endogeic

Endogeic is a term used in soil ecology to describe earthworm species that dwell within the mineral soil rather than in the litter layer. Endogeic worms inhabit the upper to middle soil horizons, especially the A and B horizons, and form dense networks of horizontal burrows. They are typically medium-sized, cylindrical, and lack the conspicuous surface casts produced by epigeic earthworms.

Feeding occurs by ingesting soil along with organic matter, and they excrete casts within the soil. Their burrowing and ingestion mix soil layers, contributing to bioturbation.

Ecological role: endogeic earthworms accelerate decomposition, redistribute nutrients, improve soil structure, and increase macroporosity and infiltration. By mixing soil horizons, they help integrate surface material into deeper layers and stimulate microbial activity in the drilosphere.

Habitat: they prefer moist, well-aerated soils with neutral to slightly acidic pH and are commonly found in cultivated fields, forests, and grasslands. Their distribution is influenced by moisture, temperature, soil texture, and organic matter content. They are sensitive to extreme drought and to soil disturbance that disrupts their burrow networks.

Relevance: endogeic species are often used as indicators of soil health and biological activity. Management practices that alter soil structure and moisture, such as tillage, drainage, and liming, can affect their populations and, in turn, soil biogeochemical processes.

Examples: common endogeic groups include species in the genera Aporrectodea (such as Aporrectodea caliginosa and Aporrectodea trapezoides) and Octolasion.