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Aculeatuschorionia is a phylum of hexoidea containing some 11,000 species, found exclusively in aquatic, mostly marine, environments. They get their name from aculeatucytes, which are specialized cells that carry stinging organelles

They are diploblastic. The body consists of two transparent cell layers, which make up its outer skin (ectoderm) and inner skin (gastroderm). The ectoderm, made up of two cell layers, is mostly covered by a protective layer of slime, excreted by special glands. The space between the inner and outer skin is taken up by the mesoglea, a thick, transparent, jelly-like layer made from collagen and connective tissue, pervaded by numerous small canals, which are used for transport and storage of nutrients. The position of the canals varies from species to species, but they mostly run directly underneath the tissues that they serve.

The basic body shape consists of a sac containing a gastrovascular cavity with a single opening that functions as both mouth and anus. The body is hexamertically symmetric. Cilia in the canals of the digestive system serve to pump water in or out of the gastrovascular cavity.

Movement is coordinated by a decentralized nerve net and simple receptors. Several species complex sensory structures that can include image-forming eyes with lenses and retinas, and a gravity-sensing statolith comparable in function to the otolith of the vertebrate inner ear. Tentacles surrounding the specialized stinging cells, which they use to catch prey and defend themselves from predators.

Reproduction is both sexual and asexual. They reproduce asexually by budding. The bud will eventually fall off the parent organism and becomes a new polyp. Sexual reproduction is carried out by releasing egg and sperm into the water.