Zoosporic fungi of Oceania. IV. Additional monocentric chytrids

Summary Several monocentric chytrid species of the generaPhlyctochytrium,Rhizidium,Chytridium,Chytriomyces andKarlingia were isolated on various substrata from soils of Oceania. Among these are two new species,Phlyctochytrium megastomum andRhizidium endosporangiatum. The former species is characterized chiefly by sporangia with an usually large apical, subapical, or a lateral exit orifice, the persistence of remnants of the pailla wall at the edge of the exit orifice, and by small zoospores.Rhizidium endosporangiatum is characterized at first primarily by predominantly spherical sporangia which develop 1 to 8 broad papillae. At maturity these papillae give them an angular shape. The exit papillae deliquesce at the tip, and through them protrude prominent arms of an endosporangium which expands and in which the zoospores usually swarm briefly.Willoughby'sChytridium parasiticum occurred abundantly as a parasite ofNowakowskiella sp.,Pythium sp., andPhytophthora sp. and developed epibiotic resting spores like those ofChytriomyces. Accordingly, this parasite is transferred to this genus and renamedChytriomyces willoughbyii because the nameparasiticum is preempted by the author's previously describedChytriomyces parasiticus.This study has been supported by a grant from the National Science Foundation, Washington, D.C.     

Zoosporic fungi of Oceania. VI. Species with biflagellate zoospores

Summary Several species of the Plasmodiophoraceae, Olpidiopsidaceae and Lagenidiaceae were isolated on various substrata from the soils of Oceania. Among these were two parasites of rotifer eggs,Lagenidium septatum andMyzocytium fijiensis. The former species is characterized primarily by septation of the thallus into segments which develop into resting spores without sexual fusions.Mycozytium fijiensis resembles somewhatM. zophthorium but differs from it by smaller zoospores which are delimited outside of the sporangium.     

Zoosporic fungi in freshwater ecosystems

A review of the modern state of knowledge of zoosporic fungi in freshwater plankton and benthos is given. The effects of abiotic factors upon the distribution and development of these fungi are discussed, along with the problem of the role zoosporic fungi play in lake ecosystems.     

Zoosporic true fungi and heterotrophic straminipiles assemblages from soil of Brazilian Cerrado areas

The influence of seasonal fluctuations and environmental factors on the occurrence and distribution of zoosporic true fungi and heterotrophic straminipiles in terrestrial ecosystems is poorly understood. This contribution analyses the species composition, frequency, abundance and diversity of zoosporic true fungi and heterotrophic straminipiles assemblages from two areas of Cerrado in the State of São Paulo, Brazil. Samples of soil were collected at four dates during the rainy and dry seasons. Twenty-one abiotic factors were measured. The assemblages showed a high diversity and evenness and were represented by 30 taxa of Chytridiomycota and Oomycota. Some abiotic factors appeared to have influenced the patterns of distribution and occurrence of the taxa in different areas and/or seasons. Even so, the biotic factors (richness, diversity indices and evenness) and the Sorensen index showed high similarity between the assemblages.     

Zoosporic fungi from Tunisia,and the Seychelles Islands (Indian Ocean)

Twenty-two zoosporic fungi were recovered from soil samples collected in Tunisia and in the Seychelles Islands in the Indian Ocean. One, Phlyctochytrium chandlerii is described as new. Most of the others are referred, sometimes tentatively, to existing species or genera.     

Zoosporic marine fungi from the Pacific Northwest (U.S.A.)

Summary An investigation of the zoosporic fungi in the vicinity of the Friday Harbor Laboratory, San Juan Is., Washington, revealed the presence of great numbers of fungi. With one exception (Olpidium sp.) these were all biflagellate organisms. Predominating were species (11) of Thraustochytriaceae which abounded in water, in association with seaweeds, intertidal sands, and particularly on the surface of bottom samples down to depths of 298 m. A twelfth species of this group has several peculiarities and needs further investigation. Of the algal parasites, one on Polysiphonia and Pterosiphonia is considered new and termed Eurychasma joycei n. sp.The assistance of Drs. R. E. Norris and G. J. Hollenberg in calling my attention to certain algal parasites is gratefully acknowledged. I am also indebted to my colleague Dr. H. C. Whisler, and to Dr. C. Anastasiou for assistance in photographic work.     

