Brycon Orbignyanus Research Articles

Sequential Bayesian approach for genetic diversity analysis of the piracanjuba fish (Brycon orbignyanus)

In the sequential Bayesian approach, the sample size is not fixed before the experiment; it is determined based on the observations made. The procedure concludes when there is enough information to estimate the parameters, according to a stopping criterion. A parameter of interest in population genetics is the proportion obtained from the allele frequency at one or more loci to verify Hardy-Weinberg equilibrium (HWE). The objective of this study was to assess the occurrence of HWE in a population of piracanjuba fish (Brycon orbignyanus) by estimating the allele proportion and expected genotype proportions using a sequential Bayesian approach. Additionally, a comparison was made with frequentist and Bayesian approaches. Initially, genotypic profiles were analyzed at a microsatellite DNA locus, Bh6, in 49 fish, to determine the frequency of observed alleles and genotypes at the UFSJ Genetic Resources Laboratory. Seven allele classes were observed; thus, under the assumption of sampling independence, the likelihood is multinomial. The estimation of allele and genotype proportions was then carried out using frequentist, Bayesian, and sequential Bayesian approaches. A uniform prior and a cost of 10–3 were considered. The estimates from the three approaches were compared, and it was concluded that the sequential approach proved effective, utilizing only 55.1% of the available data, thereby reducing the sample size and optimizing the procedure. Using a chi-square test at a 5% probability level, it was concluded that the studied sample is in Hardy-Weinberg equilibrium (p-value: 0.9800245).

Dispersion of hooks on the anal fins of primary and secondary males in Brycon orbignyanus (Characiformes: Bryconidae): a secondary sexual trait for breeder selection

Dispersion of hooks on the anal fins of primary and secondary males in Brycon orbignyanus (Characiformes: Bryconidae): a secondary sexual trait for breeder selection

Parasites of juvenile Salminus brasiliensis and Brycon orbignyanus (Characiformes, Bryconidae) in the middle Paraná River, Argentina

Piscivorous Salminus brasiliensis and herbivorous/omnivorous Brycon orbignyanus often form mixed schools in the same habitats. The aims of this study were: (a) to analyze and compare ecto- and endoparasite communities in juvenile S. brasiliensis and B. orbignyanus in the Middle Paraná River, Argentina; and (b) to evaluate the possible relationships between degree of parasitic infestation and body condition (Kn) of the fish. Fish necropsy was performed in search of endo- and ectoparasites, which were mounted in permanent or semi-permanent preparations for taxonomic study using helminthological techniques. A total 24 macroparasite taxa were recorded from the two host species. The parasitic infracommunities of both hosts were competitively structured. Ectoparasite communities were more similar than endoparasite communities. The abundance of parasitic species was not correlated with the standard length, weight and Kn of host individuals, except for the abundance of the copepod E. lacusauratus in the host S. brasiliensis, which was positively related to fish condition. New records of parasites were observed for native hosts, extending the geographic range of several species already known in the Upper Paraná River. The general structure of parasite communities can be determined by several factors, such as parasite-host relationship, host trophic level, and environment. In concordance with the similarity in habitat preferences, and the strong differences in trophic preferences, ectoparasite communities were found to be more similar than endoparasite communities between the two host species.

The effects of simulated hydropower turbine rapid decompression on two Neotropical fish species

