Search Results (14)

Background: Primordial germ cells (PGC) are the progenitor cells of sperm and eggs during the embryonic stage. The maternal gene vasa has been widely studied for its role in PGC origin, and other genes like dead end (dnd) have also been identified. Objectives: Spotted sea bass is an important economic marine fish, and the study of its germ cell characteristics provides important basic data for future population breeding and protection. Methods: In this study, we cloned the full-length sequences of Lmvasa (2384 bp, encoding 1905 aa) and Lmdnd (1523 bp, encoding 386 aa) using RACE. Temporal and spatial expression patterns of Lmvasa and Lmdnd in embryos and gonads were analyzed by PCR, immunohistochemistry, and in situ hybridization. We also used microinjections of chimeric RNA containing GFP and Lmvasa 3′ UTR to visualize PGCs. Results: Our results showed that Lmvasa and Lmdnd are expressed primarily in early embryonic development (pre-blastula stage) and were expressed only in the gonads. Immunohistochemistry revealed abundant expression of Lmvasa and Lmdnd proteins in spermatogonia, weak expression in spermatocytes, and no expression in spermatozoa. In ovaries, both genes were expressed throughout oogenesis. Furthermore, PGCs in spotted sea bass belonged to an early localization pattern. Microinjection experiments demonstrated that Lmvasa 3′ UTR effectively labeled PGCs in embryos of spotted sea bass, zebrafish, and medaka. Conclusions: These findings may contribute to understanding PGC development in spotted sea bass and other Percidae. Full article

Understanding the spatial distribution of freshwater fish in heterogeneous aquatic environments is crucial for understanding riverine ecosystems and the rational use of aquatic biological resources. This study investigates the distribution patterns of juvenile fish in the lower reaches of the Irtysh River, including hydrodynamic conditions during different water level regimes. With hydroacoustic surveys, we assessed fish density and distribution in two wintering riverbed depressions during the spring flood and summer low water period. The main fish aggregations consisted of Cyprinidae and Percidae, with juveniles predominantly occupying areas with reduced flow velocities (0.15–0.75 m s⁻¹). Correlation analysis showed strong direct relationships between the area occupied by juvenile carp and perch and zones with specific flow velocities. The study highlights that hydrodynamic characteristics, particularly flow velocity, are key factors influencing the distribution and aggregation of juvenile fish. These findings underscore the importance of considering hydrodynamic factors and species-specific traits in understanding fish distribution patterns and in managing freshwater ecosystems effectively. This research contributes to the understanding of the multifunctional roles of riverbed depressions in supporting juvenile fish populations and emphasizes the importance of hydroacoustics to predict fish distributions in dynamic aquatic environments. Full article

Invasive species are often central to conservation efforts, particularly when concerns involve potential impacts on rare, endemic native species. The lower New River drainage of the eastern United States is a watershed that warrants conservation assessment, as the system is naturally depauperate of native fish species and it is nearly saturated with non-native fish species: there are 31 natives, including at least nine endemic taxa, and 63 non-natives. For endemic taxa, we examined temporal distribution shifts (range expansions or contractions) based on percent change in the occupied watershed area. We contrasted these findings with time series analyses on distribution trends of non-native minnows (Leuciscidae) and darters (Percidae) based on growth curve models of the cumulative sum of the total area of occupied 12-digit hydrologic unit codes. We documented range reductions for six of nine endemic taxa. We determined that 11 of 18 non-native minnows and 6 of 8 non-native darters were invasive based on range expansions and associated invasion curve models. The endemic taxa are of conservation concern given the limited distribution ranges and documented population declines. Although among-species comparisons of range shifts do not support causal inference, documentation of changes in distribution ranges of endemic and invasive species is critical to inform conservation efforts. Full article

A pilot ichthyological index was developed for use within the Water Framework Directive in the area of Central and Eastern Europe for dam reservoirs, which are heavily modified water bodies. This is the first approach to assessing this water body type based on ichthyofauna in Poland. Various fishing gear types were used. The tested dam reservoirs were scattered throughout the country, from lowland to mountainous areas, with very diverse hydrological and morphological characteristics and pressure ranges based on the TSI index. In preliminary work, a correlation matrix with the TSI index’s pressure indicator was tested based on the abundance or biomass of fish species, fish families present, fishing gear used, and fishing depth range for a total of 588 cases. As a result of the tests carried out, the preliminary indicator was based on the ratio of the number of the two families Cyprinidae and Percidae. The correlation between the developed indicator and the pressure index was strong (r = 0.77; p < 0.001). The Percidae family exhibited a strong correlation with the most connections in the matrix. Based on the obtained results, the principle of using already confirmed relationships, such as the ratio between Cyprinidae and Percidae fish families, in the assessment of eutrophication was confirmed to be effective, guaranteeing the effective initial assessment of ecological potential. Full article

