Supplemental description of Gyrodactylus pseudorasborae (Gyrodactylidae) parasitic on topmouth gudgeon Pseudorasbora parva (Cyprinidae) in South China.

Based on morphology and ITS sequence data, we identify and supplementally describe Gyrodactylus pseudorasborae Ondracková, Seifertová & Tkachenko, 2023 on the fins of topmouth gudgeon (Pseudoraspora parva) from freshwaters of southern China. The highest similarity (99.57% and 99.47%) to G. pseudorasborae suggested they were the same species. Prevalence and mean intensity were 45% and 2.3, respectively. The gyrodactylid species morphologically resembled G. pseudorasborae recorded from the same host species P. parva in Czech Republic, Ukraine, and Central China. But there were slight morphological differences in the shape and size of the marginal hook. Comparisons of marginal hook sickles of various Gyrodactylus species suggested that G. pseudorasborae and G. parvae were members of the G. wageneri-group. A molecular phylogeny of G. pseudorasborae with related species is presented and discussed within the context of the mechanism of local evolution of these sister species.

Unveiling the rise of non-native fishes in eastern alpine mountain rivers: Population trends and implications.

Insufficient knowledge about the occurrence and spread of non-native fish in mountain regions has impeded effective management strategies worldwide. To address this gap, this study analysed over 1300 electrofishing surveys across 650 sites, encompassing a vast 7400 km2 area in the Eastern Alps. The primary objectives were to quantify the occurrence of non-native species and predict their spread in different river types. Furthermore, the study estimated population sizes and biomass trends for over 150 sites that were surveyed multiple times between 2000 and 2020. Out of the 42 fish species in the study region, 11 were identified as non-native. Notably, two invasive species of Union concern, Lepomis gibbosus and Pseudorasbora parva, increased their population sizes by 8% and 9% per year, over the past decades, supposedly supported by increasing water temperatures. Among the non-native species relevant for recreational fishing, Oncorhynchus mykiss populations showed a significant increase of approximately 7% per year, Salmo trutta populations remained stable, and Salvelinus fontinalis populations experienced a notable decline of approximately 7.4% per year. These varying population trends may be attributed to disparities in stocking intensities, with S. fontinalis receiving minimal stocking compared to the other species. This study revealed that non-native and invasive fish species are a relevant part of fish communities in mountain rivers. Non-salmonid non-natives thrive in warm rivers at lower elevations, whereas salmonid non-natives consolidate in steeper habitats. Because rising temperatures in mountain rivers will accelerate the spread and growth of these species, this first quantification of the current extent will improve fish management strategies in mountainous areas.

Anthropogenic noise does not strengthen multiple-predator effects in a freshwater invasive fish.

Anthropogenic noise has the potential to alter community dynamics by modifying the strength of nested ecological interactions such as predation. Direct effects of noise on per capita predation rates have received much attention but the context in which predation occurs is often oversimplified. For instance, many animals interact with conspecifics while foraging and these nontrophic interactions can positively or negatively influence per capita predation rates. These effects are often referred to as multiple-predator effects (MPEs). The extent to which noise can modulate MPEs and thereby indirectly alter per capita predation remains unknown. To address this question, we derived the relationship between per capita predation rate and prey density, namely the functional response (FR), of single and pairs of the invasive topmouth gudgeon Pseudorasbora parva when feeding on water fleas under two noise conditions: control ambient noise estimated at 95 dB re 1 µPa and ambient noise supplemented with motorboat sounds whose relative importance over ambient noise ranged from 4.81 to 27 dB. In addition, we used video recordings to track fish movements. To detect MPEs, we compared the observed group-level FRs to predicted group-level FRs inferred from the individual FRs and based on additive effects only. Regardless of the number of fish and the noise condition, the FR was always of type II, showing predation rate in a decelerating rise to an upper asymptote. Compared to the noiseless condition, the predation rate of single fish exposed to noise did not differ at high prey densities but was significantly lower at low prey densities, resulting in an FR with the same asymptote but a less steep initial slope. Noise also reduced fish mobility, which might explain the decrease in predation rate at low prey densities. Conspecific presence suppressed the individual response to noise, the FRs of two fish (observed group-level FRs) being perfectly similar between the two noise conditions. Although observed and predicted group-level FRs did not differ significantly, observed group-level FRs tended to fall in the low range of predicted group-level FRs, suggesting antagonism and a negative effect of nontrophic interactions on individual foraging performance. Interestingly, the difference between predicted and observed group-level FRs was not greater with noise, which means that noise did not strengthen MPEs. Our results show that when considering the social context of foraging, here through the presence of a conspecific, anthropogenic noise does not compromise foraging in the invasive P. parva.

