Earthworms including compost worms or red wigglers are soil or compost dwelling detritivores. Detritivores obtain nutrients by consuming detritus or decomposing plant and animal parts. Detritivores and decomposers such as bacteria, microscopic fungi, and mushrooms are often used interchangeably because in the food web or food cycle detritivores generally play the roles of decomposers.
Decomposers mostly saprotroph are organisms that breakdown dead or decaying organisms. Basically, earthworms eat microscopic decomposers and the mechanism to obtain the nutrients and energy are different with the saprotrophs, herbivores, and carnivores.
The process of decomposition of the organic matter is one of the most common senses and important processes in the planet to support the new generation of life. As organic matter decomposes within a medium or substrate in which saprotroph organisms is residing, the saprotroph breaks such matter down into its composites and gives more spaces to all living creatures to thrive.
Proteins are broken down into amino acids by enzyme proteases. Lipids are broken down into fatty acids and glycerol by enzyme lipases. Starch is broken down into pieces of simple sugar by enzyme amylases. Cellulose, a major portion of plant cells, and therefore a major constituent of decaying matter is broken down into sugar by enzyme cellulases produced by bacteria, fungi, and protozoans. Earthworms eat the bacteria (bacterivores), fungi (fungivores), and protozoans that growth on the decomposing materials not directly the proteins, fatty acids, and sugars from the waste.
There is a symbiotic mutualism between the earthworm as decomposer and saprotrophic organism. In order saprotrophic organisms and decomposers to facilitate optimal growth and repair, favorable conditions and nutrients must be present. Optimal conditions are the utmost important, refer to several conditions which optimize the growth of bacteria, fungi and earthworms including compost worms.
The presence of water (75 – 80%), presence of oxygen (aerobic), neutral-acidic pH (6 – 6.5), low-medium temperature (0 – 25 degrees Celsius), and majority of nutrients are also important for the growth of the saprotroph and decomposer organisms. Dead and organic matter provide rich source of carbon, nitrogen, protein, carbohydrate, minerals, and vitamins. Waste selection and smaller particle size of the waste are important to give more surface areas of the microorganisms to grow and will support the growth and reproduction of the earthworms especially the compost worms.
Naturally, several macroscopic saprotroph organisms or soil critters are involved during the decomposition processes of the organic waste. In the closed or self-contained vermiculture-vermicomposting in small systems, people are trying to avoid those organisms including flies, ants and other bugs for the aesthetic purposes and sanitation or cleanliness of the household habitat. In most of cases, the right species and high density of the compost worms will be dominance and the bugs cannot compete with the worms.
During the decomposition of the garden waste, farm waste, and kitchen waste in the semi natural compost pile, the presence of the bugs can be neglected but then the new problem will arise because some of worm predators such as amphibians, reptiles, birds, mice even racoons will dig the piles and eat the worms before the freezing Winter coming. Tarps and chicken wires are good protectors for the red wigglers or compost worms against the worm predators and the harsh weathers in the compost pile.
The illustration above is the food web of the compost pile courtesy from the book: Ecology of Compost by Daniel L. Dindal (1971), Sunny CESF, Syracuse NY. The bottom levels are the organic residues or renewable feedstocks of the compost worms. The first levels are the actinomycetes, molds, bacteria, rotifers, protozoans, and microscopic nematodes. According to the recent findings in soil biology, they are regularly ingested by the compost worms.
The second levels of the illustration on compost food web are the others decomposers as close friends of the compost worms such as pot worms, springtails, mold mites, woodlice or sowbugs, millipedes, some beetles, and slugs. The third levels are the most common predators of the compost worms. They are predatory mites, ground beetles, pseudoscorpions, centipedes, rove beetles, ants, and soil flatworms. The highest level of the larger predators of the red wigglers in the compost piles such as mice and birds, are not presented in this illustration.