Water quality in a shallow eutrophic lake is unaffected by extensive thinning of planktivorous and benthivorous fish species.

Ambitious to fulfill the European Water Framework Directive obligations, the European governments support projects to rehabilitate lakes with poor water quality. However, most lake restorations having relied on biomanipulation by fish thinning have failed to improve or even maintain water quality. Previous attempts removed all target fish species simultaneously, thus making it impossible to assess the specific impact of each feeding group on water chemistry. Lake Bromme was selected for extensive, time-selective fish biomanipulation to improve water clarity and promote submerged macrophytes and piscivorous fish stocks over a three-year monitoring period. Thinning of adult benthivorous bream (Abramis brama) and tench (Tinca tinca) was conducted throughout year one while thinning in years two and three targeted planktivorous roach (Rutilus rutilus), juvenile bream, and small perch (Perca fluviatilis). Yearly fish surveys assessed changes in fish population structure and biomass. Water quality parameters were monitored continually, and the cover of submerged macrophytes was surveyed annually via sonar. We found no improvement in water clarity or reductions of nutrients, organic particles, chlorophyll concentrations, or watercolor, despite a 6-fold thinning of total estimated fish biomass, from 112 to 19 kg ha-1. Over the period, the macrophyte cover increased from 0.8 to 13.5 %, but no recruitment of large piscivorous fish (perch and pike (Esox lucius) > 10 cm) was detected. We found higher correlations of particle concentration and water clarity to water temperature than to wind speed, which indicates sediment particle resuspension by the remaining fish community (mostly carp Cyprinus carpio) that forage on benthos in shallow lakes. Further system-ecological research in Lake Bromme should evaluate whether thinning the stock of carp and increasing plant cover may improve water quality and test which optical properties sustain high water turbidity and prevent shallow, eutrophic lakes like Lake Bromme from responding to intense fish thinning.

Cold thermopeaking-induced drift of nase Chondrostoma nasus larvae.

Research on how intermittent water releases from hydropower plants affect the early life stages of fish has advanced in the last years, focusing not only on the direct impacts of rapid flow changes (hydropeaking), but also on the short-term fluctuations in water temperature (thermopeaking). Flow and thermal fluctuations caused by hydropeaking may affect fish movement patterns and migration at critical stages of a species' life cycle, e.g., by inducing passive downstream drift. Using two experimental outdoor channels, we investigated how nase (Chondrostoma nasus, Cypriniformes) larvae respond to a rapid drop in water temperature during hydropeaking (simulating a cold thermopeaking event), reaching on average 5.5 °C under peak flow (maximum discharge) conditions, in comparison with a hydropeaking treatment with a constant water temperature regime. Responses of fish larvae were analyzed during acclimation, up-ramping (increase in discharge), peak flow and down-ramping (decrease in discharge) phases. Fish drift increased during peak flow in the cold thermopeaking treatment compared to hydropeaking. Higher drift rates were also negatively associated with pronounced water temperature drops during peak flow conditions. In addition, the starting temperature of the experiment influenced drift during up-ramping. Overall, the results suggest that cold thermopeaking may increase drift in the early life stages of cypriniform fish compared with hydropeaking with stable water temperature. Hence, monitoring and active water temperature adjustments following hydropower releases should be adopted as strategies to mitigate power plant-related impacts on aquatic organisms. Supplementary Information: The online version contains supplementary material available at 10.1007/s00027-023-00955-x.

Cardiac Hypoxia Tolerance in Fish: From Functional Responses to Cell Signals.

Aquatic animals are increasingly challenged by O2 fluctuations as a result of global warming, as well as eutrophication processes. Teleost fish show important species-specific adaptability to O2 deprivation, moving from intolerance to a full tolerance of hypoxia and even anoxia. An example is provided by members of Cyprinidae which includes species that are amongst the most tolerant hypoxia/anoxia teleosts. Living at low water O2 requires the mandatory preservation of the cardiac function to support the metabolic and hemodynamic requirements of organ and tissues which sustain whole organism performance. A number of orchestrated events, from metabolism to behavior, converge to shape the heart response to the restricted availability of the gas, also limiting the potential damages for cells and tissues. In cyprinids, the heart is extraordinarily able to activate peculiar strategies of functional preservation. Accordingly, by using these teleosts as models of tolerance to low O2, we will synthesize and discuss literature data to describe the functional changes, and the major molecular events that allow the heart of these fish to sustain adaptability to O2 deprivation. By crossing the boundaries of basic research and environmental physiology, this information may be of interest also in a translational perspective, and in the context of conservative physiology, in which the output of the research is applicable to environmental management and decision making.

