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Scavengers and Decomposers: The Unsung but Vital Heroes of Nature – Part II

Updated: Dec 21, 2023

Worms and Millipedes
Worms! Millipedes! Harmless but very useful. Photo credit: Jakob Pedersen

Welcome back! Our last blog was all about the scavengers. Here, we will talk about the next vital chain in this link called the decomposers.

What are Decomposers?

After the scavengers have eaten their fill, the decomposers aka saprophytes, break down the remains into chemical nutrients like carbon and nitrogen which are released back into the soil, air, and water. This nutrient matter is then consumed by the plants or the producers and thus, essential components re-enter the food cycle. The decomposers might be at the bottom of the food chain, but they are critical for the other parts of the food chain to thrive.

There are two major groups of decomposers: detritivores and saprotrophs. Detritivores include animal decomposers whereas saprotrophs include fungi and bacteria only. The terms decomposers and detritivores are sometimes found interchanged, however, there are distinct differences.

Detritivores are organisms that feed by ingesting the dead matter and then digesting it in their digestive tract. This leads to what is called the decomposition of animal or plant matter. Examples include flies and earthworms.

Decomposers on the other hand, absorb nutrients directly through external chemical or biological process. They are also called heterotrophic, because they, like the herbivores and carnivores, obtain their energy, carbon, and nutrients from the organic matter they consume. Many decomposer species like bacteria are microscopic in size and so cannot be seen by naked eye. Others can be large like mushrooms, which belong to the fungi family.

Some species of decomposers break down fruits and vegetable. Mushrooms are fungus and can devour dead branches of trees.
Some species of decomposers break down fruits and vegetable. Mushrooms are fungus and can devour dead branches of trees. Photo credit: Unsplash/Volodymyr Tokar

Examples of Decomposers in Action

· Actinomycete: These are microscopic decomposers

Actinomycete are a type of bacteria and can be either terrestrial or aquatic. They are of immense help in agriculture and forest realms because they decompose the organic matter of dead organisms, enabling molecules to be absorbed by the plants. Although fungi also perform similar function, these bacteria are much smaller, huge in number, and occupy many different habitats as well.

· Aquatic Scavengers and Decomposers: The Water Dwelling Decomposers

Decomposers are also found in fresh waters such as rivers, ponds, and lakes, as well as in the ocean. Few examples of the freshwater species include fish and scuds. Scuds are crustaceans which means that they belong to the group that includes lobster, crab, and shrimp. Also called "sideswimmers", the scuds are scavengers, feeding on decaying plant and animal material. They are usually found near the bottom of a pond or under aquatic vegetation. They look like large fleas. Examples of deep-sea decomposers include fish and Lysianassoid amphipods. Amphipods are crustaceans with no carapace or hard upper shell and with generally laterally compressed body. They can be either decomposers or detritivores. Lysianassoid amphipods possess telescope-like antenna which scientists believe only helps with detecting food, mate, or danger. That is, it does not play any part in scavenging. Nevertheless, this little crustacean is one of the champions that helps keep the sea environment free of debris. Last but not the least, any water body has myriad types of bacteria which help dispose of any leftovers and help release nutrients in water and soil.

A typical lysianassoid amphipod
A typical lysianassoid amphipod. Photo credit: Tandberg

Why Are the Scavengers Important?

If there were no decomposers, the tiny bits of flesh and blood from a decaying animal would again give rise to germs and disease. There would be no nutrients absorbed back into any habitat and eventually the ecosystem will suffer.

Bacteria like Actinomycete
Bacteria like Actinomycete break down dead plants including hard to break down plants and waste of herbivores. Pic credit:

Did you know?

·The Dynamics of the Dead

When an organism dies and decomposers begin their work, its remains go through a five stage process:

1. Fresh: This stage starts as soon as the heart stops beating. Oxygen supply stops, and carbon dioxide builds up inside the carcass. Autolysis commences when lack of oxygen causes the cellular enzymes to break down cells and tissues. Putrefaction starts when microbes grow and multiply throughout the body.

2. Bloat: Next, gases build up which makes the carcass bloat. Some gas and liquid might escape.

3. Active decay: Carcass loses mass. Liquefaction and disintegration of tissues commence. Bacteria produce gases such as ammonia, hydrogen sulfide, and methane causing strong odor.

4. Advanced decay: Depending on the size of the victim, after some time, not much mass is left to be decomposed. If the body was on land, the soil will absorb large quantity of nitrogen, which is so beneficial nutrient for plants.

5. Final Stage: Finally, only skin, cartilage and bones remain. Several different plants may grow around the remains due rich nutrients absorbed by the soil. Then, only bones will be left. All living organisms would have left. Only silence remains, broken only by the sounds of the living flora or fauna.


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