Hybrid Fish Research Articles

Companion Diagnostics (CDx) Based on Molecular Biology Techniques

Molecular profiling based on genomic mutations provides clinically important diagnostic and prognostic information. Companion diagnostic (CDx) testing, which is based on targeted drug therapy, is being applied to a variety of molecular diagnostic techniques (e.g., fluorescent in situ hybridization—FISH; polymerase chain reaction—PCR; and next-generation sequencing—NGS) to diagnose complex etiologies using a minimal number of specimens, replacing immunohistochemical analysis, which may show bias at certain stages. The safety and effectiveness of CDx testing using molecular diagnostic technology in precision medicine is an important factor in determining the treatment outcome and prognosis of patients. Meeting minimum safety and effectiveness performance standards is essential for CDx testing, and a thorough understanding of regulatory considerations is necessary to plan and design the optimal product. In this review, we focus on the diagnostic field of precision medicine and discuss the safety and effectiveness that each molecular diagnostic technology must meet according to CDx testing diversity.

Multi-omics reveals the molecular mechanisms of rapid growth in distant hybrid fish

Distant hybridization usually results in heterosis. In previous studies, we obtained an improved fish (WR-II, 2n = 100) with rapid growth through distant hybridization. To investigate the molecular mechanisms underlying the rapid growth of WR-II, the intestinal structure, microbiome and metabolome of the gut and the transcriptome of muscle were compared between WR-II and its parents (WCC and RCC, 2n = 100). The results revealed that WR-II had more intestinal folds, and the height, width and goblet cell density of the intestinal folds were greater than those of its parents. The absolute abundances of the probiotics Ralstonia and Salinivibrio were significantly greater in WR-II than in the parents (p < 0.05), and the probiotic Cupriavidus was found in only WR-II. A total of 481 and 718 differentially abundant metabolites (DMs) were identified in WR-II vs. WCC and WR-II vs. RCC, respectively. These DMs were enriched mainly in pathways related to metabolism, protein synthesis and development, such as fumaric acid, sphingosine, betaine and 5′-adenylic acid (AMP). A total of 5680 and 11,795 differentially expressed genes (DEGs) were identified in WR-II vs. WCC and WR-II vs. RCC, respectively. These DEGs were enriched mainly in pathways related to protein synthesis and substance metabolism. Growth-related genes such as irs1, irs2, foxo1, igf1r, and akt were upregulated in WR-II. Multi-omics analysis revealed that Salinivibrio can promote the level of AMP, which then regulates the expression of irs1 and foxo1, thus promoting the growth of WR-II. This study revealed the mechanism of rapid growth of WR-II from the probiotics, metabolites and genes, which provides evidence for the molecular mechanism of heterosis.

Does time matter? Intraspecific diversity of ribosomal RNA genes in lineages of the allopolyploid model grass Brachypodium hybridum with different evolutionary ages

BackgroundPolyploidisation often results in genome rearrangements that may involve changes in both the single-copy sequences and the repetitive genome fraction. In this study, we performed a comprehensive comparative analysis of repetitive DNA, with a particular focus on ribosomal DNA (rDNA), in Brachypodium hybridum (2n = 4x = 30, subgenome composition DDSS), an allotetraploid resulting from a natural cross between two diploid species that resemble the modern B. distachyon (2n = 10; DD) and B. stacei (2n = 20; SS). Taking advantage of the recurrent origin of B. hybridum, we investigated two genotypes, Bhyb26 and ABR113, differing markedly in their evolutionary age (1.4 and 0.14 Mya, respectively) and which resulted from opposite cross directions. To identify the origin of rDNA loci we employed cytogenetic and molecular methods (FISH, gCAPS and Southern hybridisation), phylogenetic and genomic approaches.ResultsUnlike the general maintenance of doubled gene dosage in B. hybridum, the rRNA genes showed a remarkable tendency towards diploidisation at both locus and unit levels. While the partial elimination of 35S rDNA units occurred in the younger ABR113 lineage, unidirectional elimination of the entire locus was observed in the older Bhyb26 lineage. Additionally, a novel 5S rDNA family was amplified in Bhyb26 replacing the parental units. The 35S and 5S rDNA units were preferentially eliminated from the S- and D-subgenome, respectively. Thus, in the more ancient B. hybridum lineage, Bhyb26, 5S and 35S rRNA genes are likely expressed from different subgenomes, highlighting the complexity of polyploid regulatory networks.ConclusionComparative analyses between two B. hybridum lineages of distinct evolutionary ages revealed that although the recent lineage ABR113 exhibited an additive pattern of rDNA loci distribution, the ancient lineage Bhyb26 demonstrated a pronounced tendency toward diploidisation manifested by the reduction in the number of both 35S and 5S loci. In conclusion, the age of the allopolyploid appears to be a decisive factor in rDNA turnover in B. hybridum.