Dietary watermelon residue influencing the nonspecific immunity of juvenile Pseudorasbora parva.

The study explored the improvement of disease resistance, non-specific immunity and anti-oxidation reactions for Pseudorasbora parva (PP) using dietary watermelon residue. The cumulative PP mortality and the pathogenic bacteria number in 15-45% groups reduced relative to those in control group (CK). Under 15-45% groups, AKP, ACP activities and akp, acp genes expression levels were increased markedly in nonspecific immunity system. Similarly, antioxidant response (SOD, CAT activities) and their genes was promoted also at 15-45% groups. Organic matter (vitamin and polyphenols) in watermelon residue improved AKP, ACP, SOD, CAT activities by increasing corresponding gene expressions. Theoretically, they could also function as stimulus signal, active center or composition to modulate enzyme activities and gene expressions. Besides, watermelon residue ameliorated NF-kB, mTOR responses pathway, and consequently suppressed Aeromonas hydrophila which augmented disease resistance.

Temperature surpasses the effects of velocity and turbulence on swimming performance of two invasive non-native fish species.

Global climate change continues to impact fish habitat quality and biodiversity, especially in regard to the dynamics of invasive non-native species. Using individual aquaria and an open channel flume, this study evaluated the effects of water temperature, flow velocity and turbulence interactions on swimming performance of two lentic, invasive non-native fish in the UK, pumpkinseed (Lepomis gibbosus) and topmouth gudgeon (Pseudorasbora parva). Burst and sustained swimming tests were conducted at 15, 20 and 25°C. Acoustic Doppler velocimetry was used to measure the flume hydrodynamic flow characteristics. Both L. gibbosus and P. parva occupied the near-bed regions of the flume, conserving energy and seeking refuge in the low mean velocities flow areas despite the relatively elevated turbulent fluctuations, a behaviour which depended on temperature. Burst swimming performance and sustained swimming increased by up to 53% as temperature increased from 15 to 20°C and 71% between 15 and 25°C. Furthermore, fish test area occupancy was dependent on thermal conditions, as well as on time-averaged velocities and turbulent fluctuations. This study suggests that invasive species can benefit from the raised temperatures predicted under climate change forecasts by improving swimming performance in flowing water potentially facilitating their further dispersal and subsequent establishment in lotic environments.

Visual Cues Have a More Extensive Effect on Topmouth Gudgeon (Pseudorasbora parva) than Chemosensory Cues in Identifying Novel Predators.

Through population expansion and accidental or deliberate introduction, prey commonly encounter novel predators they had never seen before. Several studies have shown that animals can generalize their learned recognition of a familiar predator to novel ones according to predators' identical or similar features. This process in fish mainly depends on the visual and chemosensory cues they receive. However, there is a lack of understanding of the different effects of these two cues. Topmouth gudgeons (Pseudorasbora parva) that had never seen turtles were captured and used as the subjects, and three freshwater turtles of different genera were used as predators. Before and after using one turtle for predator training treatment of topmouth gudgeons, fish responses to visual and chemosensory cues of each turtle were tested and recorded, and it was found that predator training promoted topmouth gudgeons' recognition of the risks represented by visual cues of all three turtles and by chemosensory cues of the turtle that were used in training. These results further verify the generalization of predator recognition in fish and indicate that visual cues have a more extensive effect on fish than chemosensory cues in identifying novel predators, especially predators that are distantly related to the familiar threats.

Effects of 17 α-methyltestosterone on the transcriptome, gonadal histology and sex steroid hormones in Pseudorasbora parva.

