. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. POLARITY AND PARTICLE SELECTION IN A SPONGE 121 the amphiblastula larvae of Calcarea, the flagellate cells of the anterior pole make the initial contact with the sub- stratum (Bergquist and Green, 1977). In Demospongiae, several authors have suggested that the coeloblastula or parenchymella larvae express an existing polarity in their attachment to the substrate. But such views are highly speculative, because distinguishing between an anterior and a posterior hemisphere in these animals is difficult (see Simpson, 1984, for a
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. POLARITY AND PARTICLE SELECTION IN A SPONGE 121 the amphiblastula larvae of Calcarea, the flagellate cells of the anterior pole make the initial contact with the sub- stratum (Bergquist and Green, 1977). In Demospongiae, several authors have suggested that the coeloblastula or parenchymella larvae express an existing polarity in their attachment to the substrate. But such views are highly speculative, because distinguishing between an anterior and a posterior hemisphere in these animals is difficult (see Simpson, 1984, for a review). The aims of this work are to verify—through labora- tory experiments and scanning electron microscopy (SEM) — the capacity of both kinds of ectosome of Chon- drosia reniformis to develop specificity towards siliceous and calcareous materials, and to demonstrate the cellular basis of that specificity. Materials and Methods Along the rocky cliff of the Portofino Promontory (Li- gurian Sea, Italy) Chondrosia reniformis lives from the surface to the base of the cliff (about 50 m depth). The specimens used in this study were collected during Janu- ary 1997, at 10 m depth, on calcareous substrates. We performed our experiments with specimens having a surface area of 112-156 cm2. These specimens were reared at 15°C in 200-1 aquaria containing natural seawa- ter with a salinity of 37%o. The medium was aerated by bubbling, and it was replaced twice a week. The collected sponges attached to the aquarium bottom in about 10 days. The sandy materials used in testing sponge selectivity were white polycrystalline quartz with a particle size of mm (BDH laboratory sand); red calcareous sand of the same particle size obtained from the organ-pipe coral Tubipora niusica; and fragments of a coralline alga, Lithothamnium sp., 3-5 mm in size. To test the differences in behavior between the upper and lower surfaces of the sponge ectosome, a thin layer of a mixture (1:1) of the
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