Evaluating the Presence of Interspecific Hybrids Among Piaractus mesopotamicus, Piaractus brachypomus and Colossoma macropomum in the Upper Paraná River Using Genetic Markers

ABSTRACTFish hybridization is common in aquaculture worldwide, including in Brazil, with cross‐breeding between species of the genera Piaractus and Colossoma taking the lead. However, little is known about the genetic damage caused by hybrids that escape into natural environments. In the upper Paraná River region, hybrid fishes are overproduced; therefore, the use of molecular techniques for their monitoring and identification is necessary. This study aimed to detect the presence of possible hybridization between Piaractus and Colossoma in the upper Paraná River using the molecular markers cytochrome c oxidase subunit 1 (COI) and α‐tropomyosin (TROP). Fragments from 53 fish samples were analysed, and 41 samples were considered hybrids, with 12 confirmed pure, six as Piaractus mesopotamicus (pacu) and six as Piaractus brachypomus (pirapitinga). This is the first record of P. brachypomus, which is an invasive species in this basin, while Colossoma macropomum has not been observed. Molecular markers efficiently detected hybrids in the Ivinhema and Paraná rivers. The results showed a predominance of hybrid specimens from P. mesopotamicus × P. brachypomus. Our study suggests that more restrictions on hybridization and better supervision of fish farms are needed to prevent the escape of hybrids and the consequent ecological and genetic damage to native populations. We warn of the risk of a decline in the population of P. mesopotamicus, as this species is of great importance for fishing and maintaining the ecosystem.

Study on sperm cryopreservation of hybrid fish derived from Carassius cuvieri (♀) × Carassius auratus red var (♂)

Cryopreservation of sperm is an effective method for conserving germplasm resources in fish genetic breeding. The high-quality hybrid fish (WR) derived from white crucian carp (Carassius cuvieri, WCC, ♀) and red crucian carp (C. auratus red var., RCC, ♂), possesses valuable traits such as high survival rates, strong resistance, and rapid growth, representing an important germplasm resources of crucian carp. This study compared the effects of different antifreeze solutions on sperm viability among three varieties (WR, WCC, and RCC) and examined changes in enzyme activity, fertilization rates, and hatching rates after cryopreservation, aiming to enhance the cryogenic sperm cryopreservation technique in hybrid fish and investigate the mechanisms underlying spermatozoa damage caused by cryopreservation. The results showed that the antifreeze combination of D14 with 15 % dimethyl sulfoxide (DMSO) had the best effect in preserving the sperm of WR and WCC, while D20 with 10 % DMSO was the optimal combination for RCC sperm. After ultra-low temperature preservation, the longevity, fertilization, and hatching rates of frozen sperm were significantly lower (P < 0.05) compared to fresh sperm. The enzyme activities of superoxide dismutase (SOD), lactate dehydrogenase (LDH), and creatine kinase (CK) were significantly decreased (P < 0.05) in spermatozoa, whereas they showed a significant increase (P < 0.05) in sperm plasma. Succinate dehydrogenase (SDH) activity was significantly reduced (P < 0.05) in frozen spermatozoa of RCC compared to fresh spermatozoa, and exhibited lower activity in frozen spermatozoa of WCC and WR. Additionally, SDH activity was significantly elevated (P < 0.05) in frozen sperm plasma, and glutathione reductase (GR) activity was significantly lower (P < 0.05) in both frozen sperm plasma and spermatozoa across all three species. The study demonstrated that cryopreservation had a significant effect on the enzyme activities of spermatozoa and sperm plasma in all three species. These findings provide important technical support for the conservation of high-quality fish germplasm resources, particularly for novel varieties resulting from distant hybridization in fish.

