Pampus Argenteus Research Articles

Morphological and Molecular Functional Evidence of the Pharyngeal Sac in the Digestive Tract of Silver Pomfret, Pampus argenteus.

The pharyngeal sac is a comparatively rare organ in the digestive tract among teleost fishes. However, our understanding of this remarkable organ in the silver pomfret (Pampus argenteus) is limited. In the present study, we examined the various morphological and histological characteristics of the pharyngeal sac using histochemical techniques and electron microscopy. The pharyngeal sac showed unique characteristics such as well-developed muscular walls, weakly keratinized epithelium, numerous goblet cells, and needle-like processes on the papillae. The porous cavity of the papillae contained numerous adipocytes and was tightly enveloped by type I collagen fibers. These structures might provide mechanical protection and excellent biomechanical properties for grinding and shredding prey. A comparison of gene expression levels between the pharyngeal sac and esophagus using RNA-seq showed that phenotype-associated genes (epithelial genes and muscle genes) were upregulated, whereas genes related to nutrient digestion and absorption were downregulated in the pharyngeal sac. These results support the role of the pharyngeal sac in shredding and predigesting food. Overall, these findings provide a clearer understanding of the pharyngeal sac morphology and explain the morphological adaptations of the digestive tract for feeding on gelatinous prey. To our knowledge, this is the first report on pharyngeal sac gene expression in P. argenteus.

Analyses of growth performance and realized heritability of the second generation of Indo-Pacific Pampus argenteus.

Silver pomfret (Pampus argenteus) is one of the most important fishery products in the Indo-Pacific Ocean. Nonetheless, little is known about the genetic parameters of economic traits. To determine whether the selective breeding programme would improve economic traits, the authors evaluated the growth performance of the selected group and the control group at 60, 90 and 120 days, and the growth performance parameters of the selected group were higher than those of the control group. Through Pearson correlation analysis, the authors found that the morphological traits that are highly related to the weight of P. argenteus are body length and body height. Genetic gain and realized heritability for body weight were highest at day 90, which were 12.72% and 0.23%, respectively. Therefore, the authors speculate that day 90 may be a critical time for screening. The average coefficient of variation for body weight reached over 30%. All three morphological traits reached moderate realized heritability at day 90 after hatching. These implied that selective breeding has the potential to improve the growth traits of P. argenteus. In addition, the reproductive performance of P. argenteus parent fish was obviously improved after gonadal strengthening. These results provide important information for future breeding programmes for P. argenteus.

Estimation of Peak Spawning Season, Length at Maturity (Lm) and Sex Ratio of Silver Pomfret (Pampus argenteus) in the Bay of Bengal, Bangladesh

Estimation of Peak Spawning Season, Length at Maturity (Lm) and Sex Ratio of Silver Pomfret (Pampus argenteus) in the Bay of Bengal, Bangladesh

Triflumizole Induces Developmental Toxicity, Liver Damage, Oxidative Stress, Heat Shock Response, Inflammation, and Lipid Synthesis in Zebrafish.

Triflumizole (TFZ) toxicity must be investigated in the aquatic environment to understand the potential risks to aquatic species. Accordingly, the adverse effects of TFZ exposure in zebrafish were investigated. Results demonstrate that, after TFZ exposure, the lethal concentration 50 (LC50) in 3 d post-fertilization (dpf) embryos and 6 dpf larvae were 4.872 and 2.580 mg/L, respectively. The development (including pericardium edema, yolk sac retention, and liver degeneration) was apparently affected in 3 dpf embryos. Furthermore, the alanine aminotransferase (ALT) activity, superoxide dismutase (SOD) activity, catalase (CAT) activity, and malondialdehyde (MDA) content in 6 dpf larvae were significantly increased. Additionally, the expression of heat shock response genes (including hsp70, grp78, hsp90, and grp94), inflammatory genes (including p65-nfκb, il-1β, and cox2a), and lipid synthetic genes (including srebp1, fas, acc, and ppar-γ) in 3 dpf embryos was significantly increased, which was also partially observed in the intestinal cell line form Pampus argenteus. Taken together, TFZ could affect the development of zebrafish, accompanied by disturbances of oxidative stress, heat shock response, inflammation, and lipid synthesis. Our findings provide an original insight into the potential risks of TFZ to the aquatic ecosystem.

Screening and identification of miRNAs regulating Tbx4/5 genes of Pampus argenteus.

