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ABSTRACT Petalomonads are particularly important for understanding the early evolution of euglenids, but are arguably the least studied major group within this taxon. We have established a culture of the biflagellate petalomonad Notosolenus urceolatus, and conducted electron microscopy observations and molecular phylogenetic analysis. Notosolenus urceolatus has eight pellicular strips bordered by grooves and underlain by close-set microtubules. There are ventral and dorsal Golgi bodies. Mitochondria apparently contain fibrous inclusions, as in Petalomonas cantuscygni. A previously undocumented type of large, globular extrusome is present instead of the tubular extrusomes characteristic of Euglenozoa. The feeding apparatus lacks rods and vanes, and is partly supported by an 'MTR'. The flagella have complex transition zones that are extremely elongated but unswollen. Only the emergent portion of the anterior flagellum has an organised paraxonemal rod, and also has very fine mastigonemes. The basal bodies are offset and lack connecting fibres. 18S rRNA gene phylogenies show that N. urceolatus is closely related to Petalomonas sphagnophila and P. cantuscygni, not Notosolenus ostium, confirming that current generic assignments based on the number of emergent flagella are phylogenetically unreliable, and making it difficult to infer whether features shared by N. urceolatus and P. cantuscygni (for example) are general for petalomonads. [ABSTRACT FROM AUTHOR]

Although archigregarines are poorly understood intestinal parasites of marine invertebrates, they are critical for understanding the earliest stages in the evolution of the Apicomplexa. Previous studies suggest that archigregarines are a paraphyletic stem group from which other lineages of gregarines, and possibly all other groups of apicomplexans, evolved. However, substantiating this inference is difficult because molecular phylogenetic data from archigregarines, in particular, and other gregarines, in general, are severely limited. In an attempt to help fill gaps in our knowledge of archigregarine diversity and phylogeny, we set out to discover and characterize novel lineages of archigregarines with high-resolution light and scanning electron microscopy and analyses of small subunit ( SSU) rDNA sequences derived from single-cell ( SC) PCR techniques. Here, we describe two novel species of Selenidium, namely Selenidium idanthyrsae n. sp. and S. boccardiellae n. sp., and demonstrate the surface morphology and molecular phylogenetic position of the previously reported species S. cf. mesnili. We also describe a novel genus of archigregarine, Veloxidium leptosynaptae n. gen., n. sp., which branches with an environmental sequence and, together, forms the nearest sister lineage to a diverse clade of marine eugregarines (i.e. lecudinids and urosporids). This molecular phylogenetic result is consistent with the hypothesis that archigregarines are deeply paraphyletic within apicomplexans, and suggests that convergent evolution played an important role in shaping the diversity of eugregarine trophozoites. [ABSTRACT FROM AUTHOR]

Persistent difficulties in resolving clear lineages in diverging populations of prokaryotes or unicellular eukaryotes (protistan polyphyletic groups) are challenging the classical species concept. Although multiple integrated approaches would render holistic taxonomies, most phylogenetic studies are still based on single-gene or morphological traits. Such methodologies conceal natural lineages, which are considered 'cryptic.' The concept of species is considered artificial and inadequate to define natural populations. Social organisms display differential behaviors toward kin than to nonrelated individuals. In 'social' microbes, kin discrimination has been used to help resolve crypticity. Aggregative behavior could be explored in a nonsocial protist to define phylogenetic varieties that are considered 'cryptic.' Two Entamoeba invadens strains, IP-1 and VK-1:NS are considered close populations of the same 'species.' This study demonstrates that IP-1 and VK-1:NS trophozoites aggregate only with alike members and discriminate members of different strains based on behavioral and chemical signals. Combined morphological, behavioral/chemical, and ecological studies could improve Archamoebae phylogenies and define cryptic varieties. Evolutionary processes in which selection acted continuously and cumulatively on ancestors of Entamoeba populations gave rise to chemical and behavioral signals that allowed individuals to discriminate nonpopulation members and, gradually, to the emergence of new lineages; alternative views that claim a 'Designer' or 'Creator' as responsible for protistan diversity are unfounded. [ABSTRACT FROM AUTHOR]

The genus Hyperamoeba Alexeieff, 1923 was established to accommodate an aerobic amoeba exhibiting three life stages—amoeba, flagellate, and cyst. As more species/strains were isolated, it became increasingly evident from small subunit (SSU) gene phylogenies and ultrastructure that Hyperamoeba is polyphyletic and its species occupy different positions within the class Myxogastria. To pinpoint Hyperamoeba strains within other myxogastrid genera we aligned numerous myxogastrid sequences: whole small subunit ribosomal (SSU or 18S rRNA) gene for 50 dark-spored (i.e. Stemonitida and Physarida) Myxogastria (including a new “ Hyperamoeba” /Didymium sequence) and a ∼400-bp SSU fragment for 147 isolates assigned to 10 genera of the order Physarida. Phylogenetic analyses show unambiguously that the type species Hyperamoeba flagellata is a Physarum ( Physarum flagellatum comb. nov.) as it nests among other Physarum species as robust sister to Physarum didermoides. Our trees also allow the following allocations: five Hyperamoeba strains to the genus Stemonitis; Hyperamoeba dachnaya, Pseudodidymium cryptomastigophorum, and three other Hyperamoeba strains to the genus Didymium; and two further Hyperamoeba strains to the family Physaridae. We therefore abandon the polyphyletic and redundant genus Hyperamoeba. We discuss the implications for the ecology and evolution of Myxogastria, whose amoeboflagellates are more widespread than previous inventories supposed, being now found in freshwater and even marine environments. [ABSTRACT FROM AUTHOR]

ABSTRACT Dinophysoid dinoflagellates are usually considered a large monophyletic group. Large subunit and small subunit ( SSU) rDNA phylogenies suggest a basal position for Amphisoleniaceae ( Amphisolenia, Triposolenia) with respect to two sister groups, one containing most Phalacroma species plus Oxyphysis and the other Dinophysis, Ornithocercus, Dinophysoid dinoflagellates are usually considered a large monophyletic group. Large subunit and small subunit ( SSU) rDNA phylogenies suggest a basal position for Amphisoleniaceae ( Amphisolenia, Triposolenia) with respect to two sister groups, one containing most Phalacroma species plus Oxyphysis and the other Dinophysis, Ornithocercus, Histioneis, Citharistes and some Phalacroma species. We provide here new SSU rDNA sequences of Pseudophalacroma (pelagic) and Sinophysis (the only benthic dinophysoid genus). Molecular phylogenies support that they are very divergent with respect to the main clade of Dinophysales. Additional molecular markers of these two key genera are needed to elucidate the evolutionary relations among the dinophysoid dinoflagellates. Histioneis, Citharistes and some Phalacroma species. We provide here new SSU rDNA sequences of Pseudophalacroma (pelagic) and Sinophysis (the only benthic dinophysoid genus). Molecular phylogenies support that they are very divergent with respect to the main clade of Dinophysales. Additional molecular markers of these two key genera are needed to elucidate the evolutionary relations among the dinophysoid dinoflagellates. [ABSTRACT FROM AUTHOR]