UBE2J1 suppresses interferon signaling by facilitating the ubiquitination and degradation of IRF7

Ubiquitin-binding enzyme E2J1 (UBE2J1) is a predominant member of the UBE2 family. In mammals, it is involved in antiviral immunity, ER-misfolded protein degradation, and ubiquitination. However, the function of UBE2J1 in teleost has not been elucidated. In the present study, we cloned the homolog of UBE2J1 in triploid hybrid fish and investigated its regulatory role in the antiviral interferon (IFN) signaling. We determined that the full-length coding sequence of the triploid fish UBE2J1 (3nUBE2J1) consists of 939 base pairs and encodes 313 amino acids. Upon SVCV infection, the mRNA levels of 3nUBE2J1 were increased in the spleen, liver, kidney, and the caudal fin cell line of triploid fish. Knockdown of 3nUBE2J1 in host cells and fish enhanced their antiviral response and curtailed SVCV replication. Conversely, overexpression of 3nUBE2J1 inhibited the activation of IFN promoter induced by SVCV, poly (I:C), or RLR pathway factors. Further studies revealed that 3nUBE2J1 interacted with 3nIRF7 and suppressed both the protein level and antiviral activity of 3nIRF7. Finally, we demonstrated that 3nUBE2J1 enhanced the K27- and K29-linked ubiquitination of 3nIRF7, leading to its degradation. Collectively, our findings indicate that triploid fish UBE2J1 serves as a novel negative regulator of IFN signaling by inhibiting 3nIRF7.

The Research Advances in Distant Hybridization and Gynogenesis in Fish

ABSTRACTDistant hybridization and gynogenesis are two prevalent breeding techniques for fishes. Drawing from the research achievements of our team and the existing literature, we summarize the reproductive traits and genetic features of fishes derived from distant hybridizations and gynogenesis, and we deduce the fundamental mechanisms of these two methods and compare them, discerning their common and different characteristics. Both distant hybridization and gynogenesis techniques can alter genotypes and phenotypes, thus establishing them as significant breeding methods. Additionally, the genetic principles and the basic biological characteristics of distant hybridization and gynogenesis in fish have been inferred. We propose the concepts of macro‐hybrid and micro‐hybrid based on extensive experimental findings from fish distant hybridizations and gynogenesis. The term “macro‐hybrid” refers to offspring from distant hybridization that possess two distinct subgenomes, each inherited from one of the two parental species, such as allodiploid and allotetraploid lineages. The concept of “micro‐hybrid” refers to offspring, including autodiploid and autotetraploid lineages, as well as those resulting from artificial gynogenesis, whose genome almost originates solely from the maternal parent but in which certain DNA fragments derived from the paternal parent insert. Distant hybridization and gynogenesis are vital techniques in fish genetics, breeding, and evolution. We highlight the prospective paths for research and application of distant hybridization and gynogenesis in fishes.

