Corticosteroid plasma kinetics and gonadal receptor gene expression during the reproductive cycle in female Eurasian Perch: Investigation of the roles of corticosteroids in vitellogenesis.

To improve the quality of reproduction in Eurasian perch, Perca fluviatilis L., which is a promising candidate for Eurasian freshwater aquaculture that is currently cultivated in recirculating aquaculture systems (RAS), investigating the hormones that mediate and affect reproduction in this species is indispensable. The literature defines a group of four major corticosteroids (11-deoxycorticosterone, 11-deoxycortisol, corticosterone and cortisol) that might mediate critical stages of reproduction in female perch. Unfortunately, neither the basic roles nor the kinetics of these four corticosteroids throughout the reproductive cycle of female perch have been well defined to date. In this study, we therefore elucidated the plasma kinetics of these four corticosteroids during the reproductive cycle of domesticated female perch while monitoring the expression of the different receptors and enzymes that mediate their production and possible functions. Additionally, we performed an in vitro experiment during late vitellogenesis to investigate the possible direct roles of these steroids during that stage. Our results revealed that these four corticosteroids were detectable throughout the reproductive cycle, and the levels of most of them (11-deoxycorticosterone, 11-deoxycortisol, and cortisol) fluctuated significantly depending on the stage of reproduction. 11-Deoxycorticosterone and 11-deoxycortisol exhibited their highest levels, 1.8 ng/ml and 58 ng/ml, respectively, at the beginning of the reproductive cycle. By the end of the reproductive cycle, 11-deoxycortisol and cortisol plasma levels exhibited a surge, reaching 58 ng/ml and 150 ng/ml, respectively. During the perch reproductive cycle, the corticosteroid receptor complex is not regulated only at the hormone level, as the expression levels of all corticosteroid receptor genes showed a progressive and similar decline. In vitro exposure of vitellogenic oocytes to some of these corticosteroids (11-deoxycorticosterone and 11-deoxycortisol) induced an increase in yolk globule diameter and a decrease in the density of yolk globules, which indicates the involvement of both of these hormones in yolk globule coalescence. Taken together, these results implicate corticosteroids in the reproductive cycle, although the related cellular mechanisms remain to be investigated.

Assessing Genetic Variation in Wild and Domesticated Pikeperch Populations: Implications for Conservation and Fish Farming.

The pikeperch is a freshwater/brackish water fish species with growing interest for European aquaculture. Wild populations show signs of decline in many areas of the species natural range due to human activities. The comparative evaluation of genetic status in wild and domesticated populations is extremely useful for the future establishment of genetic breeding programs. The main objective of the present study was to assess and compare the genetic variability of 13 domesticated populations from commercial farms and 8 wild populations, developing an efficient microsatellite multiplex tool for genotyping. Partial cytochrome b gene sequences were also used to infer phylogeographic relationships. Results show that on average, the domesticated populations do not exhibit significantly lower levels of genetic diversity compared to the wild ones and do not suffer from inbreeding. Nuclear data provide evidence that pikeperch populations in Europe belong to at least two genetically differentiated groups: the first one is predominantly present in Northern Europe and around the Baltic Sea, while the second one comprises populations from Central Europe. In this second group, Hungarian origin populations constitute a differentiated stock that needs special consideration. Aquaculture broodstocks analyzed appear to contain fish of a single origin with only a few exceptions.

The effect of two different experimental rearing temperatures on the quality and the large-scale cryopreservation of Eurasian perch (Perca fluviatilis) sperm.

