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De Stefano M - One of the best experts on this subject based on the ideXlab platform.
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Epiphytic diatom communities of Terra Nova Bay, Ross Sea, Antarctica: Structural analysis and relations to algal host
2013Co-Authors: Majewska R., Gambi M.c., Totti C.m., De Stefano MAbstract:Epiphytic diatoms are important constituents of the Southern Ocean coastal water ecosystem, being a key element in many of the Antarctic trophic chains. However, only limited information exists relating to these microalgal communities. Here we describe our findings of a study on epiphytic diatoms from Terra Nova Bay (Ross Sea, Antarctica) based on material collected during the summer campaigns spanning from 1990-2004. Observations of diatoms associated with three rhodophyte species (Iridaea cordata (Turner) Bory, Phyllophora antarctica Gepp & Gepp, and Plocamium cartilagineum (L.) Dixon) were carried out with the use of a scanning electron microscope. A total of 73 diatom taxa (32 genera) were distinguished, of which 20 taxa exceeded 3% of total abundance. Cocconeis fasciolata (Ehrenberg) Brown, Navicula perminuta Grunow, and Fragilariopsis nana (Steemann Nielsen) Paasche appeared in every sample. The analysis of similarities (ANOSIM) test as well as non-metric multidimensional scaling analysis indicated the nature of host organism as a major factor influencing associated diatom community structure, whereas depth, site, and time of sampling seemed to be less important. The epizooic communities associated with sessile fauna epiphytic on macroalgae differed significantly from those associated with macroalgal surface. A pronounced difference between the communities epiphytic on various host macroalgae species was also observed, although most of the dissimilarities occurred between diatom taxa of the same growth form. © Antarctic Science Ltd 2013
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Diatoms as epiphytes on macroalgae from Terra Nova Bay (Ross Sea, Antarctica)
2011Co-Authors: Majewska R., Cante M.t., De Stefano MAbstract:Epiphytic diatoms are one of the key biotic element of the Antarctic marine ecosystem. Their unusually high metabolic flexibility gives them a crucial role in the Antarctic trophic chain. Despite being fundamental to the ecosystem functioning, diatom communities associated with marine macroalgae are frequently ignored in the floristic studies of the area. Few attempts to investigate substrate preferences have been reported. The present study provides the first examination and description of the epiphytic diatom flora from Terra Nova Bay (Ross Sea, Antarctica). Material was collected during Italian Antarctic campaigns in the years 1989-2005. Samples of thalli of Iridaea cordata, Phyllophora Antarctica, and Plocamium cartilagineum were taken from different depths at five sampling sites localized along the shore. All observations have been carried out under the scanning electron microscope. The genus Cocconeis was the most common. Two identified, previously described and well known from the Antarctic waters species - Cocconeis antiqua and C. fasciolata, as well as small naviculoid species (most likely Navicula perminuta), appeared in abundance. The Cocconeis component of the assemblage was estimated to approach 105 cells per cm2 on foliose hosts such as Iridaea. Melosira adelie was the only non-pennate diatom to achieve any degree of dominance, although Paralia sol and Trigonium arcticum were common on some of the filamentous parts of host macroalgae. Our results indicate a strong relation between the diatom assemblages and the sampling site. There is no clear evidence of diatoms host specificity. However, the filamentous forms as well as topographic anomalies (e.g. colonies of hydroids or bryozoans) can provide a point of attachment for a wider range of taxa
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Epiphytic diatoms from Terra Nova Bay (Ross Sea, Antarctica)
2011Co-Authors: Majewska R., Gambi M.c., Totti C., De Stefano MAbstract:In polar waters, microalgal communities associated with macroalgae exhibit rates of primary production comparable or even higher than those of phytoplanktonic ones. These benthic communities are mainly represented by diatoms. Despite to their crucial ecological role, the biodiversity of Antarctic epiphytic diatoms is poorly studied and greatly underestimated. In the present study, the diversity of epiphytic diatom communities from coastal waters of Terra Nova Bay was investigated and described for the first time. Samplings were made during the 8 Italian Antarctic expeditions in the space of 15 years. Thalli of Iridaea cordata, Phyllophora antarctica and Plocamium cartilagineum were collected during the austral summer. Collections were made from different depths at 5 sampling sites. Taxonomical identification and counting of diatom cells has been carried out by scanning electron microscope. According to our results biomass appears to be inversely related to the diversity. The diatom community composition varied depending on the sampling site as well as on the morphology of the macroalgal host. Some differences could be observed along a depth gradient. In terms of growth form in most cases adnate (e.g. Cocconeis, Amphora) and mobile forms (e.g. Navicula, Nitzschia) dominated. Erect diatom taxa tended to be associated with animal macrofouling species
