Description
Unicellular algae occurring in 2 stages , a coccoid so-called "Phycoma" stage and a motile flagellated stage. The Phycoma stage is spherical, up to 8 0 0 11m in diameter and surrounded by a two-layered wall. It contains numerous chloroplasts, usually with pyrenoids, and is initially uninucleate . At maturity it divides into a large number of somewhat Pyramimonas-like flagellates , each with 4 flagella emanating from an anterior pit. The single parietal chloroplast of the motile cell has 2 - 4 pyrenoids located along the lateral sides of the cell and a single eyespot in the posterior part of the cell. Cell surfaces with organic scales in several layers, on the body up to 4 types , including an underlayer of very small square scales and 2 layers of larger scales . Flagella with an underlayer of small square scales overlain by limuloid scales . Hair-shaped scales are located in two opposite rows. The switch between the Phycoma stage and the motile cells appears to be related to the lunar cycle (Boalch & Parke 1971 ). The Phycoma stage contains large amounts of lipid and cells may accumulate at the sea surface in calm weather. The motile stage divides by fission . Halosphaera differs from the closely related Pachysphaera (see Parke 1966) by the cytoplasmic contents of the Phycoma stage being distributed peripherally in Halosphaera but filling the Phycoma in Pachysphaera . Motile cells of Pachysphaera are very similar to those of ; Pterosperma . Pachysphaera is sometimes merged with Tasmanites, a genus of fossil species. Halosphaera is widely distributed in the marine plankton. Halosphaera vi rid is Schmitz, 1879 (Fig . 6) . Phycoma stage 400-800 11m in diameter when mature. Outer wall smooth. Motile cells 20-28 11m long , cell body covered with 4 types of scales , one type restricted to the flagellar pit. Pterosperma moebii and P. vanhoeffenii. C, the motile stage . I, lipid globu le; p, chloroplast ; py , pyrenoid A=360x . (From Cleve , 1900) and Meunier, 1910). B=400x . (From Throndsen , 1993). C=1 OOOx . (From Parke et al. , 1978).
Type species
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Raw text
Unicellular algae occurring in 2 stages , a coccoid so-called "Phycoma" stage and a motile flagellated stage. The Phycoma stage is spherical, up to 8 0 0 11m in diameter and surrounded by a two-layered wall. It contains numerous chloroplasts, usually with pyrenoids, and is initially uninucleate . At maturity it divides into a large number of somewhat Pyramimonas-like flagellates , each with 4 flagella emanating from an anterior pit. The single parietal chloroplast of the motile cell has 2 - 4 pyrenoids located along the lateral sides of the cell and a single eyespot in the posterior part of the cell. Cell surfaces with organic scales in several layers, on the body up to 4 types , including an underlayer of very small square scales and 2 layers of larger scales . Flagella with an underlayer of small square scales overlain by limuloid scales . Hair-shaped scales are located in two opposite rows. The switch between the Phycoma stage and the motile cells appears to be related to the lunar cycle (Boalch & Parke 1971 ). The Phycoma stage contains large amounts of lipid and cells may accumulate at the sea surface in calm weather. The motile stage divides by fission . Halosphaera differs from the closely related Pachysphaera (see Parke 1966) by the cytoplasmic contents of the Phycoma stage being distributed peripherally in Halosphaera but filling the Phycoma in Pachysphaera . Motile cells of Pachysphaera are very similar to those of ; Pterosperma . Pachysphaera is sometimes merged with Tasmanites, a genus of fossil species. Halosphaera is widely distributed in the marine plankton. Halosphaera vi rid is Schmitz, 1879 (Fig . 6) . Phycoma stage 400-800 11m in diameter when mature. Outer wall smooth. Motile cells 20-28 11m long , cell body covered with 4 types of scales , one type restricted to the flagellar pit. Pterosperma moebii and P. vanhoeffenii. C, the motile stage . I, lipid globu le; p, chloroplast ; py , pyrenoid A=360x . (From Cleve , 1900) and Meunier, 1910). B=400x . (From Throndsen , 1993). C=1 OOOx . (From Parke et al. , 1978).