Actinotaenium

Abstract: Nuclear-encoded small subunit (SSU) rDNA, 1506 group I introns, and chloroplast rbcL genes were sequenced from 97 strains representing the largest desmid genus Cosmarium (45 spp.), its putative relatives Actinotaenium (5 spp.), Xanthidium (4 spp.), Euastrum (9 spp.), Staurodesmus (13 spp.), and other Desmidiaceae (Zygnematophyceae, Streptophyta) and used to assess phylogenetic relationships in the family. Analyses of single genes and of a concatenated data set (3260 nt) established 10 well-supported clades in the family with Cosmarium species distributed in six clades and one nonsupported assemblage. Most of the clades contained representatives of at least two genera highlighting the polyphyletic nature of the genera Cosmarium , Euastrum , Staurodesmus , and Actinotaenium . To enhance resolution between clades, we extended the data set by sequencing the slowly evolving chloroplast-encoded large subunit (LSU) rRNA gene from 40 taxa. Phylogenetic analyses of a concatenated data set (5509 nt) suggested a sister relationship between two clades that consisted mainly of Cosmarium species and included C. undulatum , the type species of the genus. We describe molecular signatures in the SSU rRNA for two clades and conclude that more studies involving new isolates, additional molecular markers, and reanalyses of morphological traits are necessary before the taxonomic revision of the genus Cosmarium can be attempted.

Abstract: Desmids from 12 freshwater resources in the northern part of Thailand were investigated during 2002 to 2003. A total of 91 taxa were found. They belonged to 17 genera: Actinotaenium, Spirotaenia, Netrium, Gonatozygon, Pleurotaenium, Closterium, Euastrum, Micrasterias, Cosmarium, Cosmocladium, Stuarastrum, Staurodesmus, Xanthidium, Teilingia, Spondylosium, Hyalotheca and Desmidium. The water qualities in all the water resources were classified as oligotrophic to meso-eutrophic by trophic status. The taxa that could possibly be used as bioindicators of trophic state were Staurastrum gutwinskii, Spondylosium pandurifoemae, Cosmarium capitulum, C. mediosrobiculatum var. egranutum, S. tortum, Closterium gracile var. elongatum, C. kuetzingii and Closterium dianae var. dianae. The most frequently found taxa were Staurastrum limneticum var. burmense, S. tetracerum var. tetraerum, Pleurotaenium trabecula, Closterium ehrenbergii var. ehrenbergii and C. kuetzingii. The rare taxa in this study were Actinotaenium sp. Spirotaenia condensata, Pleurotaenium burmense var. dacchense and Micrasterias apiculata. Forty-one taxa of desmids were identified as new records for Thailand.

Abstract: An ultrastructural investigation of the cell wall of Penium silvae-nigrae Raban. and P. spinospermum Josh. showed that these species possess true pores with a pore apparatus and overlapping semi-cell walls. It follows that these two taxa belong not to the Peniaceae, but to the Desmidiaceae sensu stricto; they are referred to the genus Actinotaenium Teil. on account of the shape of their cells and chloroplasts. Two other species previously included in Penium Breb. are referred to Actinotaenium. Although their cell wall structure could not be studied, they are distinguished from “typical” representatives of Penium by the following photomicroscopically observable complex of features: (pseudo-) girdle bands none, cell wall pores in longitudinal rows, zygospores not globose but of irregular shape. The following new combinations ensued: Actinotaenium borgeanum (Skuja), A. phymatosporum (Nordst.), A. silvae-nigrae (Raban.), A. silvaenigrae var. parallelum (Krieger) and A. spinospermum (Josh.). In addition the diagnosis of the genus Penium was emended and P. margaritaceum (Ehr.) ex Breb. was selected as the lectotype species. The family Gonatozy-gaceae is merged into the Peniaceae on the basis of cell wall structure.