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EPIPHYTIC DIATOMS FROM TERRA NOVA BAY (ROSS SEA, ANTARCTICA) – COMMUNITIES STRUCTURE AND DISTRIBUTION PATTERNS
2010Co-Authors: Majewska R., De Stefano MAbstract:Species diversity of microorganisms inhabiting Antarctic waters seems to be relatively low. However, they metabolic flexibility is unusually high, making them fundamental to the Antarctic ecosystem functioning. In polar waters, microalgal communities associated to macroalgae and invertebrates exhibit rates of primary production comparable or even higher than those of phytoplanktonic ones. These benthic microalgal communities are for the most part represented by diatoms. Despite to their crucial ecological role in the trophic chain, the biodiversity of antarctic epiphytic diatoms is poorly studied and greatly underestimated. In the present study, the diversity of epiphytic diatom communities from coastal waters of Terra Nova Bay (Ross Sea, Antarctic continent) has been investigated and described for the first time. Samplings were made during the Italian Antarctic expeditions in the years: 1989/90, 1990/91, 1993/94, 1994/95, 1998/1999, 2000/01, 2001/02 and 2004/05. Thalli of Iridaea cordata, Phyllophora antarctica and Plocamium cartilagineum were collected by scuba diver during the austral summer. Collections were made from different depths at five sampling sites localized along the shore and fixed with formaldehyde. To observe diatom communities originally settled on the macroalgal host preserved thalli were cut, dehydrated, placed on a stub and sputter coated with thin layer of gold. Taxonomical identification and counting of diatom cells has been carried out by scanning electron microscope. According to our results biomass appears to be inversely related to the diversity. The diatom community composition varied depending on the sampling site as well as on the morphology of the macroalgal host. Some differences could be observed also along a depth gradient. In terms of growth form in most cases adnate (e.g. Cocconeis, Amphora) and mobile forms (e.g. Navicula, Nitzschia) dominated. Erect diatom taxa tended to be associated with animal macrofouling species
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EPIPHYTIC DIATOMS FROM TERRA NOVA BAY (ROSS SEA, ANTARCTICA) - COMMUNITIES STRUCTURE AND DISTRIBUTION PATTERNS
2010Co-Authors: Majewska R., Cante M.t., De Stefano MAbstract:Species diversity of microorganisms inhabiting Antarctic waters seems to be relatively low. However, they metabolic flexibility is unusually high, making them fundamental to the Antarctic ecosystem functioning. In polar waters, microalgal communities associated to macroalgae and invertebrates exhibit rates of primary production comparable or even higher than those of phytoplanktonic ones. These benthic microalgal communities are for the most part represented by diatoms. Despite to their crucial ecological role in the trophic chain, the biodiversity of antarctic epiphytic diatoms is poorly studied and greatly underestimated. In the present study, the diversity of epiphytic diatom communities from coastal waters of Terra Nova Bay (Ross Sea, Antarctic continent) has been investigated and described for the first time. Samplings were made during the Italian Antarctic expeditions between the years 1990 and 2005. Thalli of Iridaea cordata, Phyllophora antarctica and Plocamium cartilagineum were collected by scuba diver during the austral summer. Collections were made from different depths at five sampling sites localized along the shore and fixed with formaldehyde. To observe diatom communities originally settled on the macroalgal host preserved thalli were cut, dehydrated, placed on a stub and sputter coated with thin layer of gold. Taxonomical identification and counting of diatom cells has been carried out by scanning electron microscope. According to our results biomass appears to be inversely related to the diversity. The diatom community composition varied depending on the sampling site as well as on the morphology of the macroalgal host. Some differences could be observed also along a depth gradient. In terms of growth form in most cases adnate (e.g. Cocconeis, Amphora) and mobile forms (e.g. Navicula, Nitzschia) dominated. Erect diatom taxa tended to be associated with animal macrofouling species
Francesco Soggia - One of the best experts on this subject based on the ideXlab platform.