Asexuality shapes traits in a hybrid fish

Animal morphology is influenced by several factors, including gonadal development and gametogenesis. Although their effects are well documented in male/female differentiation, much less is known about same-sex effects, such as those caused by their mode of reproduction. Here, using geometric morphometric analyses, we compare two groups of all-female triploid hybrid fish Chrosomus eos × eos-neogaeus, that differ only by their sexual and asexual reproductive strategies. We demonstrate that morphological differences arise from factors inherently associated with their mode of reproduction, with results replicated in two distinct lineages and in natural and common garden environments. Such differences provide additional insight about the costs and benefits of both reproductive strategies, which have mostly been of a demographic, population genetic, or genetic nature. In particular, these findings have important implications for the ecology of asexual organisms and contribute to the study of sex evolution by adding complexity to the paradox of sex theory.

Swordtail fish hybrids reveal that genome evolution is surprisingly predictable after initial hybridization.

Over the past 2 decades, biologists have come to appreciate that hybridization, or genetic exchange between distinct lineages, is remarkably common-not just in particular lineages but in taxonomic groups across the tree of life. As a result, the genomes of many modern species harbor regions inherited from related species. This observation has raised fundamental questions about the degree to which the genomic outcomes of hybridization are repeatable and the degree to which natural selection drives such repeatability. However, a lack of appropriate systems to answer these questions has limited empirical progress in this area. Here, we leverage independently formed hybrid populations between the swordtail fish Xiphophorus birchmanni and X. cortezi to address this fundamental question. We find that local ancestry in one hybrid population is remarkably predictive of local ancestry in another, demographically independent hybrid population. Applying newly developed methods, we can attribute much of this repeatability to strong selection in the earliest generations after initial hybridization. We complement these analyses with time-series data that demonstrates that ancestry at regions under selection has remained stable over the past approximately 40 generations of evolution. Finally, we compare our results to the well-studied X. birchmanni × X. malinche hybrid populations and conclude that deeper evolutionary divergence has resulted in stronger selection and higher repeatability in patterns of local ancestry in hybrids between X. birchmanni and X. cortezi.

Comparison of fish biological indicators of Clarias gariepinus hybrids grown in ras and pond farming conditions

To improve technologies in the field of commercial cultivation of aquaculture objects and further development of the warm-water aquaculture sector in Russia, we previously undertook breeding methods and approaches to obtain high-quality planting material for a promising commercial object — the African catfish Clarias gariepinus. This article presents, in a comparative aspect, the experience of growing hybrid offspring of African catfish, obtained from crossing two breeds — Mikhailovskaya and Tamanskaya, in a closed water supply system and in a pond farm in the Astrakhan region in the summer. It was shown that hybrid individuals of clariid catfish bred in a pond farm during the feeding period under consideration (from July to September) were characterized by a high specific growth rate and low feed ratio compared to hybrids grown in a recirculation system, respectively, 11.4% versus 9.87% and 0.96 versus 1. Also, based on the results of fishing, over two months of cultivation in a pond farm, hybrids of clariid catfish increased the total biomass by 13 times, while in a recirculating system it increased by 15 times, but the final biomass of fish turned out to be greater when reared in open reservoir (46.875 versus 10.87 kg). It was shown that the final individual mass of hybrid fish cultured in pond conditions was 11.0% higher than the final mass of individuals in the recirculation system. The conducted studies showed that in the climatic conditions of the Astrakhan region (VI fish-breeding zone), a promising direction for aquaculture of African catfish is the feeding cultivation of hybrid juveniles in pond farms. It should be taken into account that in order to obtain marketable fish products (i.e. individuals weighing over 1000 g), it is necessary to use fish seeding material with an average weight of at least 100 g.

Selective autophagy receptor p62/SQSTM1 inhibits TBK1-IRF7 innate immune pathway in triploid hybrid fish