Effect of thermo-velocity barriers on fish: influence of water temperature, flow velocity and body size on the volitional swimming capacity of northern straight-mouth nase (Pseudochondrostoma duriense).

Water temperature and flow velocity directly affect the fish swimming capacity, and thus, both variables influence the fish passage through river barriers. Nonetheless, their effects are usually disregarded in fishway engineering and management. This study aims to evaluate the volitional swimming capacity of the northern straight-mouth nase (Pseudochondrostoma duriense), considering the possible effects of water temperature, flow velocity and body size. For this, the maximum distance, swim speed and fatigue time (FT) were studied in an outdoor open-channel flume in the Duero River (Burgos, Spain) against three nominal velocities (1.5, 2.5 and 3 m s-1 ) and temperatures (5.5, 13.5 and 18.5°C), also including the changes between swimming modes (prolonged and sprint). Results showed that a nase of 20.8 cm mean fork length can develop a median swim speed that exceeds 20.7 BL s-1 (4.31 m s-1 ) during a median time of 3.4 s in sprint mode, or 12.2 BL s-1 (2.55 m s-1 ) for 23.7 s in prolonged mode under the warmest scenario. During prolonged swimming mode, fish were able to reach further distances in warmer water conditions for all situations, due to a greater swimming speed and FT, whereas during sprint mode, warmer conditions increased the swim speed maintaining the FT. In conclusion, the studied temperature range and flow velocity range influence fish swimming performance, endurance and distance travelled, although with some differences depending on the swimming mode. The provided information goes a step forward in the definition of real fish swimming capacities, and in turn, will contribute to establish clear passage criteria for thermo-velocity barriers, allowing the calculation of the proportion of fish able to pass a barrier under different working scenarios, as well designing of the optimized solutions to improve the fish passage through river barriers.

REVIVE: A feasibility assessment tool for freshwater fish conservation translocations in Mediterranean rivers.

Conservation translocation is a management action applied for population recovery of threatened freshwater fishes, often however with partially successful outcome, mainly due to inadequate feasibility assessment prior to the translocation. Up to date, feasibility assessments have been mainly focused on economically important species (e.g., salmonids) inhabiting perennial rivers, while little attention has been given to fish translocations in rivers in Mediterranean climate areas. In this study, we developed a robust feasibility assessment tool for freshwater fish translocations in Mediterranean-type riverine ecosystems within an interdisciplinary, multispecies approach. The REVIVE tool integrates quantitative and semi-quantitative data, incorporates uncertainty and consists of two main components. The first component is the evaluation of the potential release water bodies (R-WBs) for their suitability for the planned translocation, incorporating a number of essential criteria for Mediterranean rivers, with emphasis on flow regime and habitat quantity. Additional criteria include the current and historical presence of the target species, water and biological quality, habitat suitability in terms of the ecological requirements of the target species, alien invasive species' pressure, and hydromorphological pressures, including their mitigation potential. The second component is the evaluation of the potential source water bodies (S-WBs) in terms of genetic compatibility and provision of a sufficient number of propagules. A trial application in a Mediterranean basin (Vassilopotamos River, Southern Greece) for the potential translocation of two threatened cyprinids in five R-WBs indicated the robustness of the tool. This integrative, flexible tool combines several elements identified as essential in reintroduction biology and can have wider applications, for a multitude of freshwater fish taxa and riverine systems, maximizing the success of planned translocation actions by natural resources' managers. Modifications to enable its transferability to other river types or fish taxa are also discussed.

Length-weight relationship: eight species of Cyprinidae from river Panjkora, Khyber Pakhtunkhwa, Pakistan / Relação peso-comprimento: oito espécies de Cyprinidae do rio Panjkora, Khyber Pakhtunkhwa, Paquistão

Seven hundred and twenty four fish specimens were captured from March to September 2016. The materials used in the current study were cast nets, hand nets. Eight cyprinid fish species were studied for their length weight relationships. Parameter b in the LWR was 3.03, 3.06, 3.02, 2.29, 2.82, 3.43, 2.73 and 2.47 for Schizothorax plagiostomus, Schizothorax esocinus, Racoma labiata, Tor putitora, Barilius vagra, Garra gotyla, Puntius ticto and Arassius auratus respectively. Current study is the first attempt on the LWRs of cyprinid species, provide a baseline approach for conservation and /management of local fish fauna of economic importance.