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Arsenobetaine is a significant arsenical constituent of the red Antarctic alga Phyllophora antarctica
Environmental Chemistry, 2008Co-Authors: Marco Grotti, Walter Goessler, Francesco Soggia, Cristina Lagomarsino, Kevin A. FrancesconiAbstract:Environmental context. Although arsenic occurs in marine animals at high concentrations, the pathways by which it is biotransformed and accumulated remain largely unknown. The observation that some species of algae can contain significant concentrations of arsenobetaine, a major marine arsenic species, is relevant to explanations of the source of this compound to marine animals and its transport through the marine food web. Abstract. Significant amounts of arsenobetaine (up to 0.80 μg As g–1 dry mass, representing 17% of the extractable arsenic) were found in the extracts of all four samples of the red alga Phyllophora antarctica collected from two sites in Antarctica (Terra Nova Bay and Cape Evans). The assignment was made with high performance liquid chromatography–inductively coupled plasma mass spectrometry (HPLC-ICPMS) based on exact cochromatography with a standard compound with two chromatographic systems (cation-exchange and ion-pairing reversed-phase), each run under two sets of mobile phase conditions. Particular care was taken during sample preparation to ensure that the arsenobetaine was of algal origin and did not result from epiphytes associated with the alga. Another red alga, Iridaea cordata, collected from Terra Nova Bay, did not contain detectable concentrations of arsenobetaine. For both algal species, the majority of the extractable arsenic was present as arsenosugars. Confirmation that marine algae can contain significant amounts of arsenobetaine allows a simpler explanation for the widespread occurrence of this arsenical in marine animals.
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the utilization of the antarctic environmental specimen bank bcaa in monitoring cd and hg in an antarctic coastal area in terra nova bay ross sea northern victoria land
Chemosphere, 2004Co-Authors: Dalla S. Riva, Maria Luisa Abelmoschi, Emanuele Magi, Francesco SoggiaAbstract:The first projects relating to levels of Cd and Hg on marine biota and sediments from Terra Nova Bay (Ross Sea––Antarctica) and their bioaccumulation and biomagnification in this trophic web have been carried out by research programmes pertaining to the Italian Antarctic Research Program (PNRA) since 1989. Making use of this data, and checking the same metals after 10 years thanks to the samples stored in the BCAA, we have looked for the levels of Cd and Hg in a coastal marine ecosystem of Terra Nova Bay, and have proposed using some organisms to monitor the levels of these two heavy metals in this environment where the Italian Base is located, using the data determinate in this work as background levels. In our work, the amount of Hg and Cd concentrations have been determined in biota from the inner shelf of Terra Nova Bay (Adamussium colbecki, Laternula elliptica, Odontaster validus, Sterechinus neumayeri, Trematomus bernacchii, Iridaea cordata, Phyllophora antarctica, Parborlasia corrugatus), and in two different size fractions of sieved marine sediments (<2000 μm and <63 μm). To widen the distribution of Cd and Hg in this ecosystem we have also investigated the fraction of these metals bound to the labile phase of the marine sediments, and their presence in the particulate matter found in pack-ice cores, recent snow, water column and sea microlayer.
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Biogeochemical cycle of Pb in the coastal marine environment at Terra Nova Bay, Ross Sea
'Cambridge University Press (CUP)', 2003Co-Authors: Dalla S. Riva, Marco Grotti, M.l. Abelmoschi, M.c. Chiantore, E. Magi, Francesco SoggiaAbstract:The biogeochemical cycle of lead in the marine coastal environment of Terra Nova Bay has been investigated by determining the lead concentration in a large number of matrices: marine sediments, pack ice, snow, seawater, marine microlayer, aerosol and eight species of marine organisms (the bivalve molluscs Adamussium colbecki and Laternula elliptica, the seastar Odontaster validus, the sea urchin Sterechinus neumayeri, the fish Trematomus bernacchii, the seaweeds Iridaea cordata and Phyllophora antarctica, and the nemertine worm Parborlasia corrugata). The study of solid speciation of sediment showed that the site is not influenced by human activity and is hence suitable to examine natural processes. The concentration values found in the suspended particulate matter (SPM) of pack ice core, aerosol, marine microlayer and seawater as well as the particulate morphology, investigated by SEM, seem to support the hypothesis that particulate lead is transferred from the atmosphere to the water column through three different mechanisms: (i) release of SPM from the pack ice during its melting, (ii) input from the continental land through wet deposition, (iii) transport by aerosol and marine microlayer. Concentration data both in the whole organism and in some target organs indicated two suitable biomonitor organisms: the bivalva Laternula elliptica (particularly its digestive gland) and the fish Trematomus bernacchii (particularly its bones)
M Cormaci - One of the best experts on this subject based on the ideXlab platform.