The production of type I interferon is tightly regulated to prevent excessive immune activation. However, the role of selective autophagy receptor SQSTM1 in this regulation in teleost remains unknown. In this study, we cloned the triploid fish SQSTM1 (3nSQSTM1), which comprises 1371 nucleotides, encoding 457 amino acids. qRT-PCR data revealed that the transcript levels of SQSTM1 in triploid fish were increased both in vivo and in vitro following spring viraemia of carp virus (SVCV) infection. Immunofluorescence analysis confirmed that 3nSQSTM1 was mainly distributed in the cytoplasm. Luciferase reporter assay results showed that 3nSQSTM1 significantly blocked the activation of interferon promoters induced by 3nMDA5, 3nMAVS, 3nTBK1, and 3nIRF7. Co-immunoprecipitation assays further confirmed that 3nSQSTM1 could interact with both 3nTBK1 and 3nIRF7. Moreover, upon co-transfection, 3nSQSTM1 significantly inhibited the antiviral activity mediated by TBK1 and IRF7. Mechanistically, 3nSQSTM1 decreased the TBK1 phosphorylation and its interaction with 3nIRF7, thereby suppressing the subsequent antiviral response. Notably, we discovered that 3nSQSTM1 also interacted with SVCV N and P proteins, and these viral proteins may exploit 3nSQSTM1 to further limit the host's antiviral innate immune responses. In conclusion, our study demonstrates that 3nSQSTM1 plays a pivotal role in negatively regulating the interferon signaling pathway by targeting 3nTBK1 and 3nIRF7.

Hybridization in the Anthropocene - how pollution and climate change disrupt mate selection in freshwater fish.

Chemical pollutants and/or climate change have the potential to break down reproductive barriers between species and facilitate hybridization. Hybrid zones may arise in response to environmental gradients and secondary contact between formerly allopatric populations, or due to the introduction of non-native species. In freshwater ecosystems, field observations indicate that changes in water quality and chemistry, due to pollution and climate change, are correlated with an increased frequency of hybridization. Physical and chemical disturbances of water quality can alter the sensory environment, thereby affecting chemical and visual communication among fish. Moreover, multiple chemical compounds (e.g. pharmaceuticals, metals, pesticides, and industrial contaminants) may impair fish physiology, potentially affecting phenotypic traits relevant for mate selection (e.g. pheromone production, courtship, and coloration). Although warming waters have led to documented range shifts, and chemical pollution is ubiquitous in freshwater ecosystems, few studies have tested hypotheses about how these stressors may facilitate hybridization and what this means for biodiversity and species conservation. Through a systematic literature review across disciplines (i.e. ecotoxicology and evolutionary biology), we evaluate the biological interactions, toxic mechanisms, and roles of physical and chemical environmental stressors (i.e. chemical pollution and climate change) in disrupting mate preferences and inducing interspecific hybridization in freshwater fish. Our study indicates that climate change-driven changes in water quality and chemical pollution may impact visual and chemical communication crucial for mate choice and thus could facilitate hybridization among fishes in freshwater ecosystems. To inform future studies and conservation management, we emphasize the importance of further research to identify the chemical and physical stressors affecting mate choice, understand the mechanisms behind these interactions, determine the concentrations at which they occur, and assess their impact on individuals, populations, species, and biological diversity in the Anthropocene.

Variation and Interaction of Distinct Subgenomes Contribute to Growth Diversity in Intergeneric Hybrid Fish.

Intergeneric hybridization greatly reshapes regulatory interactions among allelic and non-allelic genes. However, their effects on growth diversity remain poorly understood in animals. In this study, we conducted whole-genome sequencing and RNA sequencing (RNA-seq) analyses in diverse hybrid varieties resulting from the intergeneric hybridization of goldfish (Carassius auratus red var.) and common carp (Cyprinus carpio). These hybrid individuals were characterized by distinct mitochondrial genomes and copy number variations. Through a weighted gene correlation network analysis, we identified 3693 genes as candidate growth-regulated genes. Among them, the expression of 3672 genes in subgenome R (originating from goldfish) displayed negative correlations with growth rate, whereas 20 genes in subgenome C (originating from common carp) exhibited positive correlations. Notably, we observed intriguing patterns in the expression of slc2a12 in subgenome C, showing opposite correlations with body weight that changed with water temperatures, suggesting differential interactions between feeding activity and weight gain in response to seasonal changes for hybrid animals. In 40.31% of alleles, we observed dominant trans-regulatory effects in the regulatory interaction between distinct alleles from subgenomes R and C. Integrating analyses of allelic-specific expression and DNA methylation data revealed that the influence of DNA methylation on both subgenomes shapes the relative contribution of allelic expression to the growth rate. These findings provide novel insights into the interaction of distinct subgenomes that underlie heterosis in growth traits and contribute to a better understanding of multiple allele traits in animals.