Um total de 724 espécimes de peixes foi capturado de março a setembro de 2016. Os materiais usados no presente estudo foram redes de lançamento, redes de mão. Oito espécies de peixes ciprinídeos foram estudadas quanto às suas relações peso/comprimento. O parâmetro b no LWR foi 3,03, 3,06, 3,02, 2,29, 2,82, 3,43, 2,73 e 2,47 para Schizothorax plagiostomus, Schizothorax esocinus, Racoma labiata, Tor putitora, Barilius vagra, Garra gotyla, Puntius ticto e Arassius auratus respectivamente. O estudo atual é a primeira tentativa sobre os LWRs de espécies de ciprinídeos, fornecendo uma abordagem de base para a conservação e o manejo da ictiofauna local de importância econômica.

Length-weight relationship: eight species of Cyprinidae from river Panjkora, Khyber Pakhtunkhwa, Pakistan

Abstract Seven hundred and twenty four fish specimens were captured from March to September 2016. The materials used in the current study were cast nets, hand nets. Eight cyprinid fish species were studied for their length-weight relationships. Parameter b in the LWR was 3.03, 3.06, 3.02, 2.29, 2.82, 3.43, 2.73 and 2.47 for Schizothorax plagiostomus, Schizothorax esocinus, Racoma labiata, Tor putitora, Barilius vagra, Garra gotyla, Puntius ticto and Arassius auratus respectively. Current study is the first attempt on the LWRs of cyprinid species, provide a baseline approach for conservation and /management of local fish fauna of economic importance.

Resumo Um total de 724 espécimes de peixes foi capturado de março a setembro de 2016. Os materiais usados no presente estudo foram redes de lançamento, redes de mão. Oito espécies de peixes ciprinídeos foram estudadas quanto às suas relações peso/comprimento. O parâmetro b no LWR foi 3,03, 3,06, 3,02, 2,29, 2,82, 3,43, 2,73 e 2,47 para Schizothorax plagiostomus, Schizothorax esocinus, Racoma labiata, Tor putitora, Barilius vagra, Garra gotyla, Puntius ticto e Arassius auratus respectivamente. O estudo atual é a primeira tentativa sobre os LWRs de espécies de ciprinídeos, fornecendo uma abordagem de base para a conservação e o manejo da ictiofauna local de importância econômica.

Length-weight relationship: eight species of Cyprinidae from river Panjkora, Khyber Pakhtunkhwa, Pakistan / Relação peso-comprimento: oito espécies de Cyprinidae do rio Panjkora, Khyber Pakhtunkhwa, Paquistão

Abstract Seven hundred and twenty four fish specimens were captured from March to September 2016. The materials used in the current study were cast nets, hand nets. Eight cyprinid fish species were studied for their length-weight relationships. Parameter b in the LWR was 3.03, 3.06, 3.02, 2.29, 2.82, 3.43, 2.73 and 2.47 for Schizothorax plagiostomus, Schizothorax esocinus, Racoma labiata, Tor putitora, Barilius vagra, Garra gotyla, Puntius ticto and Arassius auratus respectively. Current study is the first attempt on the LWRs of cyprinid species, provide a baseline approach for conservation and /management of local fish fauna of economic importance.

Resumo Um total de 724 espécimes de peixes foi capturado de março a setembro de 2016. Os materiais usados ​​no presente estudo foram redes de lançamento, redes de mão. Oito espécies de peixes ciprinídeos foram estudadas quanto às suas relações peso/comprimento. O parâmetro b no LWR foi 3,03, 3,06, 3,02, 2,29, 2,82, 3,43, 2,73 e 2,47 para Schizothorax plagiostomus, Schizothorax esocinus, Racoma labiata, Tor putitora, Barilius vagra, Garra gotyla, Puntius ticto e Arassius auratus respectivamente. O estudo atual é a primeira tentativa sobre os LWRs de espécies de ciprinídeos, fornecendo uma abordagem de base para a conservação e o manejo da ictiofauna local de importância econômica.

Fish Innate Immune Response to Viral Infection-An Overview of Five Major Antiviral Genes.

