Friedmannia

Abstract: Zoospore ultrastructure in the green algaFriedmannia israelensis has been studied in detail using serial section and absolute configuration analysis The zoospores are naked, biflagellate and considerably flattened In addition they exhibit an asymmetric external shape and an asymmetric distribution of major cell organelles There is only a single contractile vacuole/cell 3-dimensional reconstructions of mitochondrial profiles show the presence of a single branched mitochondrial reticulum/cell The nucleus is pear-shaped and exhibits an anterior projection In a concave depression of this projection lies the single dictyosome of the zoospore The nuclear envelope presumably buds off small vesicles at the forming face of the dictyosome The single chloroplast lacks an eyespot and pyrenoid A single microbody is characteristically located posterior to the nucleus in close association with an elongated mitochondrial profile The zoospores contain a peculiar system of three major ER-cisternae, of which an anterior one is linked to a mitochondrial profile The flagellar apparatus has been studied in detail and its absolute configuration has been determined The two basal bodies are displaced (in the 11/5 o'clock direction) and overlap at their proximal ends They are interconnected by a principal non-striated capping plate and two smaller striated connecting fibres The flagellar root system consists of a cruciate microtubular root system (4-2-4-2 or 5-2-5-2 system) and a greatly reduced system II fibre which connects one basal body with the nuclear membrane and runs along a smooth ER-cisterna The 4- or 5-stranded roots are proximally associated with a terminal cap-like structure which consists of a number of parallel striations spaced 13 nm Zoospores ofFriedmannia are structurally most similar to those of the Chaetophoralean green algaMicrothamnion It is concluded that these two genera form a natural group and taxonomic implications are discussed The absolute configuration analysis of the flagellar apparatus indicates thatFriedmannia has an Ulvaphycean-type flagellar apparatus Phylogenetic aspects of the absolute configuration of the flagellar apparatus in green algae are discussed

Abstract: Eight complete nuclear-encoded small-subunit ribosomal RNA (18S rRNA) gene sequences were determined for four genera of the Microthamniales (Pleurastrophyceae) and for Gloeotilopsis planctonica Iyengar & Philipose (Ulvophyceae, Ulotrichales) to investigate evolutionary relationships within the Microthamniales and the taxonomic position of this order within the green algae. Phylogenies inferred from these data revealed specific relationships at the level of genera and species that disagree with those inferred from vegetative cell morphology but agree with those inferred from motile cell characters. The rRNA phylogenies provide even better resolution than that gained from morphology alone. The coccoid lichen alga Trebouxia spp. is specifically related to other coccoid lichen and soil algae (i.e. Myrmecia biatorellae Boye-Petersen and Friedmannia israelensis Chantanachat & Bold), forming the “Lichen Algae Group,” an evolutionarily distinct lineage within the Microthamniales. Trebouxia is a paraphyletic and Pleurastrum a polyphyletic genus in rRNA phylogenies. In contrast to previous hypotheses based on morphology, Pleurastrum terrestre Fritsch & John is not closely related to Trebouxia but occupies an isolated position within the Microthamniales. The filamentous alga Microthamnion kuetzingianum is not ancestral to coccoid members of the Microthamniales but is closely related with the coccoid Fusochloris perforata (Lee & Bold) Floyd, Watanabe & Deason. The Microthamniales are inferred to be an array of independent lineages that radiate nearly simultaneously and may also include some autosporic coccoid taxa previously classified in the Chlorophyceae. Monophyly of the Microthamniales could not be demonstrated unequivocally. In contrast to a hypothesis based on ultrastructure, the Microthamniales are evolutionarily distinct from the Ulotrichales. The latter are ancestral to the radiation of the Microthamniales and the Chlorophyceae in the rRNA phylogenies.

Abstract: Complete nuclear-encoded small-subunit ribosomal RNA (18S rRNA) coding sequences were determined for the coccoid green algae Dictyochloropsis reticulata (Tschermak-Woess) Tschermak-Woess, Myrmecia astigmatica Vinatzer, and M. bisecta Reisigl, to investigate the taxonomic position of Dictyochloropsis Geitler and of the genus Myrmecia Printz. Phylogenies inferred from these data revealed a sister-group relationship between D. reticulata and certain coccoid green algae that lack motile stages (autosporic coccoids) within the order Microthamniales. The monophyletic origin of the Microthamniales, including autosporic coccoids previously classified in the Chlorophyceae, is clearly resolved by the rRNA sequence data. This finding. shows the considerable taxonomic breadth of that order, whose taxonomic position has been unclear so far. A new class, Trebouxiophyceae, is proposed for this group of green algae. Phylogenetic inferences from the rRNA sequences show paraphyly of the genus Myrmecia. The 18S rRNA sequence data suggest that, among taxa that share similar vegetative cell morphologies, the zoospore characters resolve better the actual genus and species boundaries. Within identical zoospore types, the rRNA data allow further resolution of taxonomic relationships. On the basis of the.se findings, I propose that the genus Friedmannia Chantanachat ± Bold be merged into Myrmecia and that only those species be left in the genus Myrmecia that are identical in particular zoospore characters (i.e. those described in detail for M. israeliensis (Chantanachat ± Bold) comb, nov.), namely M. astigmatica, M. biatorellae (Tschermak-Woess ± Ptesst) Petersen, and M. israeliensis. Myrmecia bisecta has to be excluded from Myrmecia; its taxonomic position within the Trebouxiophyceae is unclear.