FACULTATIVE PARASITISM OF SPIROGYRA SP. (CHLOROPHYTA) BY SAPROLEGNIA ASTEROPHORA AND PYTHIUM GRACILE (EUMYCOTA, OOMYCETES)¹

Abstract

Spirogyra sp. Link was found to be parasitized by filamentous fungi tentatively identified as Saprolegnia asterophora de Bary and Pythium gracile Schenk, in field samples and when maintained in unaltered pond water in an 18 h fluorescent light–6 h dark regime at 18 ± 2°C. Collections were made periodically between March 1978, and November 1979, from a pond in Mill Seek Sanctuary near Oyster Bay, Nassau Co., Long Island, New York. Initially, less than 1% of the total field population of Spirogyra sp. was infected by either fungal parasite with Saprolegnia asterophora being the dominant parasite present generally alone in most samples or present in 80–95% of the total number of infected algal filaments when occurring concurrently with P. gracile. However, in the laboratory, approximately 100% of the Spirogyra sp. filaments in any given sample became infected by Saprolegnia asterophora and/or P. gracile within a 1—2 wk and 3–4 wk period, respectively, with vegetative hyphae involved in the spread of infection to neighboring algal filaments. Infection of algal filaments occurred at random points with cell to cell hyphal extension within the filament causing disruption of host cells. Development of S. asterophora, and possibly P. gracile, sexual reproductive structures was common in relation with the host with asexual sporangial production not observed. Saprolegnia asterophora and P. gracile were cultured on glucose, yeast extract, malt extract (GYM) medium from infected Spirogyra sp. filaments, with infection of healthy algal filaments using these cultures by Saprolegnia asterophora, but not by P. gracile, induced in the laboratory. Growth responses and tropic responses of the fungi to the algal host could not be demonstrated.

Virulence, cultivating conditions, and phylogenetic analyses of oomycete parasites in Daphnia

“…Those two are actually the same species, but with interchangeable names (Dick, 1969 b ). Both isolates were of unknown origin, but S. asterophora is a common parasite of green algae (Beck and Erb, 1984). The WM_3 isolate clustered with S. parasitica (ITS), a known parasite of fish (Kitancharoen et al 1996).…”

EFFECTS OF TEMPERATURE AND IRRADIANCE ON THE SEASONAL VARIATION OF A SPIROGYRA (CHLOROPHYTA) POPULATION IN A MIDWESTERN LAKE (U.S.A.)

“…The potential of microorganisms to cause mortality in the field also is not thought to be great. For example, Beck and Erb (1984) found only 1% of filaments in natural populations of Spirogyra to be infected with a potentially destructive oomycete. Although we never observed parasitized filaments, more intensive studies are needed to rule out parasites as causative factors in filament form death.…”

INFECTION, GROWTH, AND COMMUNITY‐LEVEL CONSEQUENCES OF A DIATOM PATHOGEN IN A SONORAN DESERT STREAM1

“…Neither viral particles nor fungal hyphae were evident when infected algae were examined with T E M or light microscopy. Additionally, this pathogen was relatively broad in its action, affecting all diatom taxa to at least some degree; parasitic fungi are typically more host-specific (Canter andJaworski 1978, Beck andErb 1984). Few diatom viruses have been isolated (Van Etten et al 1991, but see Suttle et al 1991), and little is known of their ecology.…”