Sponge Organism Cell Connectome
A sponges organism only has about 20 cell types, which get together to perform various life processes. Therefore, in general these ~20 cell types can function as a unique cell connectome.
Overall, the sponges cell types are summarized in the following table (Ref: Musser et al., 2021):
Index | Cell Type Name | Code | Cell Type Family | Name from Weissenfels (1989) | Description and explanation of naming |
---|---|---|---|---|---|
1 | Archaeocytes | Arc | Archaeocytes and relatives | Archaocyten | Large mesenchymal cells with prominent nucleolus found throughout mesohyl. Principal stem cell in sponges and one of the most abundant cells in the mesohyl. |
2 | Sclerocytes | Scl | Archaeocytes and relatives | Skleroblasten | Elongate mesenchymal cells, often containing growing spicule. |
3 | Mesocytes l | Mes1 | Archaeocytes and relatives | Medium-sized and irregularly-shaped mesenchymal cell with nucleolus that are relatively uncommon in mesohyl. Name refers to localization in mesohyl and relationship with two other novel mesenchymal cell types. | |
4 | Mesocytes 2 | Mes2 | Archaeocytes and relatives | Medium-sized egg-shaped mesenchymal cells with nucleolus, smaller than archaeocytes. May represent the collencytes referred to by Weissenfels (6). However, the term collencyte has also confusingly been used in other sponges to refer to a type of pinacocyte progenitor, and several authors recommend discontinuing its use (93). Name refers to localization in mesohyl and relationship with two other novel mesenchymal cell types. | |
5 | Mesocytes 3 | Mes3 | Archaeocytes and relatives | Very rare elongate or fusiform mesohyl cell. Distributional pattern within S. lacustris, beyond presence in the mesohyl, is unclear. Name refers to localization in mesohyl and relationship with two other novel mesenchymal cell types. | |
6 | Incurrent Pinacocytes 1/2 | incPin 1/2 | Endymocytes | Exopinacocyten, Prosendopinacocyten, Porocyten | Epithelial cells forming external tent, outer layer of osculum, and lining subdermal lacunae and incurrent canals. Our single-cell analysis suggests exopinacocytes of the outer tent layer are genetically similar to prosendopinacocytes lining the vestibule and incurrent canals. In contrast, apendopinacocytes lining the excurrent canals and inner layer of the osculum are more distinct. Thus, the traditional term "endopinacocyte" that unites both proesndo- and apendo- pinacocytes appears to be inconsistent with our genetic findings in S. lacustris. Our name reflects the fact that these cells broadly coincide to the incurrent system in sponges. |
7 | Apendopinacocytes 1/2 | apnPin1/2 | Endymocytes | Apendopinacocyten | Epithelial cells lining excurrent channels and inner layer of osculum, sometimes ciliated. We observed ciliated cells in both the osculum as well as in excurrent channels near choanocyote apopyles. |
8 | Basopinacocytes | basPin | Endymocytes | Exopinacocyten | Epithelial cells forming layer adherent to substratum, which express spongin short-chain collagen and enwrap mature spicules, cementing them into the base of the sponge. Weissenfels (6) referred to both cells of the basal substratum and cells in the outer layer of the epithelial tent together as "exopinacocytes", which we find as genetically distinct. However, Weissenfels recognized that the cells along the basal substratum were responsible for producing spongin, similar to our findings and those of Nakayama (16). Whether basopinacocytes are synonymous with "spongocytes" described in other sponges to secrete spongin collagen and play a role in gemmule epithelial formation is unclear (93). |
9 | Sclerophorocytes | Scp | Endymocytes | Begleitzellen | Mesenchymal cells typically observed in contact with mature spicules, which function in spicule transport and skeletogenesis and described as "transport cells" in (16). Here, we propose a new Greek translation that honors previous names and recognizes their role in transporting spicules. |
10 | Lophocytes | Lph | Endymocytes | Lophocyten | Migratory cells with filopodia and elongate, asymmetric shape. Most prevalent near basopinacocytes and incurrent pinacocytes. Described across porifera as being important in collagen synthesis (93), consistent with our findings that they upregulate distinct collagens. |
11 | Metabaloyctes 1/2 | Met1/2 | Endymocytes | Large, multipolar mesohyl cells lacking nucleolus. Relatively uncommon in mesohyl, although often found in proximity to baso- and incurrent pinacocytes. This cell type does not clearly correspond to any previously-defined morphological cell type in freshwater sponges, and its homology to mesenchymal cell types in other sponges is unclear. The name was chosen to reflect their apparent functional role as metabolic cells. | |
12 | Choanoblasts 1/2 | Chb1/2 | Peptidocytes | Choanoblasten | Proliferative medium-size cells lacking collar and cilium that are progenitors of choanocytes and apopylar cels. Often found in the mesohyl in close proximity to choanocyte chambers |
13 | Choanocytes (Cellcard, Wiki) | Cho | Peptidocytes | Choanocyten | Mature choanocytes, small cells with collar and cilium that play a central role in feeding and driving water flow. |
14 | Apopylar Cells | Apo | Peptidocytes | Konuszellen | Cells forming the excurrent pore of mature choanocyte chamber. Cilium present but lacks microvilli collar. |
15 | Myopeptidocytes 1/2 | Myp1/2 | Peptidocytes | Medium-sized mesechymal cells with prominent vacuoles and long projections forming cellular network, nucleolus absent. Their name reflects their expression profile, which combines both muscle contractile genes and genes involved in phagocytosis and digestion. | |
16 | Amoebocytes | Amb | Amoeboid-Neuroid | Amobocyten | Small mesenchymal cells lacking nucleolus, observed engulfing other cells, similar to that noted by Weissenfels (6). |
17 | Neuroid | Nrd | Amoeboid-Neuroid | Small, multipolar mesenchymal cells with thin projections, usually found in choanocyte chambers. Similar to the neuroid cells described by Pavans de Ceccatty (23), which he later termed "neuroid" cells (94). Also synonymous with central cells described by Reiswig and Brown (24). We use "neuroid" cell as it predates the term central cell and is a better functional description of these cells. | |
18 | Granulocytes | Grl | Amoeboid-Neuroid | Granulocyten | Small mesenchymal cells with projections, scattered in mesenchyme but also often found in the tent and in proximity to pinacocytes. |
19 | Trophocyten | Nutrient cells present during gemmule formation, not sampled in our study | |||
20 | Thesocyten (statocyten) | Cells constituting the gemmule, not sampled in our study | |||
21 | Spermatogonien | Sperm cells present during sexual maturity, not sampled in our study. | |||
22 | Oogonien | Egg cells present during sexual maturity, not sampled in our study. |
References:
- Jacob M Musser, etc. Profiling cellular diversity in sponges informs animal cell type and nervous system evolution. Science. 2021 Nov 5;374(6568):717-723. doi: 10.1126/science.abj2949. PMID: 34735222. PMCID: PMC9233960. See more on the Supplemental Table 1 in its Supplemental File 1.
- N. Weissenfels, Biologie und Mikroskopische Anatomie der Susswasserschwamme (Spongillidae). Publisher: Gustav Fischer. 1989.
- Sponge cell types in Wiki: https://en.wikipedia.org/wiki/Sponge#Cell_types.