choanocytelined

Choanocytelined refers to surfaces, chambers, or regions within sponges that are lined with choanocytes, the flagellated collar cells of these animals. Choanocytes drive the aquiferous system by beating their flagella to create water flow, while their collar of microvilli traps food particles for phagocytosis. This lining is a defining feature of the sponge body plan and underpins their filter-feeding biology.

In sponges, the arrangement of choanocytes varies with the body plan. In asconoid sponges, the spongocoel—the central cavity—has an inner surface lined directly by choanocytes. In syconoid sponges, choanocytes line the radial canals, and these canals open into small choanocyte-lined chambers via prosopyles. In leuconoid sponges, choanocytes line multiple flagellated chambers embedded within a complex canal system, with water moving through a series of incurrent and excurrent canals.

Anatomically, a typical choanocyte features a single, whip-like flagellum surrounded by a collar of microvilli. The coordinated beating of many choanocytes generates the essential water current that brings in food particles and oxygen while expelling waste. The particles captured by the collar are ingested and transferred to other cell types, such as archaeocytes, for processing.

The term choanocytelined is primarily descriptive, used in anatomical and developmental contexts to indicate regions where choanocytes line the surface or interior cavities. The presence and arrangement of choanocytes are central to sponge feeding strategies and are of interest in studies of sponge evolution and the origin of multicellularity in animals. See also choanocyte, Porifera, and sponge canal systems.