Barotrauma is a major cause of injury and mortality of fish as they pass through hydropower turbines. Current understanding of hydropower related barotrauma is biased towards northern temperate and southern subtropical species with single chambered swim bladders, specifically North American and Australian species, respectively. Today, unprecedented hydropower development is taking place in Neotropical regions where many species have complex multi-chambered swim bladder architecture. This study investigated barotrauma in two dual-chambered physostomous Neotropical fish (pacu, Piaractus mesopotamicus, and piracanjuba, Brycon orbignyanus) exposed to rapid (< 1 s) decompression at different Ratios of Pressure Change (RPC), using a hypo-hyperbaric chamber. The incidence and intensity (percentage surface area of organ affected) of injury and physiological and behavioural response (hereafter just response) of each species immediately after decompression was assessed. Twenty-two injury types (e.g. gill haemorrhage and exophthalmia) and eight response categories (e.g. rising to the surface and loss of orientation) were identified and the influence of: 1) species, 2) RPC, and 3) swim bladder rupture on each was quantified. There was considerable interspecific difference with emboli type injuries occurring more frequently in piracanjuba, but injury intensity tending to be higher in pacu. Both swim bladder chambers tended to rupture in piracanjuba but only the anterior chamber in pacu. RPC was positively correlated with response, incidence and intensity of several injury types for both species with some injuries occurring at very low RPC (e.g. 50 % probability of swim bladder rupture at 2.2 and 1.75 for piracanjuba and pacu, respectively). Multiple responses (e.g. loss of orientation) and injuries (e.g. eye haemorrhage) were correlated with swim bladder rupture suggesting gas venting into the body cavity likely causes secondary injury. When directly comparing our results with those available in the published literature, both pacu and piracanjuba appear to be more susceptible to barotrauma than previously studied subtropical and temperate species.

Essential and toxic elements in juvenile migratory commercial fish species in the Paraná River alluvial valley (South America): an approach for aquatic environmental monitoring.

The Paraná River is the sixth largest in the world, and the lower section of the river is one of the largest and most productive floodplain wetlands in South America. The alluvial plain is an important habitat for nursery and feeding areas for commercial fish; however, it has been heavily anthropized due to industries, agricultural activities, and the growth and expansion of metropolitan areas. The aim of this study was to determine element accumulation (As, Cd, Cr, Cu, Fe, Mn, Pb, and Zn) in young-of-the-year fish muscle from a floodplain lagoon of the lower Paraná River (Argentina) during summer and winter seasons, in relation with abiotic matrices (water and sediment). Four commercial fish species were assessed: sábalo (Prochilodus lineatus), boga (Megaleporinus obtusidens), dorado (Salminus brasiliensis), and pirapitá (Brycon orbignyanus). The concentrations of eight elements were detected by quadrupole inductively coupled plasma mass spectrometry. In water samples, Cd, Cr, Mn, Fe, and Zn levels were under the permissible limits for aquatic biota protection in both seasons, except for Pb (> 1 μg L-1) and Cu (> 2 μg L-1). In sediment, the average concentrations of all elements were under the limits set by national and international regulatory authorities. Differences in elemental concentrations between species and seasons were found. In general, the levels of elements in water were higher in summer than in winter, while in sediment, the lowest concentrations of elements were detected during the summer. The order of element concentration in fish muscle was Cd (0.01-0.04 μg g-1) < As (0.02-0.16 μg g-1) < Pb (0.03-0.23 μg g-1) < Mn (0.77-4.32 μg g-1) < Cu (1.01-4.07 μg g-1) < Cr (1.09-4.30 μg g-1) < Zn (15.8-31.7 μg g -1) < Fe (12.6-49.7 μg g-1). The accumulation assessment showed that the four fish species significantly accumulate Cr, Cu and Zn, and As and Zn from water and sediment, respectively. The correlation analysis showed a relationship between fish size and As, Cr, Cu, Fe, Mn, and Zn concentrations. Similarly, the highest values of element concentrations in muscle were detected during the summer when the fishes are early juveniles. The level of As, Cd, and Pb detected in B. orbignyanus, M. obtusidens, and P. lineatus juveniles suggested that these species had the potential to be used as biomarkers for assessing accumulation of toxic elements in the environment. Also, this study reveals that the accumulation patterns differ between size and fish species, which should be a considered insight at the moment of selecting a bioindicator to monitor pollution in the ecosystem.

