[Annelida] An answer to an age-old earthworm question
(by g.read from niwa.co.nz)
Wed May 21 23:41:39 EST 2008
"Why do those foolish earthworms venture out of their safe burrows and get washed down my garden path overnight," Mr Darwin asked himself. He scratched in his beard thoughtfully. "And will they ever adapt to the built environment? Well, time will tell I suppose. Best get on with the blasted book."
Chuang, Shu-Chun & Chen, Jiun Hong. (2008) Role of diurnal rhythm of oxygen consumption in emergence from soil at night after heavy rain by earthworms. Invertebrate Biology, 127, 80-86.
doi:10.1111/j.1744-7410.2007.00117.x Reprint author: chenjh from ntu.edu.tw
Two species of earthworms were used to unravel why some earthworm species crawl out of the soil at night after heavy rain. Specimens of Amynthas gracilis, which show this behavior, were found to have poor tolerance to water immersion and a diurnal rhythm of oxygen consumption, using more oxygen at night than during the day. The other species, Pontoscolex corethrurus, survived longer under water and was never observed to crawl out of the soil after heavy rain; its oxygen consumption was not only lower than that of A. gracilis but also lacked a diurnal rhythm. Accordingly, we suggest that earthworms have at least two types of physical strategies to deal with water immersion and attendant oxygen depletion of the soil. The first is represented by A. gracilis; they crawl out of the waterlogged soil, especially at night when their oxygen consumption increases. The other strategy, shown by P. corethrurus, allows the earthworms to survive at a lower concentration of oxygen due to lower consumption; these worms can therefore remain longer in oxygen-poor conditions, and never crawl out of the soil after heavy rain.
Geoff Read <g.read from niwa.co.nz>
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