BackgroundSilver pomfret (Pampus argenteus) is one of the most widely distributed and economically important pelagic fish species. However, an unique morphological feature of P. argenteus is the loss of pelvic fins, which can increase the energy requirement during food capture to some extent and is therefore not conducive to artificial culture. Tbx4/5 genes are highly conserved regulatory factors that regulate limb development in vertebrates and are in turn regulated by microRNAs (miRNAs). However, the miRNAs that directly regulate the Tbx4/5 genes in P. argenteus remain to be elucidated.MethodsThe Tbx4/5 genes of P. argenteus were first cloned, and the small RNA transcriptomes were sequenced by high-throughput sequencing during the critical period of the fin development at days 1, 7, and 13 of hatching. The miRNAs regulating the Tbx4/5 genes of P. argenteus were subsequently predicted by bioinformatics analysis, and the related miRNAs were verified in vitro using a dual fluorescence reporter system.ResultsA total of 662 miRNAs were identified, of which 257 were known miRNAs and 405 were novel miRNAs were identified. Compared to day 1, 182 miRNAs were differentially expressed (DE) on day 7, of which 77 and 105 miRNAs were downregulated and upregulated, respectively, while 278 miRNAs were DE on day 13, of which 136 and 142 miRNAs were downregulated and upregulated, respectively. Compared to day 13, four miRNAs were DE on day 7, of which three miRNAs were downregulated and one miRNA was upregulated. The results of hierarchical clustering of the miRNAs revealed that the DE genes were inversely expressed between days 1 and 7, and between days 1 and 13 of larval development, indicating that the larvae were in the peak stage of differentiation. However, the number of DE genes between days 7 and 13 of larval development was relatively small, suggesting the initiation of development. The potential target genes of the DE miRNAs were subsequently predicted, and Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses of target genes were performed. The results suggested that the DE miRNAs were involved in growth, development, and signal transduction pathways, of which the Wnt and Fgfs signaling pathways are known to play important roles in the growth and development of fins. The results of dual fluorescence reporter assays demonstrated that miR-102, miR-301c, and miR-589 had a significant negative regulatory effect on the 3′-UTR of the Tbx4 gene, while miR-187, miR-201, miR-219, and miR-460 had a significant negative regulatory effect on the 3′-UTR of the Tbx5 gene. Altogether, the findings indicated that miRNAs play an important role in regulating the growth and development of pelvic fins in P. argenteus. This study provides a reference for elucidating the interactions between the miRNAs and target genes of P. argenteus in future studies.

Transcriptome profiling and differential expression analysis of the immune-related genes during the acute phase of infection with Photobacterium damselae subsp. damselae in silver pomfret (Pampus argenteus)

Silver pomfret has been widely cultured in China due to its high economic value. Photobacterium damselae subsp. damselae (PDD) is a Gram-negative bacterium that has been shown to infect many fish species. To increase knowledge of the molecular mechanisms of the host defense against PDD, we conducted transcriptome analysis of head kidney in silver pomfret at 24 h and 72 h post-infection (hpi) via Illumina sequencing. The de novo assembly resulted in the identification of 79,063 unigenes, with 59,386 (75.11%) successfully annotated in public databases (NR, NT, KO, Swiss-Prot, Pfam, GO, and KOG databases). Comparison of gene expression profiles between PBS-injected fish (sham control) and PDD-challenged fish revealed 329 and 570 differentially expressed genes (DEGs) were screened at 24 hpi and 72 hpi, respectively. The DEGs were enriched in multiple immune-related pathways such as Hepatitis C, Gastric acid secretion, CAMs and Leukocyte transendothelial migration pathways, Primary immunodeficieny, ECM-receptor interaction, PI3K-Akt signaling pathway. The data obtained in the present study offers valuable information for acute immune response of silver pomfret challenged with PDD, which will facilitate further investigations on strategies against Photobacterium spp. infection in teleosts.

Expression and cellular localization of insulin-like growth factor 3 in gonads of the seasonal breeding teleost silver pomfret (Pampus argenteus).