Temperature modulates gonadal development and sex ratio of pirancanjuba Brycon orbignyanus

In this study, we assessed the effect of temperature on gonadal development and sex ratio in Brycon orbignyanus. The fish were kept at three different temperatures (20 °C, 23 °C, and 26 °C) from the beginning of exogenous feeding. At 420 days after fertilization, 10 individuals were collected per temperature regimen for histological and hormonal evaluation of the gonads. The results showed that the sexual pattern was temperature-dependent. All individuals maintained at 20 °C were undifferentiated, with only somatic cells in their gonads. At 23 °C, most individuals were immature males (7/9, 77.8%), and at 26 °C, the majority were males still in maturation process (6/9, 66.7%) and males with gonads in the regression phase were also found. In the hormonal assay, the only treatment in which the individuals had detectable estradiol levels was 23 °C. Testosterone levels were quantified from individuals in the three treatments. We conclude that continuous treatment at 23 °C and 26 °C favors testicular development in B. orbignyanus, and gonadal development is accelerated in fish farmed at 26 °C, as the males in the latter treatment matured at one year and two months of age.

Stereological analysis of spermatogenesis in Brycon orbignyanus (Characiformes: Bryconidae)

Piracanjuba, Brycon orbignyanus, is an important rheophilic species for aquaculture studies on genetic diversity, spermatogenesis, semen cryopreservation and taxonomy. Due to anthropic actions its population has been declining, resulting in the loss of natural stocks, thus pushing the species to near extinction. No stereological analysis of spermatogenesis in piracanjuba has been performed. The present study aimed to evaluate spermatogenesis in B. orbignyanus using stereological analysis to quantify the number of germ cells and Sertoli cells, spermatogonial generations, spermatogenesis yield, meiotic index and the percentage of cell death. Testes of five 1-year-old B. orbignyanus specimens were collected, fixed in 2.5% glutaraldehyde and 4% paraformaldehyde and processed for light microscopy. Three types of spermatogonia were identified. Based on the number of B spermatogonia per cyst, it was estimated that spermatogonia underwent approximately nine mitotic divisions before differentiating into primary spermatocytes. Three types of spermatids were identified. In the final spermatid cyst, there were 1204 germ cells, indicating a spermatogenic yield of 58%. An increase in germ cells resulted in a subsequent increase in the number of Sertoli cells, with growth halted at the spermiogenic phase. Thus, stereological analysis of spermatogenesis is essential for better understanding of the reproductive processes in this species.

Cannibalism rate and mLeptin expression are influenced by photoperiod and diets in Piracanjuba, Brycon orbignyanus (Valenciennes, 1850) larvae

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.

Ictiofauna da Área de Relevante Interesse Ecológico (ARIE) de Santa Helena, Paraná, Brasil

Abstract The Relevant Ecological Interest Area (REIA), popularly known as “Refúgio Biológico de Santa Helena”, is part of the Atlantic Forest Biome and one of the 78 ecoregions mapped by IBAMA as basic unit for planning priorities focused on national biodiversity conservation. Quarterly collections were carried out from November 2017 to November 2019 to inventory the ichthyofauna of this Conservation Unit. Specimens were captured with the aid of gillnets, fishing sieve and seine. In total, 3,919 specimens belonging to two class, eight orders, 27 families and 74 species were sampled. Characiformes and Siluriformes presented the highest species richness; they accounted for 40 (54%) and 17 (23%) species, respectively. Geophagus sveni (181 individuals = 17%), Trachelyopterus galeatus (109 individuals = 10%) and Schizodon borellii (105 individuals = 10%) were the most abundant fish species captured with gillnet. Moenkhausia was the most abundant genus captured with seine and fishing sieve, with emphasis on species Moenkhausia bonita (930 individuals = 33%) and Moenkhausia gracilima (845 individuals = 30%). Moreover, two “endangered” species (Brycon orbignyanus and Pseudoplatystoma corruscans) were registered. Therefore, we present an updated inventory of species belonging to the ichthyofauna of REIA, and it may contribute to future management plans focused on this Conservation Unit.

