Porifera (sponges) are sessile, aqu

Porifera (sponges) are sessile, aquatic, multicellular animals that lack true organs and a nervous system. Instead, sponges contain loosely aggregated cells that can differentiate into a variety of cell types and produce diverse skeletal structures. These skeletal elements can be comprised of proteinaceous spongin, chitin, collagen, calcium carbonate and/or silica, depending on the species. Traditional sponge systematics defines sponge taxa by recognizing particular sets of morphological features described in sources such as Systema Porifera[1]. Although these features have been well characterized in the Thesaurus of Sponge Morphology[2,3], and used in pioneering Artificial Intelligence (AI) classification systems [4-6], the terms that are used to describe sponge morphology have not previously been organized into the framework of a modern ontology.

Sponges are conspicuous components of most benthic marine ecosystems such as shallow coral reefs, mangroves, mesophotic reefs, and deep water environments [7]. Sponges play critical roles in these ecosystems, contributing to global cycling of carbon and nitrogen, stabilizing (but also eroding) coral reef frameworks, and hosting incredibly diverse communities of macroscopic and microscopic symbionts [8,9]. Furthermore, sponges have therapeutic potential and other human applications due to their ability (or that of their symbionts) to synthesize various unusual compounds [10] and therefore present a wealth of biotechnological application opportunities.

Sponge life depends on the flow of water through an aquiferous system (Figure 1), with water flowing into the body through incurrent openings (ostia), through a network of canals that are lined by internal epithelium-like cells (pinacocytes), into chambers lined by collared, flagellated cells (choanocytes), and out of the body through excurrent openings (oscules). Choanocytes closely resemble choanoflagellates, a group of unicellular eukaryotes that are among the closest relatives to multicellular animals [11]. Sponges are of interest to evolutionary biologists studying the origins of multicellularity in animals and the origins of the nervous system [12]. Despite having no neurons or synapses, some sponges have a nearly complete set of post-synaptic protein homologs [13]. Likewise, sponges possess the elements of the cadherin and β-catenin complex that are critical for cellular adhesion in bilaterian tissues [11]. Therefore, a more formal representation of poriferan anatomy would enable more complex queries across a diversity of taxa in search of protein, network, and biological processes that have regulated the evolution of multicellularity and the nervous system.