Some of the sessile adult sponges that remain attached to the substratum are also seen to move extensively due to the various external forces such as water currents, and wave movements. So, they can be said creeping along their substrata via. However, some of the adult sponges are seen to move at ignorable speed due to the amoeboid movements of their cell. If it is an adult sponge than it is strictly sessile, and if it is a larval sponge than it is free swimming in nature. Sponges can be either sessile or motile based on the various stages of their life cycle. This happens in the cell when the cytoplasm of the cell slides and forms a pseudopodium in front to pull the cell forward. So, as the adult sponges remain sessile (non-motile) being attached to the substratum then their whole body shows slow contractile movements as its outermost layer of cells, the pinacoderm, is highly contractile in nature.Īnd, the movement of cells are amoeboid in character, rather than muscular. The substratum to which the sponges remain attached can be either the rocks, or the sandy sea bed, or either the surface of the coral reefs. The primary function of this holdfast due to its complex tangles of root-like growths is to anchor the sessile sponges and other non-motile marine animals to the substratum very firmly. It is chitinous in nature and is not spongin-based. Talking about the adult sponges, their holdfast that help them to anchor is a root-like or basal plate-like structure located at the base of the sponge’s body. However, the larval stage is free swimming in nature and can easily move from one place to another due to the forces exerted by the water currents till it settles down on a hard surface and develops into an adult sponge. How can the larval sponges move? Are sponges sessile or motile?Īdult sponges are strictly sessile and they cannot move from one place to another because they spend their whole life attached to a substratum through a holdfast.Explained: Sponges do not have well-developed locomotory organs.
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