Female sex inversion as a reason for an unbalanced sex ratio in the neotropical species Brycon orbignyanus

The objective of this study was to temporally identify sex differentiation to morphologically characterize the formation of female and male germinal epithelium and verify the occurrence of the sex disproportion reported for this species in aquaculture. Specimens of Brycon orbignyanus cultivated in water recirculation systems with a constant temperature of 27 ± 0.5°C were used. Monthly samplings of B. orbignyanus (n = 15) were performed from two months of age until 1 year of age, and posteriorly isolated sampling was performed on specimens of two and three years of age. The gonads of the specimens were removed and processed for light microscopy. In the beginning, the undifferentiated gonads develop into ovaries (females; at three months of age) and functional testicles (primary males; at five months of age); however, some of the females go through a sex inversion process creating intersex individuals and posteriorly secondary males (at five months of age). Due to the processes of sex inversion and gonadal remodelling, the population sex proportion fluctuates until it is finally established at 1♀:2♂. Females above 15 cm are differentiated, while in males (primary and secondary), differentiation will only occur after the animal reaches 20 cm. At the end of the first year of age, primary males and secondary males reach sexual maturity, while female sexual maturity is only observed at three years of age.

Functional DNA annotation from a preliminary de novo genome assembly of Brycon orbignyanus, an endangered Neotropical migratory fish

The predicted sequence for thousands of genes revealed by a preliminary low-coverage genome assembly is presented for Brycon orbignyanus, an endangered migratory fish. Neotropical migratory fish stocks have been drastically reduced due to accumulated environmental pressure. Brycon orbignyanus, once one of the main fisheries species in the Platine Basin, is now very rare in nature and relies on spawning programs and a few well preserved or still untouched sites. The use of high-throughput DNA sequencing is still untapped regarding the functional genome information from B. orbignyanus. In order to help bridging this gap, we present a dataset resulting from the first functional annotation from a de novo genome assembly for B. orbignyanus, from short reads (90 bp), obtained by the HiSeq 2000 platform (Illumina). The annotation was performed for scaffolds over 10 kb using the Maker pipeline, with reference sequences taken from the NCBI for the Characiformes order. This annotation resulted in the prediction of 12,734 genes, classified with the aid of PANTHER. The data presented here can facilitate the development of basic research in this threatened species, along with practical biotechnological tools for different areas, such as commercial and environmental fish spawning operations (e.g. hormonal induction, growth) and human health.

Sex steroid levels in females and males of Brycon orbignyanus throughout different juvenile and adult ages and during induction hormone in the mature females

The levels of reproductive hormones for fish stocked in fish farming ponds can be varying with respect to age and sex. Piracanjuba is an endangered species and broodstock are raised to be used in stocking programs. Therefore, we aimed to describe the plasma levels of the major sex steroids, 17β-estradiol (E2), 17α-hydroxyprogesterone (17α-OHP), testosterone (T) and 11-ketotestosterone (11-KT), in males and females of Brycon orbignyanus of different ages, juveniles with 12 and 24 months and adults with 48 months, and the changes before and after carp pituitary extract application in mature females. Four males and five adult females (48 months) were collected, identified through the sexual dimorphism of the species. For the other ages (12 and 24 months), 20 fish of each age were collected for sex determination through histology. Blood was collected and centrifuged; plasma was obtained for quantification of the plasma profile of E2, 17α-OHP, T and 11-KT. In B. orbignyanus males three phases of gonadal development were observed: immature, developing (12 and 24) and regressing (48). A higher level of E2 (p < 0.05) was observed in immature males, higher levels of T (p < 0.05) were observed in fish of 24 and 48 months. In females of B. orbignyanus blood pre hormonal induction (PI) and post extrusion of oocytes (PE), were collected and stimulus in the production of T, 11-KT and 17α-OHP observed. In females of different ages (12, 24 and 48 months) the E2 showed a higher level (p < 0.05) in relation to other hormones. The T was not observed in 12 and 24 month females, but in 48 month females T and 11-KT observed (p < 0.05), with respect to the 17α-OHP there was no difference in ages observed. In conclusion, E2, 17α-OHP and 11-KT were described for male and female B. orbignyanus from 12, 24 to 48 months of age in the reproductive period. The T was verified in males at 12, 24 and 48 months of age and in females only at 48 months of age. Although there is more concentration of hormones in the reproductive phase at 48 months, in females it is necessary to apply the hormone induction protocol for spawning that is used for rheophilic fish.

