Induction de la métamorphose des larves de Paracentrotus lividus (Echinodermata, Echinoidea)

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Induction of metamorphosis in Paracentrotus lividus (Echinodermata, Echinoidea) larvae

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From competent larvae to exotrophic juvenile: A morphofunctional study of the perimetamorphic period of Paracentrotus lividus (Echinodermata, Echinoida)

The perimetamorphic period in Paracentrotus lividus lasts for 8-12 days. It starts from the acquisition of larval competence, includes the change in form (metamorphosis) and the endotrophic postlarval life, and stops with the appearance of the exotrophic juvenile. All major postlarval appendages already occur in competent larvae being either grouped into the echinoid rudiment (terminal plates, early spines and primary podia) or scattered within the larval integument (genital plates and sessile pedicellariae). Competent larvae show particular behaviour which brings them close to the substratum. The latter is tested by primary podia protruding through the vestibular aperture of the larva. Primary podia are sensory-secretory appendages that are deprived ampullae. They are able to adhere to the substratum in order to allow evagination of the echinoid rudiment (i.e. metamorphosis) and substatum adhesion of the postlarva. Particular spines are borne by the postlarva; these are multifid non-mobile appendages forming a kind of protective armour. Like those of the larva, all characteristic structures of the postlarva (primary podia, multified spines and sessile pedicellariae) are transitory and regress either at the end of postlarval life (primary podia) or during early juvenile life (multifid spines and sessile pedicellariae). Other appendages that develop during postlarval life (i.e. podia with ampulla, point-tipped spines and sphaeridiae) are similar to those borne by the adults and become functional when the individual enters its juvenile life. Thus, the perimetamorphic period appears to be a fully fledged period in the life-cycle of P. lividus, and presumably in the life-cycle of any other sea-urchin species.info:eu-repo/semantics/publishe

Differentiation and fine structure of larval epaulets in the echinoid Paracentrotus lividus

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The aboral ring and the development of early gonads in the echinoid Paracentrotus lividus (Echinodermata, Echinoidea)

The development of the genital apparatus is described for the echinoid Paracentrotus lividus. This apparatus derives from the aboral ring, an annular structure that includes an inconspicuous coelom and, in juveniles, the germinal rachis. The germinal epithelium grows out from the germinal rachis, and the gonadal wall and coelom in early (tubular) gonads share similarities with their equivalents in the aboral ring. The original germinal rachis regresses to form a genital cord one cell wide in late juveniles. A genital cord was observed in a few field-collected adult individuals (>40 mm test diameter).FLWINinfo:eu-repo/semantics/publishe

The Podia, organs of adhesion and sensory perception in larvae and post-metamorphic stages of the echinoid Paracentrotus lividus (Echinodermata)

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Insectes, cadavres et scènes de crime: Principes et applications de l'entomologie médico-légale

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Study of the massive skeleton of the calcareous sponge Petrobiona massiliana

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Seasonal modifications and morphogenesis of the Mediterranean hypercalcified sponge Petrobiona massiliana Vacelet and Lévi 1958 (Porifera, Calcarea, Calcaronea)

The periodicity of sexual elements and soft tissue modifications during the life cycle of the hypercalcified sponge Petrobiona massiliana was investigated monthly from June 2006 to November 2007. Sexual reproduction, likely regulated by seawater temperatures, occurred during more than half of the year (from early April to late October); 70% of the samples appeared reproductively active. Specimens of P. massiliana displayed a high plasticity of tissue organization, allowing modulation and rearrangement of their aquiferous systems in response to life cycle phases and environmental changes. Permanent changes were observed in the basal region of the choanosome in non-reproductive specimens, such as disorganization/restructuring events leading to remodeling of the aquiferous system. Periodic modifications occurring during sexual reproduction included the transformation of choanocytes from a typical form to hourglass and vespiform shapes, and more global disorganization of the basal region of the choanosome during provisioning of oocytes and embryos, followed by restructuring after release of the larvae. Finally, episodic disorganization/reorganization phenomena occurred in a few specimens after unfavorable environmental conditions (e.g. decreasing seawater temperatures). Histological and ultrastructural observations of storage cells, located in peculiar trabecular tracts, suggest a transdifferentiation capacity that allows such soft tissue dynamics. © 2011 The American Microscopical Society, Inc.IF: 1,542SCOPUS: ar.jFLWINinfo:eu-repo/semantics/publishe

Les mesures d'instruction In Futurum [Analyse de la jurisprudence des Cours d'Angers et de Rennes]

Gosselin François-Xavier, Le Marrec Yves, De Kervénoaël Pol. Les mesures d'instruction In Futurum [Analyse de la jurisprudence des Cours d'Angers et de Rennes]. In: Revue Judiciaire de l'Ouest, 1987-2. pp. 155-172