Gut load and transit time in Hormogaster elisae (Oligochaeta, Hormogastridae) in laboratory cultures

The gut load and gut transit time (GTT) of the endogeic earthworm Hormogaster elisae in laboratory cultures at 18 degreesC and 23 degreesC were studied. The GTT, 5.25 h +/- 0.40 at 18 degreesC and 3.63 h +/- 0.46 at 23 degreesC, was determined by staining the soil with alimentary colouring (tartrazine). The gut load was calculated with two methods: earthworm mass difference, before and after voiding the gut, and dry mass of the gut content. The gut load ranged between 168 and 261 mg wet mass g live earthworm mass(-1) (mass difference method) or 137-196 mg dry mass g live earthworm mass(-1) (dry mass method). With the obtained data a potential annual soil turnover for H. elisae was calculated: 211-470 kg wet soil mass kg live earthworm mass(-1) year(-1) (mass difference method) or 176-325 kg dry soil mass kg live earthworm mass(-1) year(-1) (dry mass method). (C) 2002 Editions scientifiques et medicales Elsevier SAS. All rights reserved.