Difflugia capreolata Penard, 1902
Diagnosis: test pyriform, with a distinct large neck, with faint bulging sides. Test composed of particles of quartz, sometimes with diatom frustules. Nucleus large with very small granulated dispersed nucleoli. Zoochlorellae often present, giving the test a green appearance. Pseudopodia can be very long and branched.
Dimensions: Penard: 225-230 µm, nucleus 50-55 µm. My observations: 215-440 µm, aperture 82-115 µm, nucleus 46-75 µm.
Ecology: This species is not rare in peat bogs, ditches with Sphagnum-contact and small streams in the Netherlands. Between waterplants and on sediments, often together with D. corona and D. urceolata.
Remarks: It's a large species that can be easily identified if the typical neck with convex sides is present (Fig. 1 and 2a-b), otherwise it could be confused with species of the D. pyriformis complex (Fig. 2c and 5). The mineral particles are often rough and relatively large, giving the test a rough appearance.
I observed three times Difflugia capreolata feeding on D. oblonga and one feeding on D. corona. I also observed specimens feeding on rotifers. One rotifer was sucked empty within ten minutes.
Rotifers on their turn are parasiting on Difflugia capreolata. Several times I observed eggs of rotifers inside the test, behind the plasma. One time a young rotifer (Proales sp.) had zoochlorellae in his stomach and was eating inside the test. It seems that rotifers put their eggs inside the test to protect them against predators. A nice introduction is written by Prof. Dr. Willem De Smet.