Inherited anoxia tolerance and growth performance can result in enhanced invasiveness in hybrid fish.

Northern hemisphere freshwater ecosystems are projected to experience significant warming and shortening of winter duration in this century. This change coupled with depletion of oxygen (hypoxia) will result in a shift toward fish species with higher optimal temperatures for growth and reproduction that can mitigate hypoxic stress. Here, we tested the assumption that reproduction between two distant species, i.e. anoxic-intolerant common carp (Cyprinus carpio) and anoxic-tolerant goldfish (Carassius auratus), results in the expression of genes responsible for ethanol synthesis (alcohol dehydrogenase and pyruvate dehydrogenase subunit E1β2). The expression of this ethanol-producing pyruvate decarboxylase pathway may transform the biochemical characteristics of progeny into anoxic-tolerant hybrids, expanding their suitable environmental range and potentially increasing invasiveness. Concurrently, a genetic strategy for improving fish tolerance to oxygen-depleted environments will be a valuable physiological trait in fish culture. Differential quantification of gene expression by analyzing mRNA revealed that, compared with koi×koi, koi female×goldfish male (F1 hybrid) possessed the pyruvate dehydrogenase subunit E1β2 gene construct, which was expressed at significantly greater levels in red muscle. The potential of this hybrid to both survive in extreme anoxic conditions and grow at elevated water temperatures would likely contribute to their ecological success.

Specific anti-SVCV antibodies in hybrids of common carp (Cyprinus carpio) and gibel carp (Carassius gibelio) reflect heterosis advantage and genetic breakdown

Spring viraemia of carp virus (SVCV) is a disease with a serious economic impact on the farming of cyprinid fish. High susceptibility to SVCV has been documented mostly in common carp (Cyprinus carpio), whilst gibel carp (Carassius gibelio) is a weakly susceptible species. Specific anti-SVCV antibodies were analyzed in pure lines of common carp and gibel carp, and various generations of F1 and post-F1 hybrids. Specifically, we focused on anti-SVCV antibodies in weakly susceptible F1 hybrids and highly infected backcross and F2 hybrids, hypothesizing that the level of anti-SVCV antibodies will reflect heterosis advantage in F1 generations and hybrid breakdown in post-F1 generations.Backcross generations with common carp exhibited the most frequently symptomatic infections, followed by pure common carp. The high capacity of susceptible common carp to produce anti-SVCV antibodies was reported, whilst gibel carp expressed almost undetectable levels of anti-SVCV antibodies. We found the very good capacity of F1 hybrids to produce anti-SVCV antibodies, suggesting heterosis advantage. In contrast, we revealed different patterns of anti-SVCV antibodies production between maternal backcrosses (having parents with the same mtDNA – here, gibel carp) and paternal backcrosses (having parents with different mtDNA, i.e., resulting from reciprocal crosses of F1 hybrids with gibel carp mtDNA and pure common carp). Whilst both maternal backcross generations and the F2 generation of hybrids tended to produce low anti-SVCV antibodies, both paternal backcross generations expressed levels of anti SVCV-antibodies similar to those of highly susceptible common carp. The low capacity to produce anti-SVCV antibodies in F2 hybrids may be interpreted as a potential consequence of genetic disruption. However, the different capacity to induce an adaptive response in paternal hybrids and maternal hybrids (with mtDNA C. gibelio) may be interpreted as potential compensation for the cyto-nuclear breakdown hypothesized for paternal hybrids when coping with viral infection. Alternatively, the genetic background of hybrid fish, i.e. a combination of the genes of highly susceptible common carp and of less susceptible gibel carp in the hybrid genome may be responsible for this pattern.

