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... In Lithuania, the first molecularly confirmed cases of saprolegniasis in aquaculture were associated with Saprolegnia parasitica isolated from the skin of infected rainbow trout (Oncorhynchus mykiss Walbaum) and perch (Perca fluviatilis Linnaeus) caught in open fishponds in 2018 (Stankevičiūtė et al., 2018(Stankevičiūtė et al., , 2022. Previously, S. parasitica and S. diclina had also been isolated from water samples taken from various wild lakes and rivers in Lithuania, but their molecular identification was not carried out (Markovskaja, 2006). ...
The present work is the first comprehensive study of fungus‐like stramenopilous organisms (Oomycota) diversity in Lithuanian fish farms aimed at proper identification of saprolegniasis pathogens, which is important for water quality control, monitoring infection levels and choosing more effective treatments for this disease in aquaculture. Pathogenic to fish, Saprolegnia and other potentially pathogenic water moulds were isolated from adult fish, their eggs, fry and from water samples. All detected isolates were examined morphologically and confirmed by sequence‐based molecular methods. A total of eight species belonging to the genera Saprolegnia , Achlya , Newbya and Pythium were identified. Four species ( S. parasitica , S. ferax , S. australis and S. diclina ) were found to be the main causative agents of saprolegniasis in Lithuania. S. parasitica and S. ferax dominated both in hatcheries and open fishponds, accounting for 66.2% of all isolates. S. parasitica was isolated from all farmed salmonid fish species as well as from the skin of Cyprinus carpio , Carassius carassius and Perca fluviatilis . S. australis was isolated from water and once from the skin of Oncorhynchus mykiss , and S. diclina was detected only once on the skin of Salmo salar fish. In addition, Achlya ambisexualis , Saprolegnia anisospora and Newbia oligocantha isolated during this study are noted as a possible source of saprolegniasis. The results of this study are relevant for assessing the risk of potential outbreaks of saprolegniasis or other saprolegnia‐like infection in Lithuanian freshwater aquaculture.
... The identification of Saprolegnia isolate was performed at the species level by taxonomic analysis of the sexual structures combined with morphological characteristics of its asexual stage under light microscope Nikon eclipse Ci with phases contrast magnifications × 400 (up to × 1000). The nomenclature of identified species follows (Seymour 1970;Rietmüller 2000;Dick 2001;Markovskaja 2006). The pure living cultures of S. parasitica were isolated by the baiting technique (Seymour 1970). ...
Regardless of the wide use of glucose measurements in stress evaluation, there are some inconsistencies in its acceptance as a stress marker. To meet the challenge and test the reliability/suitability of glucose measurement in practice, we simulated different environmental/anthropogenic exposure scenarios in this study. We aimed to provoke stress in fish followed by a 2-week stress recovery period and under the cumulative effect of leachate fish exposed to pathogenic oomycetes (Saprolegnia parasitica) to represent a possible infection in fish. We selected stream-resident and anadromous brown trout ecotypes (Salmo trutta) representing salmonids with different migratory behaviour strategies. Here, we analysed glucose content in fish-holding water, blood and gills to determine glucose suitability as a potential biomarker of fish response to environmental challenges. Additionally, swimming behavioural parameters and haematocrit were measured. The results indicated that the quantity of glucose released in the holding water of stressed fish increased considerably and remained substantially higher throughout the stress recovery period than the control level. Correspondingly, the circulating levels of glucose in blood and gills decreased over time in fish exposed to different stressors. A significant decrease in swimming activity of fish was observed during the first hours of leachate exposure and increased in fish exposed to S. parasitica compared to control. Our study is the first to ensure the validity and reliability of glucose response in evaluating physiological stress in fish under chemical and biological stimuli, indicating its sensitivity and response range of glucose measurement in fish-holding water.
... Water moulds or straminipilous fungi (traditionally oomycetes) of the order Saprolegniales are common and widespread fungus-like heterotrophic microorganisms in freshwater environments (Rietmüller, 2000;Dick, 2001). Some Saprolegnia species are considered to be opportunistic facultative fish parasites found in all lotic and lentic freshwater basins (Rietmüller, 2000;Markovskaja, 2006). S. parasitica, a causal agent of saprolegniasis, is considered to be a secondary invader, because its potential to parasitize other organisms is closely related to environmental stress. ...
... The morphological identification of S. parasitica was additionally confirmed by the molecular sequence-based diagnostic method, i.e. by polymerase chain reaction (PCR) assays of the internal transcribed spacer (ITS) region of rDNA (White et al., 1990). The nomenclature of identified species follows Seymour (1970); Rietmüller (2000); Dick (2001); Markovskaja (2006). ...
