (SPI) in balanced diets, on growth performance, survival, body composition and nutrient digestibility in juvenile Pike Silverside, Chirostoma estor. Eight isonitrogenous diets (410 g kg−1): three with different substitution levels of FH (15, 30 and 45%), three with different substitution levels of SPI (15, 30 and 45%), a diet with a combination of both products (15%FH/15%SPI) and a control diet (0% FH, 0%SPI), were prepared. Juvenile fish (1376 ± 58 mg initial weight) were fed the eight diets three times a day, for eight weeks. Best growth was obtained in fish fed control diet and diets with an inclusion of 15% of both products alone or in combination (FH15, SPI15 and FH15/SPI15) (P 0.05) at the end of experiment. Dry matter, protein, lipid and energy digestibility (ADC) were influenced by ingredient type and inclusion level. There was a trend to decrease dry matter and protein ADC with increasing levels of SPI. Under the experimental conditions, the two products tested can be used separately or combined at inclusion levels up to 15%, without affecting fish growth and survival. Incorporation of 30 or 45% of either product could cause a detrimental effect on juvenile fish growth. This suggests that FH and SPI are viable protein sources at inclusion levels up to 15% in diets for juveniles of this species.

This study evaluated growth responses of white shrimp Litopenaeus vannamei by testing different combinations of Jatropha curcas kernel meal (JCK) and tilapia waste silage (FS) as dietary protein sources under laboratory and pond conditions. A reference diet (RD) based on fish meal was elaborated to contain 35% crude protein and 434 kcal/g; then, five isoproteic and isoenergetic experimental diets were formulated from RD with different FS/JCK proportions as follows: 75%FS/0%JCK; 56.25%FS/13.25%JCK; 26.5%FS/30.89%JCK; 18.75%FS/39.75%JCK; and 0%FS/53%JCK. For the laboratory trial, shrimp (2.90 g) were stocked at 10 m2 in an indoor recirculating system during 90 days. There were differences among the growth parameters of diets. Mean weight gain fluctuated from 6.71±0.61 g observed for the shrimp fed the 75%FS/ 0%JCK diet, to 9.70±0.61 g for the group fed the RD. The RD and 18.75%FS/39.75%JCK diet obtained the highest mean final weight (above 12 g), weight gain (above 9 g), and specific growth rate values (above 1.6%/day). Average final survival was 90.97%. The RD and 18.75%FS/39.75%JCK diets were used for the pond trial. Shrimp (0.49 g) were stocked at 10 m2 within 1-m3 cages into the pond for 35 days. Weight gain (3.47 g) and survival (93.33%) of shrimps were similar between the diets. Quadratic equations with the laboratory data indicated that the maximum responses for growth parameters correspond to FS and JKC inclusion levels in the range of 27.83 to 29.00%, and 32.25 to 33.64%, respectively. A combination of 18.75% FS/39.75%JCK meals as protein source is a potential alternative to effectively substitute FM in practical diets for L. vannamei at the studied ages under both laboratory and pond conditions.

A 7-week feeding trial was conducted to investigate the effects of replacing fish meal by autoclaved Salicornia bigelovii seed meal (SSM), supplemented with varying cholesterol levels, on feed intake, growth performance, body composition and survival of Nile tilapia Oreochromis niloticus fingerlings under laboratory conditions. SSM was tested at different inclusion levels (0, 25, 50 and 65 % of total protein), using different levels of cholesterol supplementation (0, 1, 2 and 2.6 %) in isonitrogenous (420 g Kg−1 DM crude protein) and isocaloric (18.52 MJ Kg−1 DM) fish meal–Soybean meal-based diets. Triplicate groups of fish (374 ± 15 mg, initial fresh body weight) were randomly stocked in 18 20-L plastic tanks at a stocking density of 20 fish per tank and were fed to satiation by hand five times a day, 7 days per week. Feed intake, growth performance and survival were significantly affected by the SSM inclusion level and the cholesterol supplementation. The lower growth performance of fish fed diets containing SSM without cholesterol is thought to result from the presence of saponins in the meal. When cholesterol is added, the saponin-induced toxicity is ameliorated, which is evident from growth and survival responses, up to 50 % of SSM protein inclusion. At the highest level of SSM inclusion (65 %), growth and survival were very poor, despite the addition of cholesterol. The results of the present work suggest that autoclaved SSM can partially substitute fish protein in diets for O. niloticus fingerlings at levels up to 50 % of the dietary protein if 2 % cholesterol is added in fish meal–SBM-based diets.

