PARENT SESSION
Contributed Oral Session 10: Aquatic Trophic Systems I
Monday, August 8, 8:00 AM - 11:30 AM, Meeting Room 519 B, Level 5, Palais des congrès de Montréal

Physiological activity and omnivory of stonefly nymphs in Japanese streams.

Miyasaka, Hitoshi^*,1, Genkai-Kato, Motomi^*,1, ¹ Center for Marine Environmental Studies, Ehime University, Matsuyama, Ehime, Japan

ABSTRACT- Diet shifts between multiple trophic levels (omnivory), especially between autotrophs and heterotrophs, require changes in physiological and morphological specialization, compared to shifts among food items within a trophic level. In streams, large stoneflies may be viewed as omnivores rather than perfect predators even in their late stages of nymphs, although they tend to shift their diet from autotrophs and detritus to animals as they grow. Their diets do not have unidirectional trends and are variable depending on species, food availability and season as well as size. However, little is known about their omnivory. Here we evaluate the seasonal changes in food items of three Plecopteran species (Perlidae), which are widespread in mountain streams of Central Japan, by analyzing their gut contents, physiological activity and food availability. Stable isotope analysis was also conducted to evaluate whether gut contents are assimilated into their body.

Key words: omnivory, stonefly, stream