Saprolegnia milanezii Pires-Zottarelli C.L.A. & Rocha S.C.O., 2016

Rocha, Sarah Cristina Oliveira, Sandoval-Sierra, Jose V., Diéguez-Uribeondo, Javier, Gonçalves, Danilo R., Jerônimo, Gustavo H., De Jesus, Ana L., Marano, Agostina V. & Pires-Zottarelli, Carmen L. A., 2016, Saprolegnia milanezii sp. nov., a new species of Saprolegniales (Oomycota, Straminipila) from Brazil, Phytotaxa 270 (4), pp. 286-294 : 289-292

Saprolegnia milanezii Pires-Zottarelli C.L.A. & Rocha S.C.O. sp. nov. ( Figs. 1 , 2 )

MycoBank number: MB817658.

Holotype: − BRAZIL. São Paulo: Cananéia city, “Parque Estadual da Ilha do Cardoso”, isolated from freshwater of the Perequê river (“ Poço das Antas ”), 20 February 2013, SP446402 (Specimen permanently preserved in a metabolically inactive state: parts preserved in absolute ethanol); ex-holotype in CCIBt 4001; ex-isotype in MMBF 02 /16. GenBank accession number ITS KX528018, and LSU KX528019 .

Additional specimens: − BRAZIL. São Paulo: Cananéia city, “Parque Estadual da Ilha do Cardoso”, isolated from freshwater of the Perequê river (“Riacho cor de chá”), 20 February 2013, SP446403 (Specimen permanently preserved in a metabolically inactive state: parts preserved in absolute ethanol), culture strain CCIBt 4027 and MMBF 03/16. GenBank accession number ITS KX528020, and LSU KX528021.

Description: − Zoosporangia typically scarce, terminal, fusiform and/or filiform, 113.8±38.3 × 27.3±5.6 μm (overall range 70.0−180.0 × 17.5−40.0 μm); renewed internally or by cymose branching, and also not rarely growing through the empty ones. Zoospore discharge saprolegnoid. Zoospores dimorphic; encysted zoospores 10.0±02.5 (overall range 7.5−12.5 μm). Gemmae present, spherical, some irregular, functioning directly as zoosporangia, germinating and forming new mycelia or differentiating into functional oogonia. Oogonia terminal, some intercalary, lateral and sessile, pyriform 75.6±16.5 × 50.0±08.1 μm (overall range 55.0−100.0 × 42.5−65.5 μm), occasionally spherical, 63.0±16.0 (overall range 45.0−97.5) μm diam., some in a racemous fashion, rarely catenulate; smooth-walled, pitted; oogonial stalks ½−7 times the diameter of the oogonium in length, some extended near the oogonium septum. Oospheres normally maturing, sometimes abortive. Oospores subcentric, spherical, 32.0±05.5 (overall range 22.5−42.5 μm), filling the oogonium, 1−6 (12) per oogonium. Antheridia scarce, monoclinous and diclinous; antheridial branches branched; antheridial cells simple, attached apically; fertilization tubes not observed.

Notes: −Characteristics of this species includes the frequent formation of structures resulted from the growth of germinating gemmae, and also the late maturation of the oospheres probably related with the rare presence of antheridia. This species presented high variation in its morphological characteristics, such as the absence of asexual reproduction after long time of preservation.

Figures

FIGURE 1. Saprolegnia milanezii.A.Empty fusiform zoosporangium.B. Zoosporangium with internal proliferation and primary zoospore discharge. C. Basipetal renewal of the zoosporangium. D. Gemma functioning as zoosporangium. E. Proliferous gemmae. F. Gemma with several tubes for zoospore discharge. Scale bar = 10 μm.

FIGURE 2. Saprolegnia milanezii. A. Oogonium with oospheres and diclinous antheridium. B. Oogonia with diclinous and monoclinous antheridia and abortive oospheres. C. Extended stalk near the oogonium septum. D. Oogonium with one pit and subcentric oospores. E. Oogonia branched in racemous fashion. F. Catenulate oogonia and subcentric oospores. Scale bar = 10 μm.