The genus Chirostoma (silversides) belongs to the family Atherinopsidae, which contains around 150 species, most of which are marine. However, Mexican silverside (Chirostoma estor) is one of the few representatives of freshwater atherinopsids and is only found in some lakes of the Mexican Central Plateau. However, studies have shown that C. estor has improved survival, growth, and development when cultured in water conditions with increased salinity. In addition, C. estor displays an unusual fatty acid composition for a freshwater fish with high docosahexaenoic acid (DHA)/ eicosapentaenoic acid (EPA) ratios. Freshwater and marine fish species display very different essential fatty acid metabolism and requirements, and so the present study investigated long-chain polyunsaturated fatty acid (LC-PUFA) biosynthesis to determine the capacity of C. estor for endogenous production of EPA and DHA, and the effect that salinity has on these pathways. Briefly, C. estor were maintained at three salinities (0, 5, and 15 ppt), and the metabolism of ¹⁴C-labeled 18:3n-3 was determined in isolated hepatocyte and enterocyte cells. The results showed that C. estor has the capacity for endogenous biosynthesis of LC-PUFA from 18-carbon fatty acid precursors, but that the pathway was essentially only active in saline conditions with virtually no activity in cells isolated from fish grown in freshwater. The activity of the LC-PUFA biosynthesis pathway was also higher in cells isolated from fish at 15 ppt compared with fish at 5 ppt. The activity was around fivefold higher in hepatocytes compared with enterocytes; although the majority of 18:3n-3 was converted to 18:4n-3 and 20:4n-3 in hepatocytes, the proportions of 18:3n-3 converted to EPA and DHA were higher in enterocytes. The data were consistent with the hypothesis that conversion of EPA to DHA could contribute, at least in part, to the generally high DHA/EPA ratios observed in the tissue lipids of C. estor.

The early development of the digestive biochemistry of three cultured Atherinopsids (two Odontesthes species and Chirostoma estor )w as investigated. Relatively high lipolytic and high alkaline proteolytic activities were found in all species. In addition, gene expression of lipase and trypsin during the early development of C. estor not only indicates an early onset of the lipase activity but also demonstrates a major importance of protein digestion in this species. However, despite all of them share similar habitats, diierences in their digestive activities were evident. The rise in the activities of brush border membrane enzymes correlated with the decrease in cytosolic activities, used as indicator of maturation of the digestive tract, was detected in both species of Odontesthes at 9 weeks after hatching. In contrast, no similar signs were measured in C. estor, this being in agreement to the long weaning period (nearly 5 months) reported for this species.

The pike silverside has high aquaculture potential despite its slow growth. In this study, thyroxine (T4) concentrations (0.13, 1.3 and 13 nM), a control with no hormonal supplement and a negative control containing 4.5 mM methimazole (MMI) were tested to evaluate the growth of this species. Juveniles (0.2 g) were exposed by immersion to these treatments for 8 h every second day for120 days, and growth evaluations were performed monthly over the entire trial period. In addition, tissue samples from each treatment group were assayed for triiodothyronine (T3) and deiodinase type 2 (D2) activity. The survival rates in all T4 groups were high, and a signi¢cant increase in growth was observed (average of 58%). The MMI treatment caused an increase in mortality and a reduction in the ¢nal body weight compared with the control. T4 administration did not aiect the tissue levels of T3, and it decreased muscular D2 activity only after 30 days of exposure. These results demonstrated that low concentrations of T4 in the culture environment could improve the growth of this species without affecting tissue hormone levels. The technique may have useful applications for early-stage aquaculture of this and other economically important species.