Eurasian perch is an important fish species for European aquaculture diversification, but the quality of reproduction still remains one of the main limitations for further industry development. In particular, the optimal condition to obtain the best quality of sperm is poorly understood. The aim of our study was to measure the possible effects of two experimental rearing temperatures (6 °C and the conventionally used 12 °C) and of hormonal stimulation, on the motility parameters (pMOT, VCL, VSL, LIN, ALH, BCF), osmolality and fertilizing capacity of Eurasian perch sperm at the end of the reproductive cycle. A prior untested, large-scale (5 mL cryotube and Polystyrene box) cryopreservation method was implemented using fresh sperm obtained from the two above mentioned temperature groups. Males were injected with 100 µg body weight kg-1 sGnRHa. No significant difference was recorded between the two rearing temperatures and between the saline control and sGnRHa treated groups on the different features of sperm quality. A similar fertilization rate was monitored in all sGnRHa treated (6 °C: 69 ± 13%, 12 °C: 81 ± 11%) and saline control groups (6 °C: 79 ± 10%, 12 °C: 87 ± 4%). Correspondingly, no significant difference in hatching rate was observed in the sGnRHa injected (6 °C: 27 ± 9%, 12 °C: 40 ± 20%) and saline control (6 °C: 35 ± 18%, 12 °C: 36 ± 7%) males. However, a notable negative effect of freezing process on sperm movement was observed following thawing in both temperature groups. No significant difference in the motility parameters was measured between the two temperature groups following large-scale cryopreservation. Furthermore, a similar result was observed in the fertilizing capacity (6 °C: 79 ± 10%, 12 °C: 75 ± 8) of thawed sperm as well as in the hatching rate (6 °C: 52 ± 13%, 12 °C: 46 ± 19%). Our results indicate that fresh Eurasian perch sperm can tolerate a reduced rearing temperature following hormonal treatment. The adopted large-scale cryopreservation method could be used efficiently in the future for the fertilization of large amounts of Eurasian perch eggs following a precise standardization process.

Split it up and see: using proxies to highlight divergent inter-populational performances in aquaculture standardised conditions.

BACKGROUND: Considering wild inter-populational phenotypic differentiation can facilitate domestication and subsequent production of new species. However, comparing all populations across a species range to identify those exhibiting suitable key traits for aquaculture (KTA; i.e. important for domestication and subsequent production) expressions is not feasible. Therefore, proxies highlighting inter-populational divergences in KTA are needed. The use of such proxies would allow to identify, prior to bioassays, the wild population pairs which are likely to present differentiations in KTA expressions in aquaculture conditions. Here, we assessed the relevance of three alternative proxies: (i) genetic distance, (ii) habitat divergence, and (iii) geographic/hydrologic distances. We performed this evaluation on seven allopatric populations of Perca fluviatilis for which divergences in KTA had already been shown. RESULTS: We showed differences in the correlation degree between the alternative proxy-based and KTA-based distance matrices, with the genetic proxy being correlated to the highest number of KTA. However, no proxy was correlated to all inter-populational divergences in KTA. CONCLUSION: For future domestication trials, we suggest using a multi-proxy assessment along with a prioritisation strategy to identify population pairs which are of interest for further evaluation in bioassays.

Neurodevelopment vs. the immune system: Complementary contributions of maternally-inherited gene transcripts and proteins to successful embryonic development in fish.

The aim of this study was to investigate the respective contribution of maternally-inherited mRNAs and proteins to egg molecular cargo and to its developmental competence in fish using pikeperch as a model. Our study provides novel insights into the understanding of type-specific roles of maternally-inherited molecules in fish. Here we show, for the first time, that transcripts and proteins have distinct, yet complementary, functions in the egg of teleost fish. Maternally-inherited mRNAs would shape embryo neurodevelopment, while maternally-inherited proteins would rather be responsible for protecting the embryo against pathogens. Additionally, we observed that processes directly preceding ovulation may considerably affect the reproductive success by modifying expression level of genes crucial for proper embryonic development, being novel fish egg quality markers (e.g., smarca4 or h3f3a). These results are of major importance for understanding the influence of external factors on reproductive fitness in both captive and wild-type fish species.

In vitro follicle culture shows that progestagens are the maturation-inducing hormones (MIH) and possible regulators of the ovulation-mediating hormone PGE2 in female Eurasian perch Perca fluviatilis.

