1,720,965 research outputs found
Sexual reproduction of the black coral Cirrhipates sp. (Anthozoa, Antipatharia) in the Indonesian Marine Park of Bunaken
No full textSperm ultrastructure of a member of the black coral family Aphanipathidae: Rhipidipathes reticulata (Anthozoa, Antipatharia)
No full textUltrastructural investigation of the sexual reproduction of some members of the black coral: A review
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sp. (Anthozoa, Antipatharia)
No full textMale polyps of the antipatharian Cirrhipathes sp., collected along the coral reef of
Siladen Island (Sulawesi, Indonesia), were studied in order to gain an insight into the reproductive
biology. Spermatocysts (maximum size 120 mm) are located within the primary gametogenic
mesenteries and are separated by mesenteric cell cytoplasmic extensions. Sperm,
maturing along radial rows, have a fairly round shape and contain a series of electron-dense
vesicles in the apical nuclear region. A single mitochondrion flanks the nucleus. A peculiar
cup-like electron-dense body, edged with regularly spaced electron-dense granules, is interposed
between the nucleus and the tail, and delimits a central region that includes two centrioles.
Cross-sections of the cup-like body reveal that the distal centriole has a pericentriolar
system, consisting of nine arms arranged in a radial pattern. Each arm branches into three
processes that are connected to the electron-dense granules. Indirect evidence of spawning is
derived fromthe accumulation of sperm in the gastric cavity. This process takes place through
the lysis of the cells bordering the mesenteries. Intact cells of this bordering layer appear to be
involved in the phagocytosis of non-expelled gametes
Biological and Ecological Relevance of Black Corals (Antipatharia) in the Benthic Environment
No full textSpicule records of Ephydatia fluviatilis as a proxy for hydrological and environmental changes in the shallow Lake Trasimeno (Umbria, Italy)
No full textThis research shows the results of an analysis of siliceous spicules found in sediment cores collected in Lake Trasimeno (Umbria, Italy), a shallow lake that experienced an important water level lowering during the last century. A morphological analysis of sedimentary sponge records revealed that the spicules accumulated in the lake sediments over the last 150 years are attributable to Ephydatia fluviatilis, the only sponge species found in the lake
in recent years. The stratigraphic analysis of the cores showed that the abundance and size of the sponge spicules (megascleres) have remarkably decreased, suggesting that a significant depletion of the sponge fauna occurred, particularly during the first half of the twentieth century. A correlation analysis has identified morpho-hydrological and related variables (the theoretical fraction of lake surface subjected to resuspension and the amount of total suspended solids) as the most significant factors explaining the change in density of sponge spicules. Two ecological explanations of the sponge decline are proposed, based on the sensitivity of the sponge both to the availability of suitable hard substrata for colonization, and to the amount of wind-resuspended solids. One-ended sigmoid response curves were obtained by regression and corresponding transfer functions were derived, which allow the mean water depth of the lake and total suspended solids to be inferred from spicule density records. The results support the use of sponge spicules as a paleohydrological and paleoecological proxy, application of which appears particularly promising for shallow-water systems
Spermatogenesis in Distichopora sp. (Cnidaria, Hydrozoa, Stylasteridae): ultrastructural aspects
No full textUtilizzo dello spazio su substrati viventi: straordinarie coevoluzioni in ambiente marino
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