A. robusta sp. nov., a new species of Achlya (Saprolegniales, Straminipila) from a polluted Argentine channel

Achlya robusta sp. nov. was found on litter (floating twigs, leaves, and roots) in an artificial polluted channel, near a petroleum refinery, in Buenos Aires province, Argentina. The species is described, illustrated and compared with other species of the genus. A. robusta produces mainly smooth and papillate, tuberculate or bullate oogonia and monoclinous antheridial branches. It develops spherical and subglobose oogonia, with the oogonial wall yellowish and containing mainly immature oospheres. The oospores are eccentric and ranging from (1) 4–17 (30) per oogonium.     

Saprolegnia multispora, a new oomycete isolated from water samples taken in a river in the Burgundian region of France

Saprolegnia multispora is described from water and floating organic matter taken in the Tille River, in the Burgundian region of France. The new species is illustrated and compared with other species of the genus. Distinguishing characteristics of S. multispora are the production of smooth-walled oogonia containing many subcentric oospores which are (1-) 11-70 (-100) per oogonium. The antheridial branches supplying the oogonia are predominantly diclinous, but at times these may be monoclinous and androgynous. Morphological features of the oomycete and the sequence of the ITS region of its rDNA as well as their comparison with related species are discussed in this article.     

A. robusta sp. nov., a new species of Achlya (Saprolegniales,Straminipila) from a polluted Argentine channel

Achlya robusta sp. nov. was found on litter (floating twigs, leaves, and roots) in an artificial polluted channel, near a petroleum refinery, in Buenos Aires province, Argentina. The species is described, illustrated and compared with other species of the genus. A. robusta produces mainly smooth and papillate, tuberculate or bullate oogonia and monoclinous antheridial branches. It develops spherical and subglobose oogonia, with the oogonial wall yellowish and containing mainly immature oospheres. The oospores are eccentric and ranging from (1) 4-17 (30) per oogonium.     

A new species of Brevilegnia (Saprolegniales, Straminipila) from Buenos Aires Province, Argentina

Brevilegnia ensenadensis sp. nov. is described from litter (floating twigs, leaves, and roots) in a man-made, polluted channel near a petroleum refinery, in Buenos Aires Province, Argentina. The species is illustrated and compared with other species of the genus; it can be identified by the preponderance of smooth or papillate oogonia, with a distinctive irregular inner wall, borne in bent or coiled oogonial stalks, which are terminal, lateral or of the intercalary position. The oogonia often are irregular in shape, and the oospheres mostly are immature. The single oospore is eccentric inside the great oogonia, and the species develops mainly diclinous antheridial branches and has fewer monoclinous and androgynous ones.     

Saprolegnia semihypogyna sp. nov., a saprolegniaceous oomycete isolated from soil in Japan

Saprolegnia semihypogyna, a saprolegniaceous oomycete (Saprolegniales, Oomycetes), is described based on two strains isolated from soil samples collected in Japan. It is characterized by having a new combination of sexual characters in the genus Saprolegnia, namely, producing mostly monosporous oogonia with subeccentric oospores and semihypogynous or androgynous antheridial branches. The species is morphologically similar to Scoliolegnia subeccentrica, although the oogonial wall of the former is smooth and that of the latter is densely ornamented. Morphological comparison of the two species indicates that the generic status of the genus Scoliolegnia is questionable. Received: February 22, 2001 / Accepted: September 5, 2001     

Production of Oogonia and Oospores of <Emphasis Type="Italic">Leptolegnia chapmanii</Emphasis> Seymour (Straminipila: Peronosporomycetes) in <Emphasis Type="Italic">Aedes aegypti</Emphasis> (L.) Larvae at Different Temperatures

The aquatic oomycete fungus Leptolegnia chapmanii Seymour is pathogenic to mosquito larvae, but it has been little studied since it was first isolated. Although studies have been performed on different biological isolates of L. chapmanii around the world, they were made on zoospores and a very little or even nothing is known about the sexual stage (oogonia and oospores), which allows L. chapmanii to remain in the environment when conditions are not favorable. The main objective of this study was to determine the relationship between temperature and time of onset of L. chapmanii oogonia and oospores in Ae. aegypti larvae. Leptolegnia chapmanii-infected IV instar Ae. aegypti larvae were incubated at different temperatures between 5 and 45°C and photoperiod-controlled for 90 days. The number of oogonia and oospores was examined daily for each tested temperature. As was expected, low temperatures extended the times of oogonia formation, as much as seven times. Likewise, temperatures significantly affect the number of oogonia produced.     

Awadhiella—A new genus of coleochaetaceae from India

The paper reports a new algal found growing on Ceratophyllum leaves in a small pond near Lucknow. It possesses a heterotrichous vegetative organization, typical Coleochaeta-like bristles and an oogamous sexual reproduction. Antheridia are simple, unspecialized, formed from vegetative cells producing several antherozoids each. Oogonia are large, swollen, oval, slightly elongate structures possessing a prominent beak. One or more oospheres are formed in each oogonium and some sterile residual cytoplasm may be left unutilized during oogenesis. Sterile cortications around the oospore or fertilized oogonia are absent. The present plant is considered a new genus of the family Coleochaetaceae (Chlorophyceae) and named Awadhiella gen. nov.     