The tilapia ¢shery in a large Mexican reservoir has declined in recent years, promoting eiorts to enhance stock quality in conjunction with feasibility studies for cage aquaculture. Spatial models to optimize cage location have been developed, incorporating aspects of topography, climate, hydrography, water quality and quantity, land use, infrastructure and socioeconomics. Three cage sizes were modelled, 5, 10 and 15 m diameter, for both high- and low-water levels. When full the, reservoir has a total area of 312 km 2 but a reduction in water level of 13 m was recorded between wet and dry seasons, signi¢cantly reducing the surface area available for cages to 265 km 2 . The results indicate a signi¢cant diierence in the availability of sites between seasons. For the small, medium and large cages at high water level, the areas classi¢ed as highly suitable or suitable were 151, 184 and 146 km 2 , respectively, while at low-water level these areas reduced to 113, 88 and 62 km 2 . Modelling this change in water level and the subsequent loss of available sites provide qualitative and quantitative guidelines for the development of aquaculture sites, their seasonal management and future monitoring, outcomes that can only be achieved using Geographical Information Systems and associated technologies.

The aim of this work was to confirm previous findings suggesting that the eyes are required for night-time melatonin production in Nile tilapia and further characterise this divergent circadian organisation. To do so, melatonin levels were firstly measured in eyecups and plasma to determine circadian patterns of melatonin production. Secondly, the effect of partial ophthalmectomy on the suppression of melatonin production was determined in vivo as well as ex vivo pineal light/dark sensitivity. Finally, to investigate whether such findings could be related to post-surgery stress, melatonin analyses were performed in the subsequent 24 h and 7 days post-ophthalmectomy with cortisol levels assessed as an indicator of stress. Our results showed an inverse pattern of melatonin production in the eye cups of tilapia compared to blood circulating levels, suggesting different roles played by melatonin in these two tissues. Results then demonstrated that total or partial ophthalmectomy resulted in the suppression of night-time melatonin production. Furthermore, although pineals in culture were shown to be photosensitive, night-time melatonin levels were much lower than seen in other species. Finally, when performing sampling immediately or one week post-surgery, no difference in the melatonin profiles were observed. It is therefore unlikely that post-surgery stress would explain such suppression in melatonin production although all fish displayed high cortisol levels most probably due to social and handling stress. Taken together, these results provide further evidence of a new type of circadian organisation in a teleost species where the eyes are required to sustain night-time melatonin levels.

Aquaculture continues to be the fastest growing animal production industry and this rate of expansion must continue if aquaculture is to satisfy global demand for fish products in the face of dwindling capture fisheries. The relationship between aquaculture and biodiversity is complex, with examples of positive and negative impacts having been reported. To enable this expansion while avoiding negative impacts from introductions of exotic species, the investigation of indigenous species becomes important and worthwhile.This paper establishes the background to development of new species for culture and describes the example of the Mexican silverside Menidia estor, which has for centuries been the principal species in an artesanal fishery in Lake Patzcuaro, Mexico. The species is geographically isolated and is unique but is now endangered because of a range of factors including overfishing, environmental degradation and introduction of exotic species. Considerable advances have been made recently in developing a closed reproductive cycle, understanding feeding and small-scale on-growing technology for the species. Based on this, a Darwin Initiative programme was developed focused on technology transfer to implement small-scale pilot on-growing thus helping to conserve the species and to improve livelihoods. This has allowed successful pilot scale development of aquaculture for the species while at the same time addressing the objectives of the international Convention on Biodiversity.