Investigation of Sexes and Fertility Potential of Female Russian Sturgeon (Acipenser gueldenstaedtii) and Male American Paddlefish (Polyodon spathula) Hybrids.

In the present study, 10 allotriploid (3nALT) and 10 allopentaploid (5nALP) six-month-old hybrid fish and two 3nALT and four 5nALP 40-month-old hybrid fish, which resulted by crossing female Russian sturgeon Acipenser gueldenstaedtii (Brandt and Ratzeberg, 1833) and male American paddlefish Polyodon spathula (Walbaum, 1792), were investigated. It was revealed that six-month-old 3nALT and 5nALP hybrids initially had "undifferentiated" gonads, while in the 40-month-old hybrids, only testes were observed in one case of 3nALT and one case of 5nALP hybrids. The testis of 3nALT hybrids was partially developed with spermatogonia, while the testis of one 5nALP hybrid was in the second developmental stage with low spermatogonia density. We could not determine gonad differentiation in any of the cases when the hybrid individuals had the W sex chromosome. We concluded that the gonad differentiation of these interfamilial hybrids follows a similar pattern to interspecific hybrids of different ploidy parent species of the family Acipenseridae, which is consistent with the classical Haldane's rule. However, it cannot be excluded that the testis of this/these hybrid(s) may produce fertile sperm after sexual maturity, depending on additional genetic, hormonal and environmental factors, and further research is required for its evaluation.

Effect of parental ploidy on reproductive system development in sturgeon hybrids in the second year of life

The paper presents the data on germ cell development in various sturgeon hybrids with various ploidy levels. The study was performed at experimental industrial sites of the Branch for Freshwater Fisheries of the Russian Federal Research Institute of Fisheries and Oceanography (VNIIPRKH). Histology samples were taken in the winter, summer and autumn. Histology slides were made following the standard procedure. The figures show all stages of germ cell development in males and females of various hybrids, depending on rearing conditions (thermal constant). Two-year-old Russian sturgeon × Kaluga fish hybrids with similar ploidy levels reached gonad maturity stage I at a thermal constant of 8,571 degree-days (547 days). Female Russian sturgeon × beluga hybrids aged 631 days (10,191 degree-days) showed accelerated germ cell development characteristic of stage I to early stage II. Male Russian sturgeon × beluga and Siberian sturgeon × beluga hybrids had sexually indifferent germ cells. These species are expected to be sterile. Male Russian sturgeon × Kaluga fish hybrids aged 374 days had sexually indifferent germ cells with occasional primary spermatogonia; cell division was observed on Day 547. The study found that distant hybrids show better growth than hybrids with similar ploidy levels, where more intensive germ cell development is observed. Further research will elucidate the effect of gonad development during reproductive system formation on the growth of sturgeon hybrids with various ploidy levels.

Enhancing Underwater Wireless Sensor Networks With Flexible Communication and Positioning

An innovative approach centred around underwater wireless communication and positioning in Underwater Wireless Sensor Networks, addressing limited coverage by proposing a dual-hop system combining optical fiber and wireless links. Time frame design and Code Division Multiplexing Access enhance multi-user signal transmission efficiency. Proof-of-concept experiments validate feasibility, with the introduction of the hybrid fish eye routing protocol further enhancing performance by intelligently combining fish-eye routing and traditional protocols for improved coverage and reliability. Moreover, the hybrid fish eye protocol incorporates adaptive routing algorithms that dynamically adjust to changes in underwater conditions, ensuring robustness and adaptability in challenging environments. Additionally, the hybrid fish eye protocol optimizes energy consumption by minimizing unnecessary transmissions, thereby prolonging the lifespan of underwater sensor networks. With full-duplex communication, precise positioning, and an extended transmission range, convergent system demonstrates significant potential for supporting high-capacity transmission among mobile nodes in forthcoming underwater scenarios