Saprolegnia oliviae sp. nov. isolated from an Argentine river (Tierra del Fuego Province,Argentina)

Saprolegnia oliviae sp. nov. is described from litter (floating dead twigs, leaves and roots) in the Olivia River, Ushuaia Department, Tierra del Fuego Province (Argentina). The new species is illustrated and compared with other species of the genus. Distinguishing characteristics of S. oliviae are the production of smooth oogonia (with some lateral or terminal projections) and the absence of antheridial branches on the majority of the oogonia, but when present, they are mostly diclinous, at times oogonia are supplied with androgynous and monoclinous antheridial branches. The oogonial stalks are predominantly short and straight or long and bent, curved or many times coiled; oospores are distinctive subcentric, (1-) 15-50 (-70) per oogonium. Morphological details of the new species and its comparison with other described species are discussed here.     

The Life-History of Marginariella urvilliana (Ach. Rich.) Tandy

In Marginariella urvilliana gametes are produced in the thirdyear and then annually for several years. On germination ofthe egg a single primary rhizoid is formed. Its early subdivisioninto four main branches is unusual amongst the Fucaceae. Growthof both the main axis and of the receptacles is carried outby a three-sided apical cell. The oogonia develop earlier thanthe antheridia. Nuclear divisions are completed within the conceptacle,often several weeks before extrusion of oospheres. The liberatedoosphere is held in a tubular stalk until after fertilizationand the sporeling has begun to develop. Marginariella has affinities with the other endemic submergedAustralasian fucoids, and together these form a rather isolatedgroup, probably rightly included within the Fucaceae.     

<Emphasis Type="Italic">Saprolegnia brachydanis</Emphasis>, A New Oomycete Isolated from Zebra Fish

Saprolegnia brachydanis is described from zebra fish (Brachydanio rerio) in Wuhan, Hubei Province, China. The species is illustrated and compared with other species of the genus. The distinctive characteristics of S. brachydanis are the production of glomerulate oogonia wrapped around by predominantly monoclinous antheridia which can be up to eight in one oogonium. The oogonial stalks are short, straight, or curved and the antheridia, twisted, can enwind one or more oogonia. The oospores cannot mature or easily abort. Morphological features of the oomycete and the ITS sequence of its rDNA as well as the comparison with related species are discussed in this article.     

Peronosporomycetes (Oomycota) from a Middle Permian Permineralised Peat within the Bainmedart Coal Measures,Prince Charles Mountains,Antarctica

The fossil record of Peronosporomycetes (water moulds) is rather sparse, though their distinctive ornamentation means they are probably better reported than some true fungal groups. Here we describe a rare Palaeozoic occurrence of this group from a Guadalupian (Middle Permian) silicified peat deposit in the Bainmedart Coal Measures, Prince Charles Mountains, Antarctica. Specimens are numerous and comprise two morphologically distinct kinds of ornamented oogonia, of which some are attached to hyphae by a septum. Combresomyces caespitosus sp. nov. consists of spherical oogonia bearing densely spaced, long, hollow, slender, conical papillae with multiple sharply pointed, strongly divergent, apical branches that commonly form a pseudoreticulate pattern under optical microscopy. The oogonia are attached to a parental hypha by a short truncated stalk with a single septum. Combresomyces rarus sp. nov. consists of spherical oogonia bearing widely spaced, hollow, broad, conical papillae that terminate in a single bifurcation producing a pair of acutely divergent sharply pointed branches. The oogonium bears a short truncate extension where it attaches to the parental hypha. We propose that similarities in oogonium shape, size, spine morphology and hyphal attachment between the Permian forms from the Prince Charles Mountains and other reported Peronosporomycetes from Devonian to Triassic strata at widely separated localities elsewhere in the world delimit an extinct but once cosmopolitan Palaeozoic to early Mesozoic branch of the peronosporomycete clade. We name this order Combresomycetales and note that it played an important role in late Palaeozoic and early Mesozoic peatland ecosystems worldwide.     

AQUATIC FUNGI OF ICELAND: ACHLYA AMERICANA

Twenty-one isolates of Achlya with smooth-walled oogonia, small, eccentric oospores, and a preponderance of monoclinous antheridial branches are characterized quantitatively and qualitatively. The isolates are separated into nine series, and the parameters through which they relate to and digress from one another are discussed. At most, three quantitative characteristics separate the various groups. The distinctive features of isolates in two series are unstable in culture. A concept of broad species limits is applied to A. americana.     

Towards a universal barcode of oomycetes – a comparison of the cox1 and cox2 loci

Oomycetes are a diverse group of eukaryotes in terrestrial, limnic and marine habitats worldwide and include several devastating plant pathogens, for example Phytophthora infestans (potato late blight). The cytochrome c oxidase subunit 2 gene (cox2) has been widely used for identification, taxonomy and phylogeny of various oomycete groups. However, recently the cox1 gene was proposed as a DNA barcode marker instead, together with ITS rDNA. The cox1 locus has been used in some studies of Pythium and Phytophthora, but has rarely been used for other oomycetes, as amplification success of cox1 varies with different lineages and sample ages. To determine which out of cox1 or cox2 is best suited as a universal oomycete barcode, we compared these two genes in terms of (i) PCR efficiency for 31 representative genera, as well as for historic herbarium specimens, and (ii) sequence polymorphism, intra‐ and interspecific divergence. The primer sets for cox2 successfully amplified all oomycete genera tested, while cox1 failed to amplify three genera. In addition, cox2 exhibited higher PCR efficiency for historic herbarium specimens, providing easier access to barcoding‐type material. Sequence data for several historic type specimens exist for cox2, but there are none for cox1. In addition, cox2 yielded higher species identification success, with higher interspecific and lower intraspecific divergences than cox1. Therefore, cox2 is suggested as a partner DNA barcode along with ITS rDNA instead of cox1. The cox2‐1 spacer could be a useful marker below species level. Improved protocols and universal primers are presented for all genes to facilitate future barcoding efforts.