Just a quick interlude from a book I recently finished reading. It wasn’t a gardening book by any means, but in one tongue-in-cheek section the author describes the behaviour of a nematode, Heterorhabditis bacteriophora, that is parasitic on insects but has a symbiotic relationship with a bacteria. I mention it here because the section refers to gardeners, because the worm is a bit of a gardener itself and because it made me smile.
H. bacteriophora has taken up farming of sorts. As it grows, it nurtures a particular bacteria in its gut. Once it reaches the third of its four juvenile stages, it sets out to find a ‘host’ insect. The worm enters the insect – through an orifice, or by breaking in through the insect body – and makes its wormy way to the insect’s body cavities. When it’s found a nice spot, it ‘plants’ the bacteria (ejecting them by vomiting or defecating, in case you weren’t enjoying this enough.) The released bacteria get to work on replicating – both feeding the growing nematode and killing the host. Once that’s done, our nematode friend gobbles up both its herd of bacteria and the insect corpse that the bacteria have kindly helped digest, before laying eggs so that the whole merry cycle can continue.
Since reading about this process, I’ve also learned that many of the eggs hatch inside the mother nematode, and the youngsters destroy the mother as they grow.
The author concludes: “Such natural means of pest control are preferred to chemicals by many gardeners who pride themselves on their sensitivity.
None of the animals involved in these extraordinary patterns of behaviour has a brain of course. *
*Except perhaps the gardeners”
- You may have used the little fellas to combat pests such as Asparagus beetle or weevils.
- The book is about Caenorhabditis Elegans, which you might find in your compost heap. Elegans is named for its graceful undulating movement, and “lives in tranquil obscurity underground, parasitising nothing, eating only bacteria and slime mould.”
- Other fascinating trivia on nematodes from the book: “A healthy worm defecates about every 45 seconds all its life.” 80,000 species of nematode are known but there may be 10 or 100 times more. Of the known, one lives in seals’ kidneys and can grow to 40″ long and “three species can live in the rectum of the American cockroach.”
- The book is called In the beginning was the worm. Finding the secrets of life in a tiny hermaphrodite, by Andrew Brown. It really isn’t a gardening book. It’s about the decades of study of C. elegans and about the scientists who did the work – work which had a huge impact of modern biology and on the sequencing of the human genome. I loved it: it’s written passionately, bringing in all sorts of different insights, with some wry humour and well-drawn character studies, and some sections of beautiful prose. I think it’s generally accessible, though coincidentally I read the first sections on genetics just after some study on the subject, so I don’t know how I’d have found it before. There are fascinating reflections on what drives scientists; the funding of scientific research; independence of thought, the commercialisation of knowledge and on what it means to be human. All of this makes it a rollicking good yarn despite a long middle section on who did what when, which seemed to lose some focus and structure, as well as some shoddy editing: perhaps there was a rush to get it out after the worm scientists received their Nobel Prize.