The aquiferous systems of three marine demospongiae

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Abstract
The aquiferous systems of three common, coastal, marine Demospongiae, Halichondria panicea (Pallas), Haliclona permollis (Bowerbank) and Microciona Prolifera (Ellis and Solander), are analyzed by measurements of cross‐sectional areas of conducting elements. The patterns in demosponges of extremely different organizational morphologies are found to be quantitatively similar. The porocyte nature of the ostia is established for all three species. Choanocyte chamber densities range from 1 to 1.8 × 107 chambers ml−1 with 57 to 95 choanocytes per chamber (means). Cross‐sectional area of the intervillar space of the choanocyte collars is calculated to be 12 to 56 times the lateral surface area of the specimen. Velocities of water movement through specific elements of the aquiferous system are calculated from cross‐sectional area data and measured oscular flow of Haliclona permollis. The calculated Reynolds numbers lie below the critical value and fluid flow is thus considered laminar throughout the aquiferous systems of these sponges.