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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ploeotia

Euglenida Butschli, 1884 (ref. ID; 4872)
  1. Ploeotia adhaerens Larsen & Patterson, 1990 (ref. ID; 4872)
  2. Ploeotia corrugata Larsen & Patterson, 1990 (ref. ID; 4872)
  3. Ploeotia costata (Triemer, 1986) Farmer & Triemer, 1988 (ref. ID; 4872) reported author and year? (ref. ID; 4826)
  4. Ploeotia decipiens Larsen & Patterson, 1990 (ref. ID; 4872)
  5. Ploeotia longifilum (ref. ID; 4872)
  6. Ploeotia oblonga Larsen & Patterson, 1990 (ref. ID; 4872)
  7. Ploeotia plumosa Ekebom, Patterson & Vors, 1995/96 (ref. ID; 4872 original paper)
  8. Ploeotia pseudanisonema Larsen & Patterson, 1990 (ref. ID; 4872)
  9. Ploeotia pseudanisonema Larsen & Patterson, 1990 (ref. ID; 4872)
  10. Ploeotia robusta (ref. ID; 4872)

Ploeotia adhaerens Larsen & Patterson, 1990 (ref. ID; 4872)

Descriptions

One cell, almost round when viewed from dorsal, flattened, with four prominent ridges on both the dorsal and ventral sides. Posterior part of the ventral side almost plane, dorsal side with inclined sides and a flat middle section. Ridges at the ventral side with rounded crests and dorsal ridges with sharper, more marked crests. The ridges project posteriorly. Flagellar pocket on the left ventral side. Two unequal flagella emerge from a flagellar groove. Both flagella slightly longer than cell. The cell glides with the anterior flagellum sweeping from side to side with an irregular wave motion, but can coil up between the two ridges at the left side when cell at rest. Posterior flagellum trails idly. Ingestion apparatus with two rods on the right side. Distance between rods decreasing posteriorly. Cell adheres tightly to substrate when jarred and flagella contract. (ref. ID; 4872)

Measurements

Cell length 34 um. (ref. ID; 4872)

Ploeotia corrugata Larsen & Patterson, 1990 (ref. ID; 4872)

Descriptions

Cell outline elliptical, flattened, with an ovate profile. Dorsal side with 5 undulating ridges, 2 further ridges forming the margins of the cell. Right half of cell slightly thicker than left, with a slight ridge down the middle of the ventral side and against which the recurrent flagellum lies. Posterior end of cell with slight indentation. Two flagella of unequal length. The anterior flagellum is about the same length as the cell, beating rapidly from side to side with an irregular wave motion when the cell glides. Posterior flagellum one to two times of cell length. Flagellar pocket to left ventral side of cell, stretching down to the middle of the cell. An ingestion apparatus with two rods extending down to the posterior end is visible at the right ventral side. Move by smooth gliding. (ref. ID; 4872)

Remarks

The cells described here are largely consistent with the original description (Larsen & Patterson 1990). However, following the description of Lentomonas applanatum which resembles P. corrugata, we have found that some cells have 7 dorsal ridges and not 6 as described by Larsen & Patterson (1990). We presume that as the marginal ridges are hard to observe that this organism typically has 5+2 dorsal ridges, not 6. In addition, in this study we were able to reveal a ventral ridge. L. applanatum was originally described as Entosiphon applanatum from freshwater (Preisig 1979). The genus Entosiphon can be distinguished from Ploeotia using light microscope because it has a protrusivle siphon, a property noted by Preisig (1979) in respect of E. applanatum. No comments were made by Farmer & Triemer (1994) on the protrusiveness of the siphon in L. applanatum. If the siphon of the organism studied by them is protrusive then comparisons are most appropriately made with Entosiphon, and we concur that a new generic vehicle for this species would be appropriate give the differences in cortical and oral ultrastructure. If the siphon of the organism described by Farmer & Triemer (1994) as L. applanatum does not have a protrusive siphon then it is not the organism described by Preisig (1979). The size of the cells recorded as P. corrugata and L. applanatum, overlap (about 10 um for L. applanatum estimated from micrographs and 7-14 um for P. corrugata; Larsen & Patterson 199; Farmer & Triemer 1994). The lengths of the flagella are similar, the pellicles of the both species have the same large ridges on the dorsal side, and both species have a posterior dimple. We may now add to this that both species have the same number of dorsal ridges. We therefore are of the view that the organism described by Farmer & Triemer (1994) is the same as that described by Larsen & Patterson (1990). Farmer & Triemer (1994) note a number of ultrastructural differences between Lentomonas and Ploeotia, but we are of the view that these are not substantial and that it is not advantageous to divide a genus on the basis of ultrastructural features alone unless the newly circumscribed taxa have distinctive ecological identities. We hold this view because ultrastructural criteria are inaccessible in ecological or biotic surveys, and this makes identification and generic assessment of flagellates difficult. On this basis we conclude that L. applanatum is a junior synonym of P. corrugata. (ref. ID; 4872)