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the macrophytobenthos of terra nova bay ross sea antarctica results of three italian scientific expeditions
Plant Biosystems, 1995Co-Authors: M CormaciAbstract:Abstract The results of a study on the benthic macroalgal flora and vegetation of Terra Nova Bay (Ross Sea) carried out during the Italian expeditions to Antarctica made in the years 1987/88, 1989/90 and 1993/94, are presented. The flora is rather poor (9 Rhodophyceae, 4 Fucophyceae, 4 Chlorophyceae), but richer than that known from adjacent areas. The vegetation is on the whole characterized by a prevalence of sciaphilous species among which Iridaea cordata, Phyllophora antarctica and Clathromorphum lemoineanum dominating in the upper infralittoral, lower infralittoral and circalittoral zones, respectively. Moreover, the results of a study on biomass of a population of I. cordata as well as of a population of P. antarctica, carried out in the austral summer 1993/94, are reported too. The values of the biomass of the population of I. cordata resulted to vary inversely with respect to those of the population of P. antarctica.
Majewska R. - One of the best experts on this subject based on the ideXlab platform.
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Epiphytic diatom communities of Terra Nova Bay, Ross Sea, Antarctica: Structural analysis and relations to algal host
2013Co-Authors: Majewska R., Gambi M.c., Totti C.m., De Stefano MAbstract:Epiphytic diatoms are important constituents of the Southern Ocean coastal water ecosystem, being a key element in many of the Antarctic trophic chains. However, only limited information exists relating to these microalgal communities. Here we describe our findings of a study on epiphytic diatoms from Terra Nova Bay (Ross Sea, Antarctica) based on material collected during the summer campaigns spanning from 1990-2004. Observations of diatoms associated with three rhodophyte species (Iridaea cordata (Turner) Bory, Phyllophora antarctica Gepp & Gepp, and Plocamium cartilagineum (L.) Dixon) were carried out with the use of a scanning electron microscope. A total of 73 diatom taxa (32 genera) were distinguished, of which 20 taxa exceeded 3% of total abundance. Cocconeis fasciolata (Ehrenberg) Brown, Navicula perminuta Grunow, and Fragilariopsis nana (Steemann Nielsen) Paasche appeared in every sample. The analysis of similarities (ANOSIM) test as well as non-metric multidimensional scaling analysis indicated the nature of host organism as a major factor influencing associated diatom community structure, whereas depth, site, and time of sampling seemed to be less important. The epizooic communities associated with sessile fauna epiphytic on macroalgae differed significantly from those associated with macroalgal surface. A pronounced difference between the communities epiphytic on various host macroalgae species was also observed, although most of the dissimilarities occurred between diatom taxa of the same growth form. © Antarctic Science Ltd 2013
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Diatoms as epiphytes on macroalgae from Terra Nova Bay (Ross Sea, Antarctica)
2011Co-Authors: Majewska R., Cante M.t., De Stefano MAbstract:Epiphytic diatoms are one of the key biotic element of the Antarctic marine ecosystem. Their unusually high metabolic flexibility gives them a crucial role in the Antarctic trophic chain. Despite being fundamental to the ecosystem functioning, diatom communities associated with marine macroalgae are frequently ignored in the floristic studies of the area. Few attempts to investigate substrate preferences have been reported. The present study provides the first examination and description of the epiphytic diatom flora from Terra Nova Bay (Ross Sea, Antarctica). Material was collected during Italian Antarctic campaigns in the years 1989-2005. Samples of thalli of Iridaea cordata, Phyllophora Antarctica, and Plocamium cartilagineum were taken from different depths at five sampling sites localized along the shore. All observations have been carried out under the scanning electron microscope. The genus Cocconeis was the most common. Two identified, previously described and well known from the Antarctic waters species - Cocconeis antiqua and C. fasciolata, as well as small naviculoid species (most likely Navicula perminuta), appeared in abundance. The Cocconeis component of the assemblage was estimated to approach 105 cells per cm2 on foliose hosts such as Iridaea. Melosira adelie was the only non-pennate diatom to achieve any degree of dominance, although Paralia sol and Trigonium arcticum were common on some of the filamentous parts of host macroalgae. Our results indicate a strong relation between the diatom assemblages and the sampling site. There is no clear evidence of diatoms host specificity. However, the filamentous forms as well as topographic anomalies (e.g. colonies of hydroids or bryozoans) can provide a point of attachment for a wider range of taxa
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Epiphytic diatoms from Terra Nova Bay (Ross Sea, Antarctica)
