Pseudofeces

Pseudofeces are particles that suspension-feeding animals reject before ingestion, formed into mucus-coated pellets or strands and expelled from the feeding apparatus. They are distinct from true feces, which are waste material that has been ingested and digested.

During filtration, many invertebrates sort the incoming material and decide what to ingest. Certain particles—such as coarse sediment, very small or refractory food items, or substances that are toxic or unpalatable—may be rejected and packaged with mucus into pseudofeces, which are expelled rather than consumed. The exact composition and rate of production depend on the species, the particle load, and the ambient environment.

Pseudofeces can influence local ecology and biogeochemistry. They affect particle dynamics in the water column and near the sediment surface, contribute to sedimentation and nutrient fluxes, and can serve as a source of detritus for microbial communities and meiofauna once deposited or degraded. In marine and estuarine systems, pseudofeces production is an important component of the feeding ecology of clams, mussels, and other suspension feeders and can be used to infer filtration efficiency and feeding selectivity.

In summary, pseudofeces are an adaptive mechanism by which suspension feeders exclude unsuitable material during feeding, shaping both the organism’s intake and the surrounding sediment and nutrient landscape.