The ultrastructural aspects of some cellular types in Aelosoma have been investigated. Aelosomatidae are aquatic Oligochaetes in which the asexual reproduction isvery common, while sexual individuals are rare or, in some species, have never been observed. Asexual reproduction occurs by fission and regenerative processes precede the separation of the daughter zooid. In this work are described the ectodermal cells of the parent's body (including gland cells) and the blastematic cells of the daughter...
L'Autrice ha studiato gli aspetti ultrastrutturali della gametogenesi delle due specie di idre Chlorohydra viridissima e Hydra attenuata, cercando di puntualizzare le prime differenze che caratterizzano l'avvio delle cellule interstiziali (cellule polivalenti, madri dei gameti, oltre che di elementi somatici come ad esempio i nematociti) alla gametogenesi maschile od a quella femminile. Si osserva che le c. germinali maschili mostrano intensi fenomeni di moltiplicazione iniziale che fanno di essi...
Evidence has been collected, especially with the help of experimental studies on sex differentiation, of the very important role of the nervous system and neurosecretion in inducing and maintaining the axial polarity of fresh-water hydras and planarians. A gradient diffusion of some low-molecular-weight polypeptide substances, elaborated as neurosecretory granules in nerve cells, seems to be the main cause of the positional information and morphogenesis along the body axis of these animals.
Evidences have been collected, expecially with the help of experimental studies on sex differentiation, of the very important role of the nervous system and neurosecretion in inducing and maintaining the axial polarity of fresh-water hydras and planarians. A gradient diffusion of some low-molecular-weight polypeptide substances, elaborated as neuro-secretory granules in nerve cells, seems to be the main cause of the positional information and morphogenesis along the body axis of these animals.
Les Auteurs ont étudié au SEM l'enveloppe de l'oeuf fécondé (embryothèque) de Chlorohydra viridissima. Il s'âgit d'un enveloppe chitinoïde qui offre des bonnes caractéristiques de classification chez les Hydridae. L'embryothèque de Chlorohydra viridissima présente à la surface des cellules polygonales à peu près de 26 dont les bords de séparation mésurent de 2,5 à 3 . Sur les bords il y a parfois des structures lamellaires en forme de bouquet. Au fond des cellules il y a des sphérules isolées...
Regenerating specimens of Chlorohydra viridissima (80 animals) were treated with dopamine or with his antagonist reserpine. Dopamine treatment resulted in accelerating regeneration and differentiation, in increasing the number of tentacles and cnidocytes, in inducing sexuality (22%), but above all in disturbing morphogenetic gradient (appearance of ectopic tentacles, cnidocytes and ovariotestes). Reserpine treatment resulted at least in dissociating tissues although some sign of regeneration is...
Observations prolonged for two months show how aged Aelosoma viride specimens increase their asexual reproductive power. Treatment of this species with some neuropharmacological agents (norepinephrine, amphetamine, reserpine) demonstrate that: 1) noradrenaline excites the growth by increasing the number of segments; 2) amphetamine excites the growth but inhibits asexual reproduction; 3) reserpine is strongly toxic; 4) growth and asexual reproduction appear as two partially separated processes.
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