I find Loxodes rostrum very often in my samples. Often it is associated with the other two species Loxodes striatus and Loxodes magnus. In body shape, these species look similar, due to the curved, beak-shaped anterior end. However, Loxodes rostrum is green in color due to the numerous oval and spindle-shaped symbiotic algae in its cytoplasm. In addition, these species can be distinguished by their nuclear apparatuses. In Loxodes rostrum the two macronuclei lie close together with a micronucleus between them, while in Loxodes striatus they are widely separated, each with a closely apposed micronucleus facing each other. In Loxodes magnus, many macronuclei are distributed in the cytoplasm.

The symbiont algae of Loxodes rostrum are particularly interesting because they are not of the widely distributed Chlorella type, but are oval or spindle shaped (s. figs. 5 and 6). They are also quite large. According to my measurements, they are 10- 12 µm long and 4-6 µm wide (s. fig. 6). I could observe bell-shaped chloroplast in the algae, which fills almost the entire cell. In addition, each algal cell has its own nucleus (s. fig. 6). To my knowledge, these algae have never been studied in detail and their taxonomic classification and origin is unknown.

The genus Loxodes has specially constructed Müller vesicles. These are constant vacuoles, in which a druse of barium sulfate crystals sits on a plasma stalk. It is assumed that this organelle serves for orientation in the water body, similar to an organ of equilibrium. Loxodes rostrum has 2–6 of these organelles, but they are very difficult to see because of the symbiotic algae.