First Report of Achlya oblongata Infection in Freshwater‐Reared Asian Seabass Lates calcarifer

Abstract

In September 2014, a freshwater oomycete was first isolated from Asian Seabass Lates calcarifer fry that were reared in freshwater at a fish hatchery in Sabah, Malaysia. A fungal strain was isolated from infected fry by using glucose yeast extract (GY) agar. From morphological identification, the strain belonged to the genus Achlya based on the mode of zoospore release. Molecular phylogenetic analysis of the internal transcribed spacer region sequences from the strain showed high similarity (99-100%) to Achlya oblongata. The isolate was able to grow on GY agar incubated at 15-35°C, in GY broth adjusted to pH 3.0-11.0, and in up to 1.0% NaCl. This is the first report of Achlya infection in freshwater-reared Asian Seabass in Malaysia.

First Record of the Water Mold Achlya bisexualis (Saprolegniaceae) Isolated from Ornamental Fish in South Africa

“…FIRST REPORT OF ACHLYA BISEXUALIS IN SOUTH AFRICA 359 cotton, wool-like appearance of mycelia covering dermal erosions or skin lesions (Chukanhom and Hatai 2004;Andrew et al 2008;Refai et al 2016;Lau et al 2018). The infectious agent from this study showed similar clinical signs, with superficial, cotton, wool-like mycelia covering the eye of an Orange Blotched Peacock Cichlid.…”

“…Achlya spp. have been confirmed as pathogenic agents causing mycoses in aquaculture, specifically in tropical environments where infection has been reported to affect economically important cultured fish species (Lawhavinit et al 2002;Webster and Weber 2007;Lau et al 2018). Infections with Achlya spp.…”

“…Achlya species have been reported as either obligate or facultative pathogens infecting both wild and cultured fish and their eggs (Lawhavinit et al 2002;Chukanhom and Hatai 2004;Czeczuga et al 2005;Prasad and Rajanaika 2010;Hunjavanit et al 2012;Mastan et al 2012;Dubey et al 2018). Infections with Achlya species are known as occasional etiological agents in aquaculture, particularly in tropical countries (Lilley and Roberts 1997;Lau et al 2018). Due to the common occurrence of Achlya species in natural water systems and their wide range of susceptible hosts under conditions that favor facultative infections (Dubey et al 2018;Lone et al 2018), it is not surprising that Achlya infections have been widely reported as secondary infections on physical injuries or in combination with other, primary pathogenic agents (Lawhavinit et al 2002).…”

“…Another species, A. inflata, has been isolated from Brown Trout Salmo trutta in Poland (Czeczuga et al 2005). More recently, A. oblongata has been reported as a pathogen of farmed Asian Seabass fry Lates calcarifer in Malaysia (Lau et al 2018).…”

“…The genus Achlya typically shares phenotypical characteristics with other members of the order Saprolegniales, including similar environmental requirements for growth and reproduction, morphology, and cotton wool-like mycelia often covering dermal erosions or skin lesions (Chukanhom and Hatai 2004;Refai et al 2016;Dubey et al 2018;Lau et al 2018). This physical similarity with other genera in Saprolegniales often results in the incorrect or inaccurate diagnosis as a Saprolegnia species or Saprolegnia-like infection.…”