Registry of saprolegniose in fish cultivated in the world: a compilation of data

Saprolegniosis is a mycological disease that causes significant economic losses in fish culture and can be considered an obstacle to the development of world fish farming. Thus, we aimed to identify which species of fish cultivated in the world have been associated with fungi of the genus Saprolegnia. The research deals with a bibliographical survey that contemplates articles published between 2007 and July of 2017. We found a relationship of saprolegniose with fish species: Oncorhynchus mykiss, Salmo trutta, Oncorhynchus tshawytscha, Labeo rohita, Pterophyllum scalare, Ctenopharyngodon idella, Sander lucioperca, Pelteobagrus fulvidraco, Oreochromis niloticus, Odonthestes bonariensis, Odonthestes humensi e Catla catla. The oomycetes found were: Saprolegnia ferax, Saprolegnia parasitica, Saprolegnia australis, Saprolegnia diclina, Saprolegnia delica, Saprolegnia glomerata, Saprolegnia terrestres, Saprolegnia uliginosa, Saprolegnia unispora, Saprolegnia hypogyna and Saprolegnia longicaulis. The species S. ferax and S. parasitica were the fungi that presented the highest infection register, mainly in salmonids. O. mykiss, S. salar and S. trout were the fish with more studies related to saprolegniose, because they are species that have great market importance in the world fish farming scenario. Despite the great importance of the species O. niloticus in the world fish culture, we observed the specie in only one article in this research, which may be related to the high resistance of the species to diseases and to the lack of research funding to identify this type of infection. It was not possible to compare the host - etiological agent among the fish, since many of the studies considered in the research did not have the purpose of identifying the pathogen.

Some new records of lower aquatic fungi from western Maharashtra, Maharashtra State, India.

Present study deals with the study of some lower aquatic fungi different regions of Maharashtra viz., Acaulopage dichotoma Drechsler belong to family Zoophagacea (Class- Zygomycetes) while Achlya oblongata de Bary, Brevilegnia megasperma Harvey, Saprolegnia ferax (Gruith) Thuret and Saprolegnia subterranae (Dissman) Seymour belongs to family Saprolegniaceae (Class - Oomycetes). All these are new records of aquatic fungi from the Maharashtra state.

Effect of salinity on biology of Saprolegnia ferax and Pythium ultimum

<i>Saprolegnia ferax</i> and <i>Pythium ultimum</i> were cultivated on the leaves of <i>Bromus catharicus</i>. Different concentrations of NaCl were used in the medium. <i>S. ferax</i> appears to be more tolerant to salinity than <i>P. ultimum</i> in CMC-ase production and the ability for growth.

Clotrimazole as a Potent Agent for Treating the Oomycete Fish Pathogen Saprolegnia parasitica through Inhibition of Sterol 14α-Demethylase (CYP51)

ABSTRACTA candidate CYP51 gene encoding sterol 14α-demethylase from the fish oomycete pathogenSaprolegnia parasitica(SpCYP51) was identified based on conserved CYP51 residues among CYPs in the genome. It was heterologously expressed inEscherichia coli, purified, and characterized. Lanosterol, eburicol, and obtusifoliol bound to purified SpCYP51 with similar binding affinities (Ks, 3 to 5 μM). Eight pharmaceutical and six agricultural azole antifungal agents bound tightly to SpCYP51, with posaconazole displaying the highest apparent affinity (Kd, ≤3 nM) and prothioconazole-desthio the lowest (Kd, ∼51 nM). The efficaciousness of azole antifungals as SpCYP51 inhibitors was confirmed by 50% inhibitory concentrations (IC50s) of 0.17 to 2.27 μM using CYP51 reconstitution assays. However, most azole antifungal agents were less effective at inhibitingS. parasitica,Saprolegnia diclina, andSaprolegnia feraxgrowth. Epoxiconazole, fluconazole, itraconazole, and posaconazole failed to inhibitSaprolegniagrowth (MIC100, >256 μg ml−1). The remaining azoles inhibitedSaprolegniagrowth only at elevated concentrations (MIC100[the lowest antifungal concentration at which growth remained completely inhibited after 72 h at 20°C], 16 to 64 μg ml−1) with the exception of clotrimazole, which was as potent as malachite green (MIC100, ∼1 μg ml−1). Sterol profiles of azole-treatedSaprolegniaspecies confirmed that endogenous CYP51 enzymes were being inhibited with the accumulation of lanosterol in the sterol fraction. The effectiveness of clotrimazole against SpCYP51 activity (IC50, ∼1 μM) and the concentration inhibiting the growth ofSaprolegniaspeciesin vitro(MIC100, ∼1 to 2 μg ml−1) suggest that clotrimazole could be used againstSaprolegniainfections, including as a preventative measure by pretreatment of fish eggs, and for freshwater-farmed fish as well as in leisure activities.

Studies on toxicity of selected Oomycetes

The MTT test is used to determine the cytotoxicity of species: <em>Achlya americana, A. caroliniana, Leptomitus lacteus, Saprolegnia ferax</em> and <em>S. lapponica</em>, which occurred in Lake Sitno in the Drawieński National Park (W Poland). It was stated that among five examined species of zoosporic fungi only one of them <em>A. caroliniana</em>, does not show cytotoxic effect. Low and mean toxicity of other tested water FLO, however, combined with the large-scale character of their appearance shows, that they can create serious threat for the spawn, fry, fish as well as the other organisms (including invertebrates) existing in water.

Aquatic fungi and straminipilous organisms in lakes of the Augustowska Primeval Forest, Poland

We analyzed species composition of aquatic fungi and straminipilous organisms in six lakes located within the Augustowska Primeval Forest, Poland. Mycological observations conducted in the spring and autumn seasons together with hydrochemical analysis in the 2010–2012 revealed the presence of 44 species (10 aquatic fungi and 34 straminipilous organisms). Among the taxa detected, there were some potential pathogens of economically valuable fish species and spawn, including Achlya americana, Ac. polyandra, Saprolegnia ferax and S. parasitica. Some of the species were crustacean pathogens, such as Lagenidium giganteum, Myzocytium microsporum and M. zoophthorum. There were also some common human pathogens Aspergillus niger and Candida tropicalis. Some species, such as Achlya klebsiana, Ac. prolifera, Nowakowskiella elegans, N. macrospora, Pythium debaryanum, Py. inflatum, Rhizophlyctis rosea and Saprolegnia litoralis were common phytosaprobionts.The largest number of species of fungi and straminipilous organisms was identified in Lake Sajenek (22), the fewest in Lake Białe (12).The quantitative composition and qualitative differentiation of mycobiota were influenced by the content of biogenic compounds and the amount of organic substance. The elevated levels of these parameters (Lake Sajenek) stimulated the growth of fungi and straminipilous organisms, whereas very low concentrations of biogenic compounds and a small amount of organic matter (Lake Białe) had an inhibitory effect.Statistical analysis of the results was conducted to determine the correlations between the number of fungal and straminipilous species and the hydrochemical parameters, i.e. water temperature, the level of nitrogen compounds (nitrate nitrogen, ammonium nitrogen), calcium carbohydrate, magnesium carbohydrate, water oxidizability and the content of dry residue, dissolved substances and suspension.