Saprolegnia - The iLumina Digital Library

SPECIMENS EXAMINED: -- INDIA (1), K. S. Bhargava (subculture of type).
UNITED STATES (2), RLS.
Saprolegnia sp. 12241
Mycotaxon 2:190, figs. 1-15. 1975
Monoecious. Sporangia oval, ovoid, pyriform, or broadly fusiform, occasionally
subspherical; apex a broad, nearly truncate papilla; renewed internally and confined
within an old sporangium or forming outside the orifice, or infrequently by sympodial
branching; 44-81 x 20-51 µm. Spores dimorphic; escaping slowly through a broad, apical
orifice as laterally biflagellate cells; swimming sluggishly and by slight amoeboid
motion becoming subapically (anteriorly) biflagellate; encysting before germinating to
produce a new hyphal system. Gemmae very sparse; pyriform; confined to discharged
sporangia. Oogonia sparse, terminal on hyphae proliferating through discharged
sporangia; spherical or obpyriform; (38-) 41-77 (-121) µm in diameter, including wall
ornamentations. Oogonial wall pitted, at first smooth, then becoming papillate or
undulate as maturation proceeds; papillae usually formed by the protrusion of wall
substance through the pits. Oospores centric; spherical; (3-) 12-24 (-64) per oogonium
and generally filling it; (14-) 16 (-19) µm in diameter; germination not observed.
Antheridial branches diclinous; slender, unbranched or sparingly branched; originating
as hyphae proliferating through discharged sporangia or as sympodial branches;
persisting. Antheridial cells simple; clavate or tubular; persisting; apically or laterally
appressed; fertilization tubes not observed.
This unusual watermold, tentatively assigned to Saprolegnia, is known only from
four sites (in Norway). The fungus was collected on chironomid exuviae, and on bits of
snakeskin baited in samples of water and sediment. One group of specimens (TWJ
12255) was parasitized by a species of Phlyctochytrium, but the chytrid disappeared as
the watermold was subcultured (in unifungal culture).
As the description shows, the planont behavior pattern in this as yet unnamed
watermold is unlike that of any other member of the family. The planonts are laterally
biflagellate on emergence, and only become anteriorly biflagellate as they move about
with amoeboid (and weak flagellar) motion upon release from the sporangium. In all
other members of the family where the primary spores are not suppressed, these cells
emerge as apically biflagellate swarmers.
A further unusual feature of the Norwegian fungus is that of the configuration of
the sexual apparatus. The oogonia are formed (always) terminally on hyphal branches
proliferating through old sporangia, and the diclinous antheridial filaments may have a
like origin. The majority of the oogonia in all collections were papillate. However, the
papillate condition was in most instances the result of wall substance() protruding
partially from pits. Such a condition has been detected in other species of Saprolegnia,
but it is by no means of common occurrence.
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