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Hidden Service Animals: Earthworms Are Only the Beginning

Photo: An earthworm, Swifts Creek, Victoria, by Fir0002/Flagstaffotos.

Without earthworms, scientists at Colorado State calculate, we would have 25 percent less food productivity from plants. How much food service do they provide for us? About 140 million metric tons is the estimate.

Earthworms help establish healthy soils by supporting plant growth in multiple ways  —  building good soil structure, assisting in water capture and aiding in the beneficial churn of organic matter that makes nutrients more available to plants. Other research has also shown that earthworms can facilitate the production of plant-growth-promoting hormones and help plants protect themselves against common soil pathogens. [Emphasis added.]

These services are delivered by soft, squishy annelid worms that are easily crushed. The soil is their dark utopia. Moving about with radial and longitudinal muscles, they “worm” their way through each crevice, plowing the soil in a way that helps plant roots navigate to nutrients the worms have made available.

How Worms Squirm

Take a look at a graphic on from the Chinese Academy of Sciences. What are those intricately sculptured concave disks? They are impressions of radial worm muscles just 1 millimeter in diameter. The structure allows the muscles to “introvert” like a plunger as the worm stretches and squeezes. They are works of art.

These particular muscles are not from earthworms (annelids) but from cycloneuralians, “a group of animals that includes roundworms, horsehair worms, mud dragons, and many other creatures.” This kind of structure is required for worms to navigate through the tight spaces in their environments. And they were detected in fossils from the early Cambrian!

In this study, the researchers described three phosphatized and millimeter-sized specimens from the early Fortunian Kuanchuanpu Formation (ca. 535 Ma) of China. Among them, one specimen (NIGP179459) is better preserved, and consists of five successively larger rings that are interconnected with 19 radial and 36 longitudinal structures. The rings were compressed to certain degrees, implying that they were pliable when alive.

Muscles imply nerves and coordination by a central nervous system. A diagram further down in the article shows the arrangement of seven kinds of radial and longitudinal muscles. The musculature in annelids (which also abruptly appeared in the Cambrian Explosion) is no less wondrous, as shown in a diagram from Penn State. The next time you bait a hook, that diagram may give you pause for what you are about to do to a marvelously designed animal. But fish need to eat, right? You’re just doing your part for the balance of nature.

The Chinese scientists published their work in the longstanding British journal, Proceedings of the Royal Society B. Did they think to mention the Cambrian Explosion? Yes, but only as a marvel of evolution. “This work supports the evolution of scalidophoran-like or priapulan-like introvert musculature in cycloneuralians at the beginning of the Cambrian Period.” Preach it, brother.

The Underworld

More than half of the world’s biodiversity, from microbes to mammals, may live underground, according to a survey conducted by Mark A. Anthony and colleagues in a PNAS paper.

Soil organisms mediate unique functions we rely on for food, fiber, and human and planetary health. Despite the significance of soil life, we lack a quantitative estimate of soil biodiversity, making it challenging to advocate for the importance of protecting, preserving, and restoring soil life. Here, we show that soil is likely home to 59% of life including everything from microbes to mammals, making it the singular most biodiverse habitat on Earth. Our enumeration can enable stakeholders to more quantitatively advocate for soils in the face of the biodiversity crisis.

This is twice previous estimates for soil biodiversity. Some 98.6 percent of annelids live underground; other species include fungi, plants, and isoptera (termites). The services they provide to the biosphere are incompletely understood. In a companion piece in PNAS, Richard Bardgett remarks about the new estimate:

Anthony et al.’s findings have far-reaching implications. They provide the first comprehensive estimate of the vast number of species inhabiting soil, and, in doing so, emphasize the enormous, and often underappreciated, diversity and complexity of the below-ground world. Indeed, the estimate that 59% of all species inhabit soil, with several taxonomic groups being almost entirely soil-based, points to soil being the most speciose, but poorly explored, habitat on Earth. This staggering level of species richness in soil, combined with growing awareness of the functional importance of soil biodiversity for supporting ecosystem services, their resilience to environmental change, and of its sensitivity to multiple global change factors, provides a strong basis to advocate for explicit inclusion of soil biodiversity in international strategies for biodiversity conservation and the protection of threatened soil species.

For us subaerial creatures who mostly think of animals like birds, cats, and dogs, it’s a sobering thought to realize that much of our livelihood depends on hidden service animals under our feet. 

Services Underwater, Too

Last August in EMBO Reports, Philip Hunter urged scientists to get beyond scratching the ocean surface. “Researchers want to better understand the nature and dynamics of the abundant life living on and in the ocean’s surface layers,” his paper begins.

Free-living organisms and microbes that live their lives on and in the ocean’s top meter of seawater are thought to play vital roles in ocean ecosystems, nutrient cycles, oxygen production, the carbon pump, and other earth processes. Yet, surprisingly, relatively little is known about these vital marine communities — collectively known as neuston — their evolution, how they develop, how they affect their environment, and how their environment affects them.

See my article from earlier this year about the carbon pump that discusses but one example of an ecosystem service performed by a strange and little-known type of animal, the salp. No knowledge of “their evolution” was required.

Organisms provide ecosystem services in freshwater, too. The humble waterflea (Daphnia) may hold the key to a cleaner environment and better human health, says an article from the University of Birmingham

Scientists and engineers have discovered a method to harness Daphnia to provide a scalable low-cost, low-carbon way of removing pharmaceuticals, pesticides, and industrial chemicals from wastewater. This approach avoids the toxic byproducts typically associated with current technologies.

Daphnia are tiny crustaceans ranging from 0.2 to 6mm in length. They move underwater in leaps like fleas do in the air. Small as they are, they contain all the organs of crustaceans: legs, eyes, antennae, a gut, muscles, and nerves. How can they remove toxic wastes from water?

Senior author Professor Luisa Orsini, from the University of Birmingham, commented: “Our profound understanding of water flea biology enabled us to pioneer a nature-inspired tertiary wastewater treatment technology. This refines municipal wastewater effluent and safeguards the ecological health of our rivers.

The water flea’s remarkable ability to remain dormant for centuries allows scientists to revive dormant populations that endured varying historical pollution pressures. Leveraging this trait, researchers sourced strains with diverse tolerances to chemical pollutants, incorporating them into the technology.”

In previous articles inspired by Michael Denton’s Privileged Species books, I enjoyed learning about the critical services provided by chemical elements — phosphoruszincnickeliron, and others — that are delivered to Earth from underground (volcanoes) or from space (meteors and dust). A previous article discussed bacteria in the air that ride the clouds to deliver possible ecosystem services. Now, we see service providers in the soil and the sea. How many habitable exoplanets that NASA searches for so eagerly will be likely to have so many critical supply chains to support a thriving biosphere? I doubt many will be so privileged.