Spermatogenesis and reproductive cycle of male piracanjuba ( Brycon orbignyanus ) raised for use in repopulation programmes

Although Brycon orbignyanus has traditionally been extensively fished in the Paraná and Uruguay basins, anthropic events and fishing pressure have substantially diminished natural stocks. Restocking programmes have, nevertheless, aided efforts to restore the stocks of this fish in its former ranges. The objective of this study was to characterize the spermatogenesis and reproductive cycle of male B. orbignyanus maintained in a commercial fish hatchery for use in future repopulation programmes. For this purpose, we monitored patterns of gonad development and variations in the gonadosomatic index of B. orbignyanus individuals through time. Biometrics and sample collections were performed for macroscopic and histological analysis of two groups of individuals with age ranging from 21 days after fertilization (DAF) to 821 DAF (Group 1) and from 976 DAF to 1416 DAF (Group 2). At each time point, testes of euthanized fish were collected for histological analysis. Testes were found to be composed of anastomosed seminiferous tubules and tubular compartments, being classified as anastomosing tubular. Five reproductive phases of B. orbignyanus were identified and described under captive conditions, namely immature, initial developing, developing, spawning capable and regressing. The “developing” phase was observed at practically all ages and in all four seasons, characterizing a rapid restart of the reproductive cycle of the species, i.e. the short and ephemeral “regenerating” phase. Males of B. orbignyanus maintained in ponds will be able to release sperm between spring and summer, with the regression stage beginning still in the summer.

Sperm characteristics, peroxidation lipid and antioxidant enzyme activity changes in milt of Brycon orbignyanus cryopreserved with melatonin in different freezing curves

The objective of this study was to evaluate extender supplemented with melatonin and freezing curves on the antioxidant enzyme activity, peroxidation lipid and sperm characteristics of cryopreserved Brycon orbignyanus milt. Males (n = 16) and females (n = 5) were hormonally induced with two doses (0.5 mg and 5.0 mg kg−1) of carp pituitary extract, and their gametes were collected by light abdominal massage. The fresh milt was diluted at a ratio of 1:4 (milt:extender) in the following solutions: (Control) 10% methyl glycol (MG) + 5% Beltsville thawing solution; (M1) Control + 1 mM melatonin; and (M2) Control + 2 mM melatonin. The freezing curves were C1 (automated freezer) and C2 (dry shipper for 24 h). After each curve was recorded, the straws were transferred to a liquid nitrogen container until the analyses were performed. The samples were thawed in a water bath (60 °C, 8 s) and evaluated using the Sperm Class Analyzer software for the parameters total motility, progressive motility, curvilinear velocity, straight line velocity, mean displacement velocity, straightness, and linearity. The following were also measured: motility time, vitality, morphology, oxidative stress (lipid peroxidation, activity of catalase and superoxide dismutase, quantification of nitric oxide), and fertilization and hatching rates. The data were analyzed within R by one-way analysis of variance and Tukey's test for comparison of means (p < 0.05). A significant difference (p < 0.05) was observed between the solutions in vitality, morphology, motility, and fertilization rate, the solutions with melatonin having the best values. Total motility, progressive motility, and motility time were significantly different. Among oxidative stress markers, only lipid peroxidation and superoxide dismutase activity showed an effect of the curve × solution interaction (p < 0.05), the solutions with melatonin yielding the lowest values. The fertilization and hatching rates were also higher under the melatonin treatments, regardless of the curve. Melatonin 2 mM and slow curve are indicated for the cryopreservation of fish species sperm as it led to the slowest detrimental spermatozoa effects and better fertilization and hatching rates.

Distribution and Accumulation of Trace Elements in Organs of Juvenile Fishes from a Freshwater System (Paraná River, South America).

