Sponge integuments have primitive characteristics. Epithelial cells at the outer most cell layer covering the body have junctional‐like complexes and collagen fibers underlying the epithelial layer, suggesting homology with bilaterian epithelia. The subdermal layer (subectosome) under the outermost epithelium (exopinacoderm) has water canals and lacunae. The subectosome has delicate connection between the ectosome and the choanosome. Porocytes are modified exopinacocytes for water to enter the subdermal canals and lacunae. The osculum is the exhalant opening at the exopinacoderms with connection to endopinacoderm. Isolated epithelial cells bearing stereocilia were reported lining the osculum.

The phylum Porifera groups originally filter‐feeding pore‐bearing animals, with carnivore sponges lacking the filtering system. Demospongiae is the class comprising sponges with silica spicule, but it is different from the Homoscleromorph. Sponge taxonomy is based on the morphology and arrangement of spicules, which are highly homoplasics. Molecular studies have importantly contributed to refine sponge taxonomy. Haplosclerida display (or partially) triangular meshes of diactinal (two‐rayed) spicules with sides of one spicule length (i.e. isodictyal reticulation). The genus Haliclona has variable morphology and consistency (erect, tube‐shaped, and branching forms, soft and fragile, and firm and elastic).