The Mexican silverside, Menidia estor, is a species with great regional importance and with very high prices in local markets. Unfortunately, due to high ¢sheries pressure, environmental degradation and pollution, the species has become endangered. Recently, there has been much progress in the biotechnology of this species, aimed at its culture, and the present paper describes the advances in feeding and nutrition of those important ¢sh. M. estor is a stomachless, zooplantophagous ¢sh, which also occasionally feeds on small ¢sh and crustaceans in the adult stage. Studies on the digestive enzymatic activities show high proteolytic capacity and a late or diierent model of digestive maturation from that described for marine stomach ¢sh. Nutritional studies on M. estor have shown that juveniles have dietary requirements of about 400 g kg 1 protein and 80 mg kg 1 vitamin C. The upper level of dietary carbohydrate for good growth and survival for juveniles is about 150 g kg 1 . Based on the high docosahexaenoic acid (DHA) content in £esh when fed on diets low in DHA, it is believed that the species has the capacity to biosynthetize420-carbon fatty acids from 18-carbon fatty acids. The high levels of DHA in £esh makes this ¢sh a very signi¢cant potential component of human nutrition. Using these ¢ndings the ¢rst practical diets for commercial culture of the species have been developed.

Anaesthesia, sedation and transportation of the Atherinopsid, Menidia estor, were investigated using benzocaine, hypothermia and combinations of the two. The optimum dose rates of benzocaine for sedation of juvenile Chirostoma estor were 15 and 18 mg L−1. When hypothermia was used alone, stable sedation of C. estor was induced at 15 and 12°C, with no mortalities and full recovery after about 8 min. There was synergism when benzocaine and hypothermia were combined, with the optimal combination being at 15°C and 12 mg L−1 benzocaine. Successful transportation was conducted over 3.5 and 8.5 h using combined benzocaine and hypothermia. Aloe vera extract used in the transportation medium reduced scale loss. This work has, for the first time, defined a systematically derived system of safe, long distance, live transportation of this species and others of the genus Menidia.

Lipid classes and fatty acid levels were analyzed in freshly fertilized eggs, early and late embryo development, and freshly hatched larvae obtained from wild and captive silverside Chirostoma estor estor broodstock, as well as in plankton, Artemia, and pelleted feed. The concentration of triglycerides (TGs) and highly unsaturated fatty acids (HUFAs) in neutral lipid fraction significantly decreased during early development and especially after hatching, whereas phospholipids and HUFA in polar lipid fraction remained constant. These results indicate that TGs rather than PLs are used as energy sources and that all HUFAs [20:4n-6/arachidonic acid (ARA), 20:5n-3/eicosapentaenoic acid (EPA), and 22:6n-3/docosahexaenoic acid (DHA)] of polar lipids are selectively conserved during early development. High levels of DHA (30%, on average, of total fatty acids) and low levels of EPA (4%) were observed in eggs, embryos, and larvae and did not reflect the proportions of these fatty acids in food. Preferential accumulation of DHA from food consumed by broodstock, and then transference to eggs, was probably occurring. The main difference between eggs from both origins was a low level of ARA in eggs from captive fish (4% of total fatty acids) compared to wild fish (9%). This could be associated with a deficiency in the diet that is not compensated for by desaturation/elongation of 18:2n-6 and, possibly, with greater stress in captive fish. In any case, particular requirements of ARA should be determined to optimize the culture of C. estor.

The growth and survival of white fish (Chirostoma estor estor) larvae were measured at different temperatures ranging from 16.1 to 34 °C. A single camera video system was used for accurate measurement of length of larval and juvenile fish, which enabled growth experiments on delicate animals with minimal handling. Use of a length/weight relationship then enabled estimation of mass. When applied to C. estor estor, the error of the system was generally less than 0.5% for length, but increased to over 1% when the distance of the larva to the grids increased. The total practical error in estimation of biomass using the video method was −2.05% for dry weight, with a range from −7.1% to +4.1%. Over a number of experiments, the recorded mortality due to the measuring process was less than 1%, representing a dramatic advance on all previous attempts to work with Chirostoma. This simple method could have wider utility for fragile larvae such as marine fish. Larvae were fed ad libitum with Brachionus rubens rotifers and Artemia franciscana nauplii for 1 month. The results showed that the optimum temperature for specific growth rates (SGR) was 28 °C, although survival was only 18% at this temperature. The best survival (53%) was at temperatures of 22 and 25 °C. The best overall temperature for growth and survival was 25 °C.