Zoosporic Phycomycetes from Hispaniola

Summary Forty-five taxa of zoosporic Phycomycetes are recorded from Hispaniola (Dominican Republic) based on 34 samples collected by the senior author in December–January 1969/70. New species are Entophlyctis obscura, Phlyctochytrium parasitans, P. mucosum, Blyttiomyces harderi, Rhizophlyctis tropicalis, Chytriomyces multioperculatus.Supported in part by N. S. F. Grant GB 3333. It was originally hoped to collect species of Physoderma on Hispaniola but none was found during the few days available for exploration.I am indebted to Prof. I. Bonnelly de Calventi, Director, Inst. de Biologia marina, Univ. Autonoma de Santo Domingo, for many courtesies.     

The mycoses of Oceania

A review of the mycoses of Oceania, defined as the Pacific islands of Melanesia, Micronesia and Polynesia, has revealed the occurrence of cutaneous, subcutaneous and systemic mycoses.Tinea versicolor is the most prevalent of the cutaneous mycotic infections. Dermatophyte infections are also common. The etiologic agents incriminated have beenEpidermophyton floccosum, Microsporum canis, members of theMicrosporum fulvum-gypseum complex,Trichophyton concentricum, T. mentagrophytes, T. rubrum, T. tonsurans andT. verrucosum. Only one case of tinea nigra has been reported and that was in Hawaii. Among the fungi that cause subcutaneous mycoses onlyAllescheria boydii, Nocardia brasiliensis, Madurella mycetomi andSporothrix schenckii have been encountered to date. Among the systemic mycoses, actinomycosis, cryptococcosis and histoplasmosis have been found to be present. The geographic distribution of these actinomycotic and mycotic infections is provided along with data on soil isolation records and histoplasmin sensitivity surveys.Paper presented at the Symposium on Microbiology, Canadian Medical Expedition to Easter Island, Montreal, April 26–28, 1971     

Women's fishing in Oceania

Women's fishing in Oceania has been overlooked in most subsistence studies in the region and, as a consequence, there are few quantitative data available upon which to base an assessment of its importance. However, in the present study, the few data available on women's fishing in Oceania are examined, and these show that women contribute significantly to marine food yields in the region. Also, it is suggested that the highly regular nature of women's fishing makes women more reliable, and therefore more effective than men as suppliers of protein for subsistence. The implications of these findings for future development policies in the region are then discussed.     

Parasitism of Xiphinema rivesi and X. americanum by Zoosporic Fungi

Living Xiphinema americanum (Xa) and X. rivesi (Xr) extracted from soil samples and stored for 1-5 days at 4 or 20 C contained aseptate fungal hyphae. The fungi directly penetrated the nematode''s cuticle from spores encysted near the head. Penetration through the stoma, vulva, or anus was rare. Catenaria anguillulae (Cat), Lagenidium caudatura (Lag), Aphanomyces sp. (Aph), and Leptolegnia sp. (Lep) were isolated into pure culture from infected nematodes. The pathogenicity of these zoosporic fungi was determined by incubating mixed freshly extracted Xa and Xr in 2% soil extract (pH = 6.7, conductivity = 48 μmhos, 20 ± 2 C) containing zoospores obtained from single-spore isolates. After 4 days, Cat, Lag, Aph, and Lep had infected 78, 18, 13, and 22%, respectively, of the nematodes. Both Xa and Xr were infected by every fungus; however, the relative susceptibility of Xa and Xr to these fungi was not determined. All noninoculated control nematodes remained uninfected and alive. In a second experiment, parasitism of Xa and Xr by Aph and Lep was increased when nematodes were incubated in 2% soil extract for 4 days before exposure to zoospores. In a third experiment, parasitism of Xa and Xr by Cat was greater in diluted saturation soil extract (conductivity = 100-400 μmhos) than in undiluted saturation extract (conductivity = 780 μmhos). Cat produced small zoospores (4-μm-d), bulbous infection hyphae, and assimilative hyphae of varying diameters in nematodes, whereas Lag, Aph, and Lep produced large zoospores (8-μm-d) and tubular, uniform infection and assimilative hyphae in nematodes.     