Insulin-like growth factor 3 plays an important role in gonad development in teleost fish. Previous studies found that igf3 was specifically expressed in gonads of silver pomfret (Pampus argenteus). Unlike in other fish, IGF3 is a membrane protein in silver pomfret, and its specific role in gonads is unclear. Herein, we explored the importance of IGF3 in oogenesis and spermatogenesis in silver pomfret by analyzing gene expression and cellular localization. During follicular development, igf3 was detected in ovaries at both mRNA and protein levels during the critical stages of vitellogenesis (IV-VI). Localization analysis detected igf3 mRNA and protein in somatic cells, including theca and granulosa cells around oocytes. Similar to cathepsin L and cathepsin K, igf3 was consistently expressed in ovaries during vitellogenesis, suggesting that it might play a key role in vitellogenesis of oocytes. During spermatogenesis, igf3 mRNA and protein levels were high in stages II, IV, and V, similar to sycp3 and dmc1, and the highest igf3 mRNA and protein levels were reached in stage VI. Furthermore, igf3 mRNA and protein were detected in spermatogonia, spermatocytes, spermatids, and surrounding Sertoli cells, but not in spermatozoon, indicating that IGF3 might be involved in differentiation and meiosis of spermatogonia.

Modeling framework for establishing the power law between length and weight of fishes and a meta-analysis for validation of LWRs for six commercially important marine fishes from the northwestern Bay of Bengal

Accurate and unbiased modeling of length-weight relationship (LWR) is essential for precise estimation of biomass from length-based abundance data for aquatic ecosystem modeling and developing resource management strategies for the sustainable utilization of aquatic living resources. The present study was conducted to develop the best modeling method for establishing the relationship between the length and weight of the fish, giving adequate priority to the variance distribution structure, which is often overlooked. Three modeling methods viz. (1) NLM: nonlinear model with additive homogeneous variance structure, (2) wNLM: weighted nonlinear model with additive heterogeneous power variance structure and (3) LM: log-transformed linear model with multiplicative heterogeneous variance structure in untransformed scale were evaluated for their performance in accurately estimating the model parameters and their confidence intervals. As variance in fish weight increases with the increase in fish size, usually, a multiplicative heterogeneous variance structure is assumed while explaining the relationship between length and weight, which was evidenced from the residual plot of NLM. As the data did not follow the additive homogenous variance assumption of NLM, the worst performance (highest AIC and BIC) was obtained when NLM was used. The variance distribution structure could be homogenized and normalized in three out of six fishes (i.e., Plicofollis layardi, Cynoglossus arel, Otolithes ruber) investigated in the study using LM, resulting in superior performance (lowest AIC and BIC) among the three models. For two out of three remaining species (i.e., Nemipterus japonicus and Parastromateus niger) for which the variance distribution cannot be normalized by log transformation (LM), the residuals could be homogenized and normalized by the wNLM which was evidenced by the lowest AIC and BIC for the model. Even for the species (i.e., Pampus argenteus), where the residuals could not be normalized by any of the models, better performance was obtained from wNLM. A meta-analysis was performed to validate the hitherto available information on the LWRs of these six species by regressing the regression parameters [log(a) vs. b] of the available LWRs and by computing the form factors. The erroneous LWRs were identified as doubtful reports by carefully scrutinizing the outliers obtained from Cook’s distance method and subsequently validating them by observing their dispersion from modeled prediction intervals (PI) and interquartile range (IQR) based outlier detection methods using the form factor analysis. The study presents the decision support framework for an appropriate modeling approach while dealing with certain assumptions such as variance normality and homoscedasticity. The study also describes a combined approach for the validation of derived LWRs by a comprehensive meta-analysis.

Identification and comparison of palmitoleic acid (C16:1 n-7)-derived lipids in marine fish by-products by UHPLC-Q-exactive orbitrap mass spectrometry

Palmitoleic acid (POA) is a monounsaturated n-7 fatty acid (16:1 n-7) that is active in modulating cardiovascular and metabolic processes. POA-structured phospholipids, diglycerides, and triglycerides (POA-PL, -DG, -TG) are abundantly present in marine life. In this study, POA and POA-lipids contained in crude lipids in visceral by-products of six seafood products (n = 6 for each sample) were analyzed using ultra-high-performance liquid chromatography Q-exactive orbitrap mass spectrometry (UHPLC-QE/MS). The results showed that sardine contains the highest percentage of POA (12.47 %), followed by bigeye tuna (7.31 %), whereas silver pomfret contains the lowest percentage (5.76 %) in total lipids. Nine POA-PLs, eight POA-DGs, and 64 POA-TGs were detected, the PCA analysis showed that although the molecular composition six fish species was similar, their relative content varied significantly across the species. The correlation heatmap showed critical POA-PL and POA-DG/TG correlation coefficients and revealed several highly correlated ions. The presence and ratio of POA-PL and POA-DG/TG molecular species led to the identification of each fish species. These findings improve the understanding of the composition of POA-lipids contained in marine by-products and provide a reference for their comprehensive exploitation.