This study tested the use of sunflower seed meal as a dietary protein replacement for fishmeal in practical diets for tilapia fingerlings. In order to determine the optimum substitution level for this species, sunflower seed meal was used to replace 10%, 20%, 30%, 40% and 50% of the fishmeal protein in diets containing 40% protein overall. During a 70-day feeding period, diets containing 10% and 20% plant protein provided the best growth and feeding efficiency results, with values statistically similar to those of the control diet based on fishmeal as the sole protein. The unitary feeding cost index showed the highest profit with diets containing 20% sunflower seed meal. Growth depletion observed with diets containing higher sunflower seed meal percentages is explained by increasing Phe and Met deficiencies, and high non-digestible fibre content. It was concluded that sunflower seed meal is a suitable feed ingredient for tilapia complete diets when it constitutes up to 20% of the dietary protein.

The growth and survival of Penaeus vannamei postlarvae was measured at temperatures of 20, 25, 30 and 35 °C and salinities of 20, 30, 35, 40 and 50%.. Groups of 30 animals were used in each combination of conditions, in triplicate. The results clearly show that juveniles of this species have their best survival between temperatures of 20 and 30 °C and salinities above 20%.. Best growth was obtained between temperatures of 25 and 35 °C, with little difference being noted among salinities. Survival and growth coincide best at around 28 to 30 °C and 33 to 40%.. Calculated overall production was shown to be best in these conditions. The results demonstrate a high coincidence between the experimentally determined optimum conditions for production and the prevailing conditions in the coastal environment from which the animals originated.

In experiments designed to demonstrate the effects of instantaneous changes in salinity, juveniles were able to resist abrupt changes from fresh water up to 15‰ salinity without mortality, and the median lethal salinity (MLS) was 24‰. In a growth trial of 12 weeks duration at salinities of 0, 5, 10, 20, 30 and 35‰, final body weight, weight gain, specific growth rate, food intake and food conversion ratios were always higher in saline environments than in fresh water although differences were not significant. The best growth was observed at 10 and 20‰, the optimum probably being between these concentrations. The fish is clearly euryhaline.

The morphometric relationships, standard length-weight, standard length-width and weight-width for Cichlasoma urophthalmus (Gunther) in the weight range 0.78-262g were: log10 weight =−4.35 + 2.95 × (log10 standard length); log10 width =−0.73 + 0 99 × (log10 Standard length) and log10 width = 0.74 + 0.33 × (log10, weight). Two box graders were designed and tested based on these data. The operation efficiency (expressed as a percentage of the sample used to test it) was 96.1 % and 95% for the two graders. Results indicated a tendency to undergrading (small fish detained by the bars) by the first grader and overgrading (large fish going between the bars) by the second, the latter as a result of the major variability in the body shape from fish as they grow. The results are satisfactory, and larger graders for commercial use could be constructed based on these relationships.

A simple trial is described to determine the effects of brown fish meal, solvent extracted soybean meal, raw wheat meal, raw starch and dextrin on diet digestibility in juveniles of the Mexican cichlid, Cichlasoma urophthalmus (Gumher). The effects of possible anti-nutrients in the feedstuffs used were assessed with the purpose of designing practical diets. The results did not show any effect attributable to anti-nutrients, but showed that high dietary fibre levels reduced digestibility. The carbohydrates of soybean meal were poorly digested compared with the other sources utilized. These results suggest that the substitution of fish meal by soybean meat and other plant proteins could be increased to reduce costs of practical diets for this species.

The feeding habits of the cichlid Cichlasoma urophthalmus were studied in a brackish-water lagoon in Yucatan Peninsula, Mexico, from spring 1985 to spring 1986. The strong mandibular, maxillary and pharyngeal teeth, and the short intestine strongly suggest that C. urophthalmus is primarily a carnivore. Subsequent gut contents analysis revealed that this species feeds principally on invertebrates throughout the year and that there were few differences between the five seasons studied. The algal material found in some stomachs may be consumed as a consequence of predation on small invertebrates, but the feeding structures and short intestine makes this species unable to digest vegetable materials efficiently. Differences with other cichlids used in aquaculture are discussed.

