Head of L. capitata. The related L. depressa feeds by holding an algal filament vertically in the groove at the front of its head while it punctures it and sucks out the cytoplasm, leaving a colourless tube. There is an apparent upper limit on the diameter of filaments that can fit into the groove, as it was observed in captivity to exhaust all available narrow filaments but to leave the thicker ones unaffected (pers. obs.). The groove (1) in front of the mouth of L. capitata is similar to that of L. depressa.

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