In recent years, the increasing use of environmental endocrine disruptors has caused serious environmental pollution and hurt aquatic organisms. It is still risky for aquatic species and humans exposed to 17α-methyltestosterone (MT), however, the harmful effect of MT on fish is still poorly understood. The main purpose of this study is to evaluate the influence of MT on Pseudorasbora parva at multi-levels. We analyzed gonadal histology, the sex steroid hormones, steroidogenic genes expression, and transcriptome profiling of gonads in response to MT in adult P. parva. Through this study, we found MT could inhibit the gonadal development of P. parva, and the growth and development of fish could be delayed by exposure to MT at 200 ng/L. MT could produce disruption effects on fish from multiple pathways, while its interference to the HPGL axis happens primarily through the steroidogenic pathway, e.g., disturbing the expression of crucial genes and sex steroids synthesis. Besides, we constructed 4 RNAseq libraries and obtained 7758 and 11,543 DEGs in females and males, respectively. Interestingly, we found MT had more obvious disruption effects on males than the females, mainly reflected in the immune system. Interestingly, we found three common pathways in both sexes after MT exposure, i.e., cell adhesion molecules, cytokine-cytokine receptor interaction, and neuroactive ligand-receptor interaction. These results confirm the suitability of P. parva as a model fish for aquatic toxicological study and provide us a multidimensional sight for the disruption effects of MT on fish.

Evaluation of toxicological responses and promising biomarkers of topmouth gudgeon (Pseudorasbora parva) exposed to fipronil at environmentally relevant levels.

Fipronil is an insecticide commonly used in agriculture. We report here on the sublethal and sub-chronic effects of fipronil on non-target topmouth gudgeon (Pseudorasbora parva) at environmentally relevant levels. The results showed that fipronil did not cause significant changes in brain acetylcholinesterase activities, glutathione S-transferase (GST) activities in the intestine, and GST, glutamic pyruvic transaminase (GPT), and glutamic oxaloacetic transaminase (GOT) activities in the liver tissues at environmentally relevant levels for 96-h exposure. In the further test for a 12-day exposure, dose-dependent responses of the serum GPT and GOT activities were observed in all treated groups with sublethal concentrations of fipronil. Furthermore, fipronil could reduce the liver mitochondrial membrane fluidity of P. parva, especially with high concentration of fipronil at high temperature. The results suggest that serum GPT and GOT in P. parva might be useful biomarkers for effects of fipronil exposure at environmentally relevant level, and reducing fluidity of liver mitochondrial membrane may be one toxic mechanism of fipronil.

The complete mitochondrial genome of a parasite at the animal-fungal boundary.

BACKGROUND: Sphaerothecum destruens is an obligate intracellular fish parasite which has been identified as a serious threat to freshwater fishes. Taxonomically, S. destruens belongs to the order Dermocystida within the class Ichthyosporea (formerly referred to as Mesomycetozoea), which sits at the animal-fungal boundary. Mitochondrial DNA (mtDNA) sequences can be valuable genetic markers for species detection and are increasingly used in environmental DNA (eDNA) based species detection. Furthermore, mtDNA sequences can be used in epidemiological studies by informing detection, strain identification and geographical spread. METHODS: We amplified the entire mitochondrial (mt) genome of S. destruens in two overlapping long fragments using primers designed based on the cox1, cob and nad5 partial sequences. The mt-genome architecture of S. destruens was then compared to close relatives to gain insights into its evolution. RESULTS: The complete mt-genome of Sphaerothecum destruens is 23,939 bp in length and consists of 47 genes including 21 protein-coding genes, 2 rRNA, 22 tRNA and two unidentified open reading frames. The mitochondrial genome of S. destruens is intronless and compact with a few intergenic regions and includes genes that are often missing from animal and fungal mt-genomes, such as, the four ribosomal proteins (small subunit rps13 and 14; large subunit rpl2 and 16), tatC (twin-arginine translocase component C), and ccmC and ccmF (cytochrome c maturation protein ccmC and heme lyase). CONCLUSIONS: We present the first mt-genome of S. destruens which also represents the first mt-genome for the order Dermocystida. The availability of the mt-genome can assist the detection of S. destruens and closely related parasites in eukaryotic diversity surveys using eDNA and assist epidemiological studies by improving molecular detection and tracking the parasite's spread. Furthermore, as the only representative of the order Dermocystida, its mt-genome can be used in the study of mitochondrial evolution of the unicellular relatives of animals.