In European aquaculture, Eurasian perch, Perca fluviatilis L., is perceived as one of the most highly valuable freshwater fish species and a strong candidate for the development of freshwater aquaculture. In the pursuit of improving the quality of reproduction in this domesticated species, investigating the hormones mediating the final oocyte maturation (FOM) is therefore indispensable. But, the exact nature of the maturation-inducing hormone (MIH) in Eurasian perch is unknown. To further validate the existence of a maturation-inducing activity behind potential hormonal candidates in this species, we in vitro tested a group of nine hormones: cortisol (Co), 11-deoxycortisol (11-D), corticosterone (coS), 11-deoxycorticosterone (DOC), 17α,20ßdihydroxy-4-pregnen-3-one (DHP) and 17α,20ß,21 trihydroxy-4-pregnen-3-one (THP), prostaglandin E2 (PGE2), estradiol-17ß (E2) and testosterone (T), in their ability to trigger FOM advancement and the production of sex steroids potentially involved in FOM. Using mature female perch, two in vitro experiments were conducted with oocytes at the start of the FOM. The follicles were incubated for 62 h in Cortland media with and without human chorionic gonadotropin (hCG). By the end of the incubation, only DHP and THP triggered the full advancement in FOM even at low doses with the effect of DHP being in vivo validated. However, the de novo productions of E2 and DHP were not shown to be regulated by either of the MIH candidates. Progestagens are hence more credible candidates as MIH than corticosteroids in Eurasian perch. Our in vitro study also revealed that both PGE2 and DHP are strongly associated with ovulation and that PGE2 might have slightly contributed to such DHP activity.

First identification of dopamine receptors in pikeperch, Sander lucioperca, during the pre-ovulatory period.

Dopamine (DA) is a ubiquitous neurotransmitter exerting a range of pleiotropic actions through two DA receptor families, the D1 and the D2. To date in vertebrates, a maximum of four receptor subtypes have been identified within the D1 family, D1 (former D1A), D5 (former D1B), D6 (former D1C and D1D) and D7 (former D1E), while the D2 family encloses five subtypes, D2, D3, D4, D8 (former D2like or D2l) and D9 (former D4-related sequence or D4-rs). In teleosts, no study has investigated in parallel all the DA receptors to identify and localize the whole receptor repertoire from both families. In pikeperch, Sander lucioperca, a species of interest for aquaculture development, the existence, number and location of the DA receptors are totally unknown. To address these questions, RNA-seq with de novo transcriptome reconstruction, functional annotation and phylogenetic analysis were performed to characterize the transcript repertoire of DA receptors in the brain of female pikeperch at the pre-ovulatory period. Ten different cDNA were identified and showed to belong to the D1 family: two D1, one D5a, one D6a and one D6b and to the D2 family: two spliced variants of D2, one D3, one D8 and one D9. Unlike zebrafish, the subtypes D4 and D7 have not yet been isolated in pikeperch. As expected D1, D3, D8 and D9 are mostly expressed in brain parts except for the cerebellum (D1 and D3). The inter-species differences in the number of DA receptors and the inter-organ differences in the gene expression of all receptors support the complexity of the dopaminergic actions in vertebrate.

Domestication modulates the expression of genes involved in neurogenesis in high-quality eggs of Sander lucioperca.

Pikeperch, Sander lucioperca, is a species of high interest to the aquaculture. The expansion of its production can only be achieved by furthering domestication level. However, the mechanisms driving the domestication process in finfishes are poorly understood. Transcriptome profiling of eggs was found to be a useful tool allowing understanding of the domestication process in teleosts. In this study, using next-generation sequencing, the first pikeperch transcriptome has been generated as well as pikeperch-specific microarray comprising 35,343 unique probes. Next, we performed transcriptome profiling of eggs obtained from wild and domesticated populations. We found 710 differentially expressed genes that were linked mostly to nervous system development. These results provide new insights into processes that are directly involved in the domestication of finfishes. It can be suggested that all the identified processes were predetermined by the maternally derived set of genes contained in the unfertilized eggs. This allows us to suggest that fish behavior, along with many other processes, can be predetermined at the cellular level and may have significant implications on the adaptation of cultured fish to the natural environment. This also allows to suggest that fish behavior should be considered as a very important pikeperch aquaculture selection trait.

Comparison of single- and multi-trait approaches to identify best wild candidates for aquaculture shows that the simple way fails.

