Search Results (249)

The swimming crab is a commercially and nutritionally important marine resource with the highest catch volumes in Mexico occurring along the East Pacific coast. Among the Pacific species of the genus Callinectes, the blue crab C. arcuatus has the widest distribution and is found throughout the year. Its close resemblance to the well-studied Atlantic blue swimming crab (C. sapidus) makes it an excellent model for molecular reproductive studies in the Mexican Pacific. Using next-generation sequencing, this study aimed to characterize maturation-associated genes in an ovary–hepatopancreas transcriptome of C. arcuatus, with a particular focus on vitellogenin (Vtg) and its expression in the ovaries and hepatopancreas across different gonadal maturity stages. The transcriptome library generated from pooled samples produced 27,729 unigenes, of which, 196 (1.81%) were identified as reproduction-related genes. Notably, 33 of these genes, including the complete Vtg sequence, have not been previously reported in this species. Vtg expression was found to be tissue-specific, with levels in the hepatopancreas up to 13 orders of magnitude higher than in the ovary. In the hepatopancreas, Vtg expression increased exponentially from stage I to stage V of gonadal maturity, whereas in the ovaries, its expression showed the opposite trend. These findings highlight that the hepatopancreas, with its abundant nutrient reserves, serves as the primary site of Vtg expression and synthesis. Full article

This study examined the effects of Bacillus probiotic strains on red abalone Haliotis rufescens reproductive performance. We supplemented plant- and fish-based feeds and compared them to fresh giant kelp Macrocystis pyrifera as a control diet. Over 180 days, abalone fed the plant–probiotic diet reached higher female gonadal maturation, with 56% of females attaining the maximum Visual Gonad Index (VGI 3). Additionally, plant-based treatment showed a female-biased sex ratio (1.5:1 female-to-male ratio, F:M) compared with the kelp control treatment (0.8:1 F:M). These results suggest that probiotics can improve nutrient utilization from soybean meal and may enhance the bioavailability of phytoestrogens and other bioactive compounds, contributing to reproductive outcomes. Although the mechanisms remain to be confirmed, this approach provides a promising strategy to reduce reliance on fishmeal and wild macroalgae while supporting faster reproductive cycles in abalone aquaculture. Future research should focus on biochemical validation, molecular pathways, and multigenerational trials to ensure the long-term safety and sustainability of probiotic–plant-based feeds. Full article

Glucocorticoids like cortisol are widely used to assess stress in fish, but their interpretation can be limited. Incorporating dehydroepiandrosterone (DHEA), a hormone with anti-glucocorticoid and neuroprotective effects, may provide a broader understanding of hypothalamic–pituitary–inter-renal (HPI) axis activity. As DHEA data in fish remain scarce, this study examined its role in rainbow trout (Oncorhynchus mykiss) subjected to acute stress (30 min confinement), considering sex and sexual maturity. Cortisol and DHEA were quantified by optimized radioimmunoassay (RIA) in serum, muscle, fin, and scales, and gonadal histology was performed to confirm reproductive status. Both hormones were successfully measured in all matrices, with serum DHEA levels notably higher than those reported to date in fish. As expected, serum cortisol increased markedly after stress and correlated with levels in muscle and fin but not in scales, which appears to reflect chronic rather than acute exposure. In contrast, serum DHEA showed no stress-induced changes and only minor sex- and maturity-related differences, although alternative matrices displayed variable patterns, particularly in muscle and fin. The cortisol/DHEA ratio in serum mirrored cortisol dynamics, suggesting limited utility for acute stress assessment, while tissue-specific DHEA variation may integrate longer-term influences. Further research is needed to clarify the role of DHEA under chronic stress and its potential origins in inter-renal tissue, gonads, or the brain. Full article

Background/Objectives: Inactivation of the dnd gene involved in the development of primordial germ cells (PGCs) leads to the loss of gametes and halts reproductive development. Studies on sterile fish allow for the identification of genes and processes associated with GC differentiation. Methods: Atlantic salmon with GC-ablated testes were produced by temporal silencing of dnd. Gene expression was analyzed in sterile and fertile testes using 44k microarray and qPCR. Results: In sterile testes, transcripts of several GC markers were detected at low levels, suggesting the presence of cells with a GC-related expression profile that failed to initiate spermatogenesis. Expression of 260 genes was undetectable in the gonads of sterile males and females, and 61.5% of these were also inactivated during first maturation of fertile testes. This group was enriched with genes highly expressed in the brain, including those involved in endocrine and paracrine regulation, synaptic transmission, and numerous genes critical for brain development; among them, 45 genes encoding homeobox proteins. Another group of 229 genes showed increased expression in developing testes and included genes involved in neurosecretion and brain development regulation. GC-ablated testes showed increased expression of reproductive regulators such as amh and sdy and numerous immune genes, suggesting a reprogramming of GC-depleted testes. Temporal silencing of dnd indicated common developmental processes in the brains and gonads of Atlantic salmon testis that become inactive in testes at first maturation. These processes may play roles in PGC homing, the creation of a specific environment required for spermatogenesis, or facilitating communication between the gonads. Full article