Cosmos and Society in Oceania

Cosmos and Society in Oceania. Daniel de Coppet and André Iteanu. eds. Oxford: Berg Publishers, 1995. 338 pp.     

Adoption and Kinship in Oceania

The frequency and form of adoption practices in Oceania recently have been cited as evidence that human behavior is inconsistent with predictions derived from sociobiological theory (Sahlins 1976). Ethnographic data reviewed here, however, suggest otherwise. In Oceania kinship is an important factor in the selection and treatment of adopted children as adoption occurs almost exclusively among close relatives. Natal children often ally against their adopted siblings over the division of their common parents' estate while adoptive parents themselves frequently apportion their land unequally among their natal and adopted children. These patterns and other data are consistent with predictions generated by a socio biological model of adoptive decisions. The model illustrates how kinship facilitates adoption as a means of modifying extreme family sizes, and how asymmetries in the degrees of relatedness between parents and their adopted and natal children provide the basis of differential treatment of them. Adoption in Oceania provides an example of a clearly cultural behavior which is consistent with socio biological predictions, and suggests that both culture and biology are relevant to an understanding of human behavior . [sociobiology, kinship, adoption, Oceania]     

Population size predicts technological complexity in Oceania

Much human adaptation depends on the gradual accumulation of culturally transmitted knowledge and technology. Recent models of this process predict that large, well-connected populations will have more diverse and complex tool kits than small, isolated populations. While several examples of the loss of technology in small populations are consistent with this prediction, it found no support in two systematic quantitative tests. Both studies were based on data from continental populations in which contact rates were not available, and therefore these studies do not provide a test of the models. Here, we show that in Oceania, around the time of early European contact, islands with small populations had less complicated marine foraging technology. This finding suggests that explanations of existing cultural variation based on optimality models alone are incomplete because demography plays an important role in generating cumulative cultural adaptation. It also indicates that hominin populations with similar cognitive abilities may leave very different archaeological records, a conclusion that has important implications for our understanding of the origin of anatomically modern humans and their evolved psychology.     

Rapid and Pervasive Occupation of Fallen Mangrove Leaves by a Marine Zoosporic Fungus

Samples of leaves of red mangrove (Rhizophora mangle) were incubated on an agar medium selective for pythiaceous oomycetes. Leaves on trees above the water did not contain oomycetes. Marine oomycetes, principally Phytophthora vesicula, had colonized leaves within 2 h of leaf submergence, probably finding them by chemotaxis. The frequency of occurrence of P. vesicula in submerged leaves reached 100% within 30 h of submergence. By 43 h most, if not all, parts of leaves were occupied, and surface treatment with a biocide indicated that leaves were occupied internally. Frequencies of P. vesicula remained near 100% through about 2 weeks of submergence and then declined to about 60% in older (≥4 weeks) leaves. Leaves of white mangrove (Laguncularia racemosa) were also extensively occupied by P. vesicula after falling into the water column, but decaying leaves of turtlegrass (Thalassia testudinum) were not colonized by oomycetes. Ergosterol analysis indicated that the standing crop of living, non-oomycete (ergosterol-containing) fungal mass in submerged red-mangrove leaves did not rise above that which had been present in senescent leaves on the tree; decaying turtlegrass leaves had an ergosterol content that was only about 2% of the maximum concentration detected for red-mangrove leaves. These results suggest that oomycetes are the predominant mycelial eucaryotic saprotrophs of mangrove leaves that fall into the water column and that for turtlegrass leaves which live, die, and decompose under submerged conditions, mycelial eucaryotes make no substantial contribution to decomposition.     

