![]() ![]() ![]() Oocytes arise by the differentiation of amoebocytes and are retained within the spongocoel, whereas spermatozoa result from the differentiation of choanocytes and are ejected via the osculum. Sponges may also become sequentially hermaphroditic, producing oocytes first and spermatozoa later. In some sponges, production of gametes may occur throughout the year, whereas other sponges may show sexual cycles depending upon water temperature. Sponges are monoecious (hermaphroditic), which means that one individual can produce both gametes (eggs and sperm) simultaneously. Sexual reproduction in sponges occurs when gametes are generated. ![]() Since gemmules can withstand harsh environments, are resistant to desiccation, and remain dormant for long periods, they are an excellent means of colonization for a sessile organism. Gemmules are capable of attaching to a substratum and generating a new sponge. They serve to recolonize the habitat once environmental conditions stabilize. In freshwater sponges, gemmules may survive hostile environmental conditions such as changes in temperature. The collagen that is normally found in the mesohyl becomes the outer protective layer. In gemmules, an inner layer of amoebocytes is surrounded by a layer of collagen (spongin) that may be reinforced by spicules. Gemmules are environmentally-resistant structures produced by adult sponges wherein the typical sponge morphology is inverted. An atypical type of asexual reproduction is found only in freshwater sponges, occurring through the formation of gemmules. The typical means of asexual reproduction is either fragmentation (where a piece of the sponge breaks off, settles on a new substrate, and develops into a new individual) or budding (a genetically-identical outgrowth from the parent eventually detaches or remains attached to form a colony). ![]() Sponges reproduce by sexual, as well as, asexual methods. This diffusion of water through the body supports major functions in the sponge. \( \newcommand\): Water flow in a sponge: In a sponge, water enters through the body pores and exits in the direction of the osculum (direction of blue arrow). ![]()
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