In this lesson, we will explore the various ways that Porifera are able to reproduce. This includes sexual and asexual methods, both of which help facilitate the survival of the many different species.
The Wide World of Porifera
So, you might be aware that Porifera are the phylum of organisms that we commonly refer to as sponges. You might also know that they come in a variety of shapes, sizes, colors, and that there are both freshwater and marine species. But did you know that these simple filter feeders are capable of both sexual and asexual reproduction? Asexual reproduction means that they do not need to exchange genetic information between individuals.
That’s right, these guys have options! So, let’s go ahead and take a look at some of the different ways that these organisms ensure the survival of their species.
As I mentioned, sponges are capable of sexual reproduction, meaning they do engage in the exchange of genetic material between two genetically distinct individuals. Now, unlike most humans, sponges are actually hermaphroditic, meaning that one sponge can produce both eggs and sperm. That’s not to say that they fertilize their own eggs though.
They use sexual reproduction to exchange genetic material with other sponges of the same species, and in doing so, increase their genetic diversity.Porifera sexual reproduction is generally referred to as spawning. This is a seasonal event resulting in the coordinated release of sperm, which is expelled through the excurrent opening into the surrounding environment. The released sperm floats through the water and is collected by other sponges of the same species via filtration.
Once fertilized, Porifera eggs develop into ciliated larvae, which means that they are larvae that have hair-like extensions. Depending upon their species, these larvae will either be released into the water shortly thereafter or will remain within the tissue of the mother sponge for some time.
Asexual Reproduction: Fragmentation
Another form of reproduction that sponges are capable of is called fragmentation. Fragmentation is a form of asexual reproduction because it does not include any transfer of genetic information between different individuals. This type of reproduction is frequently referred to as cloning, and let me tell you, sponges are masters of it.Sponges are not cephalized organisms meaning they do not have a dedicated ‘head’ or ‘tail’ region, nor do they have unique organ systems. This means that if a piece of them were to break off, or fragment, that piece would have all the necessary cells and tissues to settle on a rock and grow into a new individual that is genetically identical to the original sponge.
In other words, sponges, like sea stars, can clone themselves by breaking off a piece of themselves. Pretty cool, huh?
Asexual Reproduction: ‘Budding’ a New Generation
Another form of asexual reproduction that some sponges are capable of is called budding. Budding consists of growing an external bud, or miniature version of themselves, which is either released or broken off by the current. This budded clone is then swept by the current onto a nearby substrate where it will settle and grow into a new, genetically identical individual. Consequently, this means that some sponges have not one, but two ways of cloning themselves. Talk about a sci-fi double whammy!
Some fresh water sponges are capable of yet another type of asexual reproduction by producing a type of internal bud called a gemmule.
This is essentially a cluster of cells surrounded by a protective coating. This coating acts like a coat of armor, protecting the internal cells from everything from drying out to freezing and oxygen deprivation. Talk about a natural escape pod!Gemmules are generally produced when the environment becomes too hostile for the survival of the sponge. In other words, budding and/or spawning would be futile, as environmental conditions would not allow offspring to survive. Gemmules essentially enable the sponge to clone itself in the form of dormant eggs, which, when conditions become more favorable, will be triggered into activity.
Porifera is the phylum of organisms commonly known as sponges and is capable of both sexual and asexual reproduction. Sponges are hermaphroditic, meaning they are capable of producing both eggs and sperm, and engage in seasonal spawning events. These are when large plumes of sperm are released into the water for other sponges of the same species to filter out and fertilize their eggs with.
Fragmentation is one of a few forms of asexual reproduction that sponges are capable of. Since they aren’t cephalized, that is they lacking a dedicated ‘head’ region, and do not have any organ systems, fragments of the sponge that break off have all of the necessary cells to grow a new, genetically identical individual. Budding, another form of asexual reproduction, is when sponges grow an external copy of themselves, or a ‘bud,’ that is either released or broken off by the current and grows into a new, genetically identical individual.Gemmules, yet another form of asexual reproduction and one that is unique to freshwater sponges, refers to internal egg-like buds.
These buds are dormant clusters of cells encased in a protective shell that are produced when the environment is inhospitable for other forms of reproduction. These ‘eggs’ can withstand desiccation, freezing, and low-oxygen environments.