![]() The sperms thus releases make their way into another sponge through incoming water by ostia. Sperms are released out from sponge through the outgoing water from osculum. When fully grown the oocyte undergoes two maturation divisions to form ovum which lies in the wall of the radial canal or spongocoel, ready to be fertilized by the sperm of other sponge. These engulfed cells act as the nursing cells for the oocyte. This oocyte moves like an amoebocytes engulfing other cells. Sometimes the oocytes also arise from the choanocytes. The egg mother cell or an oocyte is derived from large archaeocytes which have distinct nucleus. ![]() The lashing movement of the tail helps the spermatozoon to reach other sponges. A matured spermatozoon consists of a rounded nucleated head and a tail. Now these spermatogonia undergo two to three maturation divisions to form spermatocytes and these spermatocytes later give rise to spermatozoa. These cover cells are derived from other amoebocytes. This spermatogonium is surrounded by one or more flattened cover cells to form spermatocyst. The sperm mother cell or a spermatogonium is the enlarged archaeocytes. Both protandry and protogyny facilitate cross fertilization. Sponges exhibit protandry, production of sperms first and ova later or protogyny, production of ova first and sperms later. The sperm and ova are also known to be derived from choanocytes which later undergo gametogenesis to form sperm or ova. The sperm and ova are derived from the undifferentiated amoebocytes called as archaeocytes. ![]() ![]() Although sponges are bisexual (hermaphrodite) cross fertilization occurs as a rule as the production timing of sperm and ova are different. Though some unisexual sponge species are also known, most sponges are monoecious or bisexual. ![]()
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