Ascospore Types Research Articles

Echinoplaca vezdana (Ostropales: Gomphillaceae): a new lichenised fungus

SummaryLücking, R. & Kalb, K.: Echinoplaca vezdana: a new lichenised fungus. ‐ Taxon 50: 837–840. 2001. ‐ ISSN 0040‐0262.The lichenised fungus Echinoplaca vezdana from the Philippines is described and illustrated. It has a comparatively large thallus, large apothecia, and 2–4 muriform ascospores per ascus. The new taxon is closely related to E. diffluens, which differs in having transversely septate ascospores. The two species form another pair of morphologically similar taxa differing in ascospore types of which five were previously known. Echinoplaca vezdana is dedicated to Antonín Vňzda, one of the outstanding lichen taxonomists of the 20th century, on the occasion of his recent 80th birthday.

Programmed Ascospore Death in the Homothallic Ascomycete Coniochaeta tetraspora

Immature asci of Coniochaeta tetraspora originally contain eight uninucleate ascospores. Two ascospore pairs in each ascus survive and mature, and two die and degenerate. Arrangement of the two ascospore types in individual linear asci is what would be expected if death is controlled by a chromosomal gene segregating at the second meiotic division in about 50% of asci. Cultures originating from single homokaryotic ascospores or from single uninucleate conidia are self-fertile, again producing eight-spored asci in which four spores disintegrate, generation after generation. These observations indicate that differentiation of two nuclear types occurs de novo in each sexual generation, that it involves alteration of a specific chromosome locus, and that the change occurs early in the sexual phase. One, and only one, of the two haploid nuclei entering each functional zygote must carry the altered element, which is segregated into two of the four meiotic products and is eliminated when ascospores that contain it disintegrate. Fusion of nuclei cannot be random—a recognition mechanism must exist. More study will be needed to determine whether the change that is responsible for ascospore death is genetic or epigenetic, whether it occurs just before the formation of each ascus or originates only once in the ascogonium prior to proliferation of ascogenous hyphae, and whether it reflects developmentally triggered alteration at a locus other than mating type or the activation of a silent mating-type gene that has pleiotropic effects. Similar considerations apply to species such as Sclerotinia trifoliorum and Chromocrea spinulosa, in which all ascospores survive but half the spores in each ascus are small and self-sterile. Unlike C. tetraspora, another four-spored species, Coniochaetidium savoryi, is pseudohomothallic, with ascus development resembling that of Podospora anserina.

Additions to the foliicolous lichen flora of the Ivory Coast and Guinea (Tropical West Africa)

Four new foliicolous lichen species are described from the Ivory Coast (Tropical West Africa): Bapalmuia ivoriensis sp. nov., Chroodiscus africanus sp. nov., C. verrucosus sp. nov., and Lasioloma inexspectatum sp. nov. In addition, the new combination Calenia inconspicua comb, nova [Bas.: Heterothecium inconspicuum] is introduced. Lasioloma inexspectatum is the first species in the genus characterized by transversely septate ascospores and provides additional evidence for phylogenetic lines regarding the evolution of ascospore types in the lichen family Ectolechiaceae. In addition, 61 new records for the Ivory Coast and seven for Guinea are presented, increasing the number of species known in these areas to 161 and 124, respectively. Five species are new for tropical Africa, and six new for the Paleotropics. Further taxonomical and ecogeographical notes on the foliicolous lichen flora of tropical West Africa are provided.

Addiciones y correcciones al conocimiento de la liquenoflora foliícola de Costa Rica. La familia Asterothyriaceae y el género Chroodiscus ( Thelotremataceae), con un análisis filogenético

