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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Trepomonas

Trepomonas Dujardin, 1841 (ref. ID; 3776, 4656)

[ref. ID; 3776]
The genus Trepomonas was created by Dujardin, 1841 for a flagellate 0.022 mm long which was capable of vigorous rotatory movements. In the single species T. agilis he observed 2 flagella. Butschli (1878) added that the organism was phagotrophic, had a contractile vacuole which discharged at the posterior end and displayed an active cyclosis of food vacuoles in the cytoplasm. He also noted the 2 flaps, one on each side of the body, which confer an "S"-shaped profile in cross section. Like Dujardin (1841), Kent (1880-1882) and Stein (1878), he believed that the 2 visible flagella arose as extensions of the flaps themselves. Klebs (1892) recognized the ingestive function of the grooves formed from the curved flaps and created of Trepomonas the order Distomata. He noted 8 flagella arranged as 2 groups of 4, each group arising from a groove. He distinguished 3 species; T. steinii and T. rotans had 2 locomotor flagella, T. agilis only 1, on each side of the body. Within the species agilis he described 3 varieties, distinguishable by structure and size. The isolates studied in the present work correspond to T. a. communis (13-25 um long), distinguished from to T. a. simplex (7-8 um) by its larger size and from T. a. angulata (30 um) by its smaller size and less angular lateral crests. (ref. ID; 3776)
  1. Trepomonas agilis Dujardin, 1841 (ref. ID; 3776, 4656) reported year? (ref. ID; 3517) reported author and year? (ref. ID; 4980)
  2. Trepomonas agilis Dujardin var. communis Klebs (ref. ID; 3342), Trepomonas agilis communis Klebs (ref. ID; 3776)
  3. Trepomonas rotans Klebs, 1892 (ref. ID; 4656) reported year? (ref. ID; 3517)
  4. Trepomonas steini Klebs, 1892 (ref. ID; 4656), steinii (ref. ID; 3517)

Trepomonas agilis Dujardin var. communis Klebs (ref. ID; 3342), Trepomonas agilis communis Klebs (ref. ID; 3776)

Descriptions

The body of T. agilis has the form of an elongate bilaterally compressed ovoid or pear, rounded or sometimes flattened at the anterior extremity. The posterior extremity appears similarly rounded or flattened when viewed from either of the 2 composed surfaces but appears considerably more pointed when viewed from the side. Two oral grooves are cut into the flattened surfaces of the body, one on either side, and run for almost the complete length of the body, conferring an S-shaped profile in cross-section. Each oral groove is skewed, beginning as a slight depression at the anterior extremity and, passing backwards in a counterclockwise direction, reaching a maximum width and depth at ~2/3 way down the length of the body. Each groove terminates as a narrow channel, the posterior channel, at the posterior extremity where it appears to be continuous with the channel from the oral groove of the other side of the body. The right lateral margin of each groove is a tenuous curved flange; the left lateral margin merges smoothly with the dilated central part of the body but is drawn into prominent crests as it approaches anterior and posterior limits of the groove. The 2 pyriform nuclei form a horseshoe configuration at the anterior extremity of the body, their broader ends closely juxtaposed to one another. There are no phase-dense inclusions in the nuclei of living flagellates. Each nucleus tapers sharply posteriorly. At its pointed end is inserted a group of 4 flagella which arise from within the oral groove. The locomotor flagella have a base-to-tip beat and like the oral flagella are acronematic. In immobilized flagellates they curve outwards in a forward direction. Each locomotor flagellum is longer than its associated 3 oral flagella. The oral flagella beat very rapidly within the confines of the oral grooves. The oral flagella appear to produce currents in the ambient medium which bring bacteria and starch granules to the oral groove surface for ingestion. Such currents can be seen when the locomotor flagella are completely motionless so these flagella probably have little to do with the feeding process. Food particles are rapidly ingested into vacuoles formed from the oral groove lining. The food vacuoles circulate in the cytoplasm in a very active dual cyclosis. Movement of vacuoles is saltatory and most active in a vortex immediately behind the nuclei and most active in a vortex immediately behind the nuclei and in the cytoplasm lying just beneath the oral grooves. Propulsion of vacuoles appressed to the nuclear surfaces becomes noticeably accelerated and may be simultaneously bidirectional vacuoles may oscillate between nuclear extremities as they transfer from one cytoplasmic stream to another or become displaced from these nuclear surface paths and be directed posteriorly along the wall of an oral groove to posterior regions of cytoplasm. Conversely, vacuoles from these posterior regions may be moved rapidly along the oral groove surfaces to join the nuclear paths of movement. The extremely active phagotrophy of T. agilis is shown by the packing of the cytoplasm with food vacuoles containing bacteria, starch granules or partially broken-down food material. In addition to vacuoles with particulate contents there are phase-lucent spherical vacuoles carried in the cyclotic flow. These fuse to form a large vacuoles which becomes stationary and undergoes further swelling just behind the postnuclear vortex. The swollen vacuole then moves along a median pathway to the posterior extremity where it may wait before being discharged into the posterior channel. Several of these contractile vacuoles may be observed at any one time in a given organism, the posteriad movement of one vacuole occurring before its predecessor has discharged. The contractile vacuoles empty every 30-50 sec in oat infusion medium. Sometimes particulate matter (including still actively swimming bacteria) is voided at the same site as the contractile vacuole contents. Particulate debris is frequently observed adhering to the posterior extremity of the flagellate. Two roughly oval phase-dense patches are visible at the posterior end of the body close to the bases of the right margins of the oral grooves. Sometimes there is a single central patch and occasionally patches may be connected to produce a more irregular reticulate formation. They have a finely granular substructure and lack a rigid boundary as is demonstrated by the ease with which actively moving vacuoles (such as contractile vacuoles) can pass through them. These patches stain bright magenta with the PAS reagent. (ref. ID; 3776)

Measurements

13-15x6-8 um. (ref. ID; 3342)
Living flagellates of the X-isolate of Trepomonas agilis measure 14.1 (10-17) x 7.4 (4-10) um (n=100); those of the T-isolate measure 17.4 (13-22) x 8.1 (6-11) um (n=50). (ref. ID; 3776)