Assessing the pomfret stock for setting catch limits in the northern Bay of Bengal, Bangladesh

Pampus argenteus and Pampus chinensis form the high-value demersal Pomfret fishery of Bangladesh. But, due to a monotonic decline in catches over the last five years, it is essential to explore the current stock status concerning the removal rate to ensure the sustainability of this fishery. Therefore, given the reliability and minimal data requirements, this study employed an extended Bayesian State-Space Surplus Production Model, JABBA (Just Another Bayesian Biomass Assessment), to assess the stock rigorously. The results revealed that the stock biomass of the Pomfret fishery in the final year of the time series is significantly lower than BMSY, the biomass required to produce MSY. Consequently, this study recommends a yearly catch limit (TAC) of 10,000 metric tons to prevent further depletion of the stock biomass. Furthermore, to avoid growth overfishing by allowing all immature fishes to reproduce at least once before being caught, this study also calculated the optimum length (Lopt) for catch for both species at which biologically maximum yield and revenue can be obtained. The estimated Lopt is 25 cm for P. argenteus and 30 cm for P. chinensis, and not to capture fishes with lengths lower than these limits, this study further calculated the minimum mesh size limits for gill and set bag nets is 7.5 cm. Though the mesh size regulation was estimated using length-based reference points derived from an empirical equation, this regulation can be used as an associate reference point when TAC is applied to assure the sustainability of this fishery.

Bilateral Asymmetry in Otolith Size of Pampus argenteus (Osteichthyes: Stromatidae) from Iraqi Marine Waters

Abstract Bilateral asymmetry is presumed to reveal the developmental variability of the fish in polluted aquatic environments. In these habitats, high-level asymmetry develops, and these fish expend more energy to balance their growth than fish that are not under an impact. A total of 121 specimens of Pampus argenteus were collected from Khor Abdulla located in the northwest part of the Arabian Gulf. The asymmetry of two otolith parameters of the marine fish species Pampus argenteus, length and width, was calculated. The results demonstrated that the level of asymmetry was highest for otolith width. The level of asymmetry in both otolith parameters was lowest in fish length ranging between 70-100 mm and the highest in fish ranging between 281-310 mm.

Proteomic and transcriptomic analysis of the effects of dietary jellyfish on the midgut of Pampus argenteus

Due to their high-water content and low nutritional value, jellyfish have long been considered ‘dead ends’ in marine food webs. However, it was revealed that silver pomfret (Pampus argenteus) preferentially hunts jellyfish, and consuming jellyfish alters intestine histology. To better understand the physiological responses of midgut tissues after consuming jellyfish, we compared the transcriptomes and proteomes of jellyfish-fed and jellyfish-unfed groups, and identified 1167 differentially expressed genes (DEGs) and 471 differentially expressed proteins (DEPs). Gene Ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that unsaturated fatty acid metabolism pathways, especially cholesterol metabolism, were the most enriched biological pathways. Apolipoprotein E was downregulated at both transcriptome and proteome levels, and it was found to negatively regulate jellyfish consumption. These results provide deep insight into the molecular mechanisms regulating jellyfish consumption in Pampus argenteus.

Analyses of growth performance and realized heritability of Pampus argenteus in a breeding program in China

Silver pomfret (Pampus argenteus) is an economically important mariculture species. However, little is known about the genetic parameters of its commercially important traits. In order to determine whether continuous progress can be achieved by selection for growth, we took the body weight trait of East China Sea P. argenteus as the target trait of mass selection. The realized heritability of P. argenteus from the selected group and control group was analyzed at the three growth times (60, 90, and 120 days). The results showed that the growth performance parameters of the selected group in the third month post hatching were higher than those in the control group, but the opposite results were found in the fourth month. The morphological traits highly correlated with the body weight of P. argenteus were found by Pearson correlation analysis and path analysis, which were body length and tail length, respectively. On the 60th, 90th, and 120th days after hatching, the genetic gains of body weight trait in the selected group were 9.44%, 17.64%, and 15.18%, respectively, and the mean values of realized heritability were at moderate level. Nevertheless, in the selected group, the genetic variation values of the two morphological traits significantly related to body weight were all below 10%, and the genetic gains were relatively low and stable, but the genetic variation values of body weight trait in the selected group were above 20%, and genetic gains were relatively high. These implied that it is possible to obtain considerable genetic gains by selecting for body weight trait, and the results provide supportive evidence for the continuity of the P. argenteus-selective breeding program.

