Class Gelatinosa In contrast to the previous class of sponges, the gelatinos sponges contain a jelly, as the name would suggest. This jelly fills the interstices of the body tissue, and the flow of water is thus restricted to a system of inhalant and exhalant canals. Order Calcarea These are sponges of the gelatinose type, … Read more
Class Nuda These are sponges that lack intercellular jelly. In other words, the star-shaped cells and the amoeba cytes form a network through which water percolates, and there are no inhalant or exhalant canals. Glass sponges (Order Hexactinellida) Sponges of this order are characterized by siliceous spicules based on a hexaradiate or six-rayed plan. Suborder … Read more
Calcareous sponges are largely confined to the littoral and the shallow seas, although a few have been dredged at depths down to 600 ft. or beyond, to a maximum depth of 2,700 ft. Hexactinellida is typically deep-sea, the majority of species living at depths greater than 600 ft., but around the Indo-Pacific islands they seem … Read more
With few exceptions, the body of a sponge is supported by a skeleton made up either of spongin fibers, usually forming a network, as in the bath sponges (Spongia), or of spicules (little spikes) of silica or carbonate of lime. Although we speak of the spicules as constituting a skeleton there are some remarkable differences … Read more
Reproduction in sponges [Phylum Parazoa] This is by both sexual and a variety of non-sexual methods. All sponges appear to bear both ova and spermatozoa, although there has recently been a suggestion that this is not invariable, and fertilization may be internal or external. With internal fertilization the embryos develop inside the sponge, which is … Read more
Body structure [Phylum Parazoa] Probably the best way to describe the body of a sponge is to define its various parts: The skin or ectosome is the outer layer or layers of cells; usually this is a single or double-layer but in a few species it takes the form of a thick cortex made up … Read more
All sponges are aquatic and most of them are marine. Where Freshwater sponges exist? Freshwater sponges are found in fair numbers—but belonging to relatively few species—in ponds and lakes, streams and rivers, even in lakes formed in the craters of extinct volcanoes 10,000 feet above sea-level. Where Marine sponges exist? Marine sponges exist in large … Read more