The concentrations of As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn (TE) in four juvenile fishes (Acestrorhynchus pantaneiro, Salminus brasiliensis, Brycon orbignyanus, and Megaleporinus obtusidens) and associated sediment water from the Lower Paraná River were measured. For muscle, gills, and liver fishes, the TE accumulation in the muscle, gills, and liver was evaluated. The TE concentration was measured by quadrupolar inductively coupled plasma mass spectrometry (Q-ICP-MS). Cadmium (0.25 ± 0.07μgL-1), Cu (3.00 ± 1.44μgL-1), Fe (612 ± 69μgL-1), and Pb (1.92 ± 1.20μgL-1) in water and As (4.1-6.9μgg-1), Cr (20.1-31.4μgg-1), Cu (10.7-19.2μgg-1), Mn (351.3-482.2μgg-1), and Ni (24.5 ± 10.9μgg-1) in sediments exceeded the guide values for the conservation of aquatic life. In general, muscle of omnivorous species (B. orbignyanus and M. obtusidens) showed higher values of elements than those of carnivorous species (A. pantaneiro and S. brasiliensis). However, TE concentrations varied with fish species and organs. Independently of the examined species, the highest concentrations of Cr and Pb were in the muscle and gills, respectively. Cadmium, Cu, and Fe concentrations were higher in the liver than in gills and muscle in all four fish species. These results were consistent with the tissue selectivity index analyzed. For the four species, major essential elements showed the highest accumulation. However, the accumulation of toxic elements in omnivorous fish was higher than in carnivorous fish. The individual pollution load index indicated that sediment was very polluted with As and Pb, but based on the combined ecological indexes, low elemental sediment pollution in the Espinillo Lake was revealed.

Vitrification protocol for immature Brycon orbignyanus ovarian tissue as an extinction escape strategy

Piracanjunba (Brycon orbignyanus) is an endangered South American fish, and ovarian tissue cryopreservation is an alternative method for preserving maternal germplasm and genetic diversity. Therefore, our aim was to test a vitrification protocol for ovarian tissue containing primary growth (PG) oocytes of B. orbignyanus as a strategy to avoid the threat of extinction. Two vitrification solutions were evaluated (VS1: 1.5 M methanol + 4.5 M propylene glycol and VS2: 1.5 M methanol + 5.5 M Me2SO) and compared using control/fresh ovarian tissue. After vitrification, the following factors were analyzed: membrane integrity using trypan blue, morphology using a histological assessment, oxidative stress (total reactive antioxidant potential (TRAP) and reduced thiol [-SH]), mitochondrial activity using MTT, and DNA damage using a comet assay. The vitrified oocytes (VS1 = 24.3 ± 0.49% and VS2 = 24.8 ± 0.69%) showed higher DNA damage than the control group (control = 20.7 ± 1.03%) (P = 0.004). In contrast, in most evaluations (membrane integrity, membrane damage, oxidative stress, and mitochondrial activity), there were no discernible differences between the control group and the vitrified samples. In addition, oocyte (P = 0.883) and nuclear diameter (P = 0.118) did not change after vitrification. VS2 treatment resulted in higher nuclear damage (15.7 ± 1.45%) than in the control treatment (3.5 ± 1.19%); however, VS1 treatment did not result in significantly more damage (9.5 ± 3.01%) than in the control (P = 0.015). Therefore, the protocol for ovarian tissue vitrification tested in this study resulted in high maintenance of PG oocyte cell integrity, making it a promising alternative for B. orbignyanus maternal genome preservation.

Gonadal development period and sexual differentiation through histological analysis in Brycon orbignyanus (Valenciennes, 1850) (Characiformes: Bryconidae)

The aim of this study was to investigate the labile period of gonadal development in Brycon orbignyanus maintained under cultivation conditions and contribute to the creation of protocols for the sexual manipulation of the species. A histological analysis observed that gonadal differentiation (testicular and ovarian) started amid the population 296 days after fertilization and comes to completion in 100% of individuals at 730 days after fertilization, when males with developing gonads were observed, while females remained immature. All individuals larger than 27 cm already had their reproductive organs completely formed. The structuring of supposed ovaries and testicles was similar, from the formation of continuous strings of germ cells to the gradual isolation of these by somatic cells for the formation of cysts of oogonia or spermatogonia. After the formation of cysts, germ cells enter meiosis to form primary growth oocytes and spermatocytes, a moment when secondary structures also emerge with the formation of the ovigerous lamellae, tunica albuginea and germinal epithelium. It is concluded that the labile period of gonadal development in the species occurs at 323 days after fertilization under the conditions of the present experiment.