Size differences are common in the aquaculture of fishes. In the larviculture of cannibalistic species such as pikeperch, they majorly influence mortality rates and consequently provoke losses in the aquaculture industry. With this study, we aim to reveal molecular differences between small and large pikeperch of the same age using a set of 20 genes associated with essential developmental processes. Hereby, we applied a general study design to early and late larval pikeperch before the onset of piscivory to explore the causes of growth differences in these developmental groups. The analysis of the expression levels showed developmental but not size-related differences in PGC1A, TGFB1, MYOD1, MRF4, and the collagens COL1A1 and COL1A2. Furthermore, increased head lengths were found in larger late larvae compared to their smaller conspecifics. While no uniquely size-related expression differences were found, the expression patterns of PGC1A in combination with TGFB1 as regulators of the citric acid cycle indicate a possible influence of mitochondrial energy metabolism. Furthermore, expression differences of MYOD1 and MRF4 point out possible temporal advantages of myogenetic processes in the larger late larval group and hypothesise growth advantages of the larger late larvae resulting from various influences, which provide a promising target for future research. Full article

This study reveals the diet of pike-perch from two habitats within the Tersko-Caspian region. The feeding habits of pike-perch in the Sulak and Terek rivers and Tersko-Caspian region were investigated based on 354 specimens sampled monthly from a commercial catch in 2019. Their diet consisted of different prey, with fish representing the most important prey group (up to 90%). Rutilus caspicus dominated with a frequency of occurrence of 20.5, and Aspius aspius, Perca fluviatilis, and Chondrostoma oxyrhynchum, had 13, 9.5, and 8.3%. In the earlier ages 1+ and 2+, zooplankton dominated, followed by mysids and chironomids, which continues into the older ages but at decreasing rates. Analysis of monthly variations in stomach fullness indicated that feeding intensity fluctuated in time, with the highest values in March–April, and lowest in September and November. It was found that the diet of pike-perch in the western Caspian changed considerably from season to season. They begin to actively feed after wintering and before, or even during, spawning period. The spectrum of the diet of Sander lucioperca includes more than 20 elements, mainly juveniles of commercially valuable fish. This fish is characterized by a relatively low ontogenetic diet diversity and flexibility, which makes it sensitive to environmental changes, including anthropogenically induced ones. This fish partially compensates for this disadvantage with its lifestyle, namely, its active foraging movements and migrations from fresh water to salt water and back, following its prey species. Full article

A procedure is proposed to assess the impact of various relationships found in the literature and is used to convert acoustic target strengths (TS) to fishes’ total length (TL) with respect to the compatibility of fish length data obtained from vertical hydroacoustics and gillnets. The study used one set of data collected with a 120 kHz echosounder across the mesotrophic, dimictic Lake Dejguny. Four general multi-species TS–TL relationships were tested for the maximum dorsoventral characteristic: (1) a relationship developed using mainly West Atlantic marine and brackish water fish for various frequencies, (2) a relationship developed using fish from the Salmonidae, Percidae, and Cyprinidae families at 120 kHz, as well as the relationship shown by two generalized equations for representatives of (3) the Cyprinidae family (200 kHz) and (4) the Percidae family (200 kHz). In addition, two other equations were developed for (5) perch (Perca fluviatilis) and (6) roach (Rutilus rutilus). The procedure for selecting the most appropriate TS–TL ratio began by determining the TS threshold that would eliminate small fish that were ineffectively caught with gillnets. Depending on the TS–TL relation, the threshold ranged from −48.5 dB to −45.5 dB, and the corresponding TL was in the range of 62.3–93.0 mm. Then, using linear regression, the relationship between the percentage of caught fish organized in length classes (TL), whose boundaries were determined using the tested TS–TL relationships, and the share of fish recorded acoustically in the corresponding TS classes (with a 1.5 dB interval) was examined. The fit of the regression model to the data (percentage) was assessed using the coefficient of determination r², the mean absolute error (MAE), the Nash–Sutcliffe model efficiency coefficient (NSE), and root mean square error (RMSE). For the data from Lake Dejguny, the most similar distribution of fish echo proportions and the corresponding distribution of total length (TL) for fish larger than 62 mm were obtained using the TS–TL relation developed using fish from the Salmonidae, Percidae, and Cyprinidae families (2), and for fish larger than 74 mm, the relation was developed for the family Pericidae (4). No evidence was found to unambiguously verify the meanings of different sound frequencies (120 and 200 kHz) for which the TS–TL relationships used in the analysis were derived. The proposed procedure can be used to select the optimal regression equation. Full article

