Spotting an outsized earthworm slithering over my patio ignited my instant interest in this critter, its origins and its life. To my surprise, I forgot about my breakfast. I felt a biological hunger instead. Darwin, here I come. At the time of this exclamation, I did not know Charles Darwin actually wrote an entire book about earthworms and spent half his life studying them. Who would have thought!
Extremely long book titles must have been okay back then or perhaps Darwin had earned the right to write whichever way he pleased. “Formation of vegetable mould, through the action of worms, with observations on their habits” was published in 1881. In the first chapter, Darwin wrote he simply became interested in earthworms wishing “to learn how far they acted consciously, and how much mental power they displayed.” He was “the more desirous to learn” since not much was known about these creatures back then.
Or in Darwin’s lingo: “(…) as far as I know, on animals so low in the scale of organization and so poorly provided with sense-organs, as are earthworms.” I wondered if Darwin talked out loud to the worms he observed. Each time I come up close and personal with any creature who shares their forest with me, I start blabbering to them. In this case: “Oh, look at you!! You’re gorgeous!!! You’re huge!!!! Where did you come from? Wow, you must be quite old to get so big! Why are you even on my patio? You’re supposed to be on the grass. In the soil. Hey, where’ you going? No, don’t go there. Hang on, let me help you!”
I felt I had to move swiftly. This magnificent specimen of a worm moved fast, but sticking to its skin were tiny husks from the seeds I feed feral sparrows and finches in the morning (winter in the Southern Hemisphere). It was also moving away from the forest and grass, not towards it. I rushed to my car, where I’m always keeping a box of gloves. I put on a pair because I didn’t want the tinted moisturizer I just smeared on my face passed on to the worm. Who knows what effect such an unnatural, fatty substance might have on its sensitive skin and nervous system. The stuff I use is not tested on animals!
The actual earthworm that inspired this story, video by the author
Wearing blue latex gloves, I carefully picked it up. It wriggled and contracted to protect itself. I threw it on the grass, hoping it would find its way to wherever it came from or wanted to go. Later I’ll learn the grass may not be the best spot for it, but I did the best I could with the knowledge I had at that moment. My patio was definitely not a good spot for it either. Imagine one of my dogs thinking this earthworm is a well-deserved treat. After all this excitement, I spent some time researching my new friend. The Te Ara Encyclopedia of New Zealand says native earthworms (not to be confused with immigrant-earthworms from for instance England) “are frequently found under logs and stones, under the bark of dead trees, in rotting logs, and in the litter of epiphytes in the axils of branches of trees.” One type, the Megascolides suteri, is found almost exclusively in rotting logs and can digest decaying fragments of wood.” It’s usually around 1.3 meters long.
I was convinced my worm was one of them. There is mainly forest here, and my visitor was large. I can tell he/she/it could easily stretch to 1.3 metres. About its extended family, Wikipedia claims that ‘the most ancient lineages of the family show a Gondwanan distribution and have been used as evidence of continental drift. Wow. There wasn’t much recent research I could find. Scientists seem predominantly interested in run of the mill earthworms as they are essential for soil health.
They’re only called exotic because they arrived from overseas, along with plants brought by 19th-century settlers in Aotearoa New Zealand. These invader-worms were spread both by accident as well as by farmers using them to improve pasture growth. They “benefit production”, usually for the dairy industry. (There are so many critters on this earth we haven’t studied and probably never will. Whatever we believe has an economic benefit or can solve our problems gets our attention. Others are left alone, which is probably for the best.)
Native earthworms of New Zealand are highly specialized inhabitants of forest soils. I figure my mysterious patio guest is probably of the leaf litter species. These characters live within the layers of forest debris, where they feed on the decaying plant material. Worldwide, there are around 2,500 described species of earthworms. And that’s a good thing.
Darwin reckoned the earthworm is among the most important animals in the history of the world! The native fauna of New Zealand includes 173 species (27 genera) we so far know of, all from the Megascolecidae bunch. 14 genera are endemic to New Zealand. Many of its native earthworm species have restricted distribution shaped by the geological history of the land.
My Megascolecidae mostly only survives in the areas that retained the undisturbed soil and native vegetation. The life cycles, distribution ranges, and environmental requirements of native earthworm species are not well known, but the keen New Zealand naturalist, Sheila Natusch provided me with quite a bit more information. In her 1967 book ‘Animals of New Zealand’ she described the anatomy of the earthworm beautifully as “looking much the same at both ends”. But as she also observed, “the forward end has a small fleshy lobe, the prostomium, poked out above the mouth.”
From Natusch, I learn that identifying earthworms involves counting their rings. The first surrounds the mouth, then come all the others, marked by grooves. All the segments that follow “have a set of bristles which act as anchors to hold one part of the body still while another part is stretched out or contracted.” The bristles can be extended or pulled in, to grip onto or let go of the soil. “This elastic, push-me-pull-you locomotion alternately stretches and bunches up the rings,” Natusch explained. It’s something my mysterious visitor did very fast.
From Natusch’ detailed description, I can tell I was looking at a sexually mature specimen. Otherwise, it/he/she would not have that thickened part on its body known as the saddle or clitellum.
Earthworms are hermaphrodites. Each individual worm has both female and male sex organs, yet they still mate to procreate. Yet it still takes two earthworms to create baby worms, starting off by mating top-and-tail.
Their lovemaking is a true feat of multitasking. Sperm from the male organ of worm A transfers from its pores onto worm B. It transfers into paired sacs in worm B’s body, where it is stored — and vice versa! They then part their ways and each worm’s saddle secretes a cocoon. It “backs out of this cocoon stern-first”, Natusch observed.
As the female organ moves through the cocoon, the eggs are laid there and as the rest of the worm slides through, the storage organs release the other worm’s sperm. Et voila; fertilized eggs, the cocoon seals up. Using the yoke of the egg, a worm-embryo hatches out and grows into the next generation earthworm.
I’m glad I was able to witness this rare and shy creature appear, even though it led to eating cold porridge that morning. It was last winter, nearly a year ago. I haven’t seen one since.
© Sitara Morgenster
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