Measurements

Cell length 12 um, range 9-13 um. (ref. ID; 4872)

Ploeotia costata (Triemer, 1986) Farmer & Triemer, 1988 (ref. ID; 4872) reported author and year? (ref. ID; 4826)

Descriptions

Cell ovoid to ovate, dorsally slightly convex, ventrally almost flat. Two parallel, slightly twisted longitudinal dorsal grooves running on left and right side of the dorsal face. Three grooves ventrally, two lateral ones follow the cell sides closely and one median. The cell surface rises up at the sides of the median ventral groove which thus seems deeper than the other two ventral grooves. Two flagella of unequal length, anterior flagellum about cell length, posterior flagellum thicker and 2-2.5 times cell length. The posterior flagellum may have attached bacteria-sized rod-like particles. An ingestion apparatus with two rods visible at the right side, extending down to about 3/4 of cell length. Right hand rod with slight lateral protrusion. Cells glide. (ref. ID; 4872)

Remarks

Larsen & Patterson (1990) note that P. costata and P. oblonga are similar, but gives 3 differences by which the species can be told apart: (1) by the ovoid to ovate cell outline, (2) by the shorter anterior flagellum and (3) by the less prominent median groove for P. costata. The latter feature has been used in this study, as the relative length of flagella appears to be open to subjective interpretation. We note that the posterior flagellum of P. costata is wider than the ventral median groove, but this is not the case for P. oblonga. Despite the slight overlap in given length range, 16-25 um for P. costata vs. 20-30 um of P. oblonga, P. costata is regarded as the smaller of the two species (Farmer & Triemer 1988; Larsen & Patterson 1990). (ref. ID; 4872)

Measurements

Cell 17 um long, range 16-18 um. (ref. ID; 4872)

Ploeotia decipiens Larsen & Patterson, 1990 (ref. ID; 4872)

Remarks

This species is unlikely to be confused with any other of the small Ploeotia species except P. corrugata which besides the smaller size has broader ridges dorsally. (ref. ID; 4872)

Measurements

Cell length 18 um. (ref. ID; 4872)

Ploeotia oblonga Larsen & Patterson, 1990 (ref. ID; 4872)

Descriptions

Cell oblong, slightly flattened dorso-ventrally, with two major grooves dorsally and three major grooves ventrally. Very fine grooves line the major grooves on both sides. The median ventral groove is more prominent that the two lateral grooves. Two flagella of unequal length. Anterior flagellum about cell length, sweeping sideways in irregular waves. Posterior flagellum twice the cell length, and thicker than the anterior flagellum. Ingestion apparatus clearly visible, extending almost to the posterior end. Right hand rod of ingestion apparatus with a knob-shaped protrusion. Moves by gliding. (ref. ID; 4872)

Remarks

In agreement with the original description, and unlikely to be mistaken for P. costata. Size range given in the original description was 20-30 um. The narrow grooves that are visible one each side of the larger grooves are not mentioned in the original description but resemble the arrangement described for P. costata. (ref. ID; 4872)

Measurements

Cell body length 25 um, range 18-30 um. (ref. ID; 4872)

Ploeotia plumosa Ekebom, Patterson & Vors, 1995/96 (ref. ID; 4872 original paper)

Diagnosis

Cell body measuring 17-35 um, outline oblong to ovate, flattened, with four grooves dorsally and five grooves ventrally, and with a variable number of slightly curved inclusions adjacent to grooves. (ref. ID; 4872)

