Talk:Klebsormidium

Description

Filaments uniseriate and unbranched, without polar differentiation. Free-floating or attached via hyaline, gelatinous, spherical-like holdfast surrounding basal cell. Cells basically cylindrical. Cell wall thin and smooth, under adverse conditions sometimes markedly thickened, lamellate, and verrucose, simultaneously with H-pieces wrapping transverse cell walls. Chloroplast single and parietal, laminate or girdle-shaped, often withdrawn and then elliptical or discoid, incompletely encircling cell lumen and not lobed, usually occupying not more than one half of cell periphery. Pyrenoid single, embedded in center of chloroplast, usually surrounded by distinct starch envelope. Asexual reproduction by biflagellate zoospores or by walled aplanospores, sometimes following dormancy. Zoospores dorsiventral with flagella subapically and asymmetrically inserted; stigma absent. Zoospores formed singly in unspecialized cells, escaping through distinct lateral pore in cell wall, producing no holdfast on germination. Vegetative multiplication by fragmentation into unicells ("Vermehrungsakineten"), or few-celled fragments. Akinetes infrequent, elliptical , surrounded by thick membrane enclosing cell contents rich in assimilates. Sexual reproduction purportedly by anisogamous fusion of biflagellate spindle-shaped gametes with distinct stigmas. Klebsormidium mostly in soil and on moist substrates but aquatic species known; one species marine. Klebsormidium proposed in 1972 to resolve confusion in application and status of Hormidium. Earlier proposals to replace Hormidium by, e.g. Hormococcus Chodat, Pseudoulothrix Pascher and Chlorhormidium Fott, illegitimate or inadequate. Ultrastructural studies showed papilla formation during sporogenesis on cell wall, marking rupture point in zoospore release; cytokinesis by furrowing sometimes associated with array of ill-defined cytokinetic microtubules; flagellar root system in zoospores asymmetric, characterized by presence of a so-called MLS (multilayered structure). Accordlingly, Klebsormidium associated with charophycean evolutionary line, this also supported by catalase activity of peroxisomes. Karyological studies indicate chromosome numbers of n= 22-26.