Promising efforts are ongoing to extend genomics resources for pikeperch (Sander lucioperca), a species of high interest for the sustainable European aquaculture sector. Although previous work, including reference genome assembly, transcriptome sequence, and single-nucleotide polymorphism genotyping, added a great wealth of genomic tools, a comprehensive characterization of gene expression across major tissues in pikeperch still remains an unmet research need. Here, we used deep RNA-Sequencing of ten vital tissues collected in eight animals to build a high-confident and annotated transcriptome atlas, to detect the tissue-specificity of gene expression and co-expression network modules, and to investigate genome-wide selective signatures in the Percidae fish family. Pathway enrichment and protein–protein interaction network analyses were performed to characterize the unique biological functions of tissue-specific genes and co-expression modules. We detected strong functional correlations and similarities of tissues with respect to their expression patterns—but also significant differences in the complexity and composition of their transcriptomes. Moreover, functional analyses revealed that tissue-specific genes essentially play key roles in the specific physiological functions of the respective tissues. Identified network modules were also functionally coherent with tissues’ main physiological functions. Although tissue specificity was not associated with positive selection, several genes under selection were found to be involved in hypoxia, immunity, and gene regulation processes, that are crucial for fish adaption and welfare. Overall, these new resources and insights will not only enhance the understanding of mechanisms of organ biology in pikeperch, but also complement the amount of genomic resources for this commercial species. Full article

Downstream migration (DSM) of larvae and fry is an important phase of the life cycle of fish as it allows them to disperse, and it increases the size and diversity of the populations via them extending rearing grounds, exchanging genes, and avoiding competition and cannibalism. Two numerous and diverse fish families of the Eurasian rivers, Cyprinidae and Percidae, are well adapted to the conditions of the riverine continuum. Having said that, the regulation of rivers (construction of dams and water reservoirs) drastically changes their hydrology and topography. In this work, we argued that novel conditions of transformed river habitats influence the DSM of young cyprinids and percids in different ways. The published results on fish DSM and spatial distribution in nine European reservoirs (Russia, Kazakhstan, Czech Republic, Bulgaria) in comparison with untransformed rivers were reanalyzed from the viewpoint of this argument. Changes in the major characteristics of DSM of young cyprinids and percids, i.e., intensity, diel (24-h period), and seasonal patterns of migrations, as caused by anthropogenic transformation of the rivers, were revealed. We found that the novel ecological barriers and filters associated with different parts of water reservoirs differently influence the lateral and longitudinal movements, and the diel and seasonal dynamics of DSM of cyprinids and percids. These effects result in significantly more intensive emigration of young percids compared to cyprinids from reservoirs with deep-water intakes. At the scale of the whole regulated river, the morphological complexity (topography) of the reservoir plays a pivotal role in controlling the intensity of the DSM of young fish. Measures for the conservation and restoration of percid and cyprinid populations should be different. Full article

In vertebrates, the carbohydrate polymer polysialic acid (polySia) is especially well known for its essential role during neuronal development, regulating the migration and proliferation of neural precursor cells, for instance. Nevertheless, sialic acid polymers seem to be regulatory elements in other physiological systems, such as the reproductive tract. Interestingly, trout fish eggs have polySia, but we know little of its cellular distribution and role during oogenesis. Therefore, we localized α2,8-linked N-acetylneuraminic acid polymers in the ovaries of Coregonus maraena by immunohistochemistry and found that prevalent clusters of oogonia showed polySia signals on their surfaces. Remarkably, the genome of this salmonid fish contains two st8sia2 genes and one st8sia4 gene, that is, three polysialyltransferases. The expression analysis revealed that for st8sia2-r2, 60 times more mRNA was present than st8sia2-r1 and st8sia4. To compare polysialylation status regarding various polySiaT configurations, we performed a comparable analysis in Sander lucioperca. The genome of this perciform fish contains only one st8sia2 and no st8sia4 gene. Here, too, clusters of oogonia showed polysialylated cell surfaces, and we detected high mRNA values for st8sia2. These results suggest that in teleosts, polySia is involved in the cellular processes of oogonia during oogenesis. Full article

