The Experts below are selected from a list of 306 Experts worldwide ranked by ideXlab platform
Michael J Stanhope - One of the best experts on this subject based on the ideXlab platform.
-
linnaeus was right all along ulva and Enteromorpha are not distinct genera
European Journal of Phycology, 2003Co-Authors: Hillary S Hayden, Jaanika Blomster, Christine A Maggs, Paul C Silva, Michael J Stanhope, Robert J WaalandAbstract:Ulva, one of the first Linnaean genera, was later circumscribed to consist of green seaweeds with distromatic blades, and Enteromorpha Link was established for tubular forms. Although several lines of evidence suggest that these generic constructs are artificial, Ulva and Enteromorpha have been maintained as separate genera. Our aims were to determine phylogenetic relationships among taxa currently attributed to Ulva, Enteromorpha, Umbraulva Bae et I.K. Lee and the monotypic genus Chloropelta C.E. Tanner, and to make any nomenclatural changes justified by our findings. Analyses of nuclear ribosomal internal transcribed spacer DNA (ITS nrONA) (29 ingroup taxa including the type species of Ulva and Enteromorphat, the chloroplast-encoded rbcL gene (for a subset of taxa) and a combined data set were carried out. All trees had a strongly supported clade consisting of all Ulva, Enteromorpha and Chloropelta species, but Ulva and Enteromorpha were not monophyletic. The recent removal of Vmbraulva olivascens (PJ.L...
-
novel morphology in Enteromorpha ulvophyceae forming green tides
American Journal of Botany, 2002Co-Authors: Jaanika Blomster, Christine A Maggs, Saara Back, David P Fewer, Mikko Kiirikki, Annamaija Lehvo, Michael J StanhopeAbstract:‘‘Green tides’’ are vast accumulations of unattached green macroalgae associated with eutrophicated marine environments. They have major ecological and economic impacts globally, so an understanding of their origin and persistence is required in order to make management decisions. Blooms predominantly consist of two common fouling genera of the Ulvales, Ulva (distromatic sheets) and Enteromorpha (monostromatic tubes). In the Baltic Sea and elsewhere green tides have increased over the last few decades. On the west coast of Finland, summer blooms consist of monostromatic sheets resembling Monostroma (Codiolales). We identified these as Enteromorpha intestinalis by comparative analyses of rDNA internal transcribed spacer 1 (ITS1), 5.8S, and ITS2 sequences, the first time monostromatic sheets have been found in the genus Enteromorpha. Ordinary attached E. intestinalis sporulated freely in culture, but the sheets reproduced only by cell regeneration into typical tubular thalli. The ITS sequences were identical to those of attached E. intestinalis populations in southwestern Finland, but differed by two substitutions from other Baltic sequences. We infer that this bloom originated from local attached populations and now reproduces clonally by fragmentation. This study provides further evidence of radical changes in gross morphology of green algae under eutrophicated conditions and the need for molecular identification.
-
molecular phylogenetic evidence for a reversible morphogenetic switch controlling the gross morphology of two common genera of green seaweeds ulva and Enteromorpha
Molecular Biology and Evolution, 1999Co-Authors: Jaanika Blomster, Christine A Maggs, G Hansen, Elina Leskinen, David G Mann, Hans J Sluiman, Michael J StanhopeAbstract:Ulva and Enteromorpha are two of the most common, ubiquitous, and environmentally important genera of green seaweeds. They are widely regarded as easily distinguishable because of their dramatically different morphologies: Ulva species are flat, lettuceli
-
molecular and morphological analysis of Enteromorpha intestinalis and e compressa chlorophyta in the british isles
Journal of Phycology, 1998Co-Authors: Jaanika Blomster, Christine A Maggs, Michael J StanhopeAbstract:The very common green seaweeds Enteromorpha intestinalis (L.) Nees and E. compressa (L.) Nees are important fouling organisms and have commonly been used as indicators of eutrophication, but their taxonomic status is problematic. The genus presents extreme difficulties because there is wide intraspecific variation in morphology, but morphological differences between species are small and difficult to detect. In this study, molecular data were used in parallel with morphological characters to resolve the taxonomic problems. Phylogenetic analysis of sequences of the internal transcribed spacers ITS1 and ITS2 and the 5.8S gene distinguished two groups of samples, which were identified by morphological characters as E. compressa (branched) and E. intestinalis (normally unbranched). There was a low level of sequence divergence within each group of samples, but divergence between groups was as great as that between either of the two species and the outgroup E. prolifera. Clades representing E. compressa and E. intestinalis were also found in analyses of an independent molecular data set, chloroplast DNA restriction fragment length polymorphisms (RFLPs). Enteromorpha intestinalis and E. compressa represent two distinct, genetically divergent species. Reinterpretation of published studies shows that these species are reproductively isolated. However, E. compressa and E. intestinalis are sometimes very difficult to distinguish from each other and could be regarded as cryptic species. The presence or absence of branching was the most useful character distinguishing these two species, but there was an element of ambiguity because low salinity or salinity shock can induce branching in E. intestinalis. If environmental factors such as salinity are taken into account, branching can be used to identify the great majority of thalli correctly. This study therefore provides a basis for identifying the two most important marine fouling macroalgae and for their use in environmental monitoring and experimentation. Typification of these two Linnaean species showed that current usage of the names accords with the lectotype and protologue of both species. Samples that resembled E. usneoides did not form a clade in any of the trees, and constraining the data to support the monophyly of this group incurred a penalty. Enteromorpha usneoides appears to be an ecotype of E. compressa.
