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The Comparative Embryology of Sponges by Alexander V. Ereskovsky download in ePub, pdf, iPad

Microtubules and microfilaments are always present. It comprises the following elements Fig. Cytoplasmic inclusions of the granular cells in the H.

Aphodal chamber is connected

Several small inclusions may also be present. Microtubules radiate from the perinuclear zone, finishing at the cell periphery. There are, correspondingly, several types of pinacocytes. The surface part of an exopinacocyte is polygonal in shape and covered with a mucous layer of self-secreted glycocalyx. The structure of the axoneme is typical of the Eukaryota.

Microsclerocytes are smaller than macrosclerocytes and lack the nucleolus Fig. After aggregation, the dissociated tissues contain large bundles of microfilaments contacting each other in focal points at the periphery of the aggregates. In Oscarella tuberculata Homoscleromorpha vacuolar cells originate by transdifferentiation of endopinacocytes Gaino et al. As noted above, sponges lack the gut epithelium and the digestive parenchyma.

Cells with Inclusions This is a heterogeneous group of cells, characterized by the presence of specific inclusions in the cytoplasm. In all Homoscleromorpha Fig. These cells, however, do have some common characters. Eurypylous is the type of chamber that connects directly with the inhalant canals through prosopyles and with the excurrent canal through an apopyle Fig. The presence of flagella appears to be associated with the involvement of endopinacocytes in the water circulation in the aquiferous system.

The trabecular syncytium widens near the flagellated chambers Fig. Although the collar bodies may be connected with the nucleated domain by an open Fig.

The choanoderm is formed by the flagellated collar cells, the choanocytes, lining the choanocyte chambers. Cells with Small Inclusions Gray cells, also known as glycocytes, were first described in the conglomerate of living cells of M. Owing to the second layer of the trabecular reticulum, bending round each collar in the flagellated chambers, the water enters the flagellated chamber freely Fig.

Aphodal chamber is connected directly with the inhalant canals through prosopyles and with the exhalant canal through an apopyle extended by an aphodus Fig. Bacteriocytes are mobile amoeboid cells with vacuoles containing prokaryotic symbionts Fig. Note the vesicles v suggesting pinocytosis arrow.

The cells that are not included into the epithelia participate in the transport of the food particles and oxygen inside the sponge body. Rounded shape and lack of pseudopodia of the hexactinellid archaeocytes testify to a lack of mobility not characteristic of the archaeocytes of other sponges.

Bacteriocytes are mobile amoeboid cells with