Gut load and food-retention time in the earthwormsLumbricus festivusandL. castaneus: A field study

摘要

Lumbricus festivusandL. castaneusconsume dung. In the field, below cow pats, their gut loads were about 0.15 and 0.14 g dry weight g-1ash-free dry weight of worm, respectively, but in “free” soil the loads were higher, about 0.21 and 0.19 g g-1ash-free dry weight of worm. The gut contents of dung were lighter than the total ingested material, at about 0.10 and 0.07 g dry weight g-1ash-free dry weight of worm, respectively. Field experiments showed that the retention time of dung ranged from>9 to 15 h forL. festivus, and from>3 to 6 h forL. castaneus. The experiments also indicated thatL. festivusexploited 20- and 36-day-old dung in different ways, since the gut load was lower in those worms consuming 20-day-old dung than in those consuming 36- to 40-day-old dung. On the basis of these results the calculated consumption rate forL. festivusis 0.08 g dung day-1g live weight of worm-1, and forL. castaneus0.15 g dung day-1, with retention times assumed to be at maximum, 15 h, forL. festivusand 6 h forL. castaneus. These calculations indicate that our field population of worms (75 g m-2) consumes 10–15 t dung ha-1180 days-1, corresponding to the amount of dung produced by 2–3 dai