Genomic footprints of a biological invasion: Introduction from Asia and dispersal in Europe of the topmouth gudgeon (Pseudorasbora parva).

Facilitated by the intensification of global trading, the introduction and dispersal of species to areas in which they are historically non-native is nowadays common. From an evolutionary standpoint, invasions are paradoxical: not only non-native environments could be different from native ones for which introduced individuals would be ill-adapted, but also small founding population size should be associated with reduced adaptive potential. As such, biological invasions are considered valuable real-time evolutionary experiments. Here, we investigated the population structure and adaptive potential of the highly invasive topmouth gudgeon (Pseudorasbora parva) across Europe and East Asia. We RAD-sequenced 301 specimens from sixteen populations and three distinct within-catchment invaded regions as well as two locations in the native range. With 13,785 single nucleotide polymorphisms, we provide conclusive evidence for a genome-wide signature of two distinct invasion events, in Slovakia and Turkey, each originating from a specific area in the native range. A third invaded area, in France, appears to be the result of dispersal within the invasive range. Few loci showed signs of selection, the vast majority of which being identified in the Slovakian region. Functional annotation suggests that faster early stage development, resistance to pollution and immunocompetence contribute to the invasion success of the local habitats. By showing that populations in the invasive range have different evolutionary histories, our study reinforces the idea that populations, rather than species, are the units to consider in invasion biology.

The complete mitochondrial genome of Pseudorasbora interrupta and phylogeny of Pseudorasbora.

We sequenced the mitochondrial genome of Pseudorasbora interrupta using Illumina technology and additional Sanger sequencing. The assembled 16601 bp mitogenome had a GC content of 40.98% and consisted of 13 protein-coding genes, 22 tRNA genes, two rRNA genes, and one non-coding control region (CR), with a gene order identical to the fishes. In addition, we downloaded the mitogenome of the closely related species Topmouth Gudgeon P. parva. The mitogenomes of P. interrupta and P. parva showed a sequence identity of 99.2% with the previously published P. parva mitogenome. The phylogenetic reconstruction based on 14 Gobioninae mitogenomes supported P. interrupta and its sister species P. parva as a monophyletic group. However, Pseudorasbora was proved to be a polyphyletic group which means amendments will be needed for the taxonomy of this genus.

The rise of the rosette agent in Europe: An epidemiological enigma.

International biodiversity assessments often overlook the role of emerging infectious pathogens in the decline of freshwater fish populations despite the many examples of emerging diseases in other more visible taxa on a global scale. Whilst the introduction of the rosette agent Sphaerothecum destruens in Europe remained an epidemiological enigma, recent findings have shown that this parasite arrived in Europe with the introduction of the healthy carrier Pseudorasbora parva from China nearly 60 years ago and its emergence went unnoticed for over 45 years despite its severe impact on European fish biodiversity. Recent reports on the host and pathogen phylogeny point towards an ancient host-pathogen co-evolution with direct implications on disease risk. Here, we postulate that the observed rapid population decline of native fish species following their infection with virulent strains of S. destruens has underpinned the rapid establishment of P. parva populations during the invasion process. We reviewed the existing evidence supporting the claim of an S. destruens' emergence worldwide and also suggest that the origin of the US strains is to be found among contaminated Asian Oncorhynchus tshawytscha living in sympatry with native Asian P. parva population. Finally, several important preventative steps are suggested as a way to manage the impact of S. destruens on local fish communities.

Selenium accumulation and the effects on the liver of topmouth gudgeon Pseudorasbora parva exposed to dissolved inorganic selenium.