2011Co-Authors: Majewska R., Gambi M.c., Totti C., De Stefano MAbstract:In polar waters, microalgal communities associated with macroalgae exhibit rates of primary production comparable or even higher than those of phytoplanktonic ones. These benthic communities are mainly represented by diatoms. Despite to their crucial ecological role, the biodiversity of Antarctic epiphytic diatoms is poorly studied and greatly underestimated. In the present study, the diversity of epiphytic diatom communities from coastal waters of Terra Nova Bay was investigated and described for the first time. Samplings were made during the 8 Italian Antarctic expeditions in the space of 15 years. Thalli of Iridaea cordata, Phyllophora antarctica and Plocamium cartilagineum were collected during the austral summer. Collections were made from different depths at 5 sampling sites. Taxonomical identification and counting of diatom cells has been carried out by scanning electron microscope. According to our results biomass appears to be inversely related to the diversity. The diatom community composition varied depending on the sampling site as well as on the morphology of the macroalgal host. Some differences could be observed along a depth gradient. In terms of growth form in most cases adnate (e.g. Cocconeis, Amphora) and mobile forms (e.g. Navicula, Nitzschia) dominated. Erect diatom taxa tended to be associated with animal macrofouling species
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EPIPHYTIC DIATOMS FROM TERRA NOVA BAY (ROSS SEA, ANTARCTICA) – COMMUNITIES STRUCTURE AND DISTRIBUTION PATTERNS
2010Co-Authors: Majewska R., De Stefano MAbstract:Species diversity of microorganisms inhabiting Antarctic waters seems to be relatively low. However, they metabolic flexibility is unusually high, making them fundamental to the Antarctic ecosystem functioning. In polar waters, microalgal communities associated to macroalgae and invertebrates exhibit rates of primary production comparable or even higher than those of phytoplanktonic ones. These benthic microalgal communities are for the most part represented by diatoms. Despite to their crucial ecological role in the trophic chain, the biodiversity of antarctic epiphytic diatoms is poorly studied and greatly underestimated. In the present study, the diversity of epiphytic diatom communities from coastal waters of Terra Nova Bay (Ross Sea, Antarctic continent) has been investigated and described for the first time. Samplings were made during the Italian Antarctic expeditions in the years: 1989/90, 1990/91, 1993/94, 1994/95, 1998/1999, 2000/01, 2001/02 and 2004/05. Thalli of Iridaea cordata, Phyllophora antarctica and Plocamium cartilagineum were collected by scuba diver during the austral summer. Collections were made from different depths at five sampling sites localized along the shore and fixed with formaldehyde. To observe diatom communities originally settled on the macroalgal host preserved thalli were cut, dehydrated, placed on a stub and sputter coated with thin layer of gold. Taxonomical identification and counting of diatom cells has been carried out by scanning electron microscope. According to our results biomass appears to be inversely related to the diversity. The diatom community composition varied depending on the sampling site as well as on the morphology of the macroalgal host. Some differences could be observed also along a depth gradient. In terms of growth form in most cases adnate (e.g. Cocconeis, Amphora) and mobile forms (e.g. Navicula, Nitzschia) dominated. Erect diatom taxa tended to be associated with animal macrofouling species
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EPIPHYTIC DIATOMS FROM TERRA NOVA BAY (ROSS SEA, ANTARCTICA) - COMMUNITIES STRUCTURE AND DISTRIBUTION PATTERNS
2010Co-Authors: Majewska R., Cante M.t., De Stefano MAbstract:Species diversity of microorganisms inhabiting Antarctic waters seems to be relatively low. However, they metabolic flexibility is unusually high, making them fundamental to the Antarctic ecosystem functioning. In polar waters, microalgal communities associated to macroalgae and invertebrates exhibit rates of primary production comparable or even higher than those of phytoplanktonic ones. These benthic microalgal communities are for the most part represented by diatoms. Despite to their crucial ecological role in the trophic chain, the biodiversity of antarctic epiphytic diatoms is poorly studied and greatly underestimated. In the present study, the diversity of epiphytic diatom communities from coastal waters of Terra Nova Bay (Ross Sea, Antarctic continent) has been investigated and described for the first time. Samplings were made during the Italian Antarctic expeditions between the years 1990 and 2005. Thalli of Iridaea cordata, Phyllophora antarctica and Plocamium cartilagineum were collected by scuba diver during the austral summer. Collections were made from different depths at five sampling sites localized along the shore and fixed with formaldehyde. To observe diatom communities originally settled on the macroalgal host preserved thalli were cut, dehydrated, placed on a stub and sputter coated with thin layer of gold. Taxonomical identification and counting of diatom cells has been carried out by scanning electron microscope. According to our results biomass appears to be inversely related to the diversity. The diatom community composition varied depending on the sampling site as well as on the morphology of the macroalgal host. Some differences could be observed also along a depth gradient. In terms of growth form in most cases adnate (e.g. Cocconeis, Amphora) and mobile forms (e.g. Navicula, Nitzschia) dominated. Erect diatom taxa tended to be associated with animal macrofouling species
Max H Hommersand - One of the best experts on this subject based on the ideXlab platform.