Descriptions

Cell outline oblong to ovate, flattened, with 4 grooves dorsally and 5 grooves ventrally. The dorsal grooves are more widely spaced than the ventral ones. There are a variable number of slightly curved inclusions located with one end touching the inner surface of the pellicular grooves. Flagellar pocket located to the left, and opening as a long slit. Two unequal flagella, one emerges from each end of the slit. The anterior flagellum about twice the cell length. The posterior flagellum 1.5 times thicker than the anterior, twice of almost three times cell length, tapering toward the tip. Cell profile slightly narrowing towards the anterior end. In the cross section, the cell with an almost flat ventral side and moderately convex dorsal side. Ingestion apparatus with two well-developed rods, converging posteriorly. Nucleus may be pushed into the shape of a kidney by a large oval posterior vacuole with homogeneous contents that is often present. Small refractile granules close to the dorsal cell surface are common. Cells glide smoothly in straight line, jerk backward occasionally and stop, then turn and continue in a new direction. The backward jerks occur also as a response to mechanical vibration. The anterior flagellum with sweeping motion. Common. (ref. ID; 4872)

Remarks

The organism described here is assigned to the genus Ploeotia on the basis of the light-microscopical characteristics: rigid body, ingestion apparatus, trailing posterior flagellum, an anterior flagellum that beats along its entire length and longitudinal surface ridges (Larsen & Patterson 1990). The size range of P. plumosa makes it to one of the larger members of the genus (along with P. oblonga, and P. robusta), but we note that there is an overlap of range with P. costata, P. decipiens, P. longifilum, and P. pseudanisonema. None of these species has the characteristic inclusions of P. plumosa. The inclusions give the grooves a feather-like appearance and hence the name P. plumosa. (ref. ID; 4872)

Measurements

Cell length 28 um, width 14 um, range 17-35 um. (ref. ID; 4872)

Ploeotia pseudanisonema Larsen & Patterson, 1990 (ref. ID; 4872)

Descriptions

A few cells observed measuring 14-18 um, with approximately 10 longitudinal narrow sharp grooves, anterior flagellum about the same length as the cell, posterior flagellum 3-4 times the length of the cell. Moves by quick gliding and is capable of Anisonema-like retractions. Ingestion apparatus with slight prominence on outer rod. (ref. ID; 4872)

Remarks

Generally in agreement with the observations by Larsen & Patterson (1990), but found in same sites as P. punctata from which it can be distinguished only with difficulty by its usually larger size and greater number of surface markings. The group of small gliding Ploeotia species requires further study. (ref. ID; 4872)

Ploeotia pseudanisonema Larsen & Patterson, 1990 (ref. ID; 4872)

Descriptions

Cells, 8-15 um, oval or obovate, with or without a slight posterior point, circular in cross-section, with 3 dorsal grooves and one or several delicate ventral grooves and some cells with well marked ventral ridge. Dorsal surface occasionally appearing corrugated. Sometimes with punctae along the pellicular marks. Flagellar pocket at the left ventral side, anterior flagellum about cell length and posterior flagellum with a range of lengths from 2-4 times cell length. Ingestion apparatus present, anterior part may project slightly from the anterior margin as a short tube, but the rods are delicate and are usually only visible at their anterior ends. The posterior flagellum trails along the ventral ridge when cell is moving. Cells move usually actively by rapid gliding (up to 80 um per second), some made Anisonema-like jerks, sometimes interrupted by halts, and may remain in an arrested position for some time. (ref. ID; 4872)

Remarks

Many small fast gliding cells were observed, showing a range of form and attributes. We have not been able to establish any clear cut boundaries and have described these under the name P. punctata. The small rapidly moving species of Ploeotia were the most common euglenids in our samples. Despite a general similarity to the original description of P. punctata, we noted a variety of forms, especially in grooving, ventral topography, relative lengths of posterior flagellum, and behaviour. Only some cells had punctae, we never recorded rapid vibration argued to be distinctive for P. punctata, and many cells observed from One Tree Island are smaller than those reported in the original description. P. punctata as described overlaps in size with P. costata, P. pseudanisonema and P. longifilum. It differs from P. costata because of the slightly flattened nature of the latter, because size overlap is at the lower end of P. costata with the upper end of P. punctata, because of the five clear grooves in P. costata and because of the well developed mouth apparatus in P. costata. P. punctata overlaps in size with P. pseudanisonema but the latter is on average larger and has many more grooves and tapering flagellum with a very thick anterior part. P. punctata is rather similar to P. longifilum but the latter is larger, 12-20 um, usually wider, and has a ventral groove and a long tapering flagellum. The motility of some cells is similar to that of Anisonema trepidum, which has similar pellicular markings and overlaps in size range. However, A. trepidum has been posterior as not having an ingestion apparatus (Larsen 1987; Larsen & Patterson 1990). We also saw on several occasions rod shaped particles that could be bacteria attached to the posterior end of the cell or to the posterior flagellum, but these were not refractile. This area is clearly in need of attention. (ref. ID; 4872)