In agriculture, diversifying production implies picking up, in the wild biodiversity, species or populations that can be domesticated and fruitfully produced. Two alternative approaches are available to highlight wild candidate(s) with high suitability for aquaculture: the single-trait (i.e. considering a single phenotypic trait and, thus, a single biological function) and multi-trait (i.e. considering multiple phenotypic traits involved in several biological functions) approaches. Although the former is the traditional and the simplest method, the latter could be theoretically more efficient. However, an explicit comparison of advantages and pitfalls between these approaches is lacking to date in aquaculture. Here, we compared the two approaches to identify best candidate(s) between four wild allopatric populations of Perca fluviatilis in standardised aquaculture conditions. Our results showed that the single-trait approach can (1) miss key divergences between populations and (2) highlight different best candidate(s) depending on the trait considered. In contrast, the multi-trait approach allowed identifying the population with the highest domestication potential thanks to several congruent lines of evidence. Nevertheless, such an integrative assessment is achieved with a far more time-consuming and expensive study. Therefore, improvements and rationalisations will be needed to make the multi-trait approach a promising way in the aquaculture development.

Repeated hormonal induction of spermiation affects the stress but not the immune response in pikeperch (Sander lucioperca).

Hormonal induction of spermiation, previously reported to be immunogenic in fishes, is a common hatchery practice in pikeperch, Sander lucioperca. The aim of the present study was to investigate the effects of repeated induction of spermiation in pikeperch, following application of either human chorionic gonadotropin (hCG) or salmon gonadoliberine analogue (sGnRHa) on sperm quality indices as well as on immune and stress response. Mature males of pikeperch (n = 7 per group) were stimulated twice with five days between injections of either hCG (hCG; 500 IU kg-1), sGnRHa (sGnRHa; 50 µg kg-1) or NaCl (control group; 1 ml kg-1) to assess spermatozoa motility with a computer-assisted sperm analysis (CASA) system. During second sampling, blood plasma was sampled for humoral innate immune (peroxidase and lysozyme activities, ACH50), stress (cortisol, glucose) and endocrine (testosterone) markers. In addition, the head kidney was dissected to assay the expression of several immune genes (such as il1, c3, hamp, tnf-α and lys genes). The results indicate that hormonal treatment significantly increased sperm production. Sperm sampled after the hormonal treatment maintained its quality throughout the study, regardless of the sampling time. However, it appears that the application of hCG induced elevated cortisol and glucose plasma levels compared to the control group. Almost all immune markers, except the relative expression of hepcidin (hamp gene), were unaffected by the two hormones applied. The results showed that the induction treatment of spermiation processes in pikeperch resulted in an important physiological stress response for which the intensity varied according to the hormonal agent used. However, this stress response (more profound following application of hCG) was weakly associated with innate immune functions. On the other hand, a significant negative correlation between the expression of several important immune markers (peroxidase activity, relative expression of c3 and il1 genes) and sperm quality indices indicates significant involvement of immune status on sperm quality. The results obtained shed light on immune-system-induced modifications to sperm quality. The data presented here highlight the need for careful revision of broodstock management and selection practices where welfare status as well as individual predispositions of fish to cope with the stress should be taken under the consideration.

Bile composition of healthy cats and cats with suspected hepatobiliary disease using point-of-care analyzers: A prospective preliminary study.

Although hepatobiliary disease is common in cats, little is known about the bile composition in either these diseased states or in healthy cats. The objectives of this study were to evaluate several analytes from the bile of healthy cats and to investigate the usefulness of measuring these variables to predict bacterial cholangitis. Cats were prospectively enrolled and divided into 3 groups: 21 healthy cats (group 1) and 14 cats with suspected hepatobiliary disease: 9 without bacterial biliary infection (group 2) and 5 with bacterial biliary infection (group 3). Percutaneous ultrasound-guided cholecystocentesis was conducted on each cat. Bile cytology and culture were carried out and bile was analyzed for pH, lactate, and glucose levels using several point-of-care (POC) devices. Reference values for several bile analytes in healthy cats were calculated and are presented in this study. Neither the pH (P = 0.88) nor the lactate concentration (P = 0.85) was significantly different among the 3 groups. Sodium concentration was significantly higher in group 3 than in group 2 (P < 0.05). Bile pH, lactate, and glucose levels were unable to predict the presence of a bacterial infection in the bile.

