71 Indian J. Fish., 65(1): 71-78, 2018 DOI: 10.21077/ijf.2018.65.1.68489-12 Taxonomic note on a rare fsh infecting freshwater mould Achlya ambisexualis Raper 1939 (Achlyaceae) isolated from Chandraprabha dam, Uttar Pradesh, India MANISH KUMAR DUBEY, ANDLEEB ZEHRA, MUKESH MEENA * AND RAM SANMUKH UPADHYAY Laboratory of Mycopathology and Microbial Technology, Centre of Advanced Study in Botany, Banaras Hindu University Varanasi - 221 005, Uttar Pradesh, India * Centre for Transgenic Plant Development, Department of Biotechnology, Faculty of Science, Hamdard University New Delhi - 110 062, India e-mail: mkmkdubey@gmail.com ABSTRACT Achlya spp. are oomycetous water moulds, responsible for freshwater fsh diseases causing great economic losses. An Achlya sp. implicated in signifcant fungal infections of both live and dead fsh as well as their eggs, has been isolated from the water and soil samples collected from Chandraprabha dam (Chandauli District, Uttar Pradesh, India) employing standard baiting method. Based on morphological characterisation, the strain was identifed as Achlya ambisexualis Raper 1939 (Saprolegniales, Oomycetes). It is a dioecious species, characterised by the presence of an achlyoid type of spore dehiscence from both primary and secondary sporangia, diferentiated by its oospheres predominantly maturing into eccentric oospores, generally 1-18 per oogonium and gemmae cylindrical in both antheridial and oogonial mycelia. In India, this species was recorded from a single collection in the past but lack proper description and illustrations. The present study describes and illustrates this species for the frst time in India and hoped to be benefcial for ichthyopathologists and researchers as A. ambisexualis is known as a necrotroph or parasite of fshes and their eggs. Keywords: Achlya ambisexualis, Achlyaceae, Chandraprabha dam, Oomycetes, Saprolegniasis, Stramenopiles, Taxonomy Introduction Achlya is an important genus of the family Achlyaceae (Saprolegniales, Oomycota), under phylum Stramenopiles (also called Heterokonta) (Dick, 2001; Johnson et al., 2002; Beakes et al., 2014). This genus is easily recognised by its profusely branched, coenocytic mycelium which gives rise to long, cylindrical and usually terminal zoosporangia that discharge their primary aplanospores from the sporangium to form a ball of spores (Johnson et al., 2002). Apart from diference in a few morphological features, the genus mostly exhibits similar properties and living conditions as the genus Saprolegnia. These fungal-like organisms with a zoosporic stage are often referred to as oomycetes or ‘‘water moulds’’ that are phylogenetically distinct from true fungi and are closer to brown algae, diatoms and plants (Alexopoulos et al., 1996; Guarro et al., 1999; Baldauf et al., 2000; Paul and Steciow, 2008). Achlya has approximately 50 valid species (Johnson et al., 2002; El Androusse et al., 2006; Paul and Steciow, 2008; Kirk et al., 2008; Jesus et al., 2015). The most included species in this genus probably are obligate saprotrophs which usually grow saprophytically serving simply as organic decomposers of animal and plant debris in freshwater and soil ecosystems worldwide (El-Hissy and Khallil, 1991; Czeczuga et al., 2002; Kiziewicz and Nalepa, 2008; Mazurkiewicz-Zapałowicz et al., 2008). However, under favourable conditions, Achlya spp. can be facultative parasites on various freshwater animals and their eggs and many members are responsible for economically important diseases afecting farmed and wild populations of aquatic animals. Several studies have reported Achlya species from infected Channa striatus (Kitancharoen et al., 1995), tilapia fsh and eggs (El-Sharouny and Badran, 1995; Hanjavanit et al., 2013; Mortada et al., 2013), salmonid eggs (Kitancharoen et al., 1997; Kitancharoen and Hatai, 1998), Oncorhynchus mykiss eggs (Kales et al., 2007; Shahbazian et al., 2010), Cyprinus carpio eggs (Chukanhom and Hatai, 2004), Ambystoma maculatum (Gomez-Mestre et al., 2006), Oreochromis niloticus (Panchai et al., 2007; Hussein et al., 2013; Panchai et al., 2014; Panchai et al., 2015; Panchai et al., 2016), Salmo trutta eggs (Czeczuga et al., 2005), Pangasianodon gigas (Abking et al., 2012), Mystus cavasius and other species (Chauhan et al., 2013), Clarias gariepinus (Hunjavanit et al., 2012), Tachysurus [Pelteobagrus] fulvidraco eggs