Sponges
Introduction: Sponges are sessile aquatic animals of the phylum Porifera; which literally means "pore-bearing. Sponges are the simplest of multi-cellular animals.
Although there are freshwater species, the great majority of sponge species are marine which could be found at various depths ranging from tidal zones to depths exceeding 8000 m. Sponges live in a wide range of oceanic habitats, from the Polar Regions to the tropics. However, most sponges live in quiet, clear waters in order to avoid the blocking of their pores by sediments stirred up by waves or a water current; that is why the greatest numbers of sponges are usually found on firm surfaces such as rocks.
The life span of sponges varies significantly depending primarily on
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Also, a few sponge species that live in food-poor environments turn carnivores that prey mainly on small crustaceans.
Reproduction and life cycle: Most sponges are hermaphroditic (having both sexes in one), but at any given time, a sponge animal plays the male role and release sperm while the other partner plays the female role. In subsequent reproduction, they may change the sexual roles. Sponges have no gonads and so the sperm and/or eggs are produced through specific arrangements. Some sponges reach their sexual maturity when only a few weeks old, while several years will be required for other species.
During spawning, sperm burst out of their cysts and released into the water and once they find another sponge of the same species, sperm are carried by water flow to the female apparatus that engulf them where fertilization occurs internally. Most sponge species retain the eggs until they hatch into planktonic larvae that float around in the water for few days with the help of its cilia. Afterwards, the swimming larvae find a place where they settle and start growing into a miniature adult