Stocking and replenishing fish are crucial for the ecological restoration of aquatic biological resources. Since 2017, a long-term stocking program of Hypophthalmichthys molitrix and Aristichthys nobilis has been underway in the Xixi River basin of the Jiulong River. To understand the status of fishery resources following this long-term stocking program, field surveys were conducted every two months from October 2023 to October 2024. Traditional netting, resource assessment and environmental DNA (eDNA) analysis methods were used to conduct a comprehensive assessment of resource abundance, stocking contribution and ecological adaptability. The research revealed that the annual survival rates for H. molitrix and A. nobilis were 40.25% and 48.19%, respectively. The current numerical ratio of H. molitrix to A. nobilis stands at 1.97:1, indicating that the survival number of H. molitrix is better than that of A. nobilis. No mature gonads were observed in any sampled individuals, demonstrating that the current population is highly dependent on artificial replenishment. This study provides valuable data support for aquatic resource restoration and ecological management in the Jiulong River Basin. Full article

The Japanese grenadier anchovy (Coilia nasus), an economically vital anadromous species in the Yangtze River, has experienced severe population decline, prompting a 10-year fishing moratorium. Comprehensive data on its population structure and spatial growth variations during this critical recovery period, however, remain scarce. This study addresses this gap by analyzing 1119 individuals sampled from four sites along the species’ migratory corridor during the 2024 spawning season. We assessed key life-history traits to quantify spatial and sex-specific dynamics. We found significant sexual dimorphism, with females attaining greater size and age than males. The population was highly structured spatially: larger individuals were captured farther upstream, and initially female-biased sex ratios became more balanced inland. Growth modeling revealed that females had higher asymptotic lengths (L_∞) but lower growth coefficients (k). Furthermore, macroscopic assessment of gonadal maturity identified contrasting reproductive schedules between sexes along the migratory route. These results demonstrate clear sex-specific life-history strategies and a strong spatial segregation by size and reproductive state. This study provides crucial baseline data from the moratorium period, underscoring the necessity of spatially explicit management—particularly the protection of upstream spawning habitats for larger, more fecund individuals—to aid the recovery of this endangered species. Full article

Background: In high-altitude regions, sporadic two-year-old immature Chinese mitten crabs (Eriocheir sinensis) would overwinter and mature in their third year, developing into three-year-old crabs (THCs) with a cold-adaptive strategy. Compared to two-year-old crabs (TWCs) from low-altitude Jiangsu, THCs from Karst landform and high-altitude Guizhou exhibit significantly larger final size but lower gonadosomatic index (GSI) (p < 0.01). Methods: To elucidate the molecular mechanisms underlying this delayed ovarian development, integrated transcriptomic and proteomic analyses were conducted. Results: Results showed downregulation of PI3K-Akt and FoxO signaling pathways, as well as upregulation of protein digestion and absorption pathways. Differentially expressed proteins indicated alterations in mitochondrial energy transduction and nutrient assimilation. Integrated omics analysis revealed significant changes in nucleic acid metabolism, proteostasis, and stress response, indicating systemic reorganization in energy-nutrient coordination and developmental plasticity. Conclusions: The observed growth-reproductive inverse relationship reflects an adaptive life-history trade-off under chronic cold stress, whereby energy repartitioning prioritizes somatic growth over gonadal investment. Our transcriptomic and proteomic data further suggest a pivotal regulatory role for FOXO3 dephosphorylation in potentially coupling altered energy sensing to reproductive suppression. This inferred mechanism reveals a potential conserved pathway for environmental adaptation in crustaceans, warranting further functional validation. Full article

This study assessed the impact of untreated wastewater discharge in the Danube River on four native fish species: barbel (Barbus barbus), vimba bream (Vimba vimba), perch (Perca fluviatilis), and white bream (Blicca bjoerkna). Biomarkers of exposure and effect were evaluated, including metal and metalloid bioaccumulation in gills, liver, and gonads, DNA damage (comet assay), chromosomal abnormalities (micronucleus assay), liver enzyme activities (ALT, AST), and erythrocyte maturation. White bream showed the highest genotoxic damage (TI% = 22.57), particularly in liver tissue, indicating high sensitivity to pollution. Perch had elevated DNA damage in blood (TI% = 22.69) and strong biomarker responses, likely due to its predatory behavior. Barbel displayed notable DNA damage in gills (TI% = 30.67) and liver (TI% = 20.35), aligning with sediment exposure due to its benthic habits. Vimba bream had the lowest responses, possibly reflecting reduced exposure or resilience. Element accumulation varied across tissues and species, with perch showing the highest overall levels. Hepatic enzyme activities (highest values: ALT = 105.69 in barbel; AST = 91.25 in white bream) and changes in erythrocyte profiles supported evidence of physiological stress. Integrated Biomarker Response (IBR) analysis identified white bream as the most sensitive species, followed by perch and barbel. These results emphasize the value of multi-species biomonitoring and the importance of species-specific traits in freshwater ecotoxicology. Full article