Fish viral diseases represent a constant threat to aquaculture production. Thus, a better understanding of the cellular mechanisms involved in establishing an antiviral state associated with protection against virus replication and pathogenesis is paramount for a sustainable aquaculture industry. This review summarizes the current state of knowledge on five selected host innate immune-related genes in response to the most relevant viral pathogens in fish farming. Viruses have been classified as ssRNA, dsRNA, and dsDNA according to their genomes, in order to shed light on what those viruses may share in common and what response may be virus-specific, both in vitro (cell culture) as well as in vivo. Special emphasis has been put on trying to identify markers of resistance to viral pathogenesis. That is, those genes more often associated with protection against viral disease, a key issue bearing in mind potential applications into the aquaculture industry.

Activity, boldness and schooling in freshwater fish are affected by river salinization.

Rivers are experiencing increasing anthropogenic pressures and salinity has shown to affect freshwater fish behaviour, potentially disrupting ecological processes. In this study, the aim was to determine the sub-lethal effects of salinization on freshwater fish behaviour, using a widespread native cyprinid species, the Iberian barbel (Luciobarbus bocagei) as the model species. Behavioural trials in a mesocosms setting were performed to assess the effects of three levels of a salinity gradient - control (no salt added to the water, 0.8 mS/cm), low (9 mS/cm), and high concentration (18 mS/cm) - on fish routine activity, shoal cohesion and boldness. Upon increasing the salinity levels in the flume-channels, fish showed a significant reduction on their i) swimming activity (76% of searching behaviour in the control vs. 57% in high salinity), and ii) shoal cohesion (0.95 shoal cohesion ratio in the control vs. 0.76 in high salinity), while iii) an increase of bolder individuals, measured by a higher number of attempts to escape the altered environment (106 total jumps in the control vs. 262 in high salinity), was simultaneously observed. Behavioural changes in fish can reflect shifts in ecological condition. Thus, the behavioural responses of fish caused by salinization stress should be further researched, in addition to the interaction with other environmental stressors, in order to understand the true scope of the consequences of salinization for fish species.

Spatial distribution of native fish species in tributaries is altered by the dispersal of non-native species from reservoirs.

Reservoirs are known to alter temperature and flow regimes, shift nutrient cycles, reduce downstream species diversity and enable a predominantly upstream spread of non-native species. However, information about the seasonal dynamics of the spread of non-natives from a reservoir to its tributaries and the further consequences regarding the spatial distribution of native species is rare. We observed the occurrence of fish in the Vltava River and its tributaries (Elbe catchment area, central Europe) upstream of the Lipno Reservoir for five consecutive years. We radio-tagged two non-native and four native species. To detect assemblage spatial variability, we sampled sites in the study area by electrofishing twice per year (spring and autumn). We expected seasonal trends in non-native species appearance in upstream reservoir tributaries and, conversely, low motivation of native fishes to descend to the reservoir. By analysing nearly 3000 individuals of 21 species from the longitudinal profile of the study area, we observed an effect of reservoir distance on the native species ratio in the upper Vltava catchment area, i.e., an increase in distance increased the native species proportion, and the opposite was observed for non-native species. Analyses of 3798 tracking positions of 193 tagged individuals showed massive spring dispersal of non-native species from the reservoir to the main tributary, the Vltava River, and their return to the reservoir for wintering. Their upstream movement positively correlated with an increase in flow rate. Native Salmo trutta showed a specific shift from the Vltava River to smaller streams during the summer, when the presence of non-native species in the Vltava River was most significant. These findings indicate that non-native species repeatedly spread from the reservoir to the upstream river stretch and its tributaries and potentially compete with native species for resources.

Condition Index, Reproduction and Feeding of Three Non-Obligatory Riverine Mekong Cyprinids in Different Environments.

Condition index, reproduction and feeding of three non-obligatory riverine Mekong cyprinids namely Hampala dispar, Hampala macrolepidota and Osteochilus vittatus were examined. The samples were from the Nam Ngiep (NN) River and Bueng Khong Long (BKL) Swamp, which are the representative of the lotic- and lentic-environments, respectively. These two habitats lay in the same geographical area but on the opposite banks of the Mekong mainstream. The samplings were conducted between May 2017 and April 2018. There were 365 H. dispar, 259 H. macrolepidota and 298 O. vittatus samples in this study. The condition index of all three species were beyond 90% implying they can live well in both lotic and lentic environments. Reproductions of all three species were taken place in both environments with two peaks at the onset and end of rainy season. The samples from BKL showed early maturation than NN samples in all three (3) species. Feeding plasticity, though dominant by insects, was observed in Hampala spp., while O. vittatus can utilise any available detritus in both environments. Results clearly show that all the three selected non-obligatory riverine fish species can live very well in either lotic or lentic environments and imply that they can adjust themselves to reservoir environment.

