Encentrum lutra Wulfert, 1936 infested by parasites
Encentrum lutra: in contrast to other Encentrum-lutra populations with transparent specimens from the same area (but other samples) many specimens from this sample stood out by their white-opaque appearance under observation in darkfield. It turns out that the pseudocoel of the rotifers was filled with small "grains" .
Encentrum lutra: detail of anterior part of a specimen showing that some part of the mastax glands is covered/ infested by these grains (arrowheads; the arrow marks the dorsal antenna). The behavior of the infested specimens was quite normal; the "grains" may be parasites. Although in permanent movement the grains did not show a flagellum; so the movement is likely a BROWN-movement.
Encentrum lutra: is a predator of (bdelloid) rotifers; one Philodina-rotifer can be seen in the stomach of this compressed Encentrum specimen. Many of the Encentrum-specimens had bdelloid rotifers in their stomach.
Encentrum lutra: detail (stomach) of the above specimen with engulfed Philidina-rotifer. The arrow points to a parasite in the bdelloid rotifer (the arrowheads mark some of the 8 nuclei of the vitellarium; Tr: trophi of Philodina with DF: 2/2). Since it is not clear which parasites infested the two rotifer species, there is a possibility that Philodina may be the intermediate host for the Encentrum-parasite (or vice versa).