Saprolegnia - The iLumina Digital Library

Saprolegniaceae, p. 56, pl. 17. 1923
(Figure 93 F-H)
Monoecious. Hyphae sparingly branched. Sporangia filiform, cylindrical,
pyriform, or irregularly clavate; straight, curved, or irregular; renewed internally, or by
cymose or sympodial branching, or in basipetalous succession; 40-432 x 10-63 µm.
Spores dimorphic, or rarely monomorphic; discharge and behavior saprolegnoid, rarely
dictyucoid or aplanoid; primary spore cysts 10-13 µm in diameter. Gemmae abundant;
spherical, oval, or irregular; terminal, rarely intercalary; catenulate or single. Oogonia
lateral, occasionally terminal, very rarely intercalary; occasionally glomerulate;
spherical, napiform, or obpyriform, rarely () apiculate; (36-) 42-56 (-106) µm in
diameter. Oogonial wall pitted or unpitted; smooth. Oogonial stalks stout; ( 1 / 4 -) 1 (-4)
times the diameter of the oogonium, in length; straight, curved, or irregular;
unbranched or branched. Oospores subcentric, rarely centric; 1-2 (-12) per oogonium,
and usually not filling it; (14-) 32-38 (-52) µm in diameter; germination not observed.
Antheridial branches, when present, monoclinous or diclinous, occasionally
androgynous; slender, curved or slightly irregular, unbranched or branched; persisting.
Antheridial cells simple; persisting; apically or laterally appressed; fertilization tubes
usually present, not persisting.
Generally, each oogonium of Saprolegnia megasperma has only one large and
prominent oospore. As Coker (loc. cit.) mentioned, the oogonia of this species
occasionally are arranged racemosely in clusters near the ends of hyphae. Furthermore,
Seymour (1970) found the oogonia to be glomerulate at times. Both of these authors
reported the monoclinous antheridial filaments to be unbranched, but in the specimen
we have from Sweden, they are occasionally once-branched.
Insofar as we can determine, the only difference between Saprolegnia megasperma
and S. unispora is that the former has antheridia but the latter does not. The
arrangement of oogonia in S. unispora in a scorpioid cyme (Coker, 1923: pl. 23, figs. 2, 3)
is a characteristic found also occasionally in S. megasperma.
An isolate identified as S. megasperma deposited at the Centraalbureau, Baarn,
lacks antheridial filaments. That specimen must therefore be identified as S. unispora.
CONFIRMED RECORDS: --AUSTRALIA: Cookson (1937:241). CANADA: Nolan
(1975a: fig. 1; 1975b: figs. 5-7). JAPAN: Shibuya (1959:147, fig. 2). LATVIA: Apinis
(1929a:218). SOUTH AMERICA: Beneke and Rogers (1970:59). UNITED STATES:
Beneke (1948b:45); R. L. Butler (1975: figs. 53-56); Coker (loc. cit.); A. W. Ziegler
(1948b:18, pl. 2, figs. 1, 2; 1952: pl. 2, fig. 3). USSR: Logvinenko and Meshcheryakova
(1971: fig. 4).
RECORDED COLLECTIONS: -- BRITISH ISLES: Dick (1962, 1963, 1966); Dick
and Newby (1961); Willoughby and Collins (1966). JAPAN: Suzuki (1961f); Suzuki and
Hatakeyama (1960). SOUTH AMERICA: Upadhyay (1967). UNITED STATES: Farr and
Paterson (1974); G. C. Hughes (1959, 1962); Poitras (1955); A. W. Ziegler (1958b).
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