Kishio Hatai

Aquatic Fungi Developing on Eggs of Salmonids

Abstract Aquatic fungi isolated from salmonid eggs incubated at six fishery stations in Japan belonged to the genera Saprolegnia, Achlya, Aphanomyces, Leptolegnia, and Pythium. The species diversity of the fungi varied according to the site studied.

Antimycotic Activity of Eugenol against Selected Water Molds

Abstract This study was conducted to investigate the antimycotic activities of eugenol, a major essential oil of clove, against some fish pathogenic species of Saprolegniaceae as well as to determine the toxicity of eugenol to selected cultured fish. Two eugenol solutions were used in this study, a 10% v/v (volume:volume) solution in dimethyl sulfoxide (DMSO) and FA 100, which contains 10% v/v eugenol. The fungal species investigated were Saprolegnia parasitica, S. diclina, S. ferax, S. salmonis, Achlya klebsiana, and Aphanomyces piscicida. The minimum inhibitory concentrations (MICs) of eugenol in DMSO against Saprolegnia spp., A. klebsiana, and A. piscicida were 500, 250, and 125 μg/mL, respectively, and the fungicidal concentrations (for complete killing) were 1,000, 500, and 250 μg/mL, respectively. In contrast, the MICs of FA 100 against S. parasitica, other Saprolegnia spp., A. klebsiana, and A. piscicida were 250, 125, 250, and 63 μg/mL, respectively, and the fungicidal concentrations were 1,000, 1...

Molecular phylogeny of an unidentified Haliphthoros-like marine oomycete and Haliphthoros milfordensis inferred from nuclear-encoded small- and large-subunit rRNA genes and mitochondrial-encoded cox2 gene

The SSU rRNA, LSU rRNA, and cox2 genes of an unidentified Haliphthoros-like marine oomycete (NJM0034) and Haliphthoros milfordensis (NJM0131) were sequenced, and their phylogenetic relationships are analyzed and discussed. All phylogenetic trees showed that NJM0034 and NJM0131 were branched before separation of the two main saprolegnian and peronosporalean clades. These data suggest that the clear phylogenetic separation of those marine oomycete endoparasites from the two main oomycete clades. Excepting the LSU rRNA gene tree, NJM0034 and Haliphthoros spp. did not form a monophyletic group. On the other hand, H. milfordensis NJM0131 clustered with H. philippinensis SANK 15178, not with H. milfordensis NJM9434 in the cox2 amino acid sequence (COII) tree. This result strongly suggests that a taxonomic reinvestigation of the genus Haliphthoros should be considered.

Characteristics of Two Saprolegnia Species Isolated from Coho Salmon with Saprolegniosis

Abstract Several fungi have been isolated from the lesions of coho salmon Oncorhynchus kisutch that have saprolegniosis. Of these fungi, one that occurred frequently was identified as Saprolegnia parasitica strain H2 (=S. diclina type 1). A much rarer fungus was identified as S. diclina strain H3 (=S. diclina type 3). This article describes the pathogenicity of the isolates to coho salmon and the relationship of pathogenicity to the lengths of the isolates, hooked hairs.

Fungicidal effect of hydrogen peroxide on fungal infection of rainbow trout eggs

Exposure to 1,500 μg/ml of hydrogen peroxide (H2O2) for 60 min at 13°C was found to be injurious to rainbow trout eggs. On the other hand, the concentration which effectively inhibited pathogenic fungi in vitro was substantially less than this toxic dosage; specifically, 500 μg/ml for 60 min at 20°C to inhibit the zoosporic stage and 1,000 μg/ml for 60 min at 20°C to inhibit the vegetative stage. From in vivo tests, treatment with 1,000 μg/ml of H2O2 for 60 min at 13°C was found to be the most effective procedure to control fungal infection and increase the hatching rate of rainbow trout eggs.

Some biochemical characteristics of fungi isolated from salmonid eggs

Fungal isolates from salmonid eggs displayed apparently unique patterns of biochemical characteristics at both the generic and specific levels. of the five genera examinedAchlya andPythium were able to assimilate 13–16 out of 19 carbohydrates.Aphanomyces was able to assimilate only glucose and starch, which was assimilated by all isolates. Members ofSaprolegnia displayed identical patterns of carbohydrate assimilation, except forS. hypogyna, which was also able to assimilate melibiose, in common withAchlya, Pythium, andLeptolegnia. Pythium was the only genus capable of assimilating salicin. OnlyAchlya andP. monospermum were able to assimilate rhamnose. In terms of amino acid assimilation isolates ofSaprolegnia ferax andS. diclina displayed an identical patterns, as did isolates ofS. parasitica andS. hypogyna. OnlyAphanomyces frigidophilus isolate was capable of assimilating cysteine. All genera exceptPythium assimilated glutamine, a fundamental amino acid. All isolates exhibited lipase and fatty acid esterase activities but no cellulase acitivity. The biochemical characteristics discovered in this study offer possibilities for identification and classification of these fungi, which are discussed herein.