La composition de la bile est méconnue tant chez les chats sains que chez les chats atteints de maladies hépatobiliaires bien que ces maladies soient fréquentes. Les objectifs de cette étude étaient d'évaluer plusieurs paramètres dans la bile de chats sains et d'investiguer l'utilité de ces derniers comme marqueurs prédictifs de cholangite bactérienne. Les chats ont été recrutés prospectivement et répartis en trois groupes : 21 chats sains (groupe 1); et 14 chats avec maladie hépatobiliaire suspectée : 9 sans infection biliaire (groupe 2) et 5 avec infection bactérienne biliaire (groupe 3). Une cholécystocentèse a été réalisée sur chaque chat. La bile a été utilisée pour cytologie, culture et analyses biochimiques incluant le pH, le lactate et le glucose avec des appareils au chevet du patient. Les valeurs de référence de plusieurs paramètres biliaires chez les chats sains ont été calculées et sont présentées dans cette étude. Le pH (P = 0,88) et la concentration en lactate (P = 0,85) n'étaient pas significativement différents entre les 3 groupes. La concentration en sodium était significativement plus élevée dans le groupe 3 comparée aux groupe 2 (P < 0,05). Les concentrations en lactate et glucose ainsi que le pH ne permettaient pas de prédire une infection bactérienne dans la bile.(Traduit par les auteurs).

The onset of piscivory in a freshwater fish species: analysis of behavioural and physiological traits.

The onset of piscivory in fish, resulting in a shift from zooplankton or invertebrate to fish prey, was studied on pikeperch (Sander lucioperca) larvae displaying and not displaying piscivorous behaviour at different ages (23, 30, 37, 44 and 52 days post-hatching) using behavioural (attack, capture and swimming activity), morphological (allometry) and digestive enzymatic (trypsin, α-amylase and pepsin) analyses. The shift from zooplanktonic food items (Artemia nauplii) to a piscivorous diet did not occur at the same time for all individuals within the same cohort. Predation tests, conducted under controlled conditions (20°C; ad libitum feeding), showed that some larvae attacked fish prey as early as the age of 3 weeks [11.0 ± 1.3 mm total length (TL)], whereas others did not start until the age of 6 weeks (16.6 ± 1.9 mm TL). Piscivorous individuals were bigger, with larger heads, longer tails, higher acid protease and lower alkaline protease activities, than non-piscivorous conspecifics. In conclusion, high interindividual variability in morphological and digestive system developments linked to the development of predatory abilities could induce cannibalism in fish.

Constant long photoperiod inhibits the onset of the reproductive cycle in roach females and males.

Photoperiod and temperature are commonly accepted as the determinant factors for the control of the reproductive cycle in freshwater fishes. However, this determining effect is dependent on fish species. While applying a constant long photoperiod has an inhibitory effect in some species, the same photoperiodic manipulation has a stimulating effect in others. In cyprinids, a decrease in temperature or photoperiod can induce the gonad recrudescence. However, in roach Rutilus rutilus an early spring spawner cyprinid, there is little knowledge about the cueing role of each environmental factor. The aim of this work was to study the effect of a constant long photoperiod on the gametogenesis in roach. Fish were kept under either naturally simulated photoperiod or artificial constant long photoperiod and sampled at three times: at the beginning of photoperiod decrease, at the beginning of temperature decrease, and at the end of temperature decrease. Morphological parameters (gonado-somatic, hepato-somatic, and viscera-somatic indexes), plasma sexual steroids, and proportion of gametogenesis stages were estimated at each sampling time. The results showed that a constant, long photoperiod exerted inhibitory effects on gametogenesis advancement in both females and males that could stem from decrease of sex steroid production. Roach displayed a similar response to photoperiodic manipulations to other early spring spawners like percids, such as European perch, yellow perch and pikeperch. These results clearly showed the cueing role of the photoperiod in the induction of the reproductive cycle in roach.

New findings associated with presumptive systemic lupus erythematosus in a kitten.

