ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1981.tb02426.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1981.00003.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACTA new member of the chlorophycean, tetrasporalean genusPalmellopsisKorschikov (1953),Palmellopsis muralisBold and King, is described from limestone in Austin, Texas, U.S.A. Certain details of ultrastructural organization are included.

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1981.tb00813.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACTThe sporophyte ofHimantothallusdevelops according to a closed pattern in which the number and position of the blades is determined by the location of trichothallic meristems in a filamentous germling. Expansion of the miniature juvenile to the massive adult thallus is accomplished by diffuse secondary growth and involves a change from filamentous rhizoids to a hapteroid holdfast, flattening of the stipe, and enormous increases in length, breadth, and thickness of both stipe and blade. The axis usually bears 1–8 lateral blades, often paired, and terminates in a flattened stub.Phaeoglossumis interpreted as a growth form ofHimantothallusin which a terminal blade develops to the exclusion of lateral blades, the latter being represented by a single spine.Phyllogigasclearly falls within the morphological spectrum ofHimantothallus, the lack of twisting being related to physical factors in the environment.Sporangia, interspersed with an equal or somewhat larger number of two‐celled paraphyses, are borne in slightly elevated sori scattered over both surfaces of the blade. Zoospore germination was not observed, nor were gametophytes, either in culture or in the field.Haptera apparently originate from the meristoderm in the lower part of the maturing stipe and lack a filamentous medulla. The mature stipe and the mature blade are anatomically similar, being composed of a superficial meristoderm, a cortex of parenchyma‐like cells, and a filamentous medulla. The meristoderm is usually a single layer of plastid‐containing cells that divide anticlinally to accommodate (or effect) expansion and periclinally to produce cortical tissue inward. Cortical cells are in radial files and increase in diameter towards the interior. They usually are densely packed with physodes. The medulla is uniquely distinguished by the presence of sheathed trumpet hyphae. Cells of the trumpet hyphae have perforate end walls with callose deposits and probably function in conduction as do the sieve filaments in Laminariales. Sheathing cells are filled with plastids. Sheathing filaments form connections among themselves and with nearby unsheathed filaments. The sheathed trumpet hyphae and their matrix of unsheathed filaments form a plexus, which in the mature blade is flattened and may be stripped intact from the other tissues.Development of the embryonic sporophyte is very similar to that inDesmarestia, as is the anatomy of the adult thallus and the sporangia. From these considerations,Himantothallusis assigned to the Desmarestiaceae (Desmares

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1981.tb00814.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACTThis study analyzes the impact of conditions associated with depth upon benthic algal communities in Lake Michigan. Diatom abundance was greater at 9.1 and 14.6 m depths than 6.5, 22.6 and 27.4 m. Shallow (6.5 m), mid‐depth (9.1 and 14.6 m) and deep (22.6 and 27.4 m) zones were distinguishable on the basis of community composition, structure and abundance. Dominance of benthic species, high diversity and low abundance in shallow communities probably resulted from substantial substrate disturbance by wave action in this productive zone. Dominance of benthic species, high diversity and high abundance characterized mid‐depth communities where less wave disturbance enabled algal accumulation. Preponderance of living planktonic taxa, low diversity and low abundance delineated deep communities where planktonic algae accumulated and low light levels reduced growth of benthic spec

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1981.tb00815.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACTPreviously reported transplantation experiments in the field showed thatGastroclonium coulteri(Harvey) Kylin could survive above its normal intertidal range (0.0–0.5 m above MLLW), except during periods of daytime low tides in spring. Net photosynthetic rate measurements in the laboratory were performed to determine which physical factors might determine the upper boundary for this species in the intertidal zone.Maximum net photosynthesis occurred between 15 and 20° C, but remained positive between 4 and 35° C. The air temperature extremes observed in the field were 2° C (only seen once) and 26° C. Net photosynthesis increased as expected with light intensity to the highest value obtainable in the laboratory, 1400 μEin m−2s−1. Plants collected from the field under higher light intensity (up to 2000 μEin m−2s−2) also showed high rates of photosynthesis. Neither the temperature nor light levels observed in the field were directly damaging to photosynthesis. Desiccation, however, resulted in a sharp decrease in both photosynthesis and respiration.G. coulterifully recovered from successive daily treatments of about 35% desiccation, but not from successive treatments of 50% desiccation. One exposure to 70% desiccation allowed no recovery of photosyn

