Loxocephalus luridus occurs in all my sampling sites that have a mud layer of decomposed plant material. In this layer Loxocephalus luridus is very common and associated with other anaerobic ciliates such as Metopus or Caenomorpha. At low magnifications, the specimens often appear black or dark brown due to the very dense granula in the cytoplasm. Loxocephalus luridus is a fast swimmer and is also quite sensitive when a coverslip is placed on it. It is therefore advisable to place the coverslip at a very high layer thickness and then observe the sample during the evaporation progress. The specimens often found attached to detritus flakes and can then be easily observed without cover glass pressure. The apical end of Loxocephalus luridus is slightly cap-shaped (s. fig. 1 a-b). 

At higher magnification the granules in the cytoplasm appear irregularly shaped with a diameter of 1–3 µm (s. fig. 4). Due to the granula it difficult to recognize the inner cell structure. The round macronucleus is located in the center of the cell, but it can be easily displaced by coverslip pressure. The contractile vacuole, which has an excretory porus on the ventral side, is also located in the center of the cell (s. fig. 4). The mouth opening is extraordinarily small for a ciliate of this size. Three adoral membranelles are located one behind the other in the oral cavity, but these are difficult to recognize without silver impregnation (s. figs. 4 and 5 a-c). The preoral suture can be seen apically on the dorsal side (s. fig. 6). It runs ventrally around the right side and ends above the mouth opening. The caudal cilia are close together and lie parallel (s. figs. 2 b and 3 b). They are all about the same length. If the focal plane is on the pellicle, a honeycomb-like structure becomes visible (s. fig. 7).