Bed and Breakfast: the parasitic life of Proales werneckii (Ploimida : Proalidae) within the alga Vaucheria (Xanthophyceae : Vaucheriales)

The unusual parasitic association between Proales werneckii (Ehrenberg, 183 4) (Ploimida: Proalidae) and the psychrophilic, coenocytic, filamentous alg a, Vaucheria De Candolle, 1801 (Xanthophyceae: Vaucheriales), is documented using light and electron microscopy. A young female rotifer colonizes a Va ucheria filament (ca. 80 mum x 10 cm) by gaining entrance to the cell at a growing region where the wall has not yet matured. After achieving access t o the cell, it disrupts development of either a gametophore or an apical ti p by inducing cell hypertrophy and formation of an excrescent gall (ca. 80- 120 x 140-1500 mum). Remaining within the vacuole of the gall for the rest of her life, the female deposits her eggs after feeding on the rich food su pply furnished by the alga's organelles which continue to translocate withi n the cytoplasm. This abundant nourishment provides the adult rotifer with energy sufficient to permit an enormous reproductive potential (e.g. galls with > 80 subitaneous eggs have been seen). Upon hatching, some offspring e migrate to other immature gametophores or growing tips within the same fila ment, while others may leave to colonize new filaments. Here, we present th e life history of this parasitic relationship, highlighting previously unkn own aspects of the association as well as noting differences among the acco unts of previous authors. To our knowledge, this is the first description o f this parasitic relationship to include electron photomicrographs.