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1981.tb00816.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACTThe holozoic dinoflagellate,Gymnodinium fungiformeAnissimova, has been observed in both asexually and sexually reproducing cultures. Asexual reproduction is characterized by zoosporangium formation and subsequent new cell release. Sexuality is gametic, and planozygotes and hypnozygotes are present. The life cycle is highly dependent on feeding, and in food‐depleted cultures the swimming cells rapidly disappear. These are replaced with resistant long‐term resting cysts. Despite its small size (8.5–19 μm),G. fungiformecan feed on prey as large as the ciliated protozoan,Condylostoma magnumSpiegel (600–1000 μm in length), or small injured metazoans, and has been cultured phagotrophically with the chlorophyte,Dunaliella salinaTeodoresco as a food source. Eleven additional species of algae including 1 chlorophyte, 7 chrysophytes and 3 rhodophytes, however, were not suitable as food sources. Feeding is characterized by the formation of ‘dynamic aggregations’ of hundreds of dinoflagellates that attach to the surface of a prey organism by a peduncle.G. fungiformeingests the cytoplasm or body fluids of its prey and a feeding aggregation can ingest aC. magnumin

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1981.tb00817.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACTLight intensity (4.5–40.0 μEin m−2s−1) and culture age had a pronounced effect on cell size and size range of a non‐toxic axenicMicrocystisisolate. The rate of cell volume increase (μm3d−1) was 1.03×light intensity (μEin m−2s−1)–6.49. Average cell volume varied from 33 to 119 μm3, cells at higher light intensities being larger and having a larger size range. The effects on a toxic axenicMicrocystisisolate were similar but less pronounced. Average cell volume ranged from 21–74 μm3. In general, cell size and especially size variability appear to be sensitive indicators of physiological state, with cells under stress conditions being larger and associated with a larger size range. The wide range of cell diameters observed at different irradiance levels (3.4–7.2 μm for the non‐toxic and 1.8–6.4 μm for the toxic isolate), makes questionable the use of cell size as a taxonomic character without careful considerat

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1981.tb00818.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACTThe nature and seasonal extent of microbial fouling onAscophyllum nodosum(L.) LeJol.,Fucus vesiculosusL.,Polysiphonia lanosa(L.) Tandy andChondrus crispusStackh. were observed by scanning electron microscopy. Bacterial filaments and smaller rod and coccoid forms dominated the fouling communities on all species, with pennate diatoms constituting a minor component in contrast to results with plastic substrates on which pennate diatoms dominated and preceded bacterial colonization. The total percent microbial coverage on the surfaces of all four seaweed species was determined by monthly stereological analyses of representative composite micrographs. These showed a simultaneous decline between April and May which could represent the die‐off of the cold water bacterial flora when water temperature increased past the threshold for obligate psychrophiles. Microbial colonization patterns were directly correlated (P = 0.005) with maximum coverage in April and November–December and reduced levels from May to October. Significant inverse (P<0.041) correlations between total percent coverage and water temperature indicate distinct seasonal cycles, however, the patterns of dominance by filamentous bacteria and rod and coccoid forms were markedly different. Total coverage patterns of both rhodophytes showed no apparent seasonal cycle and were not related to water temperature. Rod and coccoid bacteria were apparently suppressed year round onP. lanosarelative to the other species. These interspecific differences in seasonal fouling patterns are discussed in light of possible modes of regulation, especially algal antibio

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1981.tb00819.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACTValves ofS. niagaraevar.niagaraeEhr. andS. niagaraevar.magnificaFricke from geographically dispersed sediment and plankton collections were observed by light microscopy and scanning electron microscopy (LM and SEM). Measurements made by LM can be arranged so that means and ranges of diameter, areolar density, or strial density intergrade from one population into the next. Mean diameter is negatively related to increasing areolar and strial densities. No unique features observable by SEM distinguish the two described varieties. Thus,S. niagaraevar.magnifica, having large diameter valves with low areolar and strial densities, may represent one end of a trend in overall variation inS. niagarae.At the opposite extreme are the populations with small valves and high areolar densities which are often erroneously referred to asS. astraea.Type material ofS. niagaraelies intermediate to these forms. Three populations considered in this study have distinct morphological characteristics. Valves from Yellowstone Lake sediments have spine placements distinctly different from valves of all other populations. Specimens from Lake Superior have nearly flat central areas. Ribs of valves from Grand Traverse Bay (Lake Michigan) are covered with granules.

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1981.tb00820.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY