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Eduardo J Caceres - One of the best experts on this subject based on the ideXlab platform.
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female gametogenesis and female gamete germination in the anisogamous green alga Codium Fragile subsp novae zelandiae bryopsidophyceae chlorophyta
Phycological Research, 2012Co-Authors: Alicia B Miravalles, Patricia Ines Leonardi, Eduardo J CaceresAbstract:SUMMARY Female gametogenesis was studied in the dioecious siphonous green alga Codium Fragile subsp. novae-zelandiae (J. Agardh) P. C. Silva using light and electron microscopy. Early during gametogenesis the protoplasm was uniform; then it separated in portions, while fusiform chloroplasts and nuclei increased in numbers. Some features of the nuclear divisions were similar to those of other Bryopsidophyceae. They were acentric and semi-open. Pairs of parallel electron-dense lines resembling synaptonemic complexes were observed in several prophase nuclei indicating meioses. In metaphase the nuclear envelope showed polar fenestrae from which the spindle emerged. No spindle microtubule nucleating material was visible and chromosome kinetochores were evident. Mature female gametes were pyriform with a hyaline anterior end from which the two flagella emerged. Mature gametes had a spherical nucleus surrounded by a mitochondrion and numerous discoid chloroplasts. Female gametes germinated parthenogenetically in culture and also inside gametangia, involving loss of flagella, rounding and lengthening of cells, multiplication of chloroplasts with well developed thylakoid systems, vacuolization and synthesis of a fibrillar cell wall.
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male gametogenesis ultrastructure of Codium Fragile subsp novae zelandiae bryopsidophyceae chlorophyta
Phycologia, 2011Co-Authors: Alicia B Miravalles, Patricia Ines Leonardi, Eduardo J CaceresAbstract:Abstract Miravalles A.B., Leonardi P.I. and Caceres E.J. 2011. Male gametogenesis ultrastructure of Codium Fragile subsp. novae-zelandiae (Bryopsidophyceae, Chlorophyta). Phycologia 50: 370–378. DOI: 10.2216/10-25.1 Male gametogenesis was studied by light and electron microscopy in the dioecious siphonous green alga Codium Fragile subsp. novae-zelandiae. Gametangia were formed on the sides of utricules. Initially, gametangia showed vegetative interphase nuclei and chloroplasts already with a mature structure with few thylakoid lamellae and a single starch granule. Then, mitotic divisions occurred, originating a proliferation of gametic nuclei. Features of the gametangial mitosis were similar to vegetative mitoses of other Bryopsidophyceae. The fusion of minute vesicles clearly delimited uninucleate portions of protoplasm with a large mitochondrion and chloroplasts. Ultimately, the gamete final shape was delimited, and the basal-flagellar apparatus developed. Mature gametes were liberated immersed in a muc...
Patricia Ines Leonardi - One of the best experts on this subject based on the ideXlab platform.
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female gametogenesis and female gamete germination in the anisogamous green alga Codium Fragile subsp novae zelandiae bryopsidophyceae chlorophyta
Phycological Research, 2012Co-Authors: Alicia B Miravalles, Patricia Ines Leonardi, Eduardo J CaceresAbstract:SUMMARY Female gametogenesis was studied in the dioecious siphonous green alga Codium Fragile subsp. novae-zelandiae (J. Agardh) P. C. Silva using light and electron microscopy. Early during gametogenesis the protoplasm was uniform; then it separated in portions, while fusiform chloroplasts and nuclei increased in numbers. Some features of the nuclear divisions were similar to those of other Bryopsidophyceae. They were acentric and semi-open. Pairs of parallel electron-dense lines resembling synaptonemic complexes were observed in several prophase nuclei indicating meioses. In metaphase the nuclear envelope showed polar fenestrae from which the spindle emerged. No spindle microtubule nucleating material was visible and chromosome kinetochores were evident. Mature female gametes were pyriform with a hyaline anterior end from which the two flagella emerged. Mature gametes had a spherical nucleus surrounded by a mitochondrion and numerous discoid chloroplasts. Female gametes germinated parthenogenetically in culture and also inside gametangia, involving loss of flagella, rounding and lengthening of cells, multiplication of chloroplasts with well developed thylakoid systems, vacuolization and synthesis of a fibrillar cell wall.
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male gametogenesis ultrastructure of Codium Fragile subsp novae zelandiae bryopsidophyceae chlorophyta
Phycologia, 2011Co-Authors: Alicia B Miravalles, Patricia Ines Leonardi, Eduardo J CaceresAbstract:Abstract Miravalles A.B., Leonardi P.I. and Caceres E.J. 2011. Male gametogenesis ultrastructure of Codium Fragile subsp. novae-zelandiae (Bryopsidophyceae, Chlorophyta). Phycologia 50: 370–378. DOI: 10.2216/10-25.1 Male gametogenesis was studied by light and electron microscopy in the dioecious siphonous green alga Codium Fragile subsp. novae-zelandiae. Gametangia were formed on the sides of utricules. Initially, gametangia showed vegetative interphase nuclei and chloroplasts already with a mature structure with few thylakoid lamellae and a single starch granule. Then, mitotic divisions occurred, originating a proliferation of gametic nuclei. Features of the gametangial mitosis were similar to vegetative mitoses of other Bryopsidophyceae. The fusion of minute vesicles clearly delimited uninucleate portions of protoplasm with a large mitochondrion and chloroplasts. Ultimately, the gamete final shape was delimited, and the basal-flagellar apparatus developed. Mature gametes were liberated immersed in a muc...
Alicia B Miravalles - One of the best experts on this subject based on the ideXlab platform.
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female gametogenesis and female gamete germination in the anisogamous green alga Codium Fragile subsp novae zelandiae bryopsidophyceae chlorophyta
Phycological Research, 2012Co-Authors: Alicia B Miravalles, Patricia Ines Leonardi, Eduardo J CaceresAbstract:SUMMARY Female gametogenesis was studied in the dioecious siphonous green alga Codium Fragile subsp. novae-zelandiae (J. Agardh) P. C. Silva using light and electron microscopy. Early during gametogenesis the protoplasm was uniform; then it separated in portions, while fusiform chloroplasts and nuclei increased in numbers. Some features of the nuclear divisions were similar to those of other Bryopsidophyceae. They were acentric and semi-open. Pairs of parallel electron-dense lines resembling synaptonemic complexes were observed in several prophase nuclei indicating meioses. In metaphase the nuclear envelope showed polar fenestrae from which the spindle emerged. No spindle microtubule nucleating material was visible and chromosome kinetochores were evident. Mature female gametes were pyriform with a hyaline anterior end from which the two flagella emerged. Mature gametes had a spherical nucleus surrounded by a mitochondrion and numerous discoid chloroplasts. Female gametes germinated parthenogenetically in culture and also inside gametangia, involving loss of flagella, rounding and lengthening of cells, multiplication of chloroplasts with well developed thylakoid systems, vacuolization and synthesis of a fibrillar cell wall.
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male gametogenesis ultrastructure of Codium Fragile subsp novae zelandiae bryopsidophyceae chlorophyta
Phycologia, 2011Co-Authors: Alicia B Miravalles, Patricia Ines Leonardi, Eduardo J CaceresAbstract:Abstract Miravalles A.B., Leonardi P.I. and Caceres E.J. 2011. Male gametogenesis ultrastructure of Codium Fragile subsp. novae-zelandiae (Bryopsidophyceae, Chlorophyta). Phycologia 50: 370–378. DOI: 10.2216/10-25.1 Male gametogenesis was studied by light and electron microscopy in the dioecious siphonous green alga Codium Fragile subsp. novae-zelandiae. Gametangia were formed on the sides of utricules. Initially, gametangia showed vegetative interphase nuclei and chloroplasts already with a mature structure with few thylakoid lamellae and a single starch granule. Then, mitotic divisions occurred, originating a proliferation of gametic nuclei. Features of the gametangial mitosis were similar to vegetative mitoses of other Bryopsidophyceae. The fusion of minute vesicles clearly delimited uninucleate portions of protoplasm with a large mitochondrion and chloroplasts. Ultimately, the gamete final shape was delimited, and the basal-flagellar apparatus developed. Mature gametes were liberated immersed in a muc...
Robert Eric Scheibling - One of the best experts on this subject based on the ideXlab platform.
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detrital subsidy from subtidal kelp beds is altered by the invasive green alga Codium Fragile ssp Fragile
Marine Ecology Progress Series, 2012Co-Authors: Kira A Krumhansl, Robert Eric ScheiblingAbstract:Invasive species have the potential to alter the dynamics of detrital subsidy from high to low productivity areas through changes in quantity and nutritional quality of detrital material. We examined the effect of the invasive alga Codium Fragile ssp. Fragile on the nature of detrital export from subtidal algal beds off Nova Scotia, Canada, by comparing changes in mass, nutri- tional quality (%C, %N, C/N ratio), concentration of dimethylsulfoniopropionate (DMSP, a sec- ondary metabolite that deters grazers), and isotopic composition (δ 13 C and δ 15 N) between C. frag- ile and the native kelp Saccharina latissima at 4 wk intervals over 16 wk of degradation in cages on a sand bottom at 19 m depth. C. Fragile degraded more slowly, and had a consistently lower C/N and higher DMSP concentration, than S. latissima. Isotope signatures did not differ between algal species: δ 15 N became slightly enriched (~1‰) after 16 wk of degradation, with no change in δ 13 C. We also compared macrofaunal communities associated with degrading thalli of each algal species and found significantly higher abundances of invertebrates (mainly capitellid poly- chaetes) on S. latissima after 8 wk of degradation, resulting in lower evenness (J') and diversity (H') on S. latissima compared to C. Fragile. Macrofaunal community composition became similar between algal species at 12 and 16 wk in concordance with decreases in C/N ratio in S. latissima and DMSP concentration in C. Fragile. Our results indicate that differences in biochemical compo- sition and the rate of degradation between C. Fragile and native kelps result in community-level effects in areas linked to shallow algal beds via the transfer of detritus.
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spatial and temporal variation in dmsp content in the invasive seaweed Codium Fragile ssp Fragile effects of temperature light and grazing
Marine Ecology Progress Series, 2010Co-Authors: Devin A Lyons, Robert Eric Scheibling, K L Van AlstyneAbstract:The methionine-derived secondary metabolite dimethylsulfoniopropionate (DMSP) is believed to function in cryoprotection, defense against herbivory, and reduction of oxidative stress in some seaweeds. The ability to produce DMSP, and modify its concentration according to environ- mental conditions, may confer adaptive advantages to these algae. We studied the spatial and tem- poral distribution of DMSP content in Codium Fragile off the Atlantic coast of Nova Scotia. Levels of DMSP in C. Fragile were highest in boreal spring (~2% of total dry wt) and lowest in fall (~1%), and negatively related to seawater temperature. DMSP content differed among sites and tended to decrease or remain constant with depth. In tide pools, partially bleached algae contained less DMSP than undamaged individuals, consistent with the putative function of DMSP in response to oxidative stress. Results of field- and laboratory-based experiments, designed to examine plasticity in DMSP production by C. Fragile, indicate that it increases with light intensity, exposure to sea urchin grazing, and decreasing temperature.
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contrasting patterns of spread in interacting invasive species membranipora membranacea and Codium Fragile off nova scotia
Biological Invasions, 2010Co-Authors: Shana Watanabe, Robert Eric Scheibling, Anna MetaxasAbstract:In the Northwest Atlantic, overgrowth of the competitively dominant, native kelps by an invasive bryozoan Membranipora membranacea increases frond erosion, which has facilitated the establishment and spread of the invasive macroalga Codium Fragile ssp Fragile. To document the spread of both introduced species along the Atlantic coast of Nova Scotia from initial introduction points (the ‘epicentre’) southwest of Halifax, we conducted video-surveys of shallow rocky habitats along the southwestern shore of Nova Scotia (100 km linear distance, encompassing the range of M. membranacea) in 2000, and then along the entire Atlantic coast in 2007 (650 km). Membranipora membranacea was observed continuously throughout the surveyed ranges in 2000 and 2007, wherever kelps were present, suggesting natural dispersal via planktonic larvae. Codium Fragile was observed along 95 km of the surveyed range in 2000 and along 445 km in 2007, with a relatively patchy distribution beyond the epicentre, suggesting a combination of natural and anthropogenic dispersal mechanisms. Rockweed-dominated (Fucus spp.) or mixed algal assemblages common outside the epicentre may alter the interaction between M. membranacea and C. Fragile, since seaweeds other than kelp are not subject to defoliation by the bryozoan. Percent cover of kelp at the epicentre generally increased from 2000 to 2007, while that of C. Fragile generally decreased. Codium Fragile was the dominant canopy alga at 54% of sites in 2000 and at only 15% of sites in 2007. These findings indicate that, at near decadal timescales, C. Fragile does not prevent re-colonization by native kelps.