Fish reproductive biology influences their life history and can impact their vulnerability to fisheries; therefore, for sustainable management and development, a proper understanding is crucial. Reproductive biology, including maturation, spawning season, fecundity, and sex ratio, was examined throughout the year in the Java Rabbitfish, Siganus javus, in the southern South China Sea. This study is the first to examine reproductive traits by collecting a total of 339 S. javus specimens monthly from September 2017 to August 2018 through detailed gonad histology. The spawning season of female S. javus was mainly restricted to July, August, October, and December, whereas male fish were found to spawn throughout the year. Inter-species variations in the spawning season were observed within the genus, which is influenced by interspecific spawning strategies and regional environmental factors. The sex ratio close to 1:1 suggests that the fish population is in equilibrium in the region. The fecundity of S. javus ranged from 1.8 × 10⁵ to 12 × 10⁵, which was similar to that of other species in Siganus, suggesting less inter- and intra-species variation in fecundity within the family. The middle maturation stage was absent throughout the year, probably due to the different habitat uses during their life history. Reproductive biology might influence other biological aspects, such as migration and behaviour in the fish. Full article

Background/Objectives: Sex determination and differentiation exhibit remarkable molecular diversity across taxa, driven by genetic, epigenetic, and environmental factors. Invertebrates with sequential hermaphroditism, such as the Pacific oyster (Magallana gigas), represent a poorly understood system despite their role as keystone species and contribution to a substantial aquaculture industry. Methods: To identify sex-related molecular markers during gametogenesis, we repeatedly sampled hemolymph from artificially conditioned oysters over two months, and sex phenotypes were assigned at the end of the experiment by biopsy. Results: RNA-sequencing analysis of five males and five females revealed subtle yet consistent sex-specific transcriptional signatures in hemolymph. We show that gametogenesis proceeds asynchronously among oysters, even within the same sex individuals. Complex physiological trade-offs were discovered between sexes during gonad maturation; in early stages of sexual maturation, females prioritized cell division, whereas males suppressed it. Females exhibited higher expression of solute carrier family (SLC) genes, suggesting enhanced nutrient exchange during oogenesis. Temporal dynamics highlighted differential expression of genes regulating cross-membrane ion gradients (e.g., transient receptor potential channels) and signal transduction (e.g., signal transducer and activator of transcription), previously linked to environmental sex determination (ESD) in some reptilian species. Conclusions: Together, these findings underscore that gametogenesis in Pacific oysters is complex and dynamic, and that molecular pathways of ESD may be partially conserved between invertebrate and vertebrate species. Full article

The red swamp crayfish (Procambarus clarkii) is a crucial freshwater aquaculture species in China, and the reproductive capacity and farming efficiency are critically dependent on gonadal development. Consequently, the acceleration and synchronization of gonadal maturation constitutes fundamental prerequisites for intensive seedling breeding. This review systematically synthesizes current knowledge on gonadal development and its regulatory factors in P. clarkii, specifically addressing (1) histological characteristics, (2) developmental stages and cyclical patterns, and (3) key genes involved in gonadal regulation. We particularly focus on the combined effects of intrinsic and extrinsic factors—including temperature, photoperiod, nutrition, and endocrine regulation—on gonadal maturation. This comprehensive assessment offers both theoretical insights into gonadal development mechanisms and practical guidance for enhancing intensive seedling production in this economically vital species. Full article