Instituto de Investigaciones Agropecuarias y Forestales. Facultad de Biología. Facultad de Medicina Veterinaria y Zootecnia. Facultad de Agrobiología. Facultad de Químico Farmacobiología. Programa Institucional de Maestría en Ciencias Biológicas The increase in the demand for protein of animal origin, makes it an objective to maximize and optimize production, in turn increasing the susceptibility to diseases of cultured organisms. Fish are exposed to a high content of bacteria, many of them pathogenic, with bacterial infections being the biggest problem in aquaculture production. The use of additives in food as prebiotics has been an alternative for the solution of this problem since, among other effects, there is evidence that these additives favor the functioning of the fish’s immune system. In this work, the effect of the use of prebiotics in the intestinal microbiota and the growth of tilapia (Oreochromis niloticus) was evaluated. Two diets were used, one enriched with yeast cell wall, another enriched with isolated β-glucans and a control. The experimental design consisted of two experiments, one, for the effect of prebiotics on zootechnical parameters since the best weight and height gains were recorded in tilapia fed with prebiotics (yeast cell wall). Second experiment, was a sequencing analysis of the 16S rRNA gene in fish feces exposed to the different treatments, it was possible to determine the transient microbial populations and through comparisons between the different treatments, a core microbiota was identified where the genus Cetobacterium was recorded in 100% of the samples. The microbiota forms clusters, which differ from the control, this change occurs from the second and third week, becoming again similar for the fourth week. El aumento en la demanda de proteína de origen animal, hace que un objetivo sea maximizar y optimizar la producción, aumentando a su vez la susceptibilidad a enfermedades de los organismos cultivados. Los peces están expuestos a un alto contenido de bacterias muchas de ellas patógenas, siendo las infecciones bacterianas el mayor problema en la producción acuícola. El uso de aditivos en el alimento como prebióticos ha sido una alternativa para la solución de dicha problemática ya que, entre otros efectos, existen evidencias de que estos aditivos favorecen el funcionamiento del sistema inmune de los peces. En el presente trabajo se evaluó el efecto del uso de los prebióticos en la microbiota intestinal y en el crecimiento de la tilapia (Oreochromis niloticus). Se utilizaron dos dietas, una enriquecida con pared celular de levadura, otra enriquecida con ?-glucanos aislados y un control. El diseño experimental consistió de dos experimentos, uno, para el efecto de los prebióticos en los parámetros zootécnicos ya que se registraron las mejores ganancias de peso y talla en tilapias alimentadas con prebióticos (pared celular de levadura). Segundo experimento, fue un análisis de secuenciación del gen 16S rRNA en heces de peces expuestos a los diferentes tratamientos, se logró determinar las poblaciones microbianas transitorias y a través de comparaciones entre los distintos tratamientos, se identificó una microbiota núcleo en donde se registró el género Cetobacterium en el 100% de las muestras. La microbiota forma agrupaciones, que se diferencian del control, este cambio ocurre a partir de la segunda Y tercera semana, volviéndose nuevamente similar para la cuarta semana.

Instituto de Investigaciones Agropecuarias y Forestales. Maestría en Producción Agropecuaria The culture development of pike silverside (Chirostoma estor) is presently at a pilot scale and several important zootechnical aspects are still being developed. An identified problem is its apparent slow growth and the occurrence of deformities in grow-out stages. The present work evaluated the feeding rate and tank type over these phenomena. For this, 1200 three month C. estor juveniles were evenly distributed in 9 circular tanks (8,482 L ) and 3 half-pipe raceways (163 L ). The organisms were subjected o three different feeding ratio treatments (apparent satiety, ½ apparent satiety, and ¼ apparent satiety) and two type of tank treatments (circular tanks vs half-pipe raceways). Three biometric and X-ray sampling points were done across r the duration of the experiment in order to evaluate growth and asses the rate of deformities. Fish fed to apparent satiety and ½ apparent satiety showed the highest growth (mass/length) with no significant differences (p