Effect of melatonin supplementation to a cytoprotective medium on post-thawed Brycon orbignyanus sperm quality preserved during different freezing times

The aim of the present study is to verify the viability of frozen B. orbignyanus sperm cells after freezing with dilution media containing different concentrations of the melatonin and after different freezing times. Semen from 15 males was collected and pooled as five pools from three random animals. Oocytes (100) from three females were separately used for fertilization. There were three treatments: (C) Control Medium: 90% of extender Beltsville thawing solution (5% concentration) + 10% methylglycol (MG); (M1) Control Medium + 1 mM melatonin; and (M2) Control Medium + 2 mM melatonin. Sperm samples were diluted in media at a final proportion of 1:4 [125 μl sperm (25% V/V) + 337.5 μl BTS (65% V/V) + 37.5 μl MG (10% V/V)]. Melatonin was added at final solution. Three Dry shipper freezing times were used: T1 (15 min), T2 (12 h) and T3 (24 h). The samples were transferred, stored in a cryobank and thawed in a water bath at 60 °C for 5 s and evaluated concerning viability, morphology and fertilization rate. B. orbignyanus semen frozen in M2 presented the highest fertilization rate (8.40 ± 2.54%). The highest vitality (85.2 ± 2.8%), motility (64.63 ± 8.3%), motility duration (84.22 ± 11.4 s) and progressive motility (17.01 ± 1.2%) rates were maintained for M2. The highest number of altered cells was observed in C (57.4 ± 5.9%). Melatonin at 2 mmol L−1 associated with the cryoprotectant methylglycol in cryopreservation could be used to improve a cryobank for endangered Brycon orbignyanus populations.

Spawning methods affect the reproductive efficiency of piracanjuba fish (Brycon orbignyanus) in restocking programs

