800mya we had a common ancestry with Sponges

Sponges are animals of the phylum Porifera (meaning "pore bearer"). Their bodies consist of jelly-like mesohyl sandwiched between two thin layers of cells. While all animals have unspecialized cells that can transform into specialized cells, sponges are unique in having some specialized cells that can transform into other types, often migrating between the main cell layers and the mesohyl in the process. 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, and the shapes of their bodies are adapted to maximize the efficiency of the water flow. All are sessile aquatic animals and, although there are freshwater species, the great majority are marine species, ranging from tidal zones to depths exceeding 8,800 metres.

Sponges create homes for a variety of different organisms (for example snails, shrimps, brittle stars, and fishes) and protect them from predators. Sponges grow on other animals (for example molluscs, barnacles, corals and crabs) which they use as camouflage, for example decorator crabs. Sponges also have mutualistic associations with microbes such as bacteria, micro algae and fungi. The microbes have a protected environment and in return carry out a whole range of survival functions for their host sponge, including metabolic function and removal of waste products. The microbial community within a single sponge can make up 40% of the sponges volume!

The current threat to the 11,000 species of sponges comes in the form of climate change which, while not affecting the sponges directly, is disrupting their relationship with aquatic microbes on which they depend on for nutrition and energy.

For more information see:

https://greentumble.com/the-main-reason-why-sea-sponges-are-threatened/

https://www.themarinediaries.com/tmd-blog/its-a-spongy-world