Posterior Flagellum Research Articles

ULTRASTRUCTURE OF SWARMERS IN THE LAMINARIALES (PHAEOPHYCEAE). I. ZOOSPORES1

ABSTRACTZoospores of 17 species in 14 genera of Laminariales, collected in the northeast Pacific Ocean, were studied by electron microscopy. These zoospores are unique in the brown algae in lacking both an eyespot in the single chloroplast and any associated swelling at the base of the shorter, posterior flagellum. Spores of all species examined possess a distal whiplash portion on the longer, mastigoneme‐bearing anterior flagellum. This appendage may sometimes be as long as the mastigoneme‐bearing portion of the flagellum, but it is only seldom preserved in the preparations for electron microscopy. A microtubular cytoskeleton is probably responsible for maintaining the shape of the spore. It consists of a short band of about 10 microtubules between the two basal bodies, scattered tubules converging at the anterior of the spore, a band of 7–9 tubules directed anteriorly from the anterior basal body, and a band directed posteriorly from the posterior basal body. These anterior and posterior bands may form one continuous band looping around the periphery of the spore. Variation with possible taxonomic significance was found in the ultrastructure of vesicles which apparently contain adhesive material, and which are extruded through the plasmalemma when the zoospores settle.

ULTRASTRUCTURE OF SWARMERS IN THE LAMINARIALES (PHAEOPHYCEAE). II. SPERM1

ABSTRACTThe ultrastructure of sperm from 13 species in 11 genera of Laminariales collected in the northeast Pacific Ocean is unique in the brown algae. The sperm are elongate, and possess a nucleus, several mitochondria and two or three chloroplasts, but no eyespot. The anterior flagellum bears mastigonemes on the proximal half of its length; a distal “whiplash” portion lacks mastigonemes and is an extension of only the two central singlet microtubules of the axoneme. A peculiar feature of these sperm is the posterior flagellum, which is longer than the anterior flagellum and tapers distally as the doublet microtubules become singlets and decrease in number. This feature contrasts with the laminarialean zoospore, which possesses a short posterior flagellum with the usual “9 + 2” axoneme. The structure of these sperm differs from that reported for Chorda, the sperm of which resembles a primitive brown algal zoospore. The facts support the concept that Chorda is the most primitive member of the Laminariales.

Cell wall, zoospore and morphological characteristics of Australian isolates of a Pythium causing equine phycomycosis

The asexual and cultural characteristics of a number of Australian isolates of a Pythium causing equine phycomycosis are described. Oospores were not found which precludes positive identification. Zoospores were induced to form after growth in a defined medium. They are ovoid to reniform, biflagellate with flagella arising from a common point within a prominent lateral groove. The groove is overarched by outgrowths from the zoospore. Anterior flagella are of the tinsel type and are shorter than the posterior whiplash flagellum. X-ray diffraction analysis of cell walls failed to demonstrate the presence of cellulose I. Chromatograms of cell wall hydrolysates indicated that glucose is the major component with small contributions being made by mannose, galactose and rhamnose.

Gamete structure and fertilization in the brown algaHormosira banksii(Turner) Decaisne

Light microscope and fine structural studies of the gametes of Hormosira banksii show the antherozoids as typical Fucales biflagellate gametes with a posterior whiplash flagellum and an anterior flagellum with mastigonemes. The oospheres are enclosed in a plasma membrane, are highly vacuolate and contain abundant phenolic inclusions. Antherozoids attach to the surface of the oospheres by their anterior flagellum at conjugation. Following fertilization Golgi derived vesicles underlying the plasma membrane decrease in electron density and an exterior surface coat appears outside this membrane. This may be a “fertilization barrier” which prevents further penetration by other male gametes. Subsequently a fibrous layer appears which develops into a cell wall around the developing zygote. Histochemical studies show the cell wall of these young zygotes is probably made up of alginic acid. Fine structural and histochemical examination of the young zygotes suggest that whereas there is no preformed adhesive in the...

The ultrastructure of the R.S. zoospore of the Chytridiomycete Physoderma gerhardti

The fine structure of the zoospore of Physoderma gerhardti Schroeter is described. It possesses a single very large lipid body (sometimes accompanied by several smaller ones) situated laterally to the nuclear cap – nucleus complex and is associated with electron-dense material (the microbody) and the single large posteriorly located mitochondrion. The single posterior flagellum proximally terminates in a kinetosome just short of the posterior cone-shaped end of the nucleus. The kinetosome lies in a deep groove in the mitochondrion and is associated with this organelle by striated rootlets. The kinetosome terminates in electron-dense material from which an array of microtubules arises. These microtubules run along the sides of the cone-shaped nucleus and nuclear cap. There is an accessory centriole lying close to and more or less parallel with the kinetosome. The cytoplasm contains a small amount of smooth endoplasmic reticulum and several inclusion bodies in the anterior region and several small vacuoles in the posterior region of the cell. The general internal organization of the zoospore of Physoderma gerhardti more nearly resembles that of a blastocladiaceous fungus than of any chytrid thus far investigated.

IN SITU PRESERVATION OF THE TRANSVERSE FLAGELLUM OF PERIDINIUM CINCTUM (DINOPHYCEAE) FOR SCANNING ELECTRON MICROSCOPY1

ABSTRACTThree‐dimensional structure of the transverse flagellum was studied by means of scanning electron microscopy (SEM) in Peridinium cinctum (O.F.M.) Ehrenberg. Several fixation and dehydration procedures were compared. Cells fixed, rapidly in 1% osmium tetroxide and critical‐point dried showed accurate preservation of structural features seen in living cells; in particular, both transverse and posterior flagella were retained in the furrows on the cell surface. Osmium‐fixed and freeze‐dried, samples were prone to cellular collapse and loss of flagella. Glutar‐aldehyde‐fixed and critical‐point dried cells showed a layer of material covering the thecal plates, most conspicuously over the girdle region; flagella were absent. Stereo‐pair micrographs illustrate the 3‐dimensional configuration of the transverse flagellum. Modifications of previous structural models are proposed.

THE RELEASE, SETTLEMENT AND GERMINATION OF ZOOSPORES INCHORDA TOMENTOSA(PHAEOPHYCEAE, LAMINARIALES)1,2

SUMMARYDetails of zoospore germination inChorda tomentosaLyngb. are outlined. Uninucleate zoospores, when released are embedded in a mucilaginous mass of carbohydrate which dissolves and the biflagellate zoospores become motile. The long anterior flagellum is composed of a highly coiled terminal region and a rigid lower section bearing mastigonemes. The rigid, short posterior flagellum lacks mastigonemes. After initial contact by the tightly coiled region of the anterior flagellum, the zoospore draws itself to the substrate by flagellar resorbtion. After deposition of 3 wall layers the germling produces a germ tube. During this time the disc‐shaped chloroplast enlarges undergoing changes in shape. As the germ tubes reach ca. 15 μm they cease forward growth and swell at their tips. The majority of cytoplasm of the original zoospore moves into the tube. Just before the nucleus enters the tube, centriole replication occurs. Mitosis is presumed to take place somewhere in the germ tube so that at 24 h, 2‐celled gametophytes are produced.

Ultrastructure of Thraustochytrium sp. Zoospores. IV. External Morphology with Notes on the Zoospores of Schizochytrium sp

SUMMARYThe zoospores of Thraustochytrium sp. and Schizochytrium sp. are biflagellate with the posterior whiplash flagellimi being considerably shorter than the anterior tinseled flagellum. In Thraustochytrium sp. the posterior flagellum terminates in a tuft of hairs which are approximately 3.4 mμ in diam. The posterior flagellum of Schizochytrium sp. ends in a tuft of hairs approximately 3.0 mμ in diam while the anterior flagellum ends with hairs approximately 3.6 mμ in diam. The zoospores of Thraustochtyrium sp. are covered by scales.

Ultrastructure ofThraustochytriumSp. Zoospores. IV. External Morphology with Notes on the Zoospores ofSchizochytriumSp.

SUMMARYThe zoospores of Thraustochytrium sp. and Schizochytrium sp. are biflagellate with the posterior whiplash flagellimi being considerably shorter than the anterior tinseled flagellum. In Thraustochytrium sp. the posterior flagellum terminates in a tuft of hairs which are approximately 3.4 mμ in diam. The posterior flagellum of Schizochytrium sp. ends in a tuft of hairs approximately 3.0 mμ in diam while the anterior flagellum ends with hairs approximately 3.6 mμ in diam. The zoospores of Thraustochtyrium sp. are covered by scales.

Observations on vegetative reproduction and sexual life cycles of two freshwater dinoflagellates,Gymondinium pseudopalustreSchiller andWoloszynskia apiculatasp. nov.

In unialgal culture, Gymnodinium pseudopalustre Schiller (G.p.) and Woloszynskia apiculata sp. nov. (W.a.) multiply respectively by binary fission in the motile state and by motionless zoosporangia, releasing 2, 4 or 8 zoospores. Both species are isogamous, but G.p. is homothallic, W.a. heterothallic. Fusion of the planogametes leads to long-lived planozygotes, which retain two posterior flagella and, while enlarging, assume specific morphologies. The motile stage of the zygotes is terminated by formation of hypnozygotes (resting spores), globular and spiny in G.p., grossly fusiform (‘horned’) and tubercled in W.a. The composition of the hypnozygote walls is described. After their dormancy has been broken by a cold treatment of several weeks in the dark, hypnozygotes of both species germinate when brought back to higher temperature and light. In so doing, those of G.p. excyst one posteriorly biflagellate swarmer as a meiocyte, which, after a stage of nuclear cyclosis or, in karyological terms, zygotene th...

A new species of marine labyrinthulid Labyrinthuloides yorkensis gen. nov. spec. nov. ?Cytology and fine structure

The structure and life cycle of a new genus and species of labyrinthulid, Labyrinthuloides yorkensis, is described from observations of pure cultures. Uninucleate cells are capable of gliding by means of ectoplasmic nets which push or pull the cells across the substrate. The net elements do not enrobe the cells and motility is reversible. Sporulation occurs by successive bipartition or progressive cleavage of the protoplast. Biflagellated zoospores with an anterior tinseled flagellum and posterior whiplash flagellum are formed as are non-replicating amoebae and plasmodia. The fine structure includes centrioles with a single large granule in the lumen and numerous cytoplasmic inclusion bodies with associated membrane complexes. The membrane-inclusion arrays are each found within a delimiting vesicle membrane.

幼犬の下痢に認められたトリコモナス原虫

Trichomonads were isolated from a puppy in Sapporo, Hokkaido. The puppy was suffering from diarrhea of unknown etiology. The organisms had 5 anterior flagella of almost the same length, an undulating membrane extended to the tail, and a free posterior flagellum and were identified as Pentatrichomonas hominis (DAVAINE, 1860).

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 ]oycei n. sp. Aside from the few fungi noted in JoH~so~ (1966), and FlYLLER, et al. (1964), little is known of the zoosporic marine Phyeomyeetes from the Pacific Northwest coast. The observations herein reported were made during a 10-week stay at the Friday Harbor Laboratory, University of Washington, San Juan Island in the summer of 1968. It is of interest to note that only one of the zoosporic fungi found belonged to the Chytridiomyeetes, i.e., those with a single posterior flagellum on their zoospore, which are so abundant in fresh water. The others were all biflagellate forms belonging primarily to the Saprolegniales. This peculiarity had previously been noted among marine Phycomycetes from the Atlantic coast of the United States and in the Carribean area (SPaRrow, 1936, 1968). Methods Algal parasites were found by direct examination of the hosts. Saprophytes such as tile Thraustochytriaceae were obtained by baiting with pine pollen debris, bottom mud or water from the various sites. Pure cultures on solid media were obtained by use of Vishniae's agar to which had been added antibiotics (FvLL]~R et al., loe. cir.). * The assistance of Drs. R. E. NonRIs and G. J. HOLLE~B:E~a in calling my attention to certain algal parasites is gratefully acknowledged. I am also indebted to my colleague Dr. H. C. W~ISL~R, and to Dr. C. ANASTASIOU for assistance in photographic work.

Structure of Labyrinthula sp. Zoospores*

SYNOPSIS. A species of Labyrinthula closely resembling L. algeriensis was isolated from marsh grass, Spartina alterniflora. Zoosporulation was obtained in ∼50% of the cultures, which were grown on a modified Vishniac medium, when yeasts were used as food organisms; when the temperature was ∼22 C; when thiamine (0.2 mg/l, biotin (1 μg/l, Ba (1 μg/l, and cholesterol (5 mg/l) were present; and when the cells were grown on a semisolid medium (0.6% agar) rather than higher concentrations of agar. The motile cells were similar to biflagellated fungal zoospores in that they were pyriform and laterally biflagellated. The anterior flagellum (13‐15 μ long) possessed what appeared to be 2 rows of mastigonemes and was uniform in diameter while the posterior flagellum (6‐10 μ) lacked mastigonemes and was tapered distally into a whiplash. The planonts are apparently not isogametes since planogametic copulation could not be induced and since synaptinemal complexes were not observed in sectioned presporangia.

Fine Structure of the Dinoflagellate Transverse Flagellum

THE dinoflagellates have for some time been known to possess two flagella which differ from one another in their movements and in the orientation of the beating portions. One, called the posterior or longitudinal flagellum, has a relatively slow movement which has been shown to be in the form of a planar wave1,2. Electron microscopy shows that this flagellum is constructed of the normal axoneme plus organized packing material in the proximal two-thirds, all surrounded by a membrane. The transverse flagellum, often situated in a groove around the cell, has a completely different type of motion. With the light microscope it appears ribbon-like3 and has a rapid undulatory motion which recent investigations have shown to be in the form of a circular or elliptical helical wave1 (in Ceratium). In an early electron microscopical study of Gyrodinium4, it was found that this flagellum had an expanded sheath much wider than the axoneme, with an array of fine hairs along one side. Our observations have confirmed these findings and have revealed other structures which account for the unusual behaviour of this flagellum.

THE FINE STRUCTURE OF BLASTOCLADIELLA EMERSONII ZOOSPORES

The zoospore of Blastocladiella emersonii has been re‐examined with the electron microscope. The following new findings were made. A double unit‐membrane system surrounds all cell organelles except γ‐bodies, vacuoles and a few fragments of membranes. Lipid granules on one side of the large mitochondrion alternate with vesicles. The kinetosome of the posterior flagellum does not have any central fibrils as previously reported; a small, cylindrical structure is found within its anterior end. An associated centriole is located next to the kinetosome. Three striated rootlets pass from the kinetosome by separate channels through the mitochondrion. There appears to be no connection between the striated rootlets and the mitochondrion. Microtubules originating at the anterior end of the kinetosome pass into the cytoplasm between the mitochondrion and the nuclear cap. Long, dense strands were observed in some nuclei. The axoneme is taken up into the spore during encystment and is found in the freshly encysted spore. No trace of the flagellar sheath has been found in the encysted spore.

The Fine Structure of Blastocladiella emersonii Zoospores

The zoospore of Blastocladiella emersonii has been re-examined with the electron microscope. The following new findings were made. A double unit-membrane system surrounds all cell organelles except γ-bodies, vacuoles and a few fragments of membranes. Lipid granules on one side of the large mitochondrion alternate with vesicles. The kinetosome of the posterior flagellum does not have any central fibrils as previously reported; a small, cylindrical structure is found within its anterior end. An associated centriole is located next to the kinetosome. Three striated rootlets pass from the kinetosome by separate channels through the mitochondrion. There appears to be no connection between the striated rootlets and the mitochondrion. Microtubules originating at the anterior end of the kinetosome pass into the cytoplasm between the mitochondrion and the nuclear cap. Long, dense strands were observed in some nuclei. The axoneme is taken up into the spore during encystment and is found in the freshly encysted spore. No trace of the flagellar sheath has been found in the encysted spore.

The Anatomy of Tetratrichomonas didelphidis (Hegner and Ratcliffe, 1927) comb. n. from the Opossum