Effects of dietary vitamin C on growth, antioxidant enzyme activity and immune‐related gene expression ofPampus argenteus

Effects of dietary vitamin C on growth, antioxidant enzyme activity and immune‐related gene expression of<i>Pampus argenteus</i>

A checklist of fish and shellfishes of the Poonthura estuary, southwestern coast of India

A systematic checklist of fish and shellfishes of the Poonthura estuary, Kerala, India is provided including notes on their conservation status. This checklist includes 66 finfish and five shellfish, belonging to 17 orders, 35 families, and 60 genera. Carangiformes is the richest order (11 species, eight genera, and three families), representing 15.4% of the total fish diversity. Carangidae, is the most diverse family with nine representatives, contributing to 12.6% of the total fish diversity. Following the IUCN Red List Categories, of the total 69 species (excluding both exotic and transplanted fish species), 59 belong to the ‘Least Concern’, while one species Pampus argenteus is listed as ‘Vulnerable’, four are ‘Data Deficient’ (Megalops cyprinoides, Arius maculatus, Cynoglossus semifasciatus, and Epinephelus tauvina) and five are ‘Not Evaluated’ (Nuchequula blochii, Channa pseudomarulius, Penaeus indicus, P. monodon, and Scylla serrata). Around 94% of the recorded fish fauna have commercial value and contribute to subsistence fisheries throughout the year. Taxonomy and diversity of fish fauna of least studied or isolated estuarine ecosystems should be updated with proper documentation of their conservation status, in order to design and implement pragmatic management and conservation programs.

Oocytes Skipped Spawning Through Atresia Is Regulated by Somatic Cells Revealed by Transcriptome Analysis in Pampus argenteus

In teleost, follicle atresia is a common degenerative process that can occur at different stages of ovarian development. In this study, we depicted the cellular morphology of silver pomfret (Pampus argenteus) follicular atresia in detail and divided it into four different stages from Aα to Aδ stages based on the main cellular characteristics. High-throughput RNA sequencing was used to profile follicle atresia from Aα to Aδ stages, and many stage-specific genes were identified. In early atretic ovary, a great number of genes in cytokine-cytokine receptor interaction were obviously downregulated, suggesting that somatic cells might directly induce the follicle atresia by disrupting the normal conservation with germ cells. Meanwhile, the regulatory network of immune cell–related pathways was discovered in the process of atresia. The genes enriched in Th cell differentiation, leukocyte transendothelial migration, cholesterol metabolism, and so on were abundantly expressed, indicating that the immune cells play key roles in the process of in follicle atresia. Moreover, a model was proposed to illustrate how somatic cells mediate the process of follicle atresia. The study provides important insights into the molecular networks underlying follicle atresia in teleost.

In-vitro self-assembly and antioxidant properties of collagen type I from Lutjanus erythropterus, and Pampus argenteus skin

The fish processing by-products are rich source of various novel and valuable biomolecules such as collagen and gelatin. Herein, we have extracted and purified collagen from the skin of two different marine fish species-crimson snapper (Lutjanus erythropterus) and silver pomfret (Pampus argenteus). The processing of these fishes produces huge quantities of by-products such as skin, fins, and bones. So, the extraction of collagen will be promising for the value addition to their by-products. Finally, the yield is moderately high viz. 13% (crimson snapper) and 7.5% (silver pomfret) on dry weight basis, respectively. The isolated proteins were characterized by different physicochemical techniques like FTIR, CD, SDS-PAGE, Zeta potential analyzer, SEM, and EDX. The denaturation temperatures (Td) as determined by CD was 34.54 °C and 33.58 °C for crimson snapper and silver pomfret, respectively. The Td is close to the mammalian collagen and hence, they serve as better alternative to mammalian collagen. The collagen from both the sources had lowest solubility at a basic pH (8–10), and lower ionic strength while higher solubility in acidic pH (1–5), and higher ionic strength. Further, the fibrillogenesis process was studied to understand the effects of temperature and ionic strength on collagen in vitro self-assembly. Collagen self-assembly is advantageous in making collagen-based gels for cell culture, and biomedical applications. In addition, the antioxidant activities of collagen and collagen hydrolysates prepared by enzyme (trypsin) were examined by DPPH, FRAP, NO and TAP antioxidant assays. The hydrolysates showed outstanding antioxidant activities as compared to native collagen solution. The result shows that fish waste is the potential and sustainable sources of collagen where its applications are not limited by religious conflicts and threats of various transmittable diseases.