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its1 sequences of type specimens of gigartina and sarcothalia and their significance for the classification of south african gigartinaceae gigartinales rhodophyta
European Journal of Phycology, 2002Co-Authors: Jeffery R Hughey, Paul C Silva, Max H HommersandAbstract:Uncertainties about the identity of type specimens of red algae have frequently led to taxonomic and nomenclatural confusion. A procedure for extracting PCR-amplifiable DNA from formalin-fixed material and herbarium specimens was used to investigate the taxonomic status of several South African Gigartinaceae. We compared nucleotide sequences in the internal transcribed spacer 1 (ITS1) region in type specimens and other historically important collections presently referred to Gigartina bracteata , G. radula and G. stiriata . The following opinions are supported: (1) Fucus bracteatus S.G. Gmelin, Chondrodictyon capense Kutzing and Iridaea clathrata Decaisne represent a single species of South African Gigartina ( G. bracteata (S.G. Gmelin) Setchell & Gardner) in which the disintegration of tetrasporangial sori results in a reticulate thallus. (2) Mastocarpus polycarpus Kutzing, M. incrassatus Kutzing and Iridaea lapathifolia Kutzing represent a single species of South African Gigartina ( G. polycarpa (Kutzing) Setchell & Gardner) that has often, but erroneously, been called G. radula (Esper) J. Agardh. (3) Mastocarpus verrucosus Kutzing is a later heterotypic synonym of Iridaea papillosa Bory ( Sarcothalia papillosa (Bory) Leister) and was based on material that probably came from southern South America rather than from South Africa, the provenance given by Kutzing. (4) Fucus stiriatus Turner and Sphaerococcus burmannii C. Agardh represent a single species of South African Sarcothalia ( S. stiriata (Turner) Leister).
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solving taxonomic and nomenclatural problems in pacific gigartinaceae rhodophyta using dna from type material
Journal of Phycology, 2001Co-Authors: Jeffery R Hughey, Paul C Silva, Max H HommersandAbstract:Molecular data obtained by a procedure for extracting PCR-amplifiable nuclear and chloroplast DNA from old and formalin-fixed red algal herbarium specimens were used to elucidate problems in the systematics of Pacific Gigartinaceae. Correspondence between nucleotide sequences of the internal transcribed spacer 1 region or the RUBISCO spacer from type specimens and modern collections supports the following conclusions. (1) The type of Fucus cordatus Turner, now Iridaea cordata (Turner) Bory, came from the southern hemisphere (probably from Isla de los Estados, Argentina) rather than from Banks Island, B.C., Canada. (2) The type of Iridaea heterocarpa P. et R. [ Mazzaella heterocarpa (P. et R.) Fred.] represents the tetrasporangial phase of a species of Chondrus , possibly C. crispus Stackh. (3) The types of Iridaea lilacina P. et R., I. phyllocarpa P. et R., and Iridophycus furcatum S. et G. represent a single species from Alaska, Mazzaella phyllocarpa (P. et R.) Perest., currently but incorrectly called M. heterocarpa. (4) The type of Iridophycus oregonum Doty represents the tetrasporangial phase of the species from southern Alaska to southern California known incorrectly as M. heterocarpa . (5) Mazzaella splendens (S. et G.) Fred. is more closely related to M. linearis (S. et G.) Fred. than it is to M. flaccida (S. et G.) Fred. (6) Iridophycus coriaceum S. et G. is conspecific with M. splendens , whereas Rhodoglossum coriaceum E.Y. Dawson is an independent species: Mazzaella coriacea (E.Y. Dawson) Hughey. (7) Iridaea cornucopiae P. et R. is conspecific with Mazzaella laminarioides (Bory) Fred., and the type probably came from Chile rather than from the North Pacific. (8) Plants attributed to Iridaea cornucopiae in Pacific North America are referable to Mazzaella parksii (S. et G.) comb. nov. (9) Rhodoglossum parvum G. M. Smith et Hollenb. is an independent species: Mazzaella parva (G. M. Smith et Hollenb.) comb. nov. (10) Grateloupia squarrulosa S. et G., Grateloupia johnstonii S. et G., and Gigartina pectinata E.Y. Dawson represent a single species: Chondracanthus squarrulosus (S. et G.) comb. nov.