Comparison of artificial spawning effectiveness of hCG, CPH and GnRHa in combination with dopamine inhibitors in a wild strain of ide Leuciscus idus (L.) in hatchery conditions.

Optimization of artificial reproduction, by increasing the survival rate of embryos and hatching rate, is of major importance for reducing genetic diversity, especially in fish captured from their natural habitat that subsequently spawn in hatcheries. The artificial reproduction of ide, Leuciscus idus (L.) was conducted in controlled conditions. The spawning agents included: different doses of human chorionic gonadotropin (hCG) that was compared with common carp pituitary homogenate (CPH), Ovopel - a commercial agent for induction of spawning that contains mammalian gonadotropin releasing hormone analogue (mGnRHa) with dopamine antagonists (DA): metoclopramide (MET) and Ovaprim - a commercial agent containing salmon gonadotropin releasing hormone analogue (sGnRHa) and a dopamine antagonists (DA): domperidone (DOM). There were no ovulations in females from control groups. There were no differences between the ovulation rates (90 %) or embryo survival (> 92 %) and hatching rates (> 91 %) when there was administration of hCG doses between 500 and 1000 IU/kg. When there was comparison of different spawning agents, the ovulation rate was 100 % for all treated groups. There were the shortest and longest latency times to the time of ovulation after administration of CPH (26 h) and hCG (79 h), respectively. The greatest embryo survival (> 93 %) and hatching (> 91 %) rates occurred as a result of hCG administration with these values being slightly greater than when there was treatment with Ovaprim. The association between latency time and hatching rate indicated that when there was a slower final oocyte maturation (FOM) there were greater hatching rates.

Overlapping niches between two co-occurring invasive fish: the topmouth gudgeon Pseudorasbora parva and the common bleak Alburnus alburnus.

Invasive fish species impact aquatic ecosystems and modify native communities, often leading to a decline in local species. These ecological impacts include the transmission of pathogens, predation, competition as well as hybridization. Two invasive fish species, the common bleak Alburnus alburnus and the topmouth gudgeon Pseudorabora parva, have both been recently found co-occurring in several regions of southern Europe, such as the Italian Arno River. Nonetheless, the trophic relationships among invasive fish species, especially cyprinids, remain poorly understood, and no studies have reported the trophic interaction between these two species. This study compared length-weight relationship and used stomach content and stable isotope analysis of two co-occurring populations in the Arno River to characterize the growth and overlap of potential trophic niches. It also found similar allometric growth in both species, a wider generalist trophic niche for P. parva and a more specialized niche for A. alburnus. A considerable niche overlap was found, suggesting that feeding competition can occur if resources were to be limited. Moreover, the niche of P. parva was more likely to overlap with that of A. alburnus than vice versa, suggesting that P. parva can be considered as a potential over competitor. Nonetheless, the authors found in the overlapping populations no evidence of realized competition, probably avoided through a combination of fine-scale mechanisms. They also highlighted that these two invasive species can co-exist and share resources, at least in an open ecosystem like a river, thus potentially doubling up their trophic impact on local communities.

Phylogenetic and secondary RNA structure analysis of monogenean gill ectoparasites(Dactylogyrus spp.) parasitizing certain freshwater fishes.