Species diversity and conservation status of ornamental fish traded in Kupang, East Nusa Tenggara, Indonesia

Abstract. Usman Z, Hariyadi DR, Serihollo LGG. 2024. Species diversity and conservation status of ornamental fish traded in Kupang, East Nusa Tenggara, Indonesia. Biodiversitas 25: 1116-1126. The high demand for ornamental fish native to Indonesia has the potential to be used as a source of foreign exchange income. In addition to increasing the national income, the ornamental fish trade must also be considered to preserve the population of the fish species being sold. The study aimed to determine ornamental fish diversity and conservation status in Kupang City, East Nusa Tenggara. This research was conducted in Kupang City, East Nusa Tenggara, Indonesia, from August to September 2023. The research was conducted using survey (non-experiment) and observation methods. The survey method was carried out using a form to conduct interviews with sellers in 11 ornamental fish shops. At the same time, the observation method was used to identify the types of fish being traded. The study's results recorded 18 families, 39 genera, and 46 fish species (Include 1 species is hybrid fish). The highest species diversity came from the Cichlidae family with 9 species (1 species (Amphilophus citrinellus x Cichlasoma trimaculatum) is hybrid fish), followed by Cyprinidae with 7 species, whereas each species of the Characidae and Poecilidae families were 5 species. Conservation status shows 4 status groupings, namely Least Concern (LC), Vulnerable (VU), Endangered (EN), and Not Evaluated (NE). Based on these groupings, there were 32 species in the Least Concern (LC) category, 3 species in the Endangered (EN) category, 2 species in the Vulnerable (VU) category, and 8 species in the Not Evaluated (NE) and 1 unclassified category. There is only 1 species that is included in the Appendix I category, namely Scleropages formosus, and other species are Not evaluated. This is the first study conducted in Kupang City to reveal the types of ornamental fish species sold and their conservation status. The study will be useful information to the government, researchers, and other stakeholders on the potential extinction risk of each type of fish being traded.

The key role of myostatin b in somatic growth in fishes derived from distant hybridization.

The basic mechanism of heterosis has not been systematically and completely characterized. In previous studies, we obtained three economically important fishes that exhibit rapid growth, WR (WCC ♀ × RCC ♂), WR-II (WR ♀ × WCC ♂), and WR-III (WR-II ♀ × 4nAU ♂), through distant hybridization. However, the mechanism underlying this rapid growth remains unclear. In this study, we found that WR, WR-II, and WR-III showed muscle hypertrophy and higher muscle protein and fat contents compared with their parent species (RCC and WCC). Candidate genes responsible for this rapid growth were then obtained through an analysis of 12 muscle transcriptomes. Notably, the mRNA level of mstnb (myostatin b), which is a negative regulator of myogenesis, was significantly reduced in WR, WR-II, and WR-III compared with the parent species. To verify the function of mstnb, a mstnb-deficient mutant RCC line was generated using the CRISPR-Cas9 technique. The average body weight of mstnb-deficient RCC at 12 months of age was significantly increased by 29.57% compared with that in wild-type siblings. Moreover, the area and number of muscle fibers were significantly increased in mstnb-deficient RCC, indicating hypertrophy and hyperplasia. Furthermore, the muscle protein and fat contents were significantly increased in mstnb-deficient RCC. The molecular regulatory mechanism of mstnb was then revealed by transcription profiling, which showed that genes related to myogenesis (myod, myog, and myf5), protein synthesis (PI3K-AKT-mTOR), and lipogenesis (pparγ and fabp3) were highly activated in hybrid fishes and mstnb-deficient RCC. This study revealed that low expression or deficiency of mstnb regulates somatic growth by promoting myogenesis, protein synthesis, and lipogenesis in hybrid fishes and mstnb-deficient RCC, which provides evidence for the molecular mechanism of heterosis via distant hybridization.