Janet Finlay - One of the best experts on this subject based on the ideXlab platform.
-
the influence of surface wettability on the adhesion strength of settled spores of the green alga Enteromorpha and the diatom amphora
Integrative and Comparative Biology, 2002Co-Authors: Janet Finlay, Maureen Callow, Linnea K Ista, Gabriel P Lopez, James A. CallowAbstract:Abstract In this paper we report on the effect of surface wettability on surface selection and adhesion properties of settled (adhered) spores of the biofouling marine alga Enteromorpha and cells of the diatom Amphora, through the use of patterned self-assembled monolayers (SAMs). The SAMs were formed from alkanethiols terminated with methyl (CH3) or hydroxyl (OH) groups, or mixtures of the two, creating a discontinuous gradient of wettability as measured by advancing water contact angle. In the case of Enteromorpha, primary adhesion, as measured by the transition from a motile spore to a settled, sessile organism, is strongly promoted by the hydrophobic surfaces. On the other hand, adhesion strength of the settled spores, as measured by resistance to detachment in a turbulent flow cell, is greatest on a hydrophilic surface. In the case of Amphora, there is little influence of surface wettability on the primary adhesion of this organism, but motility is inhibited at contact angles ≥60° and the cells are m...
-
Adhesion Strength of Settled Spores of the Green Alga Enteromorpha
Biofouling, 2002Co-Authors: Janet Finlay, Michael P Schultz, Maureen Callow, Geoffrey W. Swain, J CallowAbstract:Strengths of attachment of spores of the green fouling alga Enteromorpha to glass have been measured using a modified water jet apparatus. Surface pressures of ,250kPa were required to quantitatively remove attached spores after 4h contact with a surface. The development of adhesive and cohesive strength is highly time-dependent; after 8h in contact with a surface spores did not detach, even at pressures in excess of 250 kPa. Spores settled in groups are more resistant to detachment than single spores, which suggests that the adaptive value of gregarious settlement behaviour may lie in the greater resistance of groups to detachment forces in a naturally turbulent environment. The interfacial forces exerted as water impinges on the surface and the derivation of adhesion strength values in terms of wall shear stress are discussed and compared with those obtained by other methods. A surface pressure of 250kPa approximates to 325 Pa wall shear stress. Calculation using the power-law formula predicts that detachment forces of this magnitude are unlikely to be realized at operating speeds for most vessels and that most Enteromorpha spores would not detach from untreated hulls.
Jaanika Blomster - One of the best experts on this subject based on the ideXlab platform.
-
linnaeus was right all along ulva and Enteromorpha are not distinct genera
European Journal of Phycology, 2003Co-Authors: Hillary S Hayden, Jaanika Blomster, Christine A Maggs, Paul C Silva, Michael J Stanhope, Robert J WaalandAbstract:Ulva, one of the first Linnaean genera, was later circumscribed to consist of green seaweeds with distromatic blades, and Enteromorpha Link was established for tubular forms. Although several lines of evidence suggest that these generic constructs are artificial, Ulva and Enteromorpha have been maintained as separate genera. Our aims were to determine phylogenetic relationships among taxa currently attributed to Ulva, Enteromorpha, Umbraulva Bae et I.K. Lee and the monotypic genus Chloropelta C.E. Tanner, and to make any nomenclatural changes justified by our findings. Analyses of nuclear ribosomal internal transcribed spacer DNA (ITS nrONA) (29 ingroup taxa including the type species of Ulva and Enteromorphat, the chloroplast-encoded rbcL gene (for a subset of taxa) and a combined data set were carried out. All trees had a strongly supported clade consisting of all Ulva, Enteromorpha and Chloropelta species, but Ulva and Enteromorpha were not monophyletic. The recent removal of Vmbraulva olivascens (PJ.L...