The current study is the first phylogenetic and secondary RNA structure analysis of Dactylogyrus species parasitising gill filaments of Iraqi cyprinid fishes. Most previous phylogenetic studies have targeted on primary DNA sequence data. Nevertheless, RNA secondary configuration is principally helpful in systematics since they comprise features that do not appear in the primary sequence and provide morphological information. The primary objective was molecular-based identification of Dactylogyrids species using evolutionary tree and secondary RNA structure prediction. A total of 681 fish were collected from the Lesser Zab River in the northeast of Iraq in the sub-district of Altun-Kopru from August 2016 to September 2017 and brought to the Zoology Research Laboratory, Salahaddin University-Erbil, Iraq. All fish were classified as 18 cyprinid species. The species of Dactylogyrus were identified by the 28S rDNA subunit using PCR and sequencing methods, and the obtained nucleotide sequences were then compared with the available GenBank sequences. Phylogenetic relationships were concluded using Neighbour-Joining (NJ), Maximum Likelihood (ML), and Minimum Evolution (ME) methods. The results justify the validation of 11 Dactylogyrus species (three of them were newly recorded in Iraq). Additionally, out of nine infected fish species, seven of them were regarded as a new host for Dactylogyrus species. Secondary RNA configuration prediction using minimum free energy was considered as a hopeful tool for species identification. This was considered the first comprehensive phylogenetic study in the area. It was concluded that PCR sequencing, phylogenetic and secondary RNA analysis were proper molecular methods for identifying Dactylogyrids species on the gills of fishes.

Imidacloprid induces adverse effects on fish early life stages that are more severe in Japanese medaka (Oryzias latipes) than in zebrafish (Danio rerio).

Neonicotinoids are widely used insecticides that have frequently been found in freshwater with concentrations ranging from ng to µg/L. It is known that these compounds impact non-target invertebrates, such as bees and gammaridae, in terms of toxicity and behavior, but impacts and species differences on vertebrates such as fish are little explored. The aim of this study was to investigate and compare the effects of one widely used neonicotinoid, imidacloprid, on development and behavior of two fish model species: Zebrafish (Danio rerio) and Japanese medaka (Oryzias latipes). Fish were exposed for 5 (zebrafish) and 14 (medaka) days from 0.2 to 2000 µg/L imidacloprid by aqueous exposure. Survival, development, behavior and histological features were monitored and organism-internal concentrations and biotransformation products measured. Imidacloprid caused sublethal effects in both species but the effects were much stronger in medaka with deformities, lesions and reduced growth being the most prominent impacts. Due to the overall longer time of development, time-integrated exposure of medaka was about 2-fold higher compared to zebrafish, potentially accounting for parts of the sensitivity differences. Our results underline the importance of taking species sensitivity differences into account especially when considering that medaka responded at imidacloprid concentrations that have been measured in the environment.

Out-of-season artificial reproduction of common dace (Leuciscus leuciscus L.) under controlled conditions.

This study focused on the artificial reproduction of common dace Leuciscus leuciscus (L.) outside the reproductive season. The results indicate there is the possibility of initiating the reproducion in individuals of this before the natural spawning season. There could be induction of spermiation by altering the environmental conditions. For females, hormonal injections were necessary for induction of final oocyte maturation and ovulation. Generally, there were high percentages of spermiation (100%) and ovulation (87%-100%) as well as low mortality (0%-11% and 7%-13% for males and females, respectively) among the induced spawners. The greatest embryo survival occurred when Ovaprim (84.4%) or hCG (89.6%) was administered, although the latency time using hCG was at least twice as long compared to when other spawning agents were used (84-92 hrs and 30-44 hrs). The results from present study could be applicable for optimization of breeding stock numbers in aquaculture enterprises and in providing insights for conservation of L. leuciscus endangered populations.

MicroRNA Alternations in the Testes Related to the Sterility of Triploid Fish.

The knowledge of understanding the molecular traits of the sterile triploid fish is sparse. Herein, we analyzed the microRNA (miRNA) alternations in the testes of the sterile triploid fish produced by crossing the tetraploid fish with the diploid fish, compared with those of tetraploids and diploids used as the controls. A total of 136, 134, and 142 conserved miRNAs and 105, 112, and 119 novel miRNAs were identified in the diploid, triploid, and tetraploid fish, respectively. The genes targeted by the differentially expressed miRNAs were identified and were enriched in the GO term cell surface receptor signaling pathway, cellular process, G-protein coupled receptor signaling pathway, and metabolic process. KEGG pathway enrichment was also assessed to evaluate the target genes with differentially expressed miRNAs and these genes were enriched in four pathways (synthesis and degradation of ketone bodies, pentose and glucuronate interconversions, cyanoamino acid metabolic process, and ascorbate and aldarate metabolism). Nine differentially expressed miRNAs were verified by quantitative real-time PCR analysis (qPCR). The upregulated miRNAs in triploids, including miR-101a, miR-199-5p, miR-214, miR-222, and miR-193a, showed the same results with high-throughput sequencing. Among the selected downregulated miRNAs, miR-7b and miR-153b had significantly lower expression levels in triploids. Dnah3 and Tekt1 genes targeted by miR-199-5p showed lower expression in triploids by qPCR. These verified differentially expressed miRNAs may participate in testicular development and sperm activity by targeting functional genes, which were identified with differential expression in the triploid. This evidence provides insights into the epigenetic regulatory mechanisms of sterility in triploid cyprinids.