Parasitic infections may cause damage to the host immune system (i.e. fish), thereby endangering its health and weakening its responses to other types of stressors. Therefore, exposure to different kinds of natural or anthropogenic stressors can lead to unexpected toxicity outcomes in aquatic organisms. This study examined the haematological, genotoxic and cytotoxic effects of the co-infection with the protozoan parasite (Trichodina sp.) and the pathogenic oomycete (Saprolegnia parasitica) in Perca fluviatilis alone and in combination with chemical stress (environmentally-relevant aqueous concentrations of metal mixtures). Haematological analyses such as red cell and white cell indices revealed that chemical and biological stressors, used singly and in combination, exerted adverse effects on fish health. Changes in haematological indices induced by exposure to each of the above-mentioned stressors separately and by combined exposure to all of them suggested the multiple stress-induced inflammation process in the exposed fish. The cytogenetic damage inflicted by the S. parasitica and Trichodina sp. co-infection and multiple stress was revealed in fish erythrocytes. This information is expected to contribute to the elucidation of how multiple stressors impact on responses of haematic indices, geno- and cytotoxicity endpoints in P. fluviatilis. Assessment of the risk associated with multiple stressors is expected to prove valuable for the effective aquatic environment management (Løkke et al., 2013 and references therein).
... During investigations of straminipilous fungi in various freshwater habitats of Lithuania species of the genus Aphanomyces and other saprolegniaceous fungi have been rather frequently observed in water samples (NOVICKAJA-MARKOVSKAJA, 1995;MARKOVSKAJA, 1996MARKOVSKAJA, , 2004MARKOVSKAJA, , 2006. Previously only two species -Aphanomyces laevis grown on hemp seed bait (NOVICKAJA-MAR- KOVSKAJA, 1995) and A. phycophilus on algae Spirogyra sp. which overgrew submerged needles of Picea abies (MARKOVSKAJA, 1996) -have been reported from freshwater habitats in Lithuania. ...
The present paper gives an account of six species of the genus Aphanomyces recorded in Lithuania.
All species are briefly described and illustrated; taxonomical position and ecology of some of them are
discussed. Four species of the genus, A. euteiches, A. helicoides, A. parasiticus and A. stellatus, are
reported for the first time in Lithuania.
Probiotics can increase feed conversion efficiency and strengthen the immune system of
aquatic animals, resulting in improved growth and survival rates. Common probiotics used in
aquaculture include lactic acid bacteria, Bacillus species, and yeast.Aquaculture can continue
to grow by using probiotics in fish breeding and rearing technology, minimizing their
exposure to diseases.This study aims to compare the effectiveness of different bioactive
substances, such as probiotics, prebiotics, and mannan oligosaccharides, in stimulating the
growth and survival of juvenile carp
This study was undertaken to investigate saprolegniasis outbreaks in Nile tilapia farms at northern Egypt and its linkage to the water quality parameters, besides, their genetic diversity across different farms and the induced ultrastructural lesions. Water quality parameters were recorded and a total of 200 Nile tilapia showing saprolegniasis like signs were collected from December 2017–March 2018 from three different regions at El-Manzala, Gamasa, and El-Sirw, located at northern Egypt. A significant increase was observed in salinity, where El-Manzala showed the lowest level lowest 0.25 g/L followed by Gamasa and El-Sirw at salinity levels of 3.5 g/L, and 2.15 g/L, respectively. The prevalence of saprolegniasis showed significant variations between different regions (P < 0.05) and across different months (P < 0.0001). El-Manzala showed the higher prevalence (90.91%, 100/10) compared to El-Sirw (77.5%, 31/40), but no significant prevalence changes were observed between Gamasa (80%, 40/50) compared to both El-Manzala and El-Sirw regions (P > 0.05). Similarly, monthly prevalence where significantly increased during all months, but March; and Saprolegnia isolates were highly recovered from skin and fins followed by gills. All strains isolated were morphologically classified in the genus Saprolegnia, and they were identified presumptively as S. parasitica/diclina, S. ferax, and S. litoralis according to their sexual characteristics. The genetic variation among the 23 Saprolegnia isolates were investigated using RAPD-PCR, an approach has not been done yet for Nile tilapia saprolegniasis, and results revealed isolates split into two distinct clades using based on genetic similarities, demonstrating that there is genetic diversity among the isolates. Clade I contains seven isolates out of 23 (30.4%), whereas clade II contains sixteen isolates out of 23 (69,5%). Ultrastructural examination revealed sexual and asexual stage of Saprolegnia with numerous mycelia, besides skin necrosis and ulceration, however the attachment components, such as appressoria and hooked hairs were not observed. Our results provide a better overview of the Saprolegnia outbreaks in different regions and their association to the risk factors contributing to Saprolegnia pathogenicity, and the ultrastructure alterations induced in fish skin confirming the disease. Further, for the first time a genetic diversity of Saprolegnia isolates among different localities has been explored in Nile tilapia.