Outbreak of Cryptocaryon irritans infection in silver pomfret Pampus argenteus cultured in China

Silver pomfret Pampus argenteus is a major cultivated marine fish species with a high market value. In summer 2021, Cryptocaryon irritans, a ciliate parasite, infected the cultured silver pomfret in aquaculture ponds in Ningbo, Zhejiang Province, China. The symptoms of infected fish include white spots on the skin and fins, increased body surface mucus, loss of appetite, irritability, and shedding of scales. After collecting white spots from moribund fish, the 18S ribosomal RNA sequence of the pathogen on the fish skin was amplified by PCR; phylogenetic analysis showed that it was closely related to C. irritans strains from Ningde, Fujian, China. Four groups of silver pomfret were tested in an artificial infection experiment over the course of 72 h, consisting of 3 infected groups (1600, 4000, and 8000 theronts fish-1) and 1 healthy group. White spots were observed on the skin and fins of the infected fish, but not on their gills. Samples were taken from the gills, liver, kidney, and spleen of both infected and healthy fish and were compared to evaluate any significant histopathological differences. As the dose of infection increased, symptoms became more pronounced. At 72 h, mortality rates were 8.3, 50, and 66.7% for the 3 different concentrations, respectively. The median lethal concentration was calculated to be 366 theronts g-1 at 72 h, 298 theronts g-1 at 84 h, and 219 theronts g-1 at 96 h. This study emphasizes the importance of developing early diagnosis methods and appropriate prevention strategies to decrease the impact of C. irritans infection in the silver pomfret aquaculture industry.

Determination of the geographical origin of Trachinotus ovatus and Pampus argenteus in China by multi-element and stable isotope analysis

This study aimed to determine whether Trachinotus ovatus and Pampus argenteus could be differentiated by multi-element composition or stable isotope ratio analysis of δ13C and δ15N. The multi-element analysis values of a total of 60 Pampus argenteus samples from three sites and 60 Trachinotus ovatus samples from four sites around China were determined, and the other 60 samples of Pampus argenteus and 51 samples of Trachinotus ovatus were tested by principal component analysis (PCA) to estimate the accuracy of origin identification. The results showed that the cross-validation accuracy rate is 92.2% for the Pampus argenteus and 98.3% for the Trachinotus ovatus. Stable isotope analysis of δ13C and δ15N also can distinguish Trachinotus ovatus from different geographical origins. These results showed that the usefulness of multi-element and stable isotope analysis as indicators for authenticating the geographical origin of two pomfrets in China.

Morphological analysis of Prochilodus argenteus ovaries in successful and unsuccessful hypophysation-induced reproduction.

Pampus argenteus is a species of economic importance for professional fishing and aquaculture. To analyse the quality of oocytes of P.argenteus, 10 females were kept in tanks of 200 m2 with an average depth of 1m in the Integrated Center of Fishing Resources and Aquaculture of Três Marias - CODEVASF. Specimens were submitted to hypophysation-induced reproduction with crude extract of common carp pituitary (EBHC). Females received two doses (0.8-1.0 and 5.0-6.6mg of EBHC/kg body weight, respectively), with a 12-h interval between doses. For males, a single dose (2.7mg/kg body weight) was applied at the same time as the females' second dose. Oocytes were extruded manually 8h after the second hormonal dose at 26°C. It was observed that seven females responded positively to the procedure while the other three released bloody and lumpy oocytes. For histological analysis, ovarian fragments were fixed in Bouin's liquid for 8-12 h and submitted to routine histological techniques. The protocol was considered successful for 70% of females and 100% of males. The fertilization rate of the females from the unsuccessful group was very low, and histological analyses showed that most of their oocytes were in follicular atresia, suggesting a delay in hormonal administration or extrusion could have occurred. Despite the hypophysation protocol being considered adequate for the induced reproduction of P.argenteus, complementary studies are necessary to evaluate the possible causes of this degenerative process.