-
novel morphology in Enteromorpha ulvophyceae forming green tides
American Journal of Botany, 2002Co-Authors: Jaanika Blomster, Christine A Maggs, Saara Back, David P Fewer, Mikko Kiirikki, Annamaija Lehvo, Michael J StanhopeAbstract:‘‘Green tides’’ are vast accumulations of unattached green macroalgae associated with eutrophicated marine environments. They have major ecological and economic impacts globally, so an understanding of their origin and persistence is required in order to make management decisions. Blooms predominantly consist of two common fouling genera of the Ulvales, Ulva (distromatic sheets) and Enteromorpha (monostromatic tubes). In the Baltic Sea and elsewhere green tides have increased over the last few decades. On the west coast of Finland, summer blooms consist of monostromatic sheets resembling Monostroma (Codiolales). We identified these as Enteromorpha intestinalis by comparative analyses of rDNA internal transcribed spacer 1 (ITS1), 5.8S, and ITS2 sequences, the first time monostromatic sheets have been found in the genus Enteromorpha. Ordinary attached E. intestinalis sporulated freely in culture, but the sheets reproduced only by cell regeneration into typical tubular thalli. The ITS sequences were identical to those of attached E. intestinalis populations in southwestern Finland, but differed by two substitutions from other Baltic sequences. We infer that this bloom originated from local attached populations and now reproduces clonally by fragmentation. This study provides further evidence of radical changes in gross morphology of green algae under eutrophicated conditions and the need for molecular identification.
-
molecular phylogenetic evidence for a reversible morphogenetic switch controlling the gross morphology of two common genera of green seaweeds ulva and Enteromorpha
Molecular Biology and Evolution, 1999Co-Authors: Jaanika Blomster, Christine A Maggs, G Hansen, Elina Leskinen, David G Mann, Hans J Sluiman, Michael J StanhopeAbstract:Ulva and Enteromorpha are two of the most common, ubiquitous, and environmentally important genera of green seaweeds. They are widely regarded as easily distinguishable because of their dramatically different morphologies: Ulva species are flat, lettuceli
-
molecular and morphological analysis of Enteromorpha intestinalis and e compressa chlorophyta in the british isles
Journal of Phycology, 1998Co-Authors: Jaanika Blomster, Christine A Maggs, Michael J StanhopeAbstract:The very common green seaweeds Enteromorpha intestinalis (L.) Nees and E. compressa (L.) Nees are important fouling organisms and have commonly been used as indicators of eutrophication, but their taxonomic status is problematic. The genus presents extreme difficulties because there is wide intraspecific variation in morphology, but morphological differences between species are small and difficult to detect. In this study, molecular data were used in parallel with morphological characters to resolve the taxonomic problems. Phylogenetic analysis of sequences of the internal transcribed spacers ITS1 and ITS2 and the 5.8S gene distinguished two groups of samples, which were identified by morphological characters as E. compressa (branched) and E. intestinalis (normally unbranched). There was a low level of sequence divergence within each group of samples, but divergence between groups was as great as that between either of the two species and the outgroup E. prolifera. Clades representing E. compressa and E. intestinalis were also found in analyses of an independent molecular data set, chloroplast DNA restriction fragment length polymorphisms (RFLPs). Enteromorpha intestinalis and E. compressa represent two distinct, genetically divergent species. Reinterpretation of published studies shows that these species are reproductively isolated. However, E. compressa and E. intestinalis are sometimes very difficult to distinguish from each other and could be regarded as cryptic species. The presence or absence of branching was the most useful character distinguishing these two species, but there was an element of ambiguity because low salinity or salinity shock can induce branching in E. intestinalis. If environmental factors such as salinity are taken into account, branching can be used to identify the great majority of thalli correctly. This study therefore provides a basis for identifying the two most important marine fouling macroalgae and for their use in environmental monitoring and experimentation. Typification of these two Linnaean species showed that current usage of the names accords with the lectotype and protologue of both species. Samples that resembled E. usneoides did not form a clade in any of the trees, and constraining the data to support the monophyly of this group incurred a penalty. Enteromorpha usneoides appears to be an ecotype of E. compressa.
Maureen Callow - One of the best experts on this subject based on the ideXlab platform.