Although aquaculture has been the fastest growing food sector for decades, there are no standardized parameters for most of the fish species regarding physical meat quality. Therefore, this study provides for the first time an overview of the physical meat characteristics of the most important fish species of the German Baltic Sea coast. Traditional farmed salmonids (rainbow trout (Oncorhynchus mykiss) and maraena whitefish (Coregonus maraena) as well as two percids (European perch, Perca fluviatilis and pikeperch, Sander lucioperca) were utilized for this comparison. The results demonstrate that the meat of the salmonids is very analogous. However, the post mortem degradation process starts faster in trout meat. In contrast, the meat quality characteristics of the percids are relatively different. The meat of pikeperch has comparatively low shear strength with a high water-holding capacity resulting in high meat tenderness. The opposite situation is present in European perch. The results indicate that it is not possible to establish the overall quality characteristics for fish or production form, as there is a high range of variability. Consequently, it is particularly important that meat quality characteristics are developed for important aquaculture species for further improvement through changes in husbandry conditions when necessary. Full article

Larval fish ecology is poorly characterized because sampling is difficult and tools for phenotypically identifying larvae are poorly developed. While DNA barcoding can help address the latter problem, ‘universal’ primers do not work for all fish species. The Roanoke River in the southeastern United States includes seven darters (Family Percide: Tribe Etheostomatini). We made 393 collections of larval fishes in 2015 and 2018, examined darter larvae for morphometric and pigmentation traits, developed PCR primers amplifying darter DNA, and evaluated three gear types for collecting larval darters. Amplified DNA sequences for 1351 larvae matched archived mitochondrial cytochrome oxidase I sequences for darters occurring in the ecosystem. Larval darters were classified to genus with 100% accuracy using the ratio of pectoral fin length to body length; however, identification to species using morphometrics alone was subject to a misclassification rate of 11.8%, which can be resolved by considering pigmentation patterns. Gear-types varied considerably in their capture efficacy for larval darters; most Percina larvae were collected in drift nets. Larval Percina species appeared in the drift before Etheostoma species in both study years. Application of molecular genetic and phenotypic tools to larval fish identification can advance understanding of larval darter ecology. Full article

Centromeric protein A (CENP-A) is the epigenetic determinant of centromeres. This protein has been shown to be adaptively evolving in a number of animal and plant species. In a previous communication we were able to demonstrate that signs of adaptive evolution were detected in the comparison of CENP-A sequences from three percid fish species. In this study we isolated the CENP-A gene from eight additional species from the Percidae family. With these sequences and those previously obtained, we carried out a more robust statistical analysis of codon specific positive selection in CENP-A coding sequences of eleven percid species. We were able to demonstrate that at least two amino acid positions within the N-terminal tail are under strong positive selection and that one of these positions is potentially a substrate for phosphorylation. While nonsynonymous substitutions were detected in the histone fold domain, these were not statistically supported as resulting from positive selection. Full article

Both centromeric alpha-satellite sequences as well as centromeric protein A (CENP-A) are highly variable in eukaryotes. CENP-A, a histone H3 variant, is thought to act as the epigenetic “mark” for assembly of centromeric proteins. While most of the histone fold domain (HFD) of the CENP-A is fairly well conserved, a portion of this HFD as well as the N-terminal tail show adaptive variation in both plants and animals. Such variation may establish reproductive barriers that may lead to speciation. The family Percidae contains over 200 species most of which are within the subfamily Etheostomatinae. This subfamily represents a species rich radiation of freshwater fishes in North America and these species exhibit both allopatric and sympatric distributions. In order to study the evolution of CENP-A in percid fish species, we have isolated and characterized the CENP-A gene from Etheostoma tallapoosae by PCR based gene walking. As a result of this study we have demonstrated that the Tallapoosa darter CENP-A gene HFD sequences can be isolated from genomic DNA by nested PCR in a manner that does not lead to the amplification of the highly sequence related histone H3 gene. We also demonstrated that PCR based walking can be subsequently used to isolate the rest of the CENP-A gene and adjacent gene sequences. These adjacent gene sequences provide us with a primer binding sites for PCR isolation of the CENP-A gene from other percid species of fishes. An initial comparison of three percid species shows that the N-terminal tail of the percid CENP-A gene shows adaptive evolution. Full article