The skeletal elements of sponges can be of two basic types:
- Protein fibers - formed by a horny protein called spongin, an insoluble substance resistant to digestion by proteolytic enzymes. The spongin is irregularly arranged in the mesenchyme;
- Mineral spicules These elements can be composed of two types of minerals:
- Calcium carbonate- CaCO spicules3can have varied shapes, from simple straight axes to complex and branched shapes;
- Silica- spicules mainly formed by H2Si3O7, are generally complex and can fuse together, resulting in a relatively solid structure in so-called glass sponges.
Reproduction of sponges may be asexual, by budding or budding, originating large colonies.
This type of reproduction occurs by clustering of amoebocytes and other undifferentiated cells that isolate and construct a thick protective membrane containing spongin and spicules. This happens as the sponge dies and disintegrates.
These twins, formed mainly at times of unfavorable environmental conditions, are true forms of resistance - they persist for a long time in the environment and are in a state of metabolic rest until external environmental conditions return to normal.
At this point, the thick membrane is ruptured and the cells resume normal activity and rearrange one or more new sponges.
Budding reproduction is the most common form of asexual reproduction. From this process, a sponge produces shoots, which develop from the mother sponge. These shoots can stay connected with each other by organizing a colony.
THE sexual reproduction It is quite peculiar, especially at the level of larval development.
The sponges can be monoecious (hermaphrodite) or dioecious (separate sexes), the eggs remaining in the mesogleia and the sperm being released to the spongiocelium and thereafter.
The eggs originate from amoebocytes and sperm may originate from amoebocytes or choanocytes. If these sperm find another sponge of the same species, fertilization will occur and a zygote will form.
Fertilization is usually internal. The zygote will give rise to a designated swimming larva. amphiblastulano more than a small ball of coanocyte flagellate cells.
This larva releases itself from the mother sponge's body and exits through the bone, eventually attaching itself to a substrate and reversing, where the flagellate cells migrate inside the ball and flattened outwards.
For this reason, development is said to be indirect in this phylum.