摘要:

ABSTRACTThe flagellar apparatus ofUrospora penicilliformis(Roth) Aresch. is unique, or at least very unusual among green algae. The flagellar axonemes are rigid, and contain wing‐like projections. There are no central microtubules in the most proximal part of the axoneme. The transition region contains a series of electron dense transverse lamellae rather than a single septum, and lacks a stellate pattern. There is no cartwheel pattern in the proximal part of the basal bodies. The latter are associated with four different types of fibrous elements: ascending striated fibers that attach to an electron dense plate in the papillar center, lateral striated fibers that parallel microtubular roots, fibrous elements that link adjacent basal bodies, and finally two massive striated fibers that descend into the cell, passing closely along the nucleus (system II fibers, or rhizoplasts). Each of the four microtubular flagellar roots is sandwiched between two system I striated structures. The roots are probably equal; they contain proximally four, and distally up to eight microtubules. Based on the zoospore flagellar apparatus, it is concluded that the multinucleateU. penicilliformisis related to the Ulvaphyceae. Finally, a possible explanation in functional terms is given for the peculiar external morphology and behavior of the zoospor

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1982.tb03151.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACTAmphidinium cryophilumsp. nov. was found in the fall of 1979 in a small pond near Madison, Wisconsin. During the ensuing winter, it became the dominant phytoplankter. Cell numbers remained high despite a thick layer of ice and snow. After the ice melted in the spring the organism disappeared from plankton samples. A successful culture ofA. cryophilumwas established only when isolates were incubated at 5–7° C. It is compared with two morphologically similar species,A. amphidinioides(Geitler) Schiller andGymnodinium inversumNygaard.Amphidinium cryophilumis distinguished from the former by its pigmentation (golden‐yellow vs. blue‐green), the location of the cingulum, and its lack of an eyespot. It differs from the latter in cell shape, the route of the sulcus and position of the n

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1982.tb03152.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACTThe dinoflagellateAmphidinium cryophilumsp. nov. is one of the few gymnodinians to be studied at the ultrastructural level. It resembles other dinoflagellates in the structure of the nucleus, trichocysts, storage materials, flagella, mitochondria, and microbodies. Other features ofA. cryophilumless commonly observed in related organisms include a network of small interconnected vesicles, a system of large, peripheral vacuoles, chloroplasts bound by two rather than three membranes, an accumulation body, thylakoid‐associated plastoglobuli, a vesiculated nuclear envelope, a complex tubular pusule, striated flagellar collars, collared pits, and a peduncle. The occurrence of a peduncle, a structure implicated in phagotrophy, in this autotrophic organism is noteworthy. The ultrastructure of the peduncle ofA. cryophilumdiffers significantly from that reported in another dinoflagellat

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1982.tb03153.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACTSolieria chordalis(C. Agardh) J. Agardh andS. tenera(J. Agardh) Wynne et Taylor exhibit multiaxial growth from a cluster of four to eight obconical apical cells. A single periaxial cell is cut off from each axial cell and successive periaxial cells are rotated 120° in a zig‐zag pattern along each axial filament. Periaxial cells produce branched, laterally diverging filaments which form the cortex. The medulla is composed of axial cells, elongate cells of lateral filaments, stretched interconnecting cells, and secondary rhizoids. The two species are nonprocarpic. Carpogonial branches are 3‐celled, inwardly directed, with a reflexed trichogyne. The auxiliary cell together with associated darkly‐staining inner cortical cells form an association, the auxiliary cell complex, that is recognizable prior to diploidization. A single, unbranched, non‐septate connecting filament issues from the fertilized carpogonium and fuses with the inner, lateral side of an auxiliary cell. Production of an involucre from surrounding vegetative cells is stimulated and a gonimoblast initial is cut off toward the interior of the thallus which divides to form a compact cluster of gonimoblast cells. A fusion cell is produced through fusion of inner gonimoblast cells with the auxiliary cell that, in turn, fuses progressively with cells of the lateral file bearing the auxiliary cell. Mature cystocarps have terminal carposporangia cut off from gonimoblast cells at the periphery of the fusion cell and are surrounded by an involucre with a distinct ostiole. Tetrasporangia are cut off laterally from surface cortical cells which then cut off one or two additional derivatives toward the outside.A lectotype is designated forSolieria chordalis, but the lectotypification ofS. tenerais questioned. We conclude thatSolieriais closely related toRhabdoniaand place the Rhabdoniaceae in synonomy with the Soli