Tetratrichomonas didelphidis (Hegner and Ratcliffe, 1927) comb. n. was found in the cecum and colon in 20 of 24 opossums (Didelphis marsupialis) in Illinois. The organisms grew best in Stuart's leptospira medium at 29 C. The trichomonads were piriform, 7 I long by 4 u wide; with four anterior flagella of unequal length averaging 17, 14, 10, and 8 4,, respectively. The slender hyaline axostyle extended 4 /u posteriorly and had an inconspicuous capitulum. A discoid parabasal body with an intensely argentophilic central granule, a long slender parabasal filament, a narrow pelta, a prominent costa, and a pronounced undulating membrane extending full length of the body and continuing as a long posterior free flagellum were present. Hegner and Ratcliffe (1927) first described Trichomonas didelphidis from the intestine of an opossum shipped to them from Ohio by Dr. Justin Andrews. Three other new species were also described, namely, Trichomonas cynomysi from the intestine of the prairie dog, Trichomonas felistomae from the mouth of the cat, and Trichomonas macacovaginae from the vagina of the rhesus monkey. Because of the slight variation in size and description and, especially, the striking similarity of the schematic illustrations of forms from the opossum, cat, and monkey, it is difficult to ascertain from the literature whether morphologic differences exist among these parasites. Additional information on the detailed anatomy of these flagellates with the aid of modern staining procedures would be helpful in determining the taxonomic and morphologic relationship of these forms to trichomonads from other hosts. To our knowledge, no subsequent reports on the occurrence or anatomy of trichomonads from the opossum exist. Because of the frequency with which trichomonads were detected in opossums used in research at the College of Veterinary Medicine, University of Illinois, it was decided to make a detailed morphologic study of these parasites. MATERIALS AND METHOD Opossums used in various research projects at the College were routinely examined at necropsy for the presence of trichomonads in the stomach, small intestine, cecum, and colon. Most of the Received for publication 29 March 1965. * This research was supported in part by research grants U. S. Public Health Service Communicable Disease Center 00037 and NIH CC-00070. animals had been captured as adults in southern Illinois, although a few were raised in captivity as littermates after females with pouched young had been obtained. In addition to the necropsy examinations, fecal samples taken periodically from caged opossums were also examined for trichomonads. When abundant organisms were detected, a small amount of the intestinal content or fecal material was inoculated into Diamond's (1957) medium without agar or phosphate buffer, Fletcher's (1928), Stuart's (1946), or Ellinghausen's and McCullough's (1965) leptospira media, or opossum cecal extract medium. The last was a modification of the cecal extract medium used by Hibler et al. (1960) and Jensen and Hammond (1964) in their investigations of porcine and bovine trichomonads. All these media were tested at 20, 25, 29, 35, and 37 C. Because of the results obtained, cultures were routinely maintained only in Stuart's medium and at 29 C. In order to secure additional infornmation on the body temperature of opossums, daily rectal temperatures were determined on eight caged adult opossums for a period of 10 days during the first part of August 1964 and on 5 days during the middle of September 1964. These measurements were made with a thermistor rectal probe and a battery-powered telethermometer. Extreme caution was used to minimize excitement of the animals. Microscopic observations of the trichomonads were made under a Zeiss photomicroscope with apochromatic objectives. Living organisms from freshly obtained material or from culture, and specimens fixed in 2% osmium tetroxide vapors were studied under phase-contrast. Stained specimens fixed in methanol, Schaudinn's fluid, Bouin's or Hollande's fixatives, and stained with Giemsa stain, Heidenhain's iron hematoxylin, or protargol (Pfaltz and Bauer, control number 6990, and ltablissements Roques Paris, control numbers 789 and 2304) were examined with the bright-field microscope. In order to make a comparison with the mensural data given by Hegner and Ratcliffe (1927), measurements of length and width were taken on 50 specimens fixed in Schaudinn's fluid and stained

Bending Waves of the Posterior Flagellum of Ceratium

Flagellar bending waves, as shown by multiple-flash photomicrographs of the posterior flagellum of Ceratium, are not sine waves. The bent regions are circular arcs; these regions are separated by short segments without bending.

THE FLAGELLATION, MOVEMENT, AND ENCYSTMENT OF SOME PHYCOMYCETOUS ZOOSPORES

The anterior flagellum of the zoospores of Phytophthora fragariae, P. megasperma, P. cambivora, Saprolegnia parasitica, Achlya americana, and Pythium aphanidermatum projects straight in front of the zoospore and never moves except during encystment whereas the posterior flagellum is active during the swimming period. In the secondary zoospore the anterior and posterior flagella are attached a short distance apart in the center of the depression on the concave side and respectively pass forward and backward through a groove and form a central axis about which the zoospore rotates. Hyaline vesicles which also have been called beads or paddles form at the base of the flagella at the beginning of encystment and glide part or all the way down the flagella. Movement of flagella after they are released from the zoospore is reported for the first time. Encystment may result from contact stimulus except in the case of Allomyces anomalus. A filament on which vesicles may occur may be secreted or retracted by the Allomyces zoospore.