-
the influence of surface wettability on the adhesion strength of settled spores of the green alga Enteromorpha and the diatom amphora
Integrative and Comparative Biology, 2002Co-Authors: Janet Finlay, Maureen Callow, Linnea K Ista, Gabriel P Lopez, James A. CallowAbstract:Abstract In this paper we report on the effect of surface wettability on surface selection and adhesion properties of settled (adhered) spores of the biofouling marine alga Enteromorpha and cells of the diatom Amphora, through the use of patterned self-assembled monolayers (SAMs). The SAMs were formed from alkanethiols terminated with methyl (CH3) or hydroxyl (OH) groups, or mixtures of the two, creating a discontinuous gradient of wettability as measured by advancing water contact angle. In the case of Enteromorpha, primary adhesion, as measured by the transition from a motile spore to a settled, sessile organism, is strongly promoted by the hydrophobic surfaces. On the other hand, adhesion strength of the settled spores, as measured by resistance to detachment in a turbulent flow cell, is greatest on a hydrophilic surface. In the case of Amphora, there is little influence of surface wettability on the primary adhesion of this organism, but motility is inhibited at contact angles ≥60° and the cells are m...
-
Adhesion Strength of Settled Spores of the Green Alga Enteromorpha
Biofouling, 2002Co-Authors: Janet Finlay, Michael P Schultz, Maureen Callow, Geoffrey W. Swain, J CallowAbstract:Strengths of attachment of spores of the green fouling alga Enteromorpha to glass have been measured using a modified water jet apparatus. Surface pressures of ,250kPa were required to quantitatively remove attached spores after 4h contact with a surface. The development of adhesive and cohesive strength is highly time-dependent; after 8h in contact with a surface spores did not detach, even at pressures in excess of 250 kPa. Spores settled in groups are more resistant to detachment than single spores, which suggests that the adaptive value of gregarious settlement behaviour may lie in the greater resistance of groups to detachment forces in a naturally turbulent environment. The interfacial forces exerted as water impinges on the surface and the derivation of adhesion strength values in terms of wall shear stress are discussed and compared with those obtained by other methods. A surface pressure of 250kPa approximates to 325 Pa wall shear stress. Calculation using the power-law formula predicts that detachment forces of this magnitude are unlikely to be realized at operating speeds for most vessels and that most Enteromorpha spores would not detach from untreated hulls.
-
Primary Adhesion in Enteromorpha. Cue Detection and Surface Selection in the Settlement and Adhesion of Enteromorpha Spores
2001Co-Authors: James A. Callow, Maureen CallowAbstract:Abstract : Enteromorpha is the most important alga fouling hulls, whether coated with conventional Cu-based paints or foul-release silicones. Since fouling by Enteromorpha is increasing as a consequence of the increased deployment of TBT-free coatings, it is important to understand the processes involved in the initiation of fouling, i.e. spore settlement and adhesion. Our results provide the most comprehensive characterisation of the settlement and adhesion processes and the roles of surface-associated cues, of any soft-fouling species to date, We have shown that spores respond to chemical, physico- chemical, biological (microbial biofilm) and topographic cues. Novel insights have been gained on communication processes involved in the development of a micro-fouling community. Thirteen papers in refereed journals and several abstracts were published.
J Callow - One of the best experts on this subject based on the ideXlab platform.
-
Adhesion Strength of Settled Spores of the Green Alga Enteromorpha
Biofouling, 2002Co-Authors: Janet Finlay, Michael P Schultz, Maureen Callow, Geoffrey W. Swain, J CallowAbstract:Strengths of attachment of spores of the green fouling alga Enteromorpha to glass have been measured using a modified water jet apparatus. Surface pressures of ,250kPa were required to quantitatively remove attached spores after 4h contact with a surface. The development of adhesive and cohesive strength is highly time-dependent; after 8h in contact with a surface spores did not detach, even at pressures in excess of 250 kPa. Spores settled in groups are more resistant to detachment than single spores, which suggests that the adaptive value of gregarious settlement behaviour may lie in the greater resistance of groups to detachment forces in a naturally turbulent environment. The interfacial forces exerted as water impinges on the surface and the derivation of adhesion strength values in terms of wall shear stress are discussed and compared with those obtained by other methods. A surface pressure of 250kPa approximates to 325 Pa wall shear stress. Calculation using the power-law formula predicts that detachment forces of this magnitude are unlikely to be realized at operating speeds for most vessels and that most Enteromorpha spores would not detach from untreated hulls.