Many species of porifers, which are fully exposed to predators, have defense mechanisms against excessive predation.
The main mechanism is chemical in nature, and it happens this way: some sponges produce a toxic substance and others produce substances with antimicrobial activity.
At the bottom of the sea, corals, cnidaria and porifs among others compete for space on solid substrates such as rocks.
In addition to acting as a defense against predators and microbial infections, these toxic substances expelled by sponges are advantageous in the competition for space that porifers lock with other invertebrates, such as corals, and even other sponges. This allows some sponges to grow quickly.
Commensal relations are also very common. The body structure of sponges and their defenses against predators make these animals excellent refuges for smaller invertebrates and even some fish. Several species depend on this protection in their young phase, otherwise their populations would not be stable.
Other common associations are those involving sponges, bacteria and cyanobacteria. Probably the sponge organism is a rich medium for the growth of bacteria and at the same time benefits from a stock of bacteria used in their nutrition.
Reproduction of porifers can be asexual or sexual.
Asexual - It occurs, for example, by budding. In this case, sprouts are formed, which can separate from the animal's body and give rise to new sponges. Observe the scheme below.
The sponges still have great regeneration capacity. If a sponge is broken into pieces, each piece may give rise to a new sponge.
Sexual. In this case, when the sperm (male gametes) are mature, they exit through the bone, along with the water stream, and penetrate another sponge, where one of them fertilizes an egg (female gamete). After fertilization, which is internal, an egg or zygote cell develops and develops into a larva. The larva leaves the body of the sponge, swims with the help of eyelashes and settles, for example, in a rock, where it develops until a new sponge is created.