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Sea Sponges


Sea Sponges
Among the 5000 or so species of sea sponges, fewer than 12 are harvested for human uses worldwide. Sea sponges are not plants, but very primitive animals with no brain or central nervous system.

Sponges are the simplest multicellular animals, and they arose as aggregates of non-differentiated cells, evolving more than 540 million years ago. The multicellularity of sponges is an adaptive path toward larger body size because the many small units allow for greater surface areas to be available for metabolic activities that simply increasing the size of a single cell would not accomplish.
Sea Sponges


A sponge body is an assemblage of different kinds of cells in a matrix, supported by a skeleton of fibrous collagen protein and needlelike spicules. These organisms do animals, so it wasn’t until the 18th as animals by zoologists.
Sponges feed by filtering plankton drawn in through incurrent canals, and their digestion is intracellular because there are no organs or tissues in this organism. Respiration and excretion are by diffusion across cell membranes.
Sponges can reproduce by asexual budding or by sexual mixing of eggs and sperm. Most sponges are monoecious; that is, they have both female and male sex cells in the same individual.
Free-swimming sponge larvae eventually settle to the ocean floor. Sea sponges then remain anchored for their entire lives. Harvest of parts of these organisms without damaging the anchoring system allows the sponge to regenerate those body parts. Additionally, entirely new sponges can develop from fragments of sponges dropped onto the seafloor.