The sperm floating in the water reach the “female” sponge (one that is producing eggs at the time of reproduction) by the pumping action of choanocytes. In the same way that food is obtained, the choanocytes trap sperm cells as they flow through the interior of the organism.
Sponges reproduce by both asexual and sexual means. 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.
Porifera Life Cycle
When it comes to sexual reproduction, a sponge can play either role. The male sponge releases sperm into the water which travels towards and enters the female sponge. After fertilization occurs, a larvae is released from the female sponge into the water.
Most sponges are hermaphrodites, meaning they produce both eggs and sperm. Since eggs and sperm are produced at different times, self-fertilization is avoided. In most species of sponges, sperm cells from one sponge enter another sponge through its pores, as shown in Figure 5.
Sponges have developed not one, not two, but three different ways to reproduce asexually. These ways are fragmentation, budding, and gemmulation. Fragmentation is the most common way sponges reproduce.
Sponges do not have nervous, digestive or circulatory systems. Instead, most rely on maintaining a constant water flow through their bodies to obtain food and oxygen and to remove wastes.
Asexual reproduction also occurs in sponges in various ways; the best known method is called gemmulation. Gemmulation begins when aggregates of cells, mostly archaeocytes, which, when they become laden with reserve food granules become isolated at the surface of a sponge and surrounded by a protective covering.
Sponges can reproduce either asexually or sexually. Asexually reproduction (without eggs and sperm) often occurs by budding, similar to growing a new branch on a tree. Cells on the side or base of the parent begin to bulge out and form a new organism.
Sexual Reproduction of Sponges
Sponges may also reproduce asexually. Gametes develop from the differentiation of either choanocytes or amoebocytes, depending on the species.
By means of external budding or gemmules, asexual reproduction in sponges takes place.
Adult sponges produce eggs and sperm. In many species, the same individuals produce both. However, they don 't produce eggs and sperm at the same time. As a result, self-fertilization is unlikely to occur.
Most of the species of sponges are hermaphrodites i.e. single parent can produce both male and female gametes. However, both the gametes cannot be produced in sponges at the same time. Therefore, self-fertilization cannot occur in sponges.
Sponges are at a cellular level of organization and thus do not have organs or even well-developed tissues; nevertheless, they produce sperm and eggs and also reproduce asexually. Some species of sponge are monoecious, others are dioecious.
The sponge also contains spermicide, which slows sperm down so it can't reach your egg.
Mankind may be descended from apes but Australian scientists have found proof of links much closer to the sea floor, with a study revealing that sea sponges share almost 70 percent of human genes.
The collar cells of sponges trap and digest food. One of the main digestive cell types is the choanocyte. These cells are commonly called “collar cells” because they have a collar of microvilli at the cell surface that is used to trap food particles flowing through the organism.
They trap (flagella of collar cell) the sperms present in water current from other sponges and bring it to the egg and fertilisation occurs. After fertilization, a zygote is formed which develops into larvae.
So, the gametes of sponges are not produced by gonads. Instead, the gametes (sperms and ova) are derived from some special types of cells, known as the Choanocytes and the Archaeocytes.
Sponges are able to reproduce both sexually using gametes and asexually by budding. Even though sponges are hermaphroditic, individuals will only make one type of gamete at a time. There are two forms of asexual reproduction that sponges can go through: external budding and internal budding.
A sponge can reproduce in several ways. Sponges are capable of sexual reproduction through spawning. They can also reproduce asexually through fragmentation, budding, or gemmules.
Usually found in the sea, sponges are some of the world's simplest animals. They have no heads, eyes, tails, or mouths, and they live most of their lives rooted in one spot. Their bodies are full of tiny holes called pores. Sponges feed by pumping water through their pores and filtering out small particles of food.
Video Solution: What is true about all sponges without exception ? Solution : Sponges are all aquatic, mostly marine but few fresh water forms also exist. Choanocytes or collar cells are only present in sponges.
Though sponges do not have traditional sensory or nervous systems, they were able to sense the stimuli applied by the scientists using only a cilium.
Sponges can live for hundreds or even thousands of years. "While not much is known about the lifespan of sponges, some massive species found in shallow waters are estimated to live for more than 2,300 years," the study authors write.