Re-evaluation of the enigmatic species complex Saprolegnia diclina–Saprolegnia parasitica based on morphological, physiological and molecular data

Morphological and molecular phylogenetic analysis of two Saprolegnia sp. (Oomycetes) isolated from silver crucian carp and zebra fish

“…Kitancharoen et al (1997) and Fregeneda-Grandes et al (2007) also reported a group of Saprolegnia isolates mostly isolated from fish eggs assigned to S. diclina, on the basis of their morphological characteristics. Isolates assigned to S. diclina, which have cysts decorated by short spines (Hatai et al 1990) appear to be distributed in different clades with high support as shown in this present study and that of Dié guez- Uribeondo et al (2007). This is probably due to misidentification of some isolates.…”

“…Clade II is a group of saprobiotic species which is relatively far from clade I and clade III as discussed by Dié guez- Uribeondo et al (2007). However, in the present study clade II is more related to clade I in the NJ phylogenetic analyses and it show more closely to Clade III in the analyses of MP/MrBayes, though the bootstrap values are not high (63 %, 63 %, 69 %).…”

“…Clade III isolates are a group of pathogenic species, most of which are obtained from fish lesions and have been the subject of an in depth analysis by Dié guez-Uribeondo et al (2007). All the isolates of this clade, except for S. hypogyna, are characterized by having bundles of long-hooked hairs on their secondary cysts and the septate cyst germination (Beakes et al 1994), although they do show significant differences in their pathogenecity (Dié guez-Uribeondo et al 2007;Fregeneda-Grandes et al 2000, 2001. Based on the high bootstrap support we conclude that the species in clade IV (S. terrestris, S. torulosa, S. monilifera and S. sp.…”

“…Traditional classification is mainly based on the precise descriptions of sexual reproductive organs including oogonia, antheridia, antheridial branch origin, oogonium ornamentation, oospore and lipid droplet position in the oospore (Dick 1969;Seymour 1970;Willoughby 1978;Neish & Hughes 1980;Leclerc et al 2000). Unfortunately, many isolates obtained from animals often fail to produce sexual structures in vitro (Hatai et al 1990;Stueland et al 2005;Dié guez-Uribeondo et al 2007) or form these structures only after a long developmental time (Leclerc et al 2000) or immature oogonia are aborted (Seymour 1970;Johnson et al 2002). Therefore, using traditional morphological criteria Saprolegnia isolates taken from fish lesions are often difficult or even impossible to name.…”

Saprolegnia brachydanis, A New Oomycete Isolated from Zebra Fish

“…Traditionally, the generic definition was mainly based on the asexual characters, especially the mode of zoospores discharge, whereas species differentiation was mainly on the features of sexual reproductive organs including oogonia, antheridia, antheridial origin, and oospore [4,5,12,15]. However, many of these characters may be variable in one species or similar in different species [8] and some strains either lose the ability to produce sexual reproduction or cannot be induced to form them under laboratory conditions [13,18]. So, it is difficult to make definitive identification only using traditional morphological criteria in species level.…”