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1982.tb03154.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACTAgardhiella subulata(C. Agardh) Kraft et Wynne is a commonly collected erect, terete, alternately branched, fleshy red alga that is found both intertidally and subtidally in the western Atlantic Ocean, Caribbean Sea and Gulf of Mexico. A single periaxial cell is cut off from each succeeding axial cell in an orthostichous file. The supporting cells of carpogonial branches are homologous with auxiliary cells, being transformed from identical inner cortical cells. The auxiliary cell together with the three to four enlarged, darkly‐staining cortical cells pit‐connected to it form the auxiliary cell complex. Following fusion of a connecting filament to an auxiliary cell the diploid nucleus divides with one nucleus remaining near the point of fusion and the other migrating to the beaked portion of the auxiliary cell. Surrounding vegetative cells divide, forming files of cells that grow toward the auxiliary cell to form the involucre. Cells of the gonimoblast fuse with nearby cortical cells producing a placenta of vegetative and gonimoblast tissue. As the cystocarp matures the inner placental cells become vacuolate while at the periphery terminal and short, unbranched files of gonimoblast cells mature into carposporangia. Tetrasporangia are cut off laterally from surface cells and undergo basal elongation followed by lateral expansion before dividing zonately.A. subulataexhibits a combination of distinctive vegetative and reproductive features when compared withSolieriaand thus serves as the type of a new tribe, the Agardhielleae, in the family Solieriac

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1982.tb03155.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACTThe dependence of growth, electron transport system activity and chemical composition on the size of diatoms was examined during the exponential phase of growth. The six different marine centric species compared ranged in volume from 7.7 μm3to 62 × 105μm3. A size dependence was observed for growth,14C uptake, respiration and the productivity index (14C/chl a). Although the size dependence of all parameters was similar, the results indicate that on a carbon basis, growth efficiency decreases with increasing size. The C/N and C/chl a ratios were not size dependent. The importance of the surface area to cell volume ratio, and the importance of carbon per unit volume in determining the observed size dependence are discuss

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1982.tb03156.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACTEdaphic (sediment‐associated) diatoms were collected from five sites along a gradient from slightly brackish to saline marsh on 30 November 1977 and 29 April 1978. Several environmental factors change along this gradient in addition to salinity, including tidal flushing and percent organic content of the soil. A total of 112 taxa were identified, withAmphora exiguaGreg.,Navicula phylleptaKütz.,N. salinarumGrun., andN. tripunctata(Müll.) Bory being among the five most abundant taxa on both sampling dates. The taxonomic composition of the diatom flora was very similar to those observed for other salt marshes located along the Gulf and Atlantic coasts. Diatom taxa were generally euryhaline and distributed continuously along the gradient from brackish to saline marsh. Species diversity (H1) and the number of taxa in a sample (S) were also similar to those reported for other North American salt marshes. The number of taxa in a sample was higher in the saline than in the brackish area on both sampling dates while species diversity was greater in the saline area only in Ap

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1982.tb03157.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACTField studies on three perennially ice‐covered Antarctic oasis lakes with little or no outflow disclosed a unique biological phenomenon. Benthic algal mats dominated by the prokaryoticPhormidium frigidumFritsch and several pennate diatoms growing in shallower, more brightly illuminated areas beneath 4 to 5.5 m of ice accumulate and entrap bubbles of photosynthetically produced oxygen. Clumps of this gas‐filled mat tear loose from the gravelly substrate, lift off and float to the bottom of the lake ice. Some of these floating mat pieces become frozen into newly forming ice with the onset of winter. Through the combination of ablation of ice from the upper surface and the formation of new ice from below, algal mat pieces reach the upper lake surface in 5–10 years. Here, they are lyophilized by polar winds and dispersed in at least a partially viable state. The process of mat lift‐off and escape is important in removing nutrients and salts from these lakes and helps to perpetuate their oligotrophic state. Neutron activation and X‐ray dispersive analyses of elements in the algal mats along with other analyses, field observations, and calculations suggest that significant quantities of organic matter, select minerals and salts are lost from the lakes annually through this process whose magnitude has not been recognized p

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1982.tb03158.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACTThe short‐ and long‐term uptake of nitrate and phosphate ions, and their interactions, were studied as functions of the preconditioning ofPavlova lutheri(Droop) Green. Populations were preconditioned in continuous culture at a variety of growth rates and N:P supply ratios. The maximum uptake rates cell−1for nitrate and phosphate were of similar magnitudes, in spite of the forty‐fold smaller requirement for phosphorus. Short‐term phosphate uptake was independent of the nitrate concentration, but the short‐term nitrate uptake rate was reduced in the presence of phosphate. The severity of inhibition of nitrate uptake by phosphate was positively correlated with the preconditioning N:P supply ratio and the preconditioning growth rate. In response to large additions of nutrients,P. lutheriwas able to increase its phosphorus content sixty‐fold, but was only able to take up enough nitrate to double its nitrogen content. The high rate of phosphate uptake relative to its requirement, the inhibition of nitrate uptake by phosphate, and the large capacity for phosphorus storage relative to its requirement, all of which were observed even under N limitation, may imply that even where nitrogen is limiting there can be interspecific competition for availa

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1982.tb03159.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACTA new species,Halimeda hummii, and a new variety ofHalimeda crypticaColinvaux and Graham both originally collected from the edge of the continental shelf on the southwest coast of Puerto Rico are newly described. The new species is irregular in its segment morphology and is the smallest species ofHalimedapresently known.Halimeda crypticavar.acerifoliafrom deep water possesses distinctive segments resembling maple leaves.Halimeda copiosaGoreau and Graham and typicalH. crypticaare also collected in deep water and are newly recorded from Puerto Rico.

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1982.tb03160.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY