Corticocolpoda
Corticocolpoda Foissner, 1993 (ref. ID; 7299 original paper)
[ref. ID; 7299]
Diagnosis; Medium-sized to large, rapacious Colpodidae with huge, cave-like vestibulum occupying anterior half of cell. Left wall of vestibulum projects over right vestibular wall. Right oral ciliary field composed of single row of dikinetids. Left oral ciliary field consists of equidistantly spaced, paired rows of monokinetids. (ref. ID; 7299)
Etymology; Composite of "cortex" (Latin, living in bark) and "coloda" (Greek, bosom). Feminine. (ref. ID; 7299)
Type species; Corticocolpoda kaneshiroae n. sp. (ref. ID; 7299)
- Corticocolpoda kaneshiroae Foissner, 1993 (ref. ID; 7299 original paper)
Diagnosis
In vivo 100-300x60-250 um. Krassniggia- to Colpoda-shaped. Single macronucleus, several micronuclei. Eighty-six somatic and 17 vestibular kineties on average. Left oral ciliary field composed of 13-20 (average=16) kinety pairs. (ref. ID; 7299)
Descriptions
Corticocolpoda kaneshiroae is, like other large colpodids, highly variable in most characters, as indicated by the high coefficients of variation (usually between 20% and 30%).
Size and shape highly variable, common and "typical" specimens about 170x120 um, broadly elliptical, with distinct hump near center of ventral side formed by vestibular bottom which projects over rectangularly notched left vestibular wall; no diagonal groove or postoral sack, both lateral surfaces thus slightly convex. Right vestibular wall neatly curved, extends utricle-like to mid-body in most specimens, as in Krassniggia auxiliaris (Foissner, 1993); however, in about 20% of cells it is more or less distinctly semicircular as in an ordinary Colpoda. Largest and overfed cells often almost circular, only slightly flattened, appear dark at low magnification due to many food vacuoles and innumerable, refractile spherical inclusions. Normal fed and starving specimens brownish to colorless and flattened up to 2:1.
Macronucleus elliptical, usally in left posterior quadrant cell; chromatine reticulate. Up to six large, lenticular to spherical micronuclei attached to macronucleus, surrounded by distinct membrane in living cells. Contractile vacuole subterminally in median of cell or slightly shifted to ventral side, buckles cell surface when completely filled, associated with single excretory pore and many fine, anastomosing canals.
Exrusomes (mucocysts) numerous, mainy around somatic dikinetids, 1.5-2x0.5 um in size, slightly fusiform, colorless but srongly refractive, embedded in 2-um-thick layer of highly viscous ectoplasm; released and stained red after addition of methyl green-pyronin, elongate to up to 50-um-long threads that form thin, tightly meshed layer around cell.
Cytoplasm colorless, viscous, usually full of 1-5 um sized, greasily shining, colorless to yellowish globules; no crystals. Very rapacious, in raw cultures feeding on Colpoda steinii, C. inflata and C. lucida, in pure cultures on Tetrahymena pyriformis and even on the large Paramecium aurelia. Prey is transported into the huge vestibulum by the powerful swirl produced by the cilia of the large vestibular bottom, and enters cell at proximal end of oral ciliary fields. Swims leisurely in wide spirals, often resting with right side on bottom of culture dish, eagerly devouring food items.
General plan of somatic and oral infraciliature as in other members of family and order (Foissner 1993). Somatic cilia approximately 12-um long, paired throughout, densely spaced in anterior body half, more loosely arranged in posterior body portion and in upper half of vestibular bottom. A stripe of condensed ciliature, evidently homologous to the diagonal (somatic) groove of Colpoda spp., is found on the ridge that extends horizontally from the left oral ciliary field to the distal end of the vestibular bottom, i.e. the ventral hump. Kineties of right and left side descend horizontally from anterior, external portion of preoral suture, which is inconspicuous and extends from keel to distal end of oral ciliary fields.
Vestibulum very large, occupies anterior half of body, dorsal margin semicircular, ventral margin (=left vesitular wall) almost rectangular notched, projects distinctly over sigmoid right vestibular wall. Inner surface of left vestibular wall bipartite by small ridge which extends cornucopia-like from anterior left body margin to dorsal posterior half of vestibulum producing a narrow channel in anterior fifth of large oral cavity. This "second vestibulum" is recognizable only in the largest specimens and less pronounced than that found in Bresslauides discoideus (Foissner, 1993).
Seventeen vestibular kineties on average on inner surface of right vestibular wall, about half abut to right oral ciliary field and have connection to somatic kineties; other (ventral) half formed by right lateral somatic kineties which turn into posterior vertex of vestibular opening and spread fan-like to anterior ventral half of vestibulum to end at internal (vestibular) portion of preoral suture. Vestibular bottom and left vestibular wall covered by postoral kinety which commence near left oral ciliary field and at preoral suture.
Right oral ciliary field follows semicircular dorsal vestibular curvature, of same length as left oral ciliary field, composed of single row of dikinetids; distance between dikinetids gradually increases from proximal to distal. Left oral ciliary field parallel to main body axis and dorsal margin of cell, in center of oral cavity and thus far from right oral ciliary field. Space between oral ciliary fields without cilia, appears wrinkled in protargol slides.
Left oral ciliary field crescentic since slightly curved as a whole and length of kineties decreases gradually at both ends, consists of pairs of slightly curved kineties; pairs at ends of field sometimes composed of single kinety only. Cilia remarkably short, viz, about 5 um.
Cytostome at proximal end of oral ciliary fields, i.e. in posterior body half and slightly right of cell median. Pharyngeal fibres inconspicuous, most originate from proximal portion of right oral ciliary field.
Silverline system colpodid, i.e. composed of quadratic to rectangular meshes connecting somatic dikinetids; meshes rather irregular in more sparsely ciliated postoral half of cell. Extrusomes usually do not impregnate with silver nitrate, except in oral cavity where they form an irregular pattern of argyophilic granules usually obscuring somatic infraciliature and silverline system.
Reproduction and morphogenesis not yet studied in detail. Division occurs in reproductive cysts covered by a thin, structureless membrane.
Most cultured cells died without forming resting cysts indicating suboptimal conditions, at least for encystment. The resting cysts observed had the following structure; spherical to slightly ellipsoid, diameter 120-180 um (average=146, n=5), black-brown at low magnification, surrounded by two distinct walls. Outer wall (ectocyst) about 20 um thick, covered by detritus and bacteria, fragile, hyaline and colorless, composed of many thin layers (membranes?) with some granular inclusions (extruded chromatin?). Inner wall (meso- and endocyst) 1-2 um thick, firm and flexible, yellowish. Extrusomes retained, form distinct seam under pellicle. (ref. ID; 7299)
Classification and comparison of Corticocolpoda kaneshiroae with related taxa
The order Colpodida contains five families (Colpodidae, Hausmanniellidae, Marynidae, Bardeliellidae, Grandoriidae) with a total of 16 genera and 74 bonafide species (Foissner 1993). All have the left oral polykinetid composed of single, equidistantly spaced rows of monokinetids. The equidistantly spaced paired rows of monokinetids found in C. kaneshiroae are thus exceptional and might justify establishing a new family. However, the remaining organization of C. kaneshiroae is very similar to that of other genera of the Colpodidae, especially Kuehneltiella and Krassniggia. Futhermore, there is an indistinct grouping of the monokinetidal rows of the left oral ciliary field in Ilsiella, a marynid colpodid (Foissner 1993). Grouped adoral organelles are common in other orders of the Colpodea, especially the Cyrtolophosidida. The discovery of such and organization in a colpodid s.str. thus further supports a monophyly of colpodids s.str. and colpodids s.l. (e.g. cyrtolophosidids). Corticocolpoda kaneshiroae has the typical characteristic of members of the family Colpodidae as defined by Foissner (1993), i.e. the vestibular opening is in the anterior half of the body and right and left oral ciliary field are approximately equal in length. The right vestibular wall of C. kaneshiroae usually extends utricle-like posteriad, as in Krassniggia, whose right oral ciliary field is, however, composd of disordered monokinetids (Foissner 1993). The right oral ciliary field of C. kaneshiroae consists of a single row of dikinetids as in Kuehneltiella (Foissner 1993). This is an important difference to the other genera of the family and might indicate that Corticocolpoda and Kuehneltiella are a distinct taxon, i.e. that the Colpodidae are polyphyletic. Howerer, similar exceptions are known from the Hausmanniellidae (Avestina) and Marynidae (Ilsiella), and most (all?) Colpoda species have an ordered row of dikinetids associated with the disordered basal bodies of the right oral ciliary field (Foissner 1993, Hofmann-Munz 1991).
The colpodids sensu lato, e.g. Platyophryides, are cosidered to represent the ancestral organization of the colpodids (Foissner 1993). They have, like C. kaneshiroae, grouped adoral organelles and a simple right oral ciliary field (paroral membrane) composed of a single row of ciliated dikinetids. It is tempting to speculate that C. kaneshiroae retained the ancestral organization and that the complex right oral ciliary field of Colpoda and related genera is a new acquisition. This would suggest two highly convergent evolutionary lines (Colpoda, Bresslaua, Maryna, Hausmanniella etc. on the one hand, and Corticocolpoda, Kuehneltiella, Ilsiella, and Avestina on the other). However, the last mentioned genera are rather specialized, both morphologically and ecologically, suggesting that their simple right oral ciliary field evolved by a secondary loss of the disordered ciliary field found in most genera of these families. This assumption seems more parsimonious than several convergent evolutionary lines. I thus suggest placing Corticocolpoda in the family Colpodidae.
No other species have been found in the literature that could be identical with C. kaneshiroae, Howeer, there are several species that superficially resemble C. kaneshiroae, viz. Krassniggia sp., Bresslaua spp., Bresslauides spp., and Kuehneltiella spp. In spite of these, C. kaneshiroae is easily determined, even in vivo, by the paired ciliary rows of the left oral ciliary field, which are well recognizable with bright field and especially with interference contrast microscopy. It is thus not necessary to use silver impregnations for a correct identification of this species, although such methods are recommended for revealing the inconspicuous right oral ciliary field. (ref. ID; 7299)
Occurrence and ecology
Corticocolpoda kaneshiroae must be a rare species since I did not find it in about 1,000 other soil, moss, and bark samples collected worldwide; it is probably endemic to the Hawaiian Archipelago. For sumptuous growth it needs substances contained in the bark, as mentioned in the material section. This distinguishes if from Colpoda cavicola, which thrives well in ordinary lettuce medium on bacteria or baker's yeast (Foissner 1993), although it has been found in nature almost exclusively in tree holes. (ref. ID; 7299)
Etymology
I dedicate this new species of the present Editor-in-Chief of the Journal of Eukaryotic Microbiology, Dr. Edna S. Kaneshiro, a native of Hawaii. The name "Kaneshiro" means "golden castle". (ref. ID; 7299)
Type location
Bark of Ohia trees (Metrosideros polymorpha) in the Bird Park of the Volcano National Park, Big Island, Hawaiian Archipelago, 155 degrees 20'W, 19 degrees 25'N. (ref. ID; 7299)
Type specimens
Two holotypes and two paratypes of C. kaneshiroae as four slides of protargol- (Wilbert technique) and silver nitrate- (Chatton-Lwoff technique) impregnated cells, respectively, have been deposited in the collection of microscope slides of the Oberosterreichische Landesmuseum in Linz, Austria. Accession numbers: 3-6/1993. (ref. ID; 7299)