The taxonomy of foliicolous representatives of the lichen families Asterothyriaceae ( Asterothyrium, Gyalidea, Psorotheciopsis) and Thelotremataceae ( Chroodiscus) in Costa Rica is revised. Seven new species and one new variety are described: Asterothyrium anomalum var. pallidum Henssen & Lücking var.n., A. aulaxinoides Lücking sp.n., A. chroodisciforme Lücking sp.n., A. rondoniense Bat. & H. Maia ex Henssen & Lücking sp.n., A. septemseptatum Lücking sp.n., A. tetrasporum Lücking sp.n., A. uniseptatum Lücking sp.n., and Chroodiscus submuralis Lücking sp.n. Asterothyrium gigantosporum Lücking and A. hedbergii Kalb & Vězda are reported from Costa Rica for the first time. On account of morphological and anatomical features, an attempt is made to trace intrageneric relationships in the genus Asterothyrium, and the ascospore type is demonstrated not to correlate well with supposedly natural groups. Furthermore, the systematics of the Asterothyriaceae is briefly discussed. The result of a phylogenetic analysis based on phenotypic characters is not in contradiction with the hypothesis that the genera Gyalidea, Solorinella, Linhartia, Psorotheciopsis, and Asterothyrium, currently placed in three different families, are easily accomodated within a single family Asterothyriaceae. Consequently, Solorinellaceae is placed into synonymy with Asterothyriaceae. In addition, Linhartia is reunited with Psorotheciopsis, since the different ascospore sizes are considered insufficient for generic separation, and the following new combinations are proposed: Psorotheciopsis gyalideoides (Vězda) Henssen & Lücking comb.n. [Bas.: Linhartia gyalideoides Vězda], Psorotheciopsis philippinensis (Rehm) Lücking comb.n. [Bas.: Linhartia philippinensis Rehm. Syn.: L. vezdana Lücking], and Psorotheciopsis varieseptata (Vězda) Henssen & Lücking comb.n. [Bas.: Linhartia varieseptata Vězda].

Ascus and ascospore morphogenesis

The diagnostic feature for members of the subdivision Ascomycotina is that sexual reproduction results in the production of endogenous ascospores within asci. A range of ascus and ascospore types is found within the group. Traditionally, asci have been classified as unitunicate, bitunicate or prototunicate, although a spectrum of intermediate types of asci also occurs. Variations occur in the structure of ascus and ascospore walls, ascus apical structures, septal pore structures, ascospore size and shape, ascospore pigmentation, the number of cell compartments within each ascospore, the number of ascospores per ascus and the arrangement of ascospores within an ascus. In filamentous ascomycetes, asci arise from ascogenous hyphae and this usually takes place asynchronously within an ascoma. Crozier formation is involved in ascus initiation in many, but not all, filamentous species. Asci exhibit determinate growth and usually represent highly specialized hyphal elements. Following ascus extension a simple to complex apical structure is commonly formed in those ascomycetes which discharge their ascospores actively. Ascospore formation involves cytoplasmic compartmentalization by double delimiting membranes between which the ascospore wall develops. Confusion in the literature about the origin of delimiting membranes is resolved by using the endomembrane concept which comprises one membrane-generating system with different levels of membrane transformation between the nuclear envelope and plasma membrane. Spindle pole bodies and microtubules play important roles in the organization of nuclei and the assembly of the delimiting membranes. Major problems with ascospore wall terminology are overcome by using a simple scheme in which wall material is either primary or secondary. Ascospore liberation from mature asci may be either an active or passive process. In actively discharging species, the motive force for discharge commonly arises from an increase in internal hydrostatic pressure arising from water uptake. To date most studies on ascus and ascospore morphogenesis have been descriptive involving light microscopy and/or electron microscopy. However, much useful information has also been obtained from mutant analysis and significant progress has recently been made in understanding the role of the mat locus in controlling dikaryon formation. Of significance in future studies will be the increased integration of traditional approaches with newer cell biological techniques to study ascus and ascospore morphogenesis.

Biodiversity of freshwater fungi

There are more than 600 species of freshwater fungi with more known from temperate, as compared to tropical regions. These includeca 340 ascomycetes, 300 deuteromycetes, and a number of lower fungi which are not discussed here.Aniptodera, Annulatascus, Massarina, Ophioceras andPseudohalonectria are common freshwater ascomycetes, which appear to be well adapted for this lifestyle either in their ascospore types or their competitive-degradative characters. The most common genera of wood-inhabiting deuteromycetes includeCancellidium, Dactylaria, Dictyosporium andHelicomyces. They are categorized into four groups depending on their form and life style: the ingoldian hyphomycetes; the aero-aquatic hyphomycetes; the terrestrial-aquatic hyphomycetes; and the submerged-aquatic hyphomycetes. The adaptations of aquatic fungi for their dispersal and subsequent attachment to new substrates are discussed.

