. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. -• •. 200 /<m FIGURE 2. Volvox carteri f. nagariensis. Vegetative individual with young daughter colonies (left) and sexualized individuals with sperm packets (center) and eggs (right). specific binding sites are localized in the extra-cellular matrix of the spheroids. Further studies indicated that the extra-cellular milieu of cyclic nucleotides, calmodulin, and Ca2+ has a very strong influence on the developmental pathway of the gonidia. Phos- phodiesterase is known to interfere with this system, and has been found to m
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. -• •. 200 /<m FIGURE 2. Volvox carteri f. nagariensis. Vegetative individual with young daughter colonies (left) and sexualized individuals with sperm packets (center) and eggs (right). specific binding sites are localized in the extra-cellular matrix of the spheroids. Further studies indicated that the extra-cellular milieu of cyclic nucleotides, calmodulin, and Ca2+ has a very strong influence on the developmental pathway of the gonidia. Phos- phodiesterase is known to interfere with this system, and has been found to mimic the inducer effect (Gilles et al, 1983). Sexual reproduction in Oedogonium The genus Oedogonium contains filamentous freshwater green algae which may be monoecious or dioecious. Female plants differentiate oogonia from filament cells. Male gametophytes show two types of differentiation: macrandrous species form male gametes which are attracted to the oogonia. Nannandrous species produce motile androspores which settle near oogonia and germinate to few-celled dwarf plants. On these plants, antheridia release a few motile spermatozoids, which eventually fertilize the egg inside the oogonium. In the macrandrous species, O. cardiacum, sperm are attracted to the oogonium (Hoffman, 1960). More detailed experiments by Machlis et al. (1974) showed that the attractant is water-soluble and sensitive to high temperature or extreme pH. Its molecular weight was estimated to be between 500 and 1500. Hormonal coordination in nannandrous species is more complex, and four stages can be distinguished (Rawitscher-Kunkel and Machlis, 1962): —Attraction of androspores to oogonium initials. —Oriented growth of dwarf male plants in relation to oogonia. —The presence of dwarf male plants is necessary for complete differentiation of oogonia. —Spermatozoids seem to be attracted to the oogonium aperture. Although the molecular size and characteristics of the attractant in Oedogoniu
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
