Thread: Sex or Gender?
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Old 27 Apr 2008, 9:39 am
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Sponges can reproduce sexually or asexually.

Asexual reproduction is through internal and external budding. External budding occurs when the parent sponge grows a bud on the outside of its body. This will either break away or stay connected. Internal budding occurs when archaeocytes collect in the mesohyl and become surrounded by spongin. The internal bud is called a gemmule, and this is seen only in the freshwater sponge family, the Spongillidae. An asexually reproduced sponge has exactly the same genetic material as the parent.

In sexual reproduction, sperm are dispersed by water currents and enter neighboring sponges. All sponges of a particular species release their sperm at approximately the same time. Fertilization occurs internally, in the mesohyl. Fertilized oocytes develop within the mesohyl. Cleavage stages are highly varied within and between groups, sometimes even within a single species. Larval development usually involves an odd type of morphogenetic movement termed an inversion of layers. When this occurs in some species (for example, in Sycon coactum ), the larva flips into the choanocyte chamber, and then can emerge via the water canal system and out through the osculum.

Although sponges are hermaphroditic (both male and female), they are not self-fertile. Most sponges are sequential hermaphrodites, capable of producing eggs or sperm, but not both at the same time

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