CASE SUMMARY: An 8-month-old neutered male domestic shorthair kitten was examined for anorexia, lethargy and palatine ulcers. Systemic lupus erythematosus (SLE) was suspected based on a positive antinuclear antibody (ANA) titer and six manifestations of autoimmunity: fever, paronychia, oral ulcers, proteinuria, thrombocytopenia and leukopenia. Mastocytemia was observed on the blood smear. Although the clinical presentation of this case meets the classification criteria for SLE in humans, tick-borne disease and histopathology evaluation of the oral and cutaneous lesions would have been necessary to support a definite diagnosis of SLE. Baseline ANA titration was performed in two laboratories with conflicting results, which may reflect substrate differences used for the titration, but a false-positive result cannot be excluded. The cat received prednisolone and all clinical and laboratory abnormalities resolved after two months of treatment. Subsequent ANA titers remained positive and were not correlated to the patient's clinical progression. RELEVANCE AND NOVEL INFORMATION: This report describes new findings associated with a presumptive diagnosis of SLE in a kitten, highlighting that SLE may not be ruled out even in young cats and may be associated with mastocytemia. ANA titration is part of the initial diagnostic work-up of SLE but is a non-specific test and discrepancies can be observed between laboratories. The titration of more specific antibodies such as those used in humans would be helpful to diagnose SLE. ANA titration may not correlate with clinical activity of SLE; hence, the interest of an ANA titer follow-up to establish disease control warrants further investigation.

Domestication may affect the maternal mRNA profile in unfertilized eggs, potentially impacting the embryonic development of Eurasian perch (Perca fluviatilis).

Domestication is an evolutionary process during which we expect populations to progressively adapt to an environment controlled by humans. It is accompanied by genetic and presumably epigenetic changes potentially leading to modifications in the transcriptomic profile in various tissues. Reproduction is a key function often affected by this process in numerous species, regardless of the mechanism. The maternal mRNA in fish eggs is crucial for the proper embryogenesis. Our working hypothesis is that modifications of maternal mRNAs may reflect potential genetic and/or epigenetic modifications occurring during domestication and could have consequences during embryogenesis. Consequently, we investigated the trancriptomic profile of unfertilized eggs from two populations of Eurasian perch. These two populations differed by their domestication histories (F1 vs. F7+-at least seven generations of reproduction in captivity) and were genetically differentiated (FST = 0.1055, p<0.05). A broad follow up of the oogenesis progression failed to show significant differences during oogenesis between populations. However, the F1 population spawned earlier with embryos presenting an overall higher survivorship than those from the F7+ population. The transcriptomic profile of unfertilized eggs showed 358 differentially expressed genes between populations. In conclusion, our data suggests that the domestication process may influence the regulation of the maternal transcripts in fish eggs, which could in turn explain differences of developmental success.

Multifactorial analyses revealed optimal aquaculture modalities improving husbandry fitness without clear effect on stress and immune status of pikeperch Sander lucioperca.

High mortality and impairment in growth rate during pikeperch (Sander lucioperca) ongrowing are among the major bottlenecks for its development in aquaculture. These failures may be related to high stress responsiveness since the rearing conditions are not yet optimized for this species. The objectives were to characterize the stress and immunological responses of pikeperch to major aquaculture modalities, and to identify the optimal aquaculture conditions for improving its welfare status. In a screening experiment, eight factors considered as relevant for the welfare of pikeperch were compared in two modalities using a fractional multifactorial design (28-4). Each experimental unit represented a combination of 8 factors in two modalities including grading, stocking density (15 vs 30kg·m-3), feed type (sinking vs mid-floating), light intensity (10 vs 100 lux), light spectrum (red vs white), photoperiod (long vs short), dissolved oxygen (60 vs 90%) and temperature (21 vs 26°C). Fish sampling occurred on days 36 and 63. Stress markers (glucose, cortisol and brain serotonergic activity), innate immune parameters (plasma lysozyme and complement activities) and expression of some immune genes were assessed. Light intensity and the type of feed clearly appeared as directive factors for pikeperch culture. A strong effect of the feed type was observed on growth parameters while survival was impacted by high light intensity. Light characteristics (intensity, spectrum and photoperiod) and temperature were identified as determining factors for physiological and immune markers. No obvious relation was established between stress status and growth parameters and further investigations are needed to improve management strategies of pikeperch culture and knowledge on the relations between environmental conditions, stress and immunity in percid fish.

Molecular investigations of outbreaks of Perch perhabdovirus infections in pike-perch.