Zoosporic Tolerance to pH Stress and Its Implications for Phytophthora Species in Aquatic Ecosystems

Phytophthora species, a group of destructive plant pathogens, are commonly referred to as water molds, but little is known about their aquatic ecology. Here we show the effect of pH on zoospore survival of seven Phytophthora species commonly isolated from irrigation reservoirs and natural waterways and dissect zoospore survival strategy. Zoospores were incubated in a basal salt liquid medium at pH 3 to 11 for up to 7 days and then plated on a selective medium to determine their survival. The optimal pHs differed among Phytophthora species, with the optimal pH for P. citricola at pH 9, the optimal pH for P. tropicalis at pH 5, and the optimal pH for the five other species, P. citrophthora, P. insolita, P. irrigata, P. megasperma, and P. nicotianae, at pH 7. The greatest number of colonies was recovered from zoospores of all species plated immediately after being exposed to different levels of pH. At pH 5 to 11, the recovery rate decreased sharply (P ≤ 0.0472) after 1-day exposure for five of the seven species. In contrast, no change occurred (P ≥ 0.1125) in the recovery of any species even after a 7-day exposure at pH 3. Overall, P. megasperma and P. citricola survived longer at higher rates in a wider range of pHs than other species did. These results are generally applicable to field conditions as indicated by additional examination of P. citrophthora and P. megasperma in irrigation water at different levels of pH. These results challenge the notion that all Phytophthora species inhabit aquatic environments as water molds and have significant implications in the management of plant diseases resulting from waterborne microbial contamination.Phytophthora species, a group of oomycetes in the kingdom of Stramenopila and well-known plant pathogens, were first listed as “water molds” by Blackwell in 1944 (5), and this notion has since been generally accepted. These species are phylogenetically close to golden-brown algae, although morphologically and physiologically, they resemble fungi. Most algae are aquatic in nature. Phytophthora species produce flagellate zoospores as their primary dispersal structure (35-37, 39). Zoospores can travel in aquatic environments actively on their own locomotion and passively through water movement (12, 13, 41).More than 20 species of Phytophthora, including P. ramorum, the sudden oak death pathogen, have been isolated from irrigation reservoirs and natural waterways (20-22, 30, 40, 43), and a number of previously unknown taxa also have been documented in aquatic environments (8, 24). These pathogens pose a threat to agricultural sustainability and natural ecosystems, as agriculture increasingly depends on recycled water for irrigation in light of rapidly spreading global water scarcity (19, 22). Recycling irrigation systems provide an efficient means of pathogen dissemination from a single point of infection to an entire farm and from a single farm to other farms sharing the same water resources (22, 24).A search of science-based solutions to this crop health issue reveals a surprising lack of information on the aquatic ecology of Phytophthora species. For instance, hydrogen ion concentration (pH) is among the most important water quality parameters which influence sporangium production and germination (1-3, 6, 32, 34, 38), survival of thick-walled chlamydospores and oospores in the soil environment, and disease development (2, 4, 33, 44). However, the effect of pH on the survival of zoospores and growth of germlings in aquatic environments is not known. As motile zoospores lack cell walls and encysted spores or cysts have thin walls, they are presumably more vulnerable to pH stress than chlamydospores and oospores are. On the other hand, the pH level is likely to fluctuate more regularly and at a greater range in aquatic systems, such as irrigation reservoirs, than in soil systems. pH can change diurnally due to respiration of aquatic plants and seasonally due to rain, oxidation of sulfide-containing sediments through the production of sulfuric acid, algal blooms, and released bases or acids from residues of fertilizer and pesticides. Thus, zoospores and aquatic systems are more prone to the influence of wide pH changes than chlamydospores/oospores in soil systems are. The aim of this study was to determine the impact of pH on zoospore survival and understand the aquatic ecology of different Phytophthora species.     

The Sweet Potato in Oceania: A Reappraisal

The Sweet Potato in Oceania:. Reappraisal . Chris Ballard, Paula Brown, Michael Bourke, and Tracy Harwood, eds. Pittsburgh: University of Pittsburgh Press, 2005. 227 pp.