Pelagothrix
Pelagothrix Wilhelm Foissner, Helmut Berger, and Jochen Schaumburg, 1999 (ref. ID; 4613 original paper)
[ref. ID; 4613]
Diagnosis; Holophryidae with large, conspicuous cortical alveoli in distinct rows, every second row of which is barren, that is, unciliated. Three adoral organelles (brosse) extending meridionally to mid-body, indistinctly enklitoloph-dexiotrop, rightmost brosse row posteriorly continuous with a somatic ciliary row. Division in freely motile condition. (ref. ID; 4613)
Etymology; Composite of the Greek words pelagos (living in the sea=planktonic) and thrix (= hair = ciliate s. l.). Feminine gender. (ref. ID; 4613)
Comparison with related genera; At first glance, the three species assigned to this new genus resemble Holophrya, as defined by Foissner et al. (1994). However, all true Holophrya species reproduce in division cysts and their cortical alveoli are never as distinct as in Pelagothrix, that is, are hardly recognizable in the light microscope. Furthermore, the adoral organelles are usually obliquely arranged and distinctly separate from the somatic ciliary rows (Foissner et al. 1994; Hiller 1993; Hiller & Bardele 1988). Other prostomatids, such as Urotricha, Bursellopsis, Longitricha and Longifragma, which divide, like Pelagothrix, in freely motile condition, have all cortical alveoli ciliated (Foissner & Pfister 1997; Foissner et al. 1994), while a row of barren alveoli is between each two ciliated rows in Pelagothrix. (ref. ID; 4613)
Other species assignable to Pelagothrix; The genus is established with two new species described bellow, viz., P. chlorelligera and P. plancticola. The conspicuous cortical alveoli as well as body size, symbiotic algae, and sparse caudal cilia relate P. chlorelligera to Urotricha alveolata Kahl, 1926, which is thus transferred to the new genus: Pelagothrix alveolata (Kahl, 1926) nov. comb. (ref. ID; 4613)
Type species; Pelagothirx chloreligera nov. spec. (ref. ID; 4613)
- Pelagothrix alveolata (Kahl, 1926) (ref. ID; 4613)
Syn; Urotricha alveolata Kahl, 1926
- Pelagothrix chlorelligera (ref. ID; 4613 original paper)
- Pelagothrix plancticola (ref. ID; 4613 original paper)
Diagnosis
Size in vivo about 50x35 um. Orderly obovoidal and circular in transverse view. Cortical alveoli 1.0-1.5 um thick. Body extrusomes about 10x0.3 um, meridionally arranged. Many simbiotic green algae, 24 somatic ciliary rows on average. One ring of ciliated perioral dikinetids continuous with anterior end of somatic ciliary rows. Oral basket conical, composed of 20-30 fine rods. (ref. ID; 4613)
Descriptions
1) Size in vivo 40-60x30-40 um, usually about 50x35 um. 2) Body very regular obovoidal, that is, looking exactly like an inverted chicken egg; circular in transverse view. 3) Macronucleus in or near mid-body, globular. One micronucleus. 4) Contractile vacuole in posterior body end with many fine canals extending anteriorly along ciliary rows; single, conspicuous excretory pore in or near pole centre. 5) Cells green due to symbiotic algae 4-7 um across. Extrusomes about 10x0.3 um, that is, long but very fine and thus easily overlooked; slightly curved, arranged in meridional rows, attached to pellicle and directed to body centre. 6) 22-27 (mean=24) meridional ciliary rows, each commencing with a basal body pair (perioral dikinetid), loosened in posterior pole area bearing some scattered, 20 um long caudal cilia. Normal somatic cilia 10 um long and widely spaced. Cortex with very conspicuous, 1.0-1.5 um thick zone of pentagonal to hexagonal alveoli, which form bright fringe and impregnate occasionally with protargol. 7) Oral opening in centre of anterior pole, circular. Oral basket inconspicuous in vivo, conical, composed of 20-30 fine rods extending to mid-body. Undulating (paroral) membrane composed of 20-30 granules (monokinetids or dikinetids), each associated with an about 1 um long ciliary stump, which can swing to and fro; encircled by perioral dikinetids bearing shortened (about 4 um) cilia and being continuous with somatic ciliary rows. Brosse (adoral organelles) indistinctly enklitoloph-dexiotrop (1-2 ciliary rows abut at steep angles to right anterior brosse end), composed of 3-4 short rows of oblique dikinetids, of which only the anterior basal bodies bear an about 3 um long, slightly inflated cilium; right brosse rows usually at anterior end of 1 or 2 shortened somatic ciliary rows. 8) Moves slowly by rotation about main body axis; does not jump. (ref. ID; 4613)
Comments
Similar to Pelagothrix alveolata (Kahl, 1926), which is, however, only 30-40 um long, has a curious triangular shape, and lacks somatic extrusomes. We do not suppose that the extrusomes were overlooked in P. alveolata because Kahl even recognized 3 um long, epipellicular bacteria, that is, studied the species with oil immersion. Pelagothrix plancticola differ from P. chlorelligera in body shape (asymmetric vs. very regularly obovoidal) and size (55-100x35-65 um vs. 40-60x30-40 um) as well as in the number of ciliary rows (34-41 vs. 22-27) and oral basket rods (30-40 vs. 20-30). (ref. ID; 4613)
Etymology
chlorelligera (Chlorella bearing) because of the symbiotic green algae. (ref. ID; 4613)
Type location
Hoglworther See, a small lake in southern Bavaria, Germany (47 degrees 49'N, 12 degrees 50'E). (ref. ID; 4613)
Type slides
Three slides (1 holotype, 2 paratypes) with protargol-impregnated specimens have been deposited in the Oberosterreichische Landemuseum in Linz (LI), Austria. The slides are of mediocre quality. (ref. ID; 4613)
Diagnosis
