Volume 23, Issue 11

The structure of the wall at various stages in the life cycle of three species of Thraustochytrium. marine coccoid fungi. has been examined. The cell walls are composed of two elements; thin organic Golgi·derived scales and a fibrillar inter-scale matrix. Cytochemical procedures have established the presence of protein and sulphated polysaccharide in the walls together with associated calcium. The presence of sulphur and calcium has been confirmed by energy dispersive E.M. X-ray analysis. These new features have been considered from the taxonomic viewpoint and appear to strengthen the concept that some affinities exist between the Thraustochytriales and the algal protists.

The distribution of marine fungi in Sierra Leone is studied in the light of hydrographic and climatic factors. Altogether 27 spp. have been identified to species level, comprising 3 Phycomycetes 14 Ascomycetes and 10 Deuteromycetes. All these spp. are considered as new records to the country and about 50 % of them are inhabitants of mangrove swamps under tidal influence. The climate of Sierra Leone is characterized by two main seasons: a wet season (May - November) and a dry season (December-April). Mangrove mycota display a seasonal periodicity, increasing in number of spp. and growth intensity in the wet . season. Degradation of wood was also active during this season, apparently more by members of Deuteromycetes such as Cirrenalia spp., Periconia prolifica and Zalerion spp. than by Ascomycetes. Sea foam was also richer in fungal ascospores (including 6 spp. of Corollospora) and conidia of Deuteromycetes in the wet than in the dry season. Estuarine foam. however. comprises several Hyphomycetes of freshwater or terrestrial origin brought in by runoff during the rainy season (e.g. Alternaria, Curvularia, Drechslera, A cro sporidium , etc.) No distinct vertical zonation was displayed by the lignicolous fungi inhabiting the mangrove. The geographical distribution of the higher marine fungi under consideration has been compared with those on the opposite side of the Atlantic as well as in the Pacific and Indian Oceans. Out of 24 spp. found in Sierra Leone, 21 spp. (88 %) occur on the opposite side of the Atlantic. while an equal number is known in the Pacific. Only 15 spp. (63 %) are recorded in the Indian Ocean. The last figure is due to our limited knowledge of Indian Ocean fungi and is expected to increase in future. The distribution of mangrove fungi encountered in Sierra Leone is considered as a "community" comprising host specific forms such as Leptosphaeria avicenniae and Cytospora rhizophorae, as well as facultative forms. Out of 14 such spp. in Sierra Leone, 13 (93 %) occur in the Western Atlantic. 12(86 %) in the Pacific and 10(72 %) in the Indian Ocean so far. The close affinities of mangrove fungi in the 3 oceans, paralleled with similar affinities of mangrove floras lend support to the theory of a common center in the West-Indo Pacific for the mangrove flora and associated mycota from which a drift took place in various directions into the 3 oceans in question. The theory was postulated by Ekman (1953) for the distribution of tropical fauna and found support by Macnae (1968) for the distribution of the mangrove flora and fauna. It also allows for an endemic element as the drift deviates from the center. The closer affinities between Eastern and Western Atlantic mycota could be explained by the current gyres to the north and south of the equator and their role in transporting mangrove seeds. wood and associated fungi between the African arid American coastlines.

Lagenidium callinectes Couch and Haliphthoros milfordensis Vishniac. facultative parasites of marine crustaceans, were subjected to a detailed analysis of their physiological and nutritional requirements. Twelve isolates, six of each species. were used in this study. Temperature, salinity, and pH ranges of growth were determined. Vitamins B 1 and B 12 were required by some isolates of L. callinectes, but not by H. milfordensis. A variety of amino acids were utilized as nitrogen sources. Urea was used also by isolates of both species, while nitrate was used by only H. milfordensis. The number of carbon sources utilized was rather limited. Some sugars, such as fructose, glucose, mannose, cellobiose (poorly), maltose and trehalose, and, of the polysaccharides tested, only soluble reserve polysaccharides, such as starch, dextran, laminarin, and glycogen, were used in nutrition. The isolates of H. milfordensis were more versatile but more uniform re'garding their nutritional requirements than the isolates of L. eallil/eetes. The latter fall into two groups, two rather fast growing, versatile isolates not requiring NaCI, and four slower growing obligately marine strains, with a more limited range of utilizeable substrates.