Instituto de Investigaciones Agropecuarias y Forestales. Instituto de Investigaciones sobre los Recursos Naturales. Instituto de Investigaciones Químico Biológicas. Facultad de Biología. Facultad de Medicina Veterinaria y Zootecnia. Facultad de Químico Farmacobiología. Programa Institucional de Doctorado en Ciencias Biológicas The use of continuous lighting is an increasingly common practice in teleost aquaculture, however the molecular interplays that modulate the growth, the feeding and the sex determination in fish are not well understood. The aim of this work is analyze the biological responses under: a) Continuous lighting photoperiod (CL) and b) Control simulated photoperiod (CS), which were applied after egg fertilization until 12 weeks after hatching. At the end of the trial the sex ratios, biometrics, feeding, circadian hormones profiles and gene expression (qPCR and RNA-seq) analyses were performed. We observed 40% of males in CS vs 73.3% of males in CL (p?0.05). The qPCR analyses indicate that 64.29% of CL individuals had a higher expression tendency of sox9 (testicular differentiation) vs foxl2 (ovarian differentiation), comparing with 35.71% in CS (p>0.05). The gene expression of oxidative stress biomarkers (sod2 and ucp2) and stress response (gcr1), did not show statistical differences between treatments (p>0.05). However, the transcripts of enzymes against oxidative stress (cat and gsr) and the activation of stress axis (crf) shows overexpression in CL (p?0.05). The fish of CL had an overgrowth (mass 66.14% and length 17.95% vs CS) and better feed conversion ratio 1.618 vs 1.95 in CS (p?0.05). With no statistical differences in survival and condition factor (p>0.05). The transcriptomic De Novo assembly indicates the presence of 68,960 contains annotated in 43,314 proteins.. El uso del fotoperiodo de luz continua es común en la acuicultura de teleósteos, sin embargo, los mecanismos moleculares que modulan el crecimiento, la alimentación y la determinación sexual no son bien comprendidos. En este trabajo se analizan algunos elementos de respuesta en: a) Fotoperiodo de luz continua (CL) y b) Fotoperiodo simulado control (CS); aplicados desde la fertilización y hasta las 12 semanas de eclosión en Chirostoma estor. Al final del experimento se identificaron histológicamente las proporciones sexuales, además se obtuvieron las variables biométricas, de alimentación, perfiles de hormonas circadianas y análisis de expresión de genes por qPCR y secuenciación masiva RNA-seq. En CS se observó un 40% de machos vs CL con 73.3% de machos (p?0.05). Los análisis por qPCR indican que en CL el 64.29% de los individuos presentan una tendencia de mayor expresión de sox9 (diferenciación testicular) vs foxl2 (diferenciación ovárica), comparado con el 35.71% en CS (p>0.05). La expresión de genes asociados al estrés oxidativo (sod2 y ucp2) y la respuesta del eje de estrés (gcr1) no muestran diferencias significativas entre CS y CL (p>0.05). Los niveles transcripcionales de enzimas asociadas a la defensa ante el estrés oxidativo (cat y gsr) y en la activación del eje de estrés (crf) presentan diferencias significativas entre CL y CS (p?0.05). Los organismos de CL presentaron un mayor crecimiento (masa, 66.14% y longitud, 17.95%) vs CS y un mejor factor de conversión alimenticia (1.618 en CL vs 1.95 en CS) (p?0.05); sin diferencias significativas en la supervivencia, ni el factor de condición (p>0.05). Los perfiles de cortisol revelan diferencias significativas (p?0.05), pero no para la producción de melatonina (p>0.05) entre tratamientos. El análisis transcriptómico De Novo en C. estor, indica que 68,960 contigs se anotaron en 43,314 proteínas.