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recent developments in the systematics of the gigartinaceae gigartinales rhodophyta based on rbcl sequence analysis and morphological evidence
Phycological Research, 1999Co-Authors: Max H Hommersand, S Fredericq, Wilson D Freshwater, Jeffery R HugheyAbstract:The phylogenetic systematics of the Gigartinaceae is discussed for seven genera and three undescribed generic lineages and 65 taxa representing 62 species based on an analysis of rbcL sequences and morphological evidence. An examination of rbcL trees resulting from analyses of these taxa identifies seven lineages: (i) ‘Gigartina’ alveata; (ii) Rhodoglossum/Gigartina; (iii) Chondracanthus; (iv) Ostiophyllum; (v) Sarcothalia; (vi) ‘Gigartina’ skottsbergii; and (vii) a large clade containing Iridaea/‘Sarcothalia’, Mazzaella and Chondrus. These lineages and Chondrus are strongly supported; however, two groups, Iridaea/‘Sarcothalia’ and Mazzaella, receive no bootstrap support. The morphology of the female reproductive system is investigated with the aid of computer-generated, color-coded tracings of photographs of cystocarps seen in cross section at different developmental stages. Seven basic cystocarp types were found which corresponded to species groups seen in rbcL trees. These were: (i) a ‘Gigartina’ alveata group in which the carposporangia-bearing filaments develop apomictically from gametophytic cells; (ii) a Rhodoglossum/Gigartina group in which gonimoblast filaments penetrate the surrounding envelope fusing progessively with envelope cells; (iii) a Chondracanthus group in which gonimoblast filaments penetrate the envelope but fuse with envelope cells only at late developmental stages; (iv) a Sarcothalia group in which the gonimoblast filaments displace an envelope composed mainly of secondary gametophytic filaments and link to envelope cells by terminal tubular gonimoblast cells; (v) an Iridaea group similar to the Sarcothalia group, but with an envelope composed of a mixture of medullary cells and secondary gametophytic filaments; (vi) a Mazzaella group that lacks a true envelope and in which gonimoblast filaments connect to modified gametophytic cells by means of terminal tubular cells; (vii) a Chondrus group in which gonimoblast filaments penetrate the medulla and link to modified medullary cells by means of conjunctor cells forming secondary pit connections. The further separation of these groups into genera is based largely on tetrasporangial characters.
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phylogenetic systematics and biogeography of the gigartinaceae gigartinales rhodophyta based on sequence analysis of rbcl
Botanica Marina, 1994Co-Authors: Max H Hommersand, S Fredericq, D. W. FreshwaterAbstract:Recently Hommersand, Guiry, Fredericq and Leister (1993, Hydrobiologia 260/261: 105-120) proposed a revised classification of the marine red algal family Gigartinaceae in which sixty-nine species were classified into four extant (Chondrus Stackhouse, Gigartina Stackhouse, Iridaea Bory, nom. cons., Rhodoglossum J. Agardh) and three reinstated (Chondracanthus Kutzing, Sarcothalia Kutzing, Mazzaella G. de Toni f.) genera based on developmental and morphological criteria. We have undertaken a preliminary study of the phylogenetic systematics and biogeography of the Gigartinaceae based on an independent data set derived from sequence analysis of rbcL, the gene that codes for the large subunit of RuBisCO. The topology of the rbcL tree, which contains 43 species, generally supports our recent systematic revision, while highlighting some taxonomic problems