espanolAntecedentes: Mantener la diversidad genetica de los peces salvajes es una consideracion importante para los programas de repoblacion, ya que la endogamia puede comprometer la supervivencia de la progenie y afectar la supervivencia de las poblaciones naturales. Objetivo: Evaluar la influencia del metodo de desove (seminatural - SN o en franjas - ST) y el numero de reproductores (1♀:3♂ y 2♀:6♂) sobre la eficiencia reproductiva y la diversidad genetica de progenies de B. orbignyanusdestinados a la restauracion de poblaciones silvestres. Metodos: Se monitorearon las tasas de fertilizacion, eclosion y mortalidad de reproductores. Para las evaluaciones geneticas (frecuencias alelicas, heterocigosidad observada y esperada, indice de Shannon, coeficiente de endogamia, analisis de varianza molecular y diferenciacion genetica) los reproductores (n=24) y su progenie (90 larvas/tratamiento) se muestrearon y analizaron utilizando ocho marcadores microsatelites. Resultados: La interaccion entre el metodo de desove y el numero de reproductores no fue significativa (p>0,05). Se obtuvieron mejores tasas de fecundacion y eclosion (p0,05). Los loci de microsatelites amplificados produjeron un total de 30 alelos con tamanos entre 80 y 225 pb, y sus frecuencias indicaron un aumento (p0,05). Conclusion: Los metodos de desove y el numero de reproductores evaluados aumentaron de la misma manera la diversidad genetica de las progenies, con baja diferenciacion genetica entre tratamientos. En contraste, las tasas de fecundacion, eclosion y mortalidad de peces reproductores revelaron que el SN tuvo la mejor eficiencia reproductiva, un hecho relacionado con el estres del manejo y las lesiones causadas por el ST. Por lo tanto, el SN demuestra ser el metodo de desove mas adecuado para B. orbignyanus en los programas de repoblacion. EnglishBackground:Preserving the genetic diversity of wild fish is an important consideration for restocking programs, as inbreeding can compromise progeny survival as well as impact the resilience of natural populations. Objective: To evaluate the influence of spawning method: semi-natural (SN) or strip-spawning (ST), and the number of breeders (1♀:3♂ and 2♀:6♂) on the reproductive efficiency and genetic diversity of B. orbignyanus progeny destined for restoration of wild stocks. Methods: Rates of fertilization, hatching and broodfish mortality were recorded. For genetic evaluations (allele frequency, observed and expected heterozygosity, Shannon index, inbreeding coefficient, molecular variance analysis, and genetic differentiation), breeders (n=24), and their progenies (90 larvae/treatment) were sampled and analyzed using eight microsatellite markers. Results: Higher fertilization and hatching rates, and lower broodfish mortality were observed for the SN method (p0.05). Interaction between spawning method and number of breeders was not significant (p>0.05). The amplified microsatellite loci produced a total of 30 alleles, with sizes between 80 and 225 bp and their frequencies indicated an increase (p0.05). Conclusion: The spawning methods and number of breeders tested increased equally the genetic diversity of the progeny, with low genetic differentiation between treatments. In contrast, rates of fertilization, hatching and brood fish mortality revealed that the SN method resulted in the best reproductive efficiency due to the handling stress and injuries caused by ST. Thus, SN proves to be the most suitable spawning-method for B. orbignyanus in restocking programs. portuguesAntecedentes: A manutencao da diversidade genetica dos peixes selvagens e uma importante consideracao para programas de repovoamento, ja que a endogamia pode comprometer a sobrevivencia da progenie, alem de impactar na resiliencia das populacoes naturais. Objetivo: Avaliar a influencia do metodo de desova (semi-natural – SN ou por extrusao – ST) e numero de reprodutores (1♀:3♂ e 2♀:6♂) na eficiencia reprodutiva e na diversidade genetica de progenie de B. orbignyanus destinados a recuperacao de estoques selvagens. Metodos: Taxas de fertilizacao, eclosao e mortalidade de reprodutores foram monitorados. Para avaliacoes geneticas (frequencias alelicas, heterozigosidade observada e esperada, indice de Shannon, coeficiente de endogamia, analise de variância molecular e diferenciacao genetica), reprodutores (n=24) e sua progenie (90 larvas/tratamento) foram amostrados e analisados utilizando oito marcadores microssatelites. Resultados: Interacao entre metodo de desova e numero de reprodutores nao foi significante (p>0,05). Melhores taxas de fertilizacao e eclosao (p0,05). Os loci microssatelites amplificados produziram um total de 30 alelos, com tamanhos entre 80 e 225 pb e suas frequencias indicaram aumento (p0,05). Conclusao: Os metodos de desova e numeros de reprodutores avaliados aumentaram igualmente a diversidade genetica das progenies, com baixa diferenciacao genetica entre tratamentos. Em contraste, as taxas de fecundacao, eclosao e mortalidade de reprodutores revelaram que SN obteve a melhor eficiencia reprodutiva, fato relacionado com o estresse de manipulacao e injurias causadas por ST. Por isso, SN se mostrou como o metodo de desova mais adequado para B. orbignyanus em programas de repovoamento.

Scientific knowledge on threatened species of the Brazilian Red List: freshwater fish as a case study

We conducted a bibliometric analysis in order to quantify and characterize the scientific knowledge about threatened freshwater fish species in Brazil based in studies published in peer-reviewed journals from Web of Science database from Clarivate Analytics. We verified an increase in the number of papers for threatened freshwater fish species in Brazil, especially in the last eleven years of studied period. The journals with the most papers were Neotropical Ichthyology, Environmental Biology of Fishes, and Journal of Fish Biology. The number of publications among the Brazilian regions and states is not homogeneous. The most studied threatened fish was piracanjuba Brycon orbignyanus. Some important gaps in scientific knowledge need to be addressed, such as the relatively small number and/or lack of studies conducted Brazilian states and with threatened freshwater fish species in Brazil.