Two new species of Couchia parasitic in midge eggs

Abstract

Two new species of Couchia are described as parasites in the eggs of midges. Couchia amphora sp. nov. typically produces terminal flask-shaped zoosporangia with occasional secondary zoosporangia arising by basipetalous succession. Oogonia contain oospores, which usually fill the oogonium. Couchia limnophila sp. nov. typically produces broadly ellipsoidal zoosporangia which are single and terminal, but sympodial renewal may rarely occur. Oospores of C. limnophila do not usually fill the oogonium. The new species are contrasted with the previously described C. circumplexa which, like C. limnophila, typically produces broadly ellipsoidal zoosporangia and which, like C. amphora, usually produces oogonia whose oospores fill the oogonium. Couchia circumplexa differs from both new species in renewing its zoosporangia by internal proliferation. Typical morphological forms and configurations of appressorial complexes produced by each of the three species are useful in species determination, however such usefulness is limited by the intergradation of forms among the three species. Drawings and full descriptions are included to aid in identification of the new species.