Instituto de Investigaciones Agropecuarias y Forestales. Facultad de Biología. Facultad de Medicina Veterinaria y Zootecnia. Facultad de Agrobiología. Facultad de Químico Farmacobiología. Programa Institucional de Maestría en Ciencias Biológicas Chirostoma estor is an endangered freshwater atherinopsid endemic to central Mexico. In this work we investigated the prescence of temperature-dependent sex determination (TSD) mechanisms that could be applied as a biotechnological tool for sex control in the culture of this species. This information could be useful also as a bioindicator of anthropogenic or climate change effects on its reproduction. For this work gametes from three single pair broods were manually fertilized, immediately divided in three groups, and incubated at 14, 21, and 29ºC. These thermal treatments were continued through hatching until 30 days after hatching (dah). All groups were then transferred to 21ºC. About 40-60 fish per treatment were sampled at 90 dah and processed histologically to determine phenotypic sex ratios. Also to determine the onset of sexual histological differentiation at 21ºC we sampled 20 larvae each week from hatching to 30 dah. The proportions of males for the first brood were 67, 65 and 90% (p≤0.01), to second brood, 57, 55 and 64 % (p≥0.05), and to the third brood 48, 75 and 92%(p≤0.01); at 14, 21, and 29oC respectively. Thermal treatments applied from fertilization show a clear effect in biased phenotypic sex ratios in brood 1 and 3, wich translates to substantial differences in the response of each brood to temperature. The histological differentiation onset was determined at 30 dah showing presumptive testis and ovaries with presence of somatic and primordial germ cells and the opening of the primordial ovarian cavity. These results suggest that incubation at high temperatures during embryonic development can lead to male-biased sex ratios in this species. The effects of lower and medium temperatures were not so clear, suggesting a mixture of genotypic and TSD mechanisms in C. estor as in other atherinopsids. Moreover, the histological differentiation onset was observed around 30 dah and suggests that molecular differentiation occurs early in the first larvae stages, however more studies are required to clarify the gonadal development in this important species. El pez blanco de Pátzcuaro Chirostoma estor es una especie endémica en peligro de extinción con un alto valor social, económico, ambiental y cultural del altiplano Mexicano. El presente trabajo fue realizado con el fin de obtener información científica sobre la determinación sexual por temperatura (DST) en esta especie, este conocimiento puede aplicarse como una herramienta biotecnológica para el control de la proporción sexual fenotípica en un cultivo comercial, así como para evaluar los efectos del cambio climático y la influencia antropogénica sobre la reproducción del pez blanco en el medio natural. A partir de 3 parejas de reproductores se obtuvieron gametos sexuales que fueron manualmente fecundados, inmediatamente después se dividieron en tres grupos y se incubaron a 14, 21 y 29ºC. Estos tratamientos térmicos se continuaron hasta 30 días post eclosión (dpe), posteriormente todos los grupos fueron trasladados a 21ºC hasta los 90 dpe. Al finalizar el experimento 40-60 peces por tratamiento fueron muestreados y procesados histológicamente para evaluar la proporción sexual fenotípica. Para determinar el inicio de la diferenciación sexual histológica a los 21ºC se muestrearon semanalmente 20 larvas desde la eclosión hasta 30 dpe. La proporción de machos para la primera progenie fueron 67, 65 y 90%(p≤0.01) para la segunda progenie, 57, 55 y 64% (p≥0.05) y la tercera progenie 48, 75 y 92%(p≤0.01) en 14, 21 y 29oC respectivamente. Los tratamientos térmicos aplicados desde la fertilización demuestran una influencia clara sobre la proporción sexual fenotípica para las parejas 1 y 3, por lo que la respuesta de cada progenie a la temperatura es significativamente diferente. El inicio de la diferenciación histológica fue determinado en el día 30 post eclosión con la presencia de testículos y ovarios en fase inicial de desarrollo, con la presencia de células germinales primordiales, somáticas y la apertura de la cavidad ovárica primordial.