Sea Sponge

The sea sponge is a part of the phylum Porifera. They are normally found in the world’s oceans and seas. Currently, there are around 5000-10000 known species on the planet. As some of the most abundant and widespread sea species, they can be found from the colder arctic waters to the warmer tropics. The universal nature of the sea sponge makes them vital to the oceanic ecosystem.

Featured image credit: Nhobgood Nick Hobgood, CC BY-SA 3.0

Appearance

One of the most interesting aspects of the sea sponge is that it has many similarities to traditional animals, but lacks some very key elements. These similarities consist of being multicellular, having no cell walls, heterotrophic, and producing sperm cells. However, incredibly they have no organs and do not have tissue. They come in a variety of colors and shapes.

Credit: icelight (CC BY 2.0)

Anatomy

The internal anatomy of sea sponges, similar to many coral species, is made up of a skeleton. These skeletons tend to be made of calcium carbonate or silicon dioxide. The sponge’s porous exterior is another key characteristic of its appearance.

Impressively, sea sponges can actually move their bodies despite not having a brain, active neurons, or any significant tissue. They can release blockages from sand, rocks, and other sediments through contractions. They can also reduce their surface area, using the same method, to make them less appealing to predators.

Habitat

Sea sponges are primarily found in saltwater environments. Some freshwater variations do exist, but a large proportion is sea-based. Many coral reefs contain a variety of sponges, as they can help with cleaning, filtering, and improving water quality. They also are utilized by other animal species.

The majority of sea sponges prefer to attach themselves to hard surfaces, such as rocks or reefs. However, there are some species that find soft sediments, such as sand or silt, and thrive.

Diet

The majority of sea sponges are filter feeders and have systems in place that allow them to extract food particles from the water column around them. This is done as the water flows through them. It is not only food that gets absorbed through this method, it is how they get their oxygen and expel carbon dioxide.

Some species are considered carnivorous as they will develop symbiotic bacteria in their bodies and then consume them.

Credit: Nhobgood Nick Hobgood, CC BY-SA 3.0

Lifespan

The lifespan of sea sponges can vary significantly depending on their habitat and environment. For example, if a sea sponge inhabits a more temperate, colder ocean, it can see a few years of life. However, when they live in more tropical oceans, such as the Indian Ocean, or deeper waters, they tend to last far longer. Lifespans of up to 200 years have been recorded by scientists, and in incredible circumstances, sponges can live up to 5000 years.

Reproduction

The majority of sea sponge species retain their eggs until they have fully developed, however, some do release their sperm into the water column. They then float around and once fertilized they turn into larvae. These larvae then hunt for the perfect conditions to grow.

Across the sea sponge group, sexual and asexual reproduction are both used. One of the most interesting forms of sea sponge reproduction is budding. This is the process of cell multiplication from one area of the specimen. It is similar to how substances like yeast multiply.

Sponges also produce gemmules, which are used to produce new individuals, when other sponges die. These nutrient pods are released by dying sponges and germinate at a later date, once the water conditions are perfect. This method is largely used by freshwater species of sponges, but there are a few saltwater species that use it also.

Despite having no gonads, or reproductive organs, the sea sponge is hermaphroditic, as it produces both sperm cells and eggs.

Credit: Nymishanandini, CC BY-SA 4.0

Threats

As a species that appears in many oceanic environments, it is no surprise that sea sponges have many threats to contend with. There are predators that prey on the sea sponge, and also environmental threats to them too.

One of these predators is the sponge fly. These opportunists have developed specialist skills to effectively target sea sponges. They will lay their eggs in the proximity of the sea sponges, then once they are fertilized and hatched, they will be released to feed on the nearest sponges. They will utilize their long mouths to tear through the spongy outer flesh. They will sometimes settle within the sponge itself and feed from the inside.

However, it is not always bad news for the sea sponge. They have some defense systems in place to fend off many organisms. Many of these organisms use the sponge to grow and feed on, trying to form a symbiotic relationship. When it isn’t in the best interest of the sponge, however, they release toxins to stop echinoderms and bryozoans from living on them.

Facts about the Sea Sponge

• The seas sponge is a hermaphrodite, as it produces the sperm cells and the eggs before fertilization.
• Feeding, respiration, and excretion are all done through one system.
• In some circumstances, sea sponges can live up to 5000 years.
• Some species can be toxic as a defense against organisms.
• Despite not having brains or tissue, they can still move and operate their simple systems.
• Some predators feed on the sponge’s cells.

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