Dietary preference of the potamid crab Geothelphusa dehaani in a mountain stream in Fukuoka, northern Kyushu, Japan

Abstract

The diet of the potamid crab Geothelphusa dehaani was studied by examining the stomach contents of middle- and large-sized crabs (carapace width mostly >10 mm) in four seasons. Crabs were collected from asmall mountain stream in Fukuoka City, Japan. Diet analysis was performed using the frequency of occurrence and percentage point methods. Geothelphusa dehaani was found to be omnivorous, with its feeding preference varying widely among individuals. However, the presence in the stomach of large amounts of tissues from various vascular plant organs was high for all seasons and size classes. The presence of moss and filamentous algae was relatively rare. The predominant animal tissue was from insects, G. dehaani preferring aquatic insects, especially caddisfly larvae (Trichoptera). Tissues of G. dehaani were also frequently found, suggesting the high prevalence of cannibalism of young crabs just after their release from maternal care. Spiders and sand were rarely found. Some fishes and snails were found, the former more common in large-sized male crabs. Feeding preferences and the postulated ecological niche were compared between the coexisting crabs G. dehaani and Eriocheir japonica: the former is an omnivore and a predator of small live animals, while the latter is an omnivore and scavenger that mainly eats detritus. © 2012, The Plankton Society of Japan, The Japanese Association of Benthology. All rights reserved.