Fish reproduction requires suitable salinity and temperature, as well as sufficient energy. This study investigated temperature and salinity effects on ovarian development of Lateolabrax maculatus and energy metabolism differences between reproduction and growth. Two salinities (4‰ and 30‰) and temperatures (18 ± 1 °C and 30 ± 1 °C) formed four treatments: SWNT (30‰, 30 ± 1 °C), SWLT (30‰, 18 ± 1 °C), FWLT (4‰, 18 ± 1 °C), and FWNT (4‰, 30 ± 1 °C). GSI and sex hormones (FSH, LH, E2, and 17α,20β-DHP) were measured. Transcriptome analysis explored how temperature and salinity regulate ovarian development in L. maculatus, while integrated transcriptomic and targeted energy metabolomic analyses revealed energy metabolism differences between ovary and muscle during this process. The results showed that low salinity (4‰) and low temperature (18 ± 1 °C) synergistically promoted ovarian development in the FWLT group, as indicated by a significant increase in GSI and elevated levels of key sex hormones (FSH, LH, E2, and 17α,20β-DHP). Transcriptome analysis showed that low temperature activated pathways involved in steroidogenesis, oocyte maturation, and meiosis, and genes such as ADCY6, PRKACB, CPEB4, FZD7-A, and CCND2 were significantly upregulated. Salinity changes mainly affected amino acid metabolism, cholesterol metabolism, and the insulin signaling pathway. Genes such as PCSK9 and CKM may regulate ovarian development by regulating hormone synthesis and energy metabolism. Comprehensive transcriptome and metabolome analyses show that glycolysis is downregulated and oxidative phosphorylation is upregulated in the ovary, suggesting that ovarian oogenesis tends to be energized by aerobic metabolism. The TCA cycle may be used more for providing biosynthetic precursors and facilitating the transport of substrates between the mitochondrion and the cytoplasm rather than just as a source of ATP. Muscle tissue relies primarily on glycolysis for rapid energy production and may redistribute energy to the gonads, prioritizing the energy needs of the ovaries and contributing to the dynamic balance between reproduction and growth. This study provides insights into the molecular mechanisms of how environmental factors regulate fish reproduction, providing a theoretical basis and potential molecular targets for the regulation of reproduction and optimization of aquaculture environments. Full article

The apple snail Pila globosa is a widely distributed mollusc in tropical freshwater ecosystems, where it plays a crucial ecological role. This study examined the morphometric features, condition indices, and reproductive traits of P. globosa to gain insights into its population structure in the Ratargul Freshwater Swamp Forest, Bangladesh. Water quality parameters were recorded, and various morphometric measurements were analysed, including their correlations and seasonal variations. The mean values for shell length, shell weight, shell width, spiral length, base length, aperture length, aperture width, and soft tissue wet weight were 4.64 ± 0.97 cm, 38.29 ± 15.27 g, 3.56 ± 0.74 cm, 2.32 ± 0.51 cm, 3.33 ± 0.74 cm, 3.46 ± 0.64 cm, 2.01 ± 0.45 cm, and 18.05 ± 11.39 g, respectively. Linear regression analyses revealed strong correlations among length–length and length–weight parameters, indicating consistent growth patterns. Monthly frequency distributions showed distinct variations in shell size and form. The sex ratio was 1:1.23 (male–female), not significantly different from parity. Histological analysis during the rainy season revealed reproductive activity, including mature ova, previtellogenic and vitellogenic oocytes, and spermatogonia and spermatids. These findings enhance understanding of the species’ biology and its interaction with environmental conditions, offering valuable data for the conservation and management of freshwater mollusc populations in wetland ecosystems. Full article

Gonadal development and spermatogenesis critically influence fish reproductive performance. Neomales (genetically female but functionally male) are indispensable for generating all-female populations, yet their spermatogenesis remains understudied. In the present study, we systematically investigated gonadal maturation in neomales of the large yellow croaker (Larimichthys crocea), an economically important marine species exhibiting sexually dimorphic growth. We examined the growth performance and gonadal development throughout the maturation process in neomales and control males. Results showed comparable growth performance but a temporal divergence in gonadal development: the gonadosomatic index (GSI) of neomales was significantly higher than control males at 400 and 430 days post-hatching (dph), but not at 460 dph during the reproductive period. Histological, ultrastructural (TEM), and immunofluorescence analyses collectively demonstrated that neomale testes contained all major spermatogenic cell types. Their morphological characteristics and expression patterns of key markers—germ cells (vasa), Sertoli cells (sox9a), and meiotic recombination (dmc1)—were similar to control males. These findings enhance understanding of gonadal development and spermatogenesis in neomales, providing a theoretical and technical foundation for large-scale production of all-female large yellow croaker. Full article

Megalobrama terminalis is a significant aquatic fish in South China, renowned for its tasty meat. Nonetheless, related studies are deficient concerning the gonadal development of M. terminalis. This paper presents the first comparative transcriptome analysis of the gonads of female and male M. terminalis. A total of 84,886 unigenes were assembled, with 42,322 effectively annotated to the Nr, SwissProt, KEGG, KOG, and GO databases. Furthermore, comparative transcriptomic analysis of M. terminalis was conducted to examine its gonadal development. A total of 14,972 differentially expressed genes (DEGs) were discovered. In the testis, the expression of 11,928 unigenes was significantly upregulated, while 3044 were significantly downregulated. Numerous DEGs associated with steroidogenesis, gonadal differentiation and development, and gametogenesis in teleost fish were identified. The results provide empirical support for further study of genes and pathways associated with sex determination and gonadal differentiation in teleost fish. Full article