. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. METAMORPHOSIS OF CALCAREOUS SPONGE 21 they are lost by exfoliation or phagocytosis during meta- morphosis (Bergquist and Glasgow 1986: Misevic et al., 1990; Kaye and Reiswig, 1991). The flagellated cells in the coeloblastulae of calcareous sponges cannot, however, be discarded, because these cells make up the greater part of the larva. The coeloblastulae of calcareous sponges have been stud- ied very rarely, and we know little about the process of their metamorphosis (Minchin. 1896; Tuzet, 1947; Borojevic, 1969). In this stu
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. METAMORPHOSIS OF CALCAREOUS SPONGE 21 they are lost by exfoliation or phagocytosis during meta- morphosis (Bergquist and Glasgow 1986: Misevic et al., 1990; Kaye and Reiswig, 1991). The flagellated cells in the coeloblastulae of calcareous sponges cannot, however, be discarded, because these cells make up the greater part of the larva. The coeloblastulae of calcareous sponges have been stud- ied very rarely, and we know little about the process of their metamorphosis (Minchin. 1896; Tuzet, 1947; Borojevic, 1969). In this study we will show the fine structure of the coeloblastula, metamorphosing larva, and juvenile sponge of Leucosolenia ld.\n in clear electron micrographs. After settlement, the larval flagellated cells dedifferentiate into a simple cell mass on the substratum; thereafter they differ- entiate again into the three principal cell types of a juvenile sponge. We discuss the multipotency of the larval flagel- lated cells of L. laxa by comparing them with the develop- mental potency of the larval flagellated cells of other sponges. Materials and Methods Sponges and larvae In early September, specimens of Leucosolenia laxa were collected from rafts in Mutsu bay in northern Japan. L. laxa is one of the most common calcareous sponges in this region. Immediately after collection, the sponges were placed in containers with seawater, brought to the laboratory of Asamushi Marine Biological station within 1 h. and kept in running seawater. To collect larvae, in the early morning sponges were placed in glassware with seawater. Under the natural illu- mination, about one-tenth of them released larvae, begin- ning soon after dawn and ceasing by noon. So the larval release of this calcareous sponge is probably controlled by light cycles, as it is in certain demosponges (Amano, 1986, 1988; Maldonado and Young, 1996). The larvae, which began swimming immediately upon release, were placed in petri dish
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
