Sexual reproduction in sponges


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Reproduction In Sponges




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They like to live in clearer waters over murky waters formed by currents. The reproducttion waters may often clog the pores on the sponges so the sponge cannot get its nutrition and oxygen to survive. What is their Importance to the Ecosystem? Sponges are important in nutrient cycles in coral reef systems. Scientists believe they may be important factors to changes in water quality, whether good or bad.

Scientists analyze reoroduction fast sponges breathe and the amount of nitrogen they release while doing so. Sponges collect bacteria when they filter the water around them. These bacteria are believed to be able to do many things. First, these bacteria may be able to create forms of nitrogen from the nitrogen gas in the water that may be nutritional for the sponge.

This process would lower excess nitrogen levels in coral reefs, also preventing harmful ecosystem changes. Scientists believe that the conversion of nitrogen gas s;onges useful nitrogen is also beneficial to the survival of other organisms in the area. They are hoping to have discovered a pathway Sexual reproduction in sponges the removal of excess reproducfion from coral reefs. Sponges are strong animals with Sexul skeletons that are well adapted to their environments. Members of the freshwater Spongillidae undergo a slightly different form of gemmulation. Gemmules consist of aggregates of archaeocytes laden with reserve granules; in addition, spongess, they are surrounded by protective membranes formed by the archaeocytes.

The protective covering is generally reinforced by spiculeswhich vary in shape according to the species and are useful in classification. Freshwater sponge reproductiion allow a species to survive unfavourable conditions in a state in which vital activities are almost completely suspended. In cold regions, gemmulation occurs in winter, and the inactive gemmules are said to hibernate; in warm regions, gemmulation occurs in summer, and the gemmules are said to estivate. In spring or autumn when favourable conditions return, the gemmules germinate, their archaeocytes emerge through an opening micropylethe various cellular types differentiateand a new sponge grows.

Other methods of asexual reproduction include formation of stolons rootlike extensions and fragmentation of individuals. Regeneration The extraordinary capacity of sponges to regenerate is manifested not only by restoration of damaged or lost parts but also by complete regeneration of an adult from fragments or even single cells. Sponge cells may be separated by mechanical methods e. The dissociated cells then settle, migrate, and form active aggregates in which the archaeocytes play an important role. In order for small aggregates of cells to form larger aggregates, the cells must generally become attached to a surface, where they flatten and develop an envelope of special cells pinacocytes ; this is called the diamorph stage.

Reconstitution of the choanocyte chambers and of the canal system follow soon afterward, resulting in a young sponge that is functional and able to grow. It is generally believed that the reconstitution process, even if it involves cell divisionis not comparable with embryonic development, because the various types of dissociated cells participate in the formation of the new sponge by sorting and rearranging themselves, rather than by differentiating from primitive cell types. Regeneration in sponges is of theoretical interest in connection with cell-to-cell recognition, adhesion, sorting out, movement, and cell properties.

During unfavourable conditions, sponges are reduced to small fragments that may consist only of masses of archaeocytes covered by layers of pinacocytes. A complete sponge forms from these fragments when favourable conditions return. The regenerative abilities of sponges, their lack of a central coordinating organ brainand the peculiar migratory ability of cells within the organisms combine to make it somewhat difficult to define sponge individuality. Zoologists involved in the study of sponges empirically define a sponge individual as a mass that is enveloped by a common ectoderm, i.

Ecology Most Porifera, very sensitive to a wide range of ecological factors, are difficult to raise in the laboratory. Habitats Light can limit sponge survival in a given habitat.

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Littoral-dwelling spongs generally develop in caves, on shadowed walls, or under repgoduction shelters such as those provided by crevices. Some species, mainly in the tropics, however, are covered by a metre or less of water and thus are exposed to considerable irradiation from the sppnges. Symbiotic relationships between algae and sponges usually occur in strongly illuminated zones; the algae may act as a protective device because they deposit pigments in the superficial cell layers of the sponge. In some sponges e. Other sponges, in particular hexactinellidsappear to be less efficient at capturing bacteria and may specialize in feeding on smaller bits of organic matter.

Still other sponges harbor symbionts such as green algaedinoflagellatesor cyanobacteriafrom which they also derive nutrients. That's right, these sponges are actually carnivorous!

Reproduction in sponges Sexual

They capture small crustaceans with their spicules which act like Velcro when they come in contact with the crustacean exoskeletons. Cells then migrate around the helpless prey and digestion takes place extracellularly. Most poriferans that reproduce by sexual means are hermaphroditic and produce eggs and sperm at different times. Sperm are frequently "broadcast" into the water column. Spongocytes make gemmules by wrapping shells of spongin, often reinforced with spicules, round clusters of Sexuwl that Seexual full of nutrients. Spognes from the same species but different individuals can join forces to form one sponge.

Sperm are produced by choanocytes or reproductjon choanocyte chambers that sink into the mesohyl and form spermatic cysts while eggs are formed by transformation of archeocytesor of choanocytes in Sexial species. Each egg generally acquires a yolk by consuming "nurse cells". During spawning, sperm burst out of their cysts and are expelled via the osculum. If they contact another sponge of the same species, the water flow carries them to choanocytes that engulf them but, instead of digesting them, metamorphose to an ameboid form and carry the sperm through the mesohyl to eggs, which in most cases engulf the carrier and its cargo.

There are four types of larvae, but all are balls of cells with an outer layer of cells whose flagellae or cilia enable the larvae to move. After swimming for a few days the larvae sink and crawl until they find a place to settle. Most of the cells transform into archeocytes and then into the types appropriate for their locations in a miniature adult sponge. Formation of gemmules Gemmules are internals buds formed within the sponge body. It is the characteristic feature of all fresh water and some marine forms like Ficula and Tethya. Gemmules eventually get detached when the parent sponge is decayed.

Gemmules help the sponge to tide over unfavourable conditions. Gemmules can withstand freezing and considerably greater degree of desiccation than the adult sponges. A gemmule is a small, round, hard ball consisting of internal mass of food laden archaeocytes surrounded by chitinous double membrane. The outer protective membrane may be strengthened by siliceous amphidisc spicules Ephidatia or by monaxon spicules Spongilla. In autumn fresh water sponges suffering from cold and food scarcity get disintegrated leaving behind number of gemmules which remain inert throughout the winter.

Gemmules are set free after the decay of the parent sponge. The gemmules thus formed may sink to the bottom or may flow away with the water. In spring, when the conditions become suitable, the gemmules begin to hatch. The living contents of the gemmules escape out through the micropylar opening and form the new sponge. These new sponge gives rise to summer generation by producing spermatozoa and ova. The summer generation dies off in autumn living behind gemmules which hatch in spring. The life history of such sponges illustrates alternation of generation.

This process is known as regeneration. The power of regeneration is greater in simple animals and simple tissues.


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