Saprolegnia - The iLumina Digital Library

CONFIRMED RECORD: -- BRITISH ISLES: Dick (loc. cit.).
RECORDED COLLECTION: -- BRITISH ISLES: Dick (1966, pro parte).
SPECIMENS EXAMINED: -- NORWAY (1), TWJ. MWD (3).
Saprolegnia australis Elliott
New Zealand J. Bot. 6:103, figs. 2, 4 c-f. 1968
(Figure 93 A-E)
Monoecious. Mycelium dense, diffuse; hyphae slender or stout. Sporangia
cylindrical or clavate; renewed internally or cymosely; primary ones 20-460 x 15-33 µm;
secondary ones usually shorter, but up to 600 µm long. Spores dimorphic; discharge
and behavior generally saprolegnoid, occasionally dictyucoid; primary spore cysts 10.5-
11.7 µm in diameter. Gemmae sparse or abundant; cylindrical, clavate, spherical, or
irregular; terminal or intercalary, usually single. Oogonia generally terminal,
occasionally lateral or intercalary, sometimes sessile; obovate, obpyriform, spherical, or
napiform, sometimes slightly irregular, fusiform or dolioform when intercalary;
(35-) 59-80 (-121) µm in diameter. Oogonial wall pitted, smooth. Oogonial stalks
generally ( 1 / 3 -) 1-3 (-4) times the diameter of the oogonium, in length; straight, curved,
twisted, or irregular; unbranched. Oospores may or may not mature, or may abort;
when mature, subcentric; spherical to subspherical; (1-) 4-12 (-32) per oogonium, but
usually not filling it; (10-) 22-27 (-36) µm in diameter; germination not observed.
Antheridial branches, when present, predominantly diclinous, occasionally or rarely,
monoclinous or androgynous; persisting or deliquescing; sparingly to moderately
branched; usually slightly irregular, sometimes conspicuously contorted. Antheridial
cells simple or branched, persisting; tubular or attached in a digitate fashion;
fertilization tubes present or absent, not persisting.
Until the report by Padgett (1976) of the recovery of specimens from eastern
North Carolina, Saprolegnia australis was known only from the type locality. Saprolegnia
australis appears to be most variable with respect to sporangium size and the
predominating oospore number and diameter (Padgett, 1976: Table 1; Nolan and
Maestres, 1978: Table 1).
The oospores of Saprolegnia australis are subcentric with the refractive droplets
surrounding the ooplasm (Fig. 93 B) or only partially so (Fig. 93 E); such oospores are
referred to by T. W. Johnson (1956b) and Seymour (1970) as types I and III, and both
types can occur in the same oogonium. The oospheres of S. australis may or may not
mature, or the oospores may develop and then abort (Fig. 93 A, C, D). In any event,
nearly all oogonia contain at least a few disintegrated cells or imperfectly formed
oospheres. Budding of oospheres -- resulting in small, spherical cells -- has been
reported (Padgett, 1976).
The preponderance of diclinous antheridial branches in Saprolegnia australis
recalls a like condition in S. diclina. The oospheres of the latter generally mature,
however, yet it must be recognized that some of the “parasitica-like” forms of S. diclina
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