Stenostomum corderoi Marcus 1945

Stenostomum corderoi Marcus, 1945 Fig. 3 A – H Sampling sites. Display case with vegetation – Tank 4 (red pits), Plastic tank with Salvinia sp., Inside leaf rosettes of Bromeliaceae 1, Sphagnum sp. 1, Sphagnum sp. 2. Description. Single worms reach up to 600 μm in length (Fig. 3 A), often occurring in longer chains consisting of up to five zooids. The body is cylindrical, narrowed in the anterior part and rounded at the posterior end with a noticeably wider pharyngeal region. The sensory pits are small and round, enclosed in the head, located in front of the brain lobes (Fig. 3 B). The animals lack refracting bodies. The pits and brain arrangement are similar to those of S. brevipharyngium and S. saliens, but the species is distinguishable by its pharyngeal region. The mouth opening is V-shaped, extending along half of the pharynx where it is glandular, with the rest of the pharynx having a characteristic creased surface (Fig. 3 B). Excretophores appear in the gut, which has a characteristic wavy margin (Fig. 3 C). The ciliary coat is uniform, with a few stiffer cilia distributed across the body. At the very posterior part, a tuft of normal cilia appears (Fig. 3 C). Some individuals found in Cabinet – Tank 4 exhibited red sensory pits, noticeable even under the dissecting microscope (Fig. 3 D, E). Initially thought to represent a different species, these individuals were, upon closer examination, found to exhibit morphology consistent with S. corderoi. Animals were separated and moved into filtered water from another location: a tank with Salvinia. After 24 h in the water from the Salvinia tank, the coloring of the pits disappeared (Fig. 3 F, G). Later, two animals from each location – both Tank 4 and the Salvinia tank were separated and put in the 4 - well plate. One of the animals was kept in the original filtered water, and the other one was put in the filtered water from the other location. After one day in changed water, the animal with red pits (Tank 4) lost the coloration, and the animal that exhibited normal pits (Tank with Salvinia) gained the red color. The color of the pits in control animals in filtered water from the same location did not change. The worms are easily culturable on Chalkley’s Medium with wheat grain at 20 ° C. They swim freely in the water column and prey on small protozoans. When starved, a few instances of cannibalism were observed (Fig. 3 H). Distribution. Brazil, bromeliads from São Paulo (Marcus 1945); France (De Beauchamp 1948); Poland, mosses from Poznań Palmhouse (Kolasa and Young 1974).