Ref ID : 6167
Edmond R. Zaborski; Allyl isothiocyanate: an alternative chemical expellant for sampling earthworms. Applied Soil Ecology 22:87-95, 2003
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Allyl isothiocyanate (AITC), a natural breakdown product of glucosinolates in many Cruciferae and a component imparting the sharp taste to mustard, was tested for its effectiveness as a chemical expellant for sampling earthworms. Testing was performed in an arable field with earthworm populations dominated by Lumbricus terrestris Linnaeus, 1758 and Aporrectodea tuberculata (Eisen, 1874). The optimal concentration was found by comparing concentrations ranging from 5 to 250 mg l-1 in water. Total biomass and numbers of earthworms collected increased hyperbolically with increasing AITC concentration, with the highest biomass and numbers collected using 100 mg l-1 AITC. Biomass and numbers of earthworms collected using 250 mg l-1 AITC, but not 150 or 200 mg l-1 AITC, were significantly less than with 100 mg l-1 AITC. Less earthworm biomass was collected by hand sorting than with chemical expulsion using 100 mg l-1 AITC, but the number of earthworms collected by the two methods were not different. A comparison of hand sorting and 100 mg l-1 AITC expulsion using analysis of similarities (ANOSIM) showed that the two methods produced samples differing in the distribution of both numbers and biomass of species-by-size classes. Hand sorting collected more of the smallest size class of L. terrestris and the largest size classes of A. tuberculata than AITC expulsion, whereas AITC expulsion recovered more of the largest size classes of L. terrestris than hand sorting. When 100 mg l-1 AITC expulsion was compared with chemical expulsion using 200 mg l-1 formalin, no differences were found in the total number, total biomass or in the species-by-size class distribution of the earthworms collected. This suggests that the AITC method may be a favorable alternative to formalin expulsion for sampling earthworms. Further studies under other environmental conditions and with other species of earthworms are warranted to establish its general utility.