Ecto- and endo-parasitic monogeneans (Platyhelminthes) on cultured freshwater exotic fish species in the state of Morelos, South-Central Mexico.

An extensive parasitological study of 365 freshwater exotic fish specimens belonging to 13 species of seven families (Cichlidae, Cyprinidae, Osphronemidae, Pangasidae, Poeciliidae, Characidae, and Loricariidae) collected from 31 Aquaculture Production Units (APU) from Central Mexico revealed the occurrence of 29 ecto- and endo-parasitic monogeneans found on gills and stomachs: Cichlidogyrussclerosus, C.thurstonae, C.tilapiae, Cichlidogyrus sp. 1, Cichlidogyrus sp. 2, Enterogyruscoronatus, E.malmbergi, Gusseviaspiralocirra, Sciadicleithrumiphthimum, Sciadicleithrum sp., Scutogyruslongicornis (all Dactylogyridae), Gyrodactyluscichlidarum, and G.yacatli (Gyrodactylidae) on Oreochromisniloticus, Pterophyllumscalare and Hemichromis sp. (Cichlidae); Dactylogyrusbaueri, D.formosus, D.intermedius, D.vastator, D.extensus, Dactylogyrus sp. (all Dactylogyridae), and G.kobayashii on Carassiusauratus, Cyprinuscarpio and Ctenopharyngodonidella (Cyprinidae); Trianchoratusacleithrium and T.trichogasterium (Dactylogyridae) on Trichogastertrichopterus (Osphronemidae); Thaparocleiduscaecus, T.siamensis (Dactylogyridae), and Dactylogyridae sp. on Pangasianodonhypophthalmus (Pangasidae); G.poeciliae on Poeciliareticulata (Poeciliidae); Diaphorocleidusarmillatus (Dactylogyridae) on Gymnocorymbusternetzy (Characidae); Unilatusunilatus (Dactylogyridae) and Gyrodactylidae sp. on Hypostomus sp. (Loricariidae). The paramount importance of the establishment of these monogeneans due to the importation/exportation of non-native ornamental and other exotic host fish species cultured for food in Mexico is briefly discussed. Quarantine is recommended for all transferred host species.

Neural connections of the pretectum in zebrafish (Danio rerio).

The pretectum is a complex region of the caudal diencephalon which in adult zebrafish comprises both retinorecipient (parvocellular superficial, central, intercalated, paracommissural, and periventricular) and non-retinorecipient (magnocellular superficial, posterior, and accessory) pretectal nuclei distributed from periventricular to superficial regions. We conducted a comprehensive study of the connections of pretectal nuclei by using neuronal tracing with fluorescent carbocyanine dyes. This study reveals specialization of efferent connections of the various pretectal nuclei, with nuclei projecting to the optic tectum (paracommissural, central, and periventricular pretectal nuclei), the torus longitudinalis and the cerebellar corpus (paracommissural, central, and intercalated pretectal nuclei), the lateral hypothalamus (magnocellular superficial, posterior, and central pretectal nuclei), and the tegmental regions (accessory and superficial pretectal nuclei). With regard to major central afferents to the pretectum, we observed projections from the telencephalon to the paracommissural and central pretectal nuclei, from the optic tectum to the paracommissural, central, accessory and parvocellular superficial pretectal nuclei, from the cerebellum to the paracommissural and periventricular pretectal nuclei and from the nucleus isthmi to the parvocellular superficial and accessory pretectal nuclei. The parvocellular superficial pretectal nucleus sends conspicuous projections to the contralateral magnocellular superficial pretectal nucleus. The composite figure of results reveals large differences in connections of neighbor pretectal nuclei, indicating high degree of nuclear specialization. Our results will have important bearings in functional studies that analyze the relationship between specific circuits and behaviors in zebrafish. Comparison with results available in other species also reveals differences in the organization and connections of the pretectum in vertebrates.