Mécano-et chémosensibilité des rosettes de pédicellaires croisés de l'astéride <i>Marthasterias glacialis</i> (Echinodermata) = Mechanical and chemical sensibility of rosettes of crossed pedicellariae of <i>Marthasterias glacialis</i>

The crossed pedicellariae of Marthasterias glacialis are clustered on dermal rosettes. Pedicellariae and rosettes are sensitive to mechanical and chemical stimulations. The obtained results suggest that the behaviour induced by mechanical stimulation is the expression of the very function of the pedicellarial rosettes (protection of the body surface against unwanted bodies) while that induced by chemical stimulations actually correspond more to the expression of the overall sensitivity of the epiderm to chemical changes in the environment

Cyclic occurrence of gregarine trophozoites (Apicomplexa) in the burrowing echinoid <i>Echinocardium cordatum</i> (Echinodermata, Spatangoidea)

The occurrence of the gregarine Urospora neapolitana in the spatangoid echinoid Echinocardium cordatum was followed monthly over a 1 yr period. Infesting stages (sporozoites) were seen only in the digestive cells of the hosts' gastric caecum while growing stages (trophozoites) only occurred in the hosts' body cavity. Sporozoites showed no variation in abundance over the investigated period. The number of trophozoites, however, clearly varied with a minimum in summer and early autumn. Trophozoite variation appears to be related to the gonadal cycle of the host

Le genre <i>Neoferdina</i> Livingstone (Echinodermata, Asteroidea: Ophidiasteridae)

8 spp of Neoferdina were described between 1840 and 1936 and only 3 of them are certainly valid: N. cumingi (Gray),N. offreti (Koehler) and N. glyptodisca (Fisher). Among the others, N. intermedia (Djakonov) is conspecific with N. offreti, and N. cancellata (Grube) is conspecific with N. cumingiN. ocellata (H.L. Clark) is discussed and for several reasons this species must be also considered as a synonym of N. cumingi. The type of N. kuhli (Muller et Troschel), the only specimen known, has been lost and, as the author's diagnosis is unclear, it is proposed to reject the species. Finally, the validity of N. insolita Livingstone is doubtful because the only known specimen is juvenile. Neoferdina mahei sp.n. from the Seychelles group, is described and the intraspecific variations of N. offreti are discussed. A revised diagnosis and a revised key of the genus are given

Land-based, closed-cycle echiniculture of <i>Paracentrotus lividus</i> (Lamarck) (Echinoldea: Echinodermata): a long-term experiment at a pilot scale

Today, most sea urchins fisheries worldwide must deal with overexploitation. Better management of exploited field populations and/or aquaculture is increasingly considered necessary to sustain sea urchin production in the future. In this context, we evaluate the potential of land-based, closed-cycle echiniculture. A long-term experiment with the edible sea urchin Paracentrotus lividus has been done on a pilot scale. The process allows total independence from natural resources, because the entire biological cycle of the echinoids is under control (closed-cycle echiniculture), and all activities are performed on land. Furthermore, a method has been set up to control the reproductive cycle with the aim to produce marketable individuals all year long. Performances obtained on each stage of the rearing process are quantified and analyzed. Overall, the results of this experiment are promising; however, some problems remain to be solved before we can claim profitability. The most important finding is that land-based, closed-cycle echiniculture is a potential viable supplement to fisheries to sustain worldwide sea urchin roe production

Les astérides (Échinodermes) du centre-ouest de l'océan Indien (Seychelles, Maldives et îles Mineures)

39 shallow-water species of asteroids have been collected during several scientific missions in the Seychelles and Maldive Archipelagoes. They include two new subspecies (Nardoa lemonnieri platyspina nov. subsp., Acanthaster brevispinus seychellesensis nov. subsp.) and 14 species new for the Seychelles area. A total of 48 shallow-water species of asteroids are known presently from the central-west part of the Indian Ocean

The secretory system of the spines of <i>Ophiocomina nigra</i> (Echinodermata, Ophiuroidea)

The morphology of the spines of the ophiuroid Ophiocomina nigra is described, with particular reference to the nervous system and the sensory and secretory structures of the epidermis. The nervous system is composed of two main spinal nerves, located at the centre of the spine, and their associated branches. There are three secretory cell-types described: (1) fibrillar secretory cells which produce long, javelin-shaped secretory pack-ages and, occurring exclusively in the basal two thirds of the spine, penetrate deeply with their basal regions lying close to the axial nerve running through the spine centre; (2) granular secretory cells, which also penetrate deep within the spine, contain secretory granules in the form of spherical dense vesicles (~1.3 μm in diameter); and (3) goblet secretory cells, filled with packages of loose amorphous material, are superficial in location and usually found associated with a type A ciliated sensory cell. The secretions of the fibrillar and granular secretory cells are thought to perform the functions of defence and feeding respectively. A number of different ciliated sensory cell-types have been identified. Apart from the situation with the goblet cells, no close association was found between secretory and sensory cells. It is suggested that the nervous, sensory and secretory cells act together to form a mucous secretion system with centralized, rather than local control. This system appears to operate when it is advantageous to produce secretion all over the body simultaneously once any portion is stimulated. Stimulation of sensory cells might result in axonal excitation of the spinal nerves and hence to the entire epineural nervous system