Fusarium oxysporum in Red Sea Bream (Pagrus sp.)

Red sea bream (Pagrus major) are cultured widely throughout the southern coastal waters of Japan, usually in floating net pens. The numbers cultured each year have increased steadily since 1965 and in 1983 reached 25,000 metric tons. The fish grow slowly and reach market sizes of 1 kg or more in weight in 3 yr. Recently, fry closely resembling P. major have been imported from Southeast Asian sources. The species has not been correctly identified, other than as a member of the genus Pagrus. One characteristic of this introduced fish is that it grows more rapidly than the Japanese red sea bream. Various

Fungal Infection of Mantis Shrimp (Oratosquilla oratoria) Caused by Two Anamorphic Fungi Found in Japan

Two fungal pathogens of the mantis shrimp (Oratosquilla oratoria) in Yamaguchi and Aichi Prefectures, Japan are described as the new species Plectosporium oratosquillae and Acremonium sp. (a member of the Emericellopsis marine clade). Both fungi infect the gills of the mantis shrimp, which become brown or black due to melanization. The former species is characterized by its slow growth on artificial seawater yeast extract peptone glucose (PYGS) agar, pale yellow to pale orange or grayish yellow colonies, short cylindrical solitary phialides with a wavy tip, and one-celled ellipsoidal conidia. Although lacking the two-celled conidia demonstrated by the type species Plectosporium tabacinum, the taxonomic placement of the new species was confirmed by DNA sequence analysis of the internal transcribed spacer (ITS) region of ribosomal DNA (ITS1, 5.8S rDNA and ITS2). Acremonium sp., the other causal pathogen, differs from P. oratosquillae by its fast growth on PYGS agar, pale orange to salmon-colored colonies, long, slender conidiophores consisting of solitary phialides with tips lacking an undulate outline, and typically cylindrical conidia. Analysis of ITS and β-tubulin gene sequences placed this fungus within the phylogenetically distinct Emericellopsis (anam. Acremonium) marine clade. Various physiological characteristics of both pathogens were also investigated. This is the first report of a fungal infection found on the mantis shrimp in Japan.

Freshwater fungi isolated from eggs of the common carp (Cyprinus carpio) in Thailand

Fungal infection in the eggs of freshwater fish is well known as a problematic disease. We had a chance to examine fungal infection in common carp (Cyprinus carpio) eggs at fish farms in Khon Kaen province, northeast Thailand, in February 2002, attempting to isolate fungi from eggs with fungal infection at three fish farms (A, B, and C). Nineteen stocks of fungi from farm A, 2 fungi from farm B, and 2 fungi from farm C were isolated and 3 of them were identified as Saprolegnia diclina, Achlya (A.) klebsiana, and Allomyces (Al.) arbuscula. S. diclina, A. klebsiana, and Al. arbuscula grew well at 25°–30°C and pH 6–7, at 30°–35°C and pH 6–7, and at 30°–40°C and pH 6–8, respectively. Saprolegnia diclina grew in a medium containing NaCl up to a concentration of 3.0%, whereas A. klebsiana and Al. arbuscula grew poorly in 1.0% NaCl. Artificial infection to platyfish (Xiphophorus maculatus) was also made using the 3 fungi selected, in which injured fish were exposed to 104 spores/ml of S. diclina and A. klebsiana and showed 100% of mortality, but none in the other experiments. This article includes the first description of Allomyces arbuscula from fish eggs in Thailand.

Three species of Lagenidiales isolated from the eggs and zoeae of the marine crab Portunus pelagicus.

Three species of Lagenidiales were isolated from the eggs and zoeae of the marine crabPortunus pelagicus. One of them,Lagenidium callinectes, is reported for the first time in Japan, with fungal infection in the eggs.Haliphthoros milfordensis was discovered from a zoea of the crab.Atkinsiella okinawaensis was also isolated from a zoea of the crab and described as a new species. Growth temperature range and optimum temperature of the fungi were examined. All of the isolates grew at various concentrations of NaCl or KCl, and optimum growth was observed on PYGS agar containing seawater. Pathogenicity to zoeae of the swimming crabPortunus trituberculatus was demonstrated by using a zoospore suspension of each fungus at 25°C.