02201nas a2200289 4500008004100000020001400041245014400055210006900199260001300268300001400281490000800295520123400303653002901537653002501566653002401591653002001615653001901635100002601654700002101680700002001701700001901721700002801740700002501768700002401793700002301817856007101840 2014 eng d a1631-069100aInvestigation of the ultrastructure of Dendrocoelum constrictum (Platyhelminthes, Tricladida) spermatogenesis and mature spermatozoa0 aInvestigation of the ultrastructure of iDendrocoelum constrictum c2014/9// a513 - 5200 v3373 a

To add to our understanding of dendrocoelid spermatozoa and to describe additional phylogenetic characters, the ultrastructure of the testis was investigated in the subterranean freshwater planarian Dendrocoelum constrictum. This is the first study investigating spermatogenesis and spermatozoon ultrastructure in a subterranean freshwater planarian species. We found that the basic structure of spermatozoa in D. constrictum is similar to that of other Tricladida that have been studied previously. In fact, D. constrictum spermatozoa possess an elongated nucleus, one giant mitochondrion, and two subterminal flagella with a 9 + ‘1’ pattern. The flagella emerge together from one side of the spermatozoon. However, D. constrictum has some characteristics that have not yet been described for other freshwater planarians. In fact, the number of cortical microtubules reaches the maximum number in the anterior and middle part of region I, and then decrease until they disappear towards the posterior extremity of the spermatozoon. The extreme tip of the anterior region of the spermatozoon exhibits a specific external ornamentation of the plasma membrane.

10aDendrocoelum constrictum10aFree-living flatworm10aMature spermatozoon10aSpermatogenesis10aUltrastructure1 aHarrath, Abdel, Halim1 aGammoudi, Mehrez1 aMansour, Lamjed1 aAhmed, Mukhtar1 aSirotkin, Alexander, V.1 aOmar, Suliman, Y. Al1 aIbrahim, Khalid, E.1 aAlwasel, Saleh, H. uhttp://www.sciencedirect.com/science/article/pii/S163106911400163202454nas a2200265 4500008004100000020001400041245018600055210006900241260001200310300001200322490000700334520158000341653001101921653002201932653002901954653001401983653001701997653001902014100002002033700001402053700001602067700001602083700001802099856007102117 2013 eng d a0040-816600aAn ultrastructural study of oogenesis and cell dynamics during cocoon shell secretion in the subterranean freshwater planarian Dendrocoelum constrictum (Platyhelminthes, Tricladida)0 aultrastructural study of oogenesis and cell dynamics during coco c02/2013 a39 - 460 v453 a

The ultrastructure of the ovary and the female atrium during cocoon formation was investigated in the subterranean freshwater planarian Dendrocoelum constrictum. In the peripheral portion of the ovary, the oogonia are recognized as undifferentiated germ cells, which are morphologically similar to neoblasts that have a high nucleus/cytoplasm ratio. Oocyte maturation is characterized by a marked growth of the cytoplasm because of the accumulation of cytoplasmic organelles and inclusions. The Golgi complexes begin to increase within the ooplasm and produce vesicles with an electron-dense content that fuse to produce larger spherical globules with homogeneous and electron-dense material. In the mature oocyte, the spherical globules migrate toward the cortical ooplasm, forming a continuous monolayer. We confirm that these spherical globules, which represent cortical granules rather than eggshell globules, vary in size up to 2 μm and their electron-dense content shows concentric thin bands. After leaving the ovary through the oviduct, the mature and fertilized oocytes reach the female atrium where they are packaged with thousands of vitelline cells in the cocoon shell. Based on our ultrastructural analysis, we demonstrate that the wall of the cocoon shell is composed of two layers, each of which has a different origin. The shell granules extruded from the vitelline cells are involved in the secretion of the inner layer of the cocoon shell, whereas the outer layer of the cocoon shell is synthesized by the epithelial cells in the genital atrium.

10aCocoon10aCortical granules10aDendrocoelum constrictum10aOogenesis10aTurbellarian10aUltrastructure1 aHarrath, A., H.1 aAhmed, M.1 aSayed, S.R.1 aSaifi, M.A.1 aAlwasel, S.H. uhttp://www.sciencedirect.com/science/article/pii/S0040816612000845