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Apr 1, 2019 3:18 PMPublication: The East Hampton Press & The Southampton Press

Notes On The Earthworm

Apr 2, 2019 9:50 AM

March 2019 followed the old saying to a T—in like a lion, and out like a lamb—with a couple of 50-degree days at month’s end. The warm weather prompted me to pull the bike out of the garage, dust off the cobwebs, and join some friends for a lap around the Peconic: Sag Harbor to Riverhead on the South Fork, east to Greenport, across Shelter Island and back to Sag Harbor.It was nice cycling once we crossed the canal. Not so on the east side. I thought back to all the hours I spent on town-appointed “bike committees” and accomplished nothing. Neither East Hampton nor Southampton has done a single thing to make this area safer for cyclists. Ever. Not one dime for creating bike lanes or bike paths. The few bike lanes in this area were created by the county and state on non-town roads.

The warm, sunny weather has heated up the ground enough to stir ants and earthworms out of their winter dormancy, as evident by their respective sign: freshly built anthills composed of sand and most noticeable on my brick patio, and excavated material from worms found in an astonishing density (several per square foot) all over the backyard. Although the latter looks just like compressed bits of soil, it is actually material that has passed through the digestive system of earthworms, called worm castings.

The ability of earthworms to rework, mix, aerate and recycle nutrients in the soil, along with their population densities, which can be as much as 1 million per acre, makes this group of animals a very important one in many ecosystems around the world. Aristotle considered them “the intestines of the earth.”

One exception is highly acid soils. They are very sensitive to acid and are rare in evergreen forests due to the acidic nature of evergreen needles that, as they decompose, create acidic soils. Therefore, earthworms may not be an integral component of our pitch pine dominated forests.

A close look at an earthworm reveals that its elongated body is pointed at both ends and is comprised of a series of concentric rings. Most of its body is taken up by its digestive system, and excluding the winter months, when they are inactive, they will consume the equivalent to their bodyweight in one day.

They are nocturnal, emerging to feed from one end of their U-shaped borrows at dusk and feeding throughout the night, usually keeping the rear end of their body anchored in the burrow and, using their amazing ability to elongate their body, reaching around to find suitable dead plant material to ingest and hauling it back into the safety of the burrow. Digestion begins outside their body via secreted enzymes that soften the plant material; once inside, the gizzard grinds it up. An analysis of castings has shown that they contain 50 percent more potassium and 45 percent more phosphorus and nitrogen than the surrounding soil.

They move through the soil by wedging their pointed front end into tiny spaces between soil particles, then expanding their body to push the particles to the sides and enlarge the space. This sounds like a slow, laborious process, but they are able to move through the soil surprisingly quickly. In very compacted soil, they resort to eating their way through, passing both organic and inorganic material through their digestive system.

I knew that their swollen segment, located closest to the head end of the earthworm, had something to do with reproduction, but I never fully understood the whole process. According to my references, earthworms are hermaphrodites, meaning each individual has both male and female sex organs. However, they are not capable of self-fertilization. Mature worms have to find a mate, one impregnating the other, resulting in both partners producing fertilized eggs, or two broods per couple, a strategy that one could consider more efficient than that of the “higher” or more evolved members of the animal kingdom.

The mating process begins by the pair lining up with heads facing in the opposite direction, with their respective clitelli in direct contact, and then secreting a fluid that temporarily binds them together. The male and female sex organs are located between the head and the clitellum, each worm secretes its eggs to the surface of its skin and its sperm to the surface of its mate’s skin. The sticky secretion covering the clitellum is then worked forward toward the head like a neck gaiter and, since the worms are lined up facing in opposite directions, they are moving in opposite directions. As worm A wriggles the sticky collar band forward, the collar picks up its eggs and worm B’s sperm; vice-versa for worm B. The collar is worked off the head, and as it does so, the sticky mass encloses to form a tight cocoon around the fertilized eggs.

Several worms will hatch from each egg and, when they are active, earthworms can produce one cocoon per week.

Although very beneficial in your garden, earthworms have been shown to be detrimental to northern deciduous forests. Earthworms were eliminated from much of the northern part of North America during the last glacial period, and they are only native to those areas that are south of the farthest advance of the glacial ice. Although these native species have slowly migrated north and recolonized former habitat with the retreat of the ice, the emphasis on that process is s-l-o-w. This migration is happening at a rate of 30 feet per year. Multiply that by 10,000 years and you get a northward advance of 300,000 feet, or 60 miles, since the last glacial period.

Most earthworms found here, including the ones in my backyard compost pile, are from Europe and Asia. They arrived in landscaping material. The spread of these non-natives has also been attributed to fishing bait. All the common bait worms sold as night crawlers are non-native species, and these often get tossed into remote forests far from landscaping material.

The uppermost layer of forest soil is largely a spongy, interwoven mass of thread-like fungi hyphae and leaves in various stages of decomposition. Decomposition and the release of nutrients into the soil is performed by the fungi and various invertebrate detritivores. In the absence of earthworms, this process takes place very slowly. An oak leaf can take three years to decompose in this setting.

The pace of the decomposition is such that a thick layer of leaves is always present on the forest floor. This organic cover has many important functions: it protects the underlying soil from drying out, insulates it from extreme fluctuations in temperature, prevents erosion, breathes, enhances seed germination, and protects roots.

Some non-native earthworm populations have been found to consume over 5 tons of organic matter per acre, producing their own weight in casts every 24 hours. Let loose in the forest, they can devour the entire leaf layer in a single year, exposing the soil to compaction and erosion and overfertilizing the forest soil. These impacts, combined with the earthworm’s ability to alter the soil pH, have led to a decline of forest wildflowers and overall forest biodiversity.

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