Size in vivo about 80x55 um. Broadly ellipsoidal with anterior body portion laterally compressed and obliquely truncate. Cortical alveoli about 2.5 um thick. Body extrusomes 13x0.3 um, meridionally arranged. Many symbiotic green algae. 38 somatic ciliary rows on average. One ring of ciliated perioral dikinetids continuous with anterior end of somatic ciliary rows. Oral basket conspicuously trumpet-shaped, composed of 30-40 fine rods. (ref. ID; 4613)
Descriptions
1) Size vivo 55-100x35-65 um, usually around 80x55 um. 2) Body ellipsoidal with anterior third laterally distinctly compressed and obliquely truncate; lateral compression not maintained in silver preparations! 3) Macronucleus usually slightly above mid-body, globular. One micronucleus. 4) Contractile vacuole in posterior body end with many fine canals extending anteriorly along ciliary rows; single, conspicuous excretory pore in or near pole centre. 5) Cells green due to symbiotic algae about 5 um across in vivo. Extrusomes about 13x0.3 um, that is, long but very fine and thus easily overlooked; slightly curved, arranged in a row each between two ciliary rows, attached to pellicle and directed to body centre. No mucocysts recognizable in vivo and after application of methyl green-pyronin. 6) 34-41, usually about 38 meridional ciliary rows, each commencing with a basal body pair (perioral dikinetid; rarely two occur), loosened in posterior pole area bearing some scattered, 25 um long caudal cilia. Normal somatic cilia about 12 um long and moderately widely space. Cortex with very conspicuous, 2.0-2.5 um thick zone of pentagonal to hexagonal alveoli, which form bright fringe in vivo and impregnate with silver. 7) Oral opening in centre of anterior pole, circular. Oral basket trumpet-shaped (becomes conical under cover glass pressure), composed of 30-40 fine rods extending to near mid-body; individual rods furcate and merging subapically forming W-shaped pattern. Undulating (paroral) membrane composed of 30-40 dikinetids, each associated with an oral basket rod and a curved fibre extending anteriorly and then posteriorly to basket centre to form short, conical (inner) oral basket; encircled by single row of perioral dikinetids having short (about 7 um) cilia and being continuous with somatic ciliary rows. Brosse (adoral organelles) rather conspicuous because extending to mid-body and bearing 3-4 um long cilia having a curious, sigmoidal shape; indistinctly enklitoloph-dexiotrop (1-4 somatic ciliary rows abut at steep angles to right anterior brosse end), composed of 3-4 (usually 3) rows of oblique dikinetids having only the anterior basal body ciliated; right brosse or posteriorly continues as normal somatic ciliary row; details of oral ciliature recognizable only after silver impregnation and not necessary of identification. 8) Moves slowly by rotation about main body axis; does not jump. (ref. ID; 4613)
Comments
Easy to identify because of the green colour and the conspicuous cortical alveoli. Pelagothrix plancticola differs from P. chlorelligera in body shape (asymmetrical vs. obovoidal) and size (55-100x35-65 um vs. 40-60x30-40 um) as well as in the number of ciliary rows (34-41 vs. 22-27) and oral basket rods (30-40 vs. 20-30). Pelagothrix alveolata (Kahl, 1926) is only 30-40 um long and has a curious, triangular shape. Originally, we identified this species as Prorodon minutes Kahl, 1927 because of distinct similarities in body size and shape and the symbiotic green algae. We assumed that Kahl overlooked the long but fine extrusomes and the conspicuous alveolar layer. However, very recently, we found a species, which matches Kahl's P. minutus much better, that is, has small (3 um), inconspicuous extrusomes and a less conspicuous alveolar layer. Thus, we classify the population described above as new species. The morphometrics and details of the infraciliature of our population are very similar to Prorodon viridis Kahl, 1927 as redescribed by Esteban & Finlay (1996). Unfortunately, these authors did not study live specimens in details. They neither mention a conspicuous alveolar layer nor provide details on the extrusomes, which are of crucial important for species identification in this kind of ciliates. Thus, Esteban & Finlay's population cannot be definitely assigned. However, it is clear that it is not Prorodon viridis as described by Kahl (1927, 1930), which is a junior synonym of Holophrya ovum Ehrenberg (Foissner et al. 1994). Esteban & Finlay (1996) used as sole feature the symbiotic green algae and neglected all other characteristics given by Kahl (1927, 1930). Kahl (1930) definitely states a size of 120-160x80 um (100-130x50-60 um in 1927 due to a calibration error: Kahl obviously had a calibration error in his early (1926-1928) studies because he corrected all measurements in 1930 and later) and 60-70 ciliary rows. Thus, Kahl's species cannot be identical with the population investigated by Esteban & Finlay (1996), which is "typically 70-90 um long and 50-80 um wide and usually has 35-39 ciliary rows". (ref. ID; 4613)
Etymology
plancticola (living in the plankton) refers to the preferred habitat. (ref. ID; 4613)
Type location
Pond near the village of Maria Sorg, surroundings of Salzburg City, Austria (N47 degrees 47'/E13 degrees 40'). (ref. ID; 4613)
Type slides
Four type slides (two protargol-impregnated; two silver nitrate-impregnated, Chatton-Lwoff technique) have been deposited in the Oberosterreichische Landesmuseum in Linz (LI), Austria. The slides contain many specimens, with relevant cells marked by a black ink circle on the cover glass. (ref. ID; 4613)