Selenite(IV) and selenate(VI) are the major forms of Se in aquatic ecosystem. In this study, Pseudorasbora parva were exposed to 10, 200 and 1000 µg L-1 selenite and selenate for 28 days. Selenium accumulation, antioxidant enzyme levels, glutathione concentrations, lipid peroxidation and histology were evaluated in livers following exposure. Our results showed that Se(IV) and Se(VI) caused different accumulation patterns in the liver, with a more rapid accumulation of Se with Se(IV) treatment. Both Se species increased hepatic lipid peroxidation after 14 and 28 d (~ 30%). Among the antioxidants examined, the activity of SOD (except day 28) and the cellular levels of GSH were induced by 72-137% at lower concentrations, while the activity of GST was at least 24% lower than that of the control at 200 and 1000 µg L-1 for both Se species at all sampling points. Both forms of Se reduced the hepatosomatic index at 1000 µg L-1 after 28 d. In addition, marked histopathological alterations (10-31%) were observed in the liver of P. parva after exposure to both Se species, with higher frequency in the Se(IV) exposed fish. Liver local necrosis was observed only in the liver of fish exposed to 1000 µg L-1 of Se(IV) (~ 20%). Our results suggest that the ecological impacts of dissolved Se in this freshwater species may also contribute to overall toxicity.

Effects of acute and chronic exposures of fluoxetine on the Chinese fish, topmouth gudgeon Pseudorasbora parva.

Fluoxetine is a selective serotonin reuptake inhibitor used as an antidepressant and has been frequently detected in aquatic environments. However, its effects in fish from Asia remain relatively less studied. In this study, the topmouth gudgeon Pseudorasbora parva was exposed to 0, 50, and 200 µg/L of fluoxetine for 4 h and 42 d. The effects of fluoxetine on biometrics were compared to biochemical endpoints indicative of stress in different fish tissues (brain, liver, gills and intestine) following exposures. In fish exposed for 42 d, lipid peroxidation endpoints were enhanced 80% in the liver and gills. Acetylcholinesterase (AChE) activity was increased 40% after exposure to 50 µg/L and 55% at 200 µg/L following 4 h exposure. In contrast AChE was increased 26% (at 50 µg/L) after 42 d of exposures. Enhanced ethoxyresorufin-O-deethylase activity (EROD) was detected only in fish exposed to 50 µg/L of fluoxetine for 4 h. The activity of α-glucosidase (α-Glu) was also induced (at 200 µg/L) after 4 h of exposure. After 4 h of exposure, the activities of proteases in the intestine were generally inhibited at 200 µg/L. Both 4 h and 42 d exposures resulted in an increased hepatosomatic index (HSI) but did not affect the condition factor (CF). Our results demonstrate that fluoxetine significantly altered biochemical endpoints in P. parva after acute exposure and the morphological changes in liver size were not observed until 42 d of exposure.

Micronuclei and dyskaryosis of erythrocytes and oxidative stress response with endosulfan exposure in topmouth gudgeon Pseudorasbora parva.

Endosulfan is a chlorinated and genotoxic insecticide extensively used worldwide in agriculture. However, residues of endosulfan can be detected in farmland soil and natural water. In this study, toxic effects of endosulfan were studied by measuring micronuclei and dyskaryosis in peripheral erythrocytes of topmouth gudgeon (Pseudorasbora parva). In addition, liver antioxidant enzyme activity and lipid peroxidation level were measured. P. parva were exposed to control and 5 doses (0.12, 0.16, 0.21, 0.31 and 0.62µg/L) of endosulfan for 48h and 96h. The frequencies of micronuclei and dyskaryosis, antioxidant enzyme activity, contents of ROS and lipid peroxidation increased by endosulfan exposure. Compared to controls, frequencies of micronuclei and dyskaryosis were significantly increased with endosulfan exposure, and an obvious dose-response relationship was found. Endosulfan has potential genotoxicity by inducing the oxidative stress and lipid peroxidation, which probably lead to the occurrence of micronuclei and dyskaryosis in erythrocytes.

Laboratory and field validation of a simple method for detecting four species of non-native freshwater fish using eDNA.

