Algal Ingestion and Digestion by Two Ephemeropteran

The ingestion and digestion of two co-existing ephemeropteran larvae, Meridialaris diguillina (Leptophlebiidae) and Baetis sp (Baetidae) were examined and their mouthpart morphologies were compared. M. diguillina bears conspicuous brushinglike maxillae and Baetis sp has toothed, scope-like lacinia-galeae and mandibles. Larvae were fed on periphyton and faeces were collected for examination. The proportions of dead, dying and live cells in faeces were compared between grazers and with periphyton. The two species showed differences in grazing efficiency. Baetis sp did not feed on prostrated diatoms while M. diguillina fed on the whole periphyton assemblage. In terms of digestion, M. diguillina presented apparent higher digestion ability than Baetis sp. These differences showed dissimilar resource exploitation and therefore the two species might influence the structure and dynamic of the algal assemblage in different ways.