Saxicolous species of the genus </i>Rinodina<i> (lichenized Ascomycetes, Physciaceae) in southern Africa

A revision of saxicolous species of the genus Rinodina (Ach.) Gray (lichenized Ascomycetes. Phvsciaceae) in southern Africa is presented. The study area covers the following countries: Angola. Namibia. Republic of South Africa. Lesotho.Swaziland, Zimbabwe, and Mozambique. Fifteen Rinodina species are treated in detail, and three of them are new to science:Rinodina longisperma Matzer H.Mayrhofer. R. scabridula Matzer H.Mayrhofer, and R. striatitunicata Matzer H.Mayrhofer. The general part of the study includes information on the most important characters of the species with a special focus on ascospore types and ontogeny, and biogeographical notes are also given. A key to the species is provided. All the species are described in detail with notes on their ascus characters, spermogonial apparatus, and chemical characteristics, and their substrate and general distribution are indicated. The descriptions are accompanied by illustrations of the ascospores. Except for Rinodina oxydata s.I., the distribution of all the species in southern Africa and other parts of Africa respectively, is mapped.Several names were referred into synonymy, including Rinodina almbornii H.Mayrhofer. a synonym of R. confragosula (Nyl. in Cromb.) Miill.Arg.. and R. depressa (Vain.) Zahlbr. and R. albicans H.Mayrhofer which are synonymous to R. huillensis Vain.A separate section encompasses nine excluded species.

Biscogniauxia anceps comb. nov. and Vivantia guadalupensis gen. et sp. nov.

Biscogniauxia anceps infrequently produces the ascospore type expected of such fungi, namely an unequally bicelled spore with a large dark-walled cell and a smaller hyaline appendage cell. The predominant ascospore type features two unequal hyaline cells. Both hyaline cells germinate readily. Vivantia guadalupensis produces bicelled ascospores that remain permanently hyaline. Both fungi produce Nodulisporium anamorphs in culture. The implications of these findings in regard to taxonomic concepts in the Xylariaceae are discussed.

On the ascus types in thePhysciaceae (Lecanorales)

Comparative studies in thePhysciaceae revealed that characters of the apical apparatus of asci differ between the various genera. Two major ascus types are observable in this family. They are found to correspond with certain ascospore types.

Prostratus, a new diaporthaceous ascomycete genus on Cyclobalanopsis from Taiwan

Prostratus cyclobalanopsidis gen. et sp. nov. is described and illustrated from Taiwan and placed in the family Melanconidaceae. This unusual ascomycete is characterized by horizontal stromatic ascomata, asci with distinct apical structures not turning blue in iodine and brown ascospores with a hyaline dwarf cell at the basal or apical end. Similar types of dwarf-celled ascospores are characteristic of some species of Anthostomella and Clypeosphaeria but this genus is clearly separable from them by its distinct diaporthaceous horizontal stromatic ascomata with an upwardly bending ostiolar beak and by asci with an apical structure not turning blue in iodine.

Airborne fungi in an Italian rice mill

Studies employing volumetric spore trap (VSP) and gravity settling culture plates (GSC) were conducted in order to analyse the air spora of a rice mill at Pavia, Italy, from October-December 1988. Results revealed a variety of fungal spores belonging to different genera and including recognized rice pathogenic fungi. The most frequent genera by GSC method includedAcremonium, Alternaria, Aspergillus, Aureobasidium, Cladosporium, Epicoccum, Fusarium, Helminthosporium, Mucor, Nigrospora, Penicillium, Rhizopus, Trichoderma, Trichothecium, and some unidentified fungi. Environmental assessment of fungal spores by VSP revealed that the most prevalent fungi were:Alternaria, Cladosporium, Epicoccum, Helminthosporium, Nigrospora, Pyricularia, Tilletia and hyaline, dark and coloured types of ascospores and basidiospores. Airborne fungal spore concentrations were particularly high (5,000–6,000 spores/m3) in the rooms of the rice mill where the initial stages of rough rice transformation take place, and dropped to 2,500 spores/m3 in the last room, where workers are. During a temporary interruption of the working processes, air spora concentration dropped below 1,000 spores/m3.Cladosporium, Epicoccum andNigrospora spores were predominant in all subdivisions of the indoor environments of the rice mill.

Ascospores hyperphoretic on mites associated with Ips typographus

Ten morphologically distinct types of ascospores were recognized from the bodies of 17 species of mites associated with adults of Ips typographus collected from pheromone traps in Sweden. The ascospores seemed to stick anywhere on the mites, with no special spore-carrying structures (sporothecae) evident. Most of the 739 mite individuals examined in this study transported one or more species of ascospore, sometimes in large numbers. One mite carried as many as six species. Ophiostoma polonicum , the most pathogenic of the blue-stain species, was noted on nine mite species, sometimes in large numbers.