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dispersal potential of the invasive green alga Codium Fragile ssp Fragile
Journal of Experimental Marine Biology and Ecology, 2009Co-Authors: Shana Watanabe, Anna Metaxas, Robert Eric ScheiblingAbstract:Since its introduction in 1989, the invasive green alga Codium Fragile ssp. Fragile (formerly Codium Fragile ssp. tomentosoides) has spread rapidly in Atlantic Canada. Although its spread has likely been facilitated by human transport, C. Fragile possesses diverse modes of natural dispersal. In addition to parthenogenetically developing swarmer cells, it can propagate through the release of vegetative buds, thallus fragments, and entire, dislodged thalli. We examined the natural dispersal potential of these propagules using a combination of field and laboratory experiments. Vegetative buds were most abundant on thalli in late August, coinciding with increasing late summer wave activity. At two locations within two field sites, we examined the effects of tidal state, wave action and topography on the dispersal of fragments and intact thalli. Over a 4-hour period, retention rate was generally lower and dispersal distance of retained propagules higher: during flood than ebb tide; at the more wave-exposed locations; and for fragments than thalli. Dispersal direction corresponded with topography or flood tide currents at certain locations, but was often bi-directional or random, suggesting an added role of wave action. Over periods of weeks, the retention rate of marked detrital thalli was negatively related to the magnitude of wave activity. In the laboratory, settling rate was negatively related to propagule length, and large buds had higher critical shear erosional velocities than either small buds or fragments. Our results indicate that large propagules of C. Fragile, such as intact adult thalli, have a generally low dispersal potential (meters), but may be transported longer distances (kilometers) during storms or when positively buoyant. Fragments and buds are regularly transported 10's of meters at a time at average flow velocities. However, they also become resuspended in average flows, and probably disperse longer distances over multiple resuspension events, or when positively buoyant. Once settled, the smallest propagules may be less easily resuspended or transported along the bottom as they become entrapped by small-scale topographic features or turf algae. The wide variety of propagules produced by C. Fragile and the variable distances over which different propagule types may be transported give C. Fragile the advantage of both short- and long-distance dispersal, and have likely played a role in the invasive success of this alga.
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grazing of the invasive alga Codium Fragile ssp tomentosoides by the common periwinkle littorina littorea effects of thallus size age and condition
Journal of Experimental Marine Biology and Ecology, 2008Co-Authors: Robert Eric Scheibling, Devin A Lyons, Catherine B T SumiAbstract:Abstract We examined the potential of herbivory by the common periwinkle Littorina littorea to limit recruitment and vegetative re-growth of the invasive green alga Codium Fragile ssp. tomentosoides in a series of manipulative field experiments in tidepools on a wave-exposed rocky shore in Nova Scotia, Canada. Snails were excluded or included from circular plots (14 to 20 cm diameter) with cages to compare growth and survival of C. Fragile against procedural (partial cages) or natural (uncaged) control plots. Our results show that L. littorea may restrict growth and survival of C. Fragile by grazing new recruits (
Micheline Grignondubois - One of the best experts on this subject based on the ideXlab platform.
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Codium Fragile subsp Fragile suringar hariot in tunisia morphological data and status of knowledge
Algae, 2016Co-Authors: Wafa Cherif, L Ktari, Monia El Bour, Abdellatif Boudabous, Micheline GrignonduboisAbstract:The Mediterranean Sea is currently facing dramatic changes and threats, including change in native species and accidental introductions. The introduced green alga Codium Fragile subsp. Fragile (Suringar) Hariot influences diversity and community structure in some parts of the world. This paper docum...