This paper presents the first phase in the development and validation of a simple and reliable environmental (e)DNA method using conventional PCR to detect four species of non-native freshwater fish: pumpkinseed Lepomis gibbosus, sunbleak Leucaspius delineatus, fathead minnow Pimephales promelas and topmouth gudgeon Pseudorasbora parva. The efficacy of the approach was demonstrated in indoor tank (44 l) trials in which all four species were detected within 24 h. Validation was through two field trials, in which L. gibbosus was detected 6-12 h after its introduction into outdoor experimental ponds and P. parva was successfully detected in disused fish rearing ponds where the species was known to exist. Thus, the filtration of small (30 ml) volumes of pond water was sufficient to capture fish eDNA and the approach emphasised the importance of taking multiple water samples of sufficient spatial coverage for detecting species of random or patchy distribution.

Associated disease risk from the introduced generalist pathogen Sphaerothecum destruens: management and policy implications.

The rosette agent Sphaerothecum destruens is a novel pathogen, which is currently believed to have been introduced into Europe along with the introduction of the invasive fish topmouth gudgeon Pseudorasbora parva (Temminck & Schlegel, 1846). Its close association with P. parva and its wide host species range and associated host mortalities, highlight this parasite as a potential source of disease emergence in European fish species. Here, using a meta-analysis of the reported S. destruens prevalence across all reported susceptible hosts species; we calculated host-specificity providing support that S. destruens is a true generalist. We have applied all the available information on S. destruens and host-range to an established framework for risk-assessing non-native parasites to evaluate the risks posed by S. destruens and discuss the next steps to manage and prevent disease emergence of this generalist parasite.

Mitochondrial DNA sequence of Pseudorasbora parva (Cyprinidae: Gobioninae).

In this study, the complete mitochondrial genome of Pseudorasbora parva (Cyprinidae: Gobioninae) was determined. The circular mtDNA molecule was 16,601 bp in length which contains 22 transfer RNA genes, 13 protein-coding genes, 2 ribosomal RNA genes and non-coding control region (D-loop). The critical central conserved sequences were also detected. Its total A + T content is 55.97%. The mitochondrial genome can contribute to the studies on geographical distribution and genetic diversity of P. parva resources, as well as molecular phylogeny and species identification in Cyprinidae.

Toxic effects of permethrin on Pseudorasbora parva.

The present study deals with acute toxicity and hematological, histopathological and genotoxical effects of permethrin, a synthetic pyrethroid, on Pseudorasbora parva. Acute toxicity of 96-hrs LC50 value was found to be 88.25 (84.60-92.63) µgl-1. Sublethal dose was taken as 8.82 µgl-1 (the 1/10 of the LC50 value) in bio-experiments. Micronucleus changes in blood erythrocyte and hemotocyte level in P. parva exposed to sub-lethal concentration were investigated. Difference between nucleolus abnormalities in the experimental and control group was found to be statistically significant (t-test). Micronucleus frequency was found to be 8.26. The hematocrit level in control and experimental groups were found to be 24.43% and 14.673%. No pathological symptoms were observed in the muscle of P. parva exposed to sublethal dose for 96 hrs. Pathological symptoms observed after 96 hours from permethrin administration in other organs were: Fusion, Telangiectasis, epithelial lifting and hyperemia in gills; hydropic degeneration, lipid degeneration and passive hyperemia in liver and enlargement of cavum glomeruli and Bowman space in kidneys and hemorrhage, edema and hyperemia in brain, respectively.

Metorchis orientalis founded in basin of Wuhu City,Anhui Province / 中国血吸虫病防治杂志

Objective To investigate the epidemic situation of Metorchis orientalis in Wuhu City Anhui Province. Meth?ods Three lakes Fengming Longwo and Kui lakes were selected in Wuhu City and the poultries around the lakes and fresh?water fishes in the lakes were captured to test the infection of M. orientalis and the infection rates were calculated. Results The adult worms of M. orientalis were found in gall bladder and hepatic duct of domestic ducks with infection rate of 16.7%. The metacercariae of M. orientalis were discovered in the muscle of Pseudorasbora parva and Pseudogobio rivularis with infection rates of 7.13%and 3.38%respectively. Conclusion M. orientalis is endemic in Wuhu City which should be paid enough at?tention to the animal husbandry aquaculture and medicine.