Ascospore Morphology and Ultrastructure of Species Assigned to the Genus Lipomyces Lodder et Kreger-van Rij

Ascospores of Lipomyces species were examined by transmission electron microscopy. The following four types of ascospore morphology were found in replicas: (i) ascospores with longitudinal ridges; (ii) ascospores with irregular folds; (iii) ascospores with slightly undulating surfaces; and (iv) ascospores with smooth surfaces. In contrast, on the basis of ultrastructure of thin sections, only three types of ascospores were identified.

Air spora of groundnut fields

Air spora over groundnut fields at Visakhapatnam was studied for a period of one year, i.e., from 1st June 1974 to 31st May 1975, using a ‘hirst spore trap’ installed with its orifice at 0·5 m above the ground level. More than 60 fungal spore types, hyphal fragments, pollen grains, epidermal hairs, insect parts and other inorganic particles were observed on the exposed trap slides. Seasonal and diurnal periodicities and per cent contributions to the total air spora were recorded for 38 components.Cladosporium was the most dominant spore type contributing 47·32% to total air spora. Basidiospore and ascospore types occurred mainly during rainy season while most of the conidial types occurred in high numbers during winter. Ascospores, basidiospores, conidia ofFusariutn and insect parts showed night peaks while most of the conidial types had peaks around noon. Based on the diurnal peak hour different spore types were grouped into eight types. Some spore types showed marked seasonal variations in their diurnal periodicity pattern. Most of the conidial types occurred in higher numbers when the temperatures were in the range of 28–33° C and relative humidities of 60–75%. Rain had a profound effect on the air spora.

Genetic Evidence for Hybridization in an Interspecific Cross in the Genus Sordaria

SUMMARY: When the two heterothallic species Sordaria heterothallis and S. thermophila are crossed, two types of viable ascospores are recovered. The first, the mature black ascospore, is produced with a mature eight-spored ascus formed from an intraspecific fusion of nuclei of the same mating type. The second, the non-pigmented germinable ascospore, is produced by the interspecific fusion of nuclei of opposite mating types within an ascus in which all other ascospores are aborted. The non-pigmented ascospore is the product of the mixed genomes of the two species. It is a recombinant spore from which either species may be obtained by the partial substitution of its genome through successive backcrosses. Its inability to develop pigmentation, the irregular growth patterns of some of the strains which it produces and their inability to react in complementation tests, appear to be the result of a lack of affinity between the two species.

Some components of the air‐spora in Jamaican banana plantations

SUMMARYThe air in several Jamaican banana plantations was sampled from July 1960 to September 1961 with an automatic volumetric spore trap. In dry weather, many fungi showed typical diurnal periodicity. Group I fungi (Deightoniella, Nigrospora, Cordana, Corynespora, Zygosporium and Zygophiala) first appeared shortly after 06.00 hr., reached a peak before 09.00 hr. and then showed a rapid fall. Group II fungi (Cladosporium, Alternaria, Curvularia, Cerebella, Pithomyces, Periconiella, Memnoniella, Ustilago and others) and pollens had peak concentrations between 09.00 and 14.00 hr. Groups I and II formed the majority of the spore catch during daylight, but they were practically absent between 20.00 and 06.00 hr. Group III fungi (represented chiefly by ascospores, especially of Leptosphaeria spp., basidiospores and splash‐dispersed types) first appeared near 20.00 hr., attained a maximum between midnight and 06.00 hr. and a minimum during daylight. In dry weather, Cladosporium conidia accounted for 23% of the total catch; coloured fusiform spores for 18%; coloured basidiospores for 16%; unclassified minute spores (including Sporobolomyces) for 14%; and Deightoniella only 0.2%.During rain, the typical dry‐air‐spora decreased and was replaced to varying extents by group III ascospore types and splash‐dispersed spores. When, after rain, the plantation dried out during daylight, group III fungi decreased while groups I and II briefly reappeared before the typical night‐time flora developed. When rain was continuous during daylight, groups I and II were rare; ascospores and splash‐dispersed spores dominated the traces. All fungi occurred in low concentrations during heavy rain, periods of drought and strong wind. With rain or under‐tree irrigation or both, the following days had varying increases of all group I fungi and certain group II fungi, probably because favourable humidity conditions caused increased sporulation.