Saprolegnia - The iLumina Digital Library

Saprolegnia torulosa is an exceptionally variable species, but all the isolates we
have examined express two characteristics, namely catenulate oogonia (which may or
may not disarticulate; Fig. 97 A), and predominantly diclinous antheridial branches
(Fig. 97 A, B) of varying densities. In a few instances watermolds identified as S. torulosa
have been described as having oogonia positioned in terminal, discharged, primary
sporangia (Fig. 97 D). This feature, however, is also quite characteristics of S. ferax. In
his description of S. monilifera (=torulosa) from Japan, Nagai (1931:8) wrote that an
antheridium-like “body” formed from the basal septum of the oogonium but was not
involved in fertilization. Prominent protrusions or extensions of the septum into the
oogonial cavity are commonly encountered in species of Saprolegnia, but are of no
consequence taxonomically.
The lengthy synonymy suggests that Saprolegnia torulosa has had a less than
tranquil taxonomic history. For the most part, contradictory reports on the morphology
of the species seem to have centered on the abundance of antheridial hyphae in isolates,
and whether or not the catenulate oogonia disarticulated. Seymour (1970) first directed
attention to the uncertain status principally of three species -- S. torulosa, Isoachlya
(=Saprolegnia) toruloides, and S. monilifera de Bary. He was unable to resolve the
taxonomy of these species, and considered them imperfectly known. From a
comparative study of a number of specimens from Iceland, Howard and his
collaborators (1970) succeeded in defining S. torulosa in a broad sense, and justifying a
lengthy synonymy. Reed (1973:43) did not follow the nomenclature proposed by
Howard and his associates. In a thesis manuscript Reed made a new combination (I.
toruloides was the basionym): Saprolegnia toruloides (Kauffman and Coker). As this name
has not been published it is excluded.
Howard et al. (1970) established experimentally that antheridial branch
abundance and the tendency of oogonia to disarticulate could be modified in
Saprolegnia torulosa. It is reasonable to suppose that the reported absence of antheridial
branches in some specimens (earlier identified as I. toruloides, for example) was
attributable to the evanescent nature of these filaments. The analysis of Saprolegnia
torulosa by Howard et al. (1970) leaves no doubt that there are no sharp distinctions
among the elements of the torulosa complex. Seymour’s (1970:64) views support the
disposition of taxa proposed by Howard and his associates.
In connection with a watermold isolated from Madeira Island Höhnk (1962) used
the name Cladolegnia toruloides (Kauffman et Coker) Johannes. This is an error since
Johannes (1955a:212) included Isoachlya toruloides with Saprolegnia torulosa, and not as a
new combination in his genus Cladolegnia.
CONFIRMED RECORDS: -- BRITISH ISLES: E. M. Brown (1938:166); R. A. Couch
(1951:115, pls. 22-24); O’Sullivan (1965:323, 343, figs. II-50- 60, II-62-74). CANADA:
Maestres (1977:147, figs. 14-20). CZECHOSLOVAKIA: Cejp (1934:88; 1957: fig. 119, 1;
1959a:203, 207, figs. 72-75). DENMARK: A. Lund (1934:17, 18, figs. 6a-e). FRANCE:
Lechmere (1911a:169-174, 175, figs. 1-19 (p. 170), 1-16 (p. 172); 1911b: fig. 1); Moreau and
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