A pathological condition occurring in the lesser octopus, Eledone cirrhosa, is described. This results in progressive ulceration of the skin of the animal, followed by oedema of body tissues and death. Light and electron microscope studies of the skin ulcers reveal the constant presence of thraustochytrid-like organism(s) and often, although not in all instances, the presence of a presumed labyrinthulid. Studies are currently in progress to identify both these organisms and to establish the role that they play in the condition described.

A preliminary study determined the presence of some Saprolegniaceae in a small estuary in the Tampa Bay Area. Traditional methods of collecting aquatic fungi were employed. The results support the previously noted occurrence of these fungi and extend the geographical range of the species of tlus taxon. These and previously reported results of estuarine studies of Saprolegniaceae suggest that some species in this family are limited in their occurrence in southeastern United States estuaries.

Field studies of the benthic macroalgae of fifteen selected Chesapeake Bay oyster communities were conducted over a period of a year (March 1977 to February 1978). Algal distribu tion and seasonal occurrence were studied in relation to changes in the physical environment. Salinity, temperature, and light availability were important factors in the spatial and temporal distributions of algae in these subtidal habitats. Seventeen species of Chlorophyta, Phaeophyta, and Rhodophyta were recorded from the fifteen study sites distributed over 130 kilometers within the Maryland portion of Chesapeake Bay. Species of Chlorophyta were associated with oyster communities throughout the year of study with maximum numbers of species and maximum biomass occurring in spring. Only once was a member of the Phaeophyta encountered; a single filamentous species, Ectocarpus, was collected during winter. Species of Rhodophyta were present throughout the year at the study sites. Most of the algae collected reproduced asexually by spores and/or vegetative fragments. Sexual reproduction occurred in some of the red algal species. The presence of tetrasporic and cystocarpic plants of Dasya baillouviana and Polysiphonia harveyi var. olneyi may indicate that the usual triphasic Florideophycean life history occurs in this estuary.

1. The ultrastructure of the unicellular rhodophyte Porphyridium cntentum Naegeli was examined prior to 8-weeks' placement in total darkness and after subsequent re-exposure to light. The algal cells were contained in inorganic seawater medium incapable of supporting growth in darkness. The "recovery" process of the darkness-inactivated alga was monitored by electron microscopy of culture samples periodically fixed from zero to 72 hours of reinstatement in continuous light. 2. Four types of cells were recognized in the course of this study: (i) nomlal (vegetative) cells from growth in light; (ii) moribund (presumed non-viable) cells from senescence; (iii) donnant (resting) cells from darkness inactivation; (iv) reactivated cells recovering from dormancy on re-exposure to light. Apart from 22% reduction in cell volume from light deprivation, these cell types differed from one another in relatively minor structural details, and there were no indications of wall thickening or other features commonly considered characteristic of spores and cysts. The donnant cells were characterized by poor stainability of all internal membranes, excessive clumping of thylakoids, absence of recognizable pyrenoid, starch bodies, endoplasmic reticulum, dictyosomes, and proliferation of plastoglobuli and cytoplasmic vacuoles. Cells with such properties intermediate between the normal and dormant types were considered reactivated by light, whilst those showing extensive damage (dilation and rupture) of membranes of vital organelles were considered moribund. Phycobilisomes were observed in all cell types. 3. The population emerging from darkness showed 90% dormant and 10% moribund cells. With increasing duration of re-illumination, the dormant cells were rapidly transformed into reactivated types, which achieved population peak at 6 hr and then declined with further transformation to normal cells. At 24-hr illumination, the normal cells were predominant, with total disappearance of donnant cells. The conversion of reactivated to normal cells was virtually complete within 48-72 hr illumination. 4. It is concluded that P. cruentum survives darkness by a process of dormancy involving minimal ultrastructural changes, and the absence of extra wall or sheath formation is inferred to facilitate the remarkably rapid activation of the alga on restoration of light.