In 2016, a total of 5 massive mortality episodes each affecting hundreds of thousands of pike-perch Sander lucioperca larvae occurred at 2 sites in 2 Western European countries. For each episode, perhabdoviruses related to the perch rhabdovirus (PRV) were detected in samples, using either PCR or cell culture combined with PCR. The sequences of the glycoprotein (g), phosphoprotein (p) and nucleoprotein (n) genes of these samples demonstrated that 2 different genotypes were present at 1 site, each associated with 1 of the 3 episodes. At the other site, a single genotype was associated with the 2 outbreaks. Furthermore, this genotype was strictly identical to 1 genotype involved in the outbreaks of the first site, strongly suggesting a common origin for these 2 viruses. The common origin was confirmed a posteriori because some larvae introduced to both sites had exactly the same geographic origin in Eastern Europe. Taken together, the molecular and epidemiological data suggest that both horizontal and vertical transmission of 2 distinct strains of perhabdoviruses were involved in the various outbreaks affecting pike-perch.

Effects of hCG and salmon gonadoliberine analogue on spermiation in the Eurasian perch (Perca fluviatilis).

This study analysed (i) the effect of human chorionic gonadotropin (hCG) and salmon gonadoliberine analogue (sGnRHa) on the effectiveness of induction of spermiation and (ii) the effect of latency time following the application of those spawning agents on the quantity and quality of the sperm of Eurasian perch, Perca fluviatilis, obtained during out-of-season spawning. For this study, pond-reared fish were used which had been acclimated to the controlled conditions. Three groups were distinguished which were treated with either saline (0.9% NaCl; control group), hCG (500 IU kg-1) or sGnRHa (100 µg kg-1). The fish were kept in a recirculating system at 12 °C throughout the study, during which sperm was collected every two days between the 2nd and 10th day following hormonal treatment. During the study, quantitative (e.g. sperm volume, total sperm production) and qualitative (measured with a computer-assisted sperm analysis system - i.e. CASA) parameters were monitored. The results of the study indicate that the hormonal treatment had a highly beneficial effect on the spermiation rate (100% in experimental groups from day 6 following injection) as well as quantity, which increased 50% in experimental groups (over 2200 × 109 of spermatozoa per kg of body weight) by day 4 following injection. For the sperm quality, both spawning agents tested had a rather positive effect, although sperm motility rate (MOT) was seen to be significantly reduced on day 10 following the application of hCG (MOT = 72.8% ± 8.1), which was not observed after the application of sGnRHa (minimum mean MOT 81.7% ± 6.1). The results clearly indicate that hormonal treatment had a positive effect on spermiation in Eurasian perch, most apparent from day 6 following injection, regardless of the hormonal agent used. Though application of sGnRHa allowed a high volume of high quality sperm to be stripped for two days longer (up to day 10 post-injection) compared to the application of hCG.

Influence of waterborne gallic and pelargonic acid exposures on biochemical and reproductive parameters in the zebrafish (Danio rerio).

Gallic and pelargonic acids are biologically derived substances receiving a growing interest as eco-friendly biocides with potential applications in freshwater system management. However, some data gaps remain to address their chronic ecotoxicity issue, particularly for fish. This work aimed at investigating the sublethal effects of a long-term waterborne exposure of zebrafish to these compounds. Mature fish were exposed to gallic or pelargonic acid at the concentrations of 0, 0.05, 0.5 and 5 mg/L during one month under semi-static conditions. Fecundity, hatching rate and median hatching time were regularly evaluated. Circulating sex hormone levels (11 ketotestosterone -11 KT, 17 ßestradiol -E2-), plasma vitellogenin (Vtg), and gonad histology were monitored in males and females after exposure. Lactate dehydrogenase (LDH), total glutathione peroxydase (GPx) and glutathione-S transferase (GST) activities were assessed as enzymatic biomarkers of exposure in fish liver. Significant increases of GPx activity were reported in females exposed to both type of chemicals regardless the contamination level. Moreover, 5 mg/L gallic acid induced a decrease in 11-KT levels for males. For fish exposed to pelargonic acid, decreases in circulating hormone levels were reported respectively at 0.05 and 5 mg/L for 11-KT in males, and at 0.5 mg/L for E2 in females. However, no histological alteration in gonads neither significant variation in reproductive performances were detected following zebrafish exposure to gallic or pelargonic acid. Additional investigations concerning the mode of application and the environmental fate of these substances may warrant their further use in freshwater systems at concentrations compatible with biocidal/allelochemical effects. © 2015 Wiley Periodicals, Inc. Environ Toxicol 32: 227-240, 2017.