Colpodidium
Colpodidium Wilbert, 1982 (ref. ID; 4861, 7706)
Suborder Colpodina Foissner, 1978: Colpodidiidae Puytrac et al., 1983 (ref. ID; 7706)
[ref. ID; 4861]
Improved diagnosis; Colpodidiidae with short, slightly curved paroral membrane, 1 large adoral organelle and two postoral kineties with dikinetids anteriorly. (ref. ID; 4861)
Type species; Colpodidium caudatum Wilbert, 1982 (by monotypy) (ref. ID; 4861)
- Colpodidium caudatum Wilbert, 1982 (ref. ID; 4861)
Colpodidium caudatum Wilbert, 1982 (ref. ID; 4861 redescribed paper)
Redescription
Size in vivo about 55-70x25-35 um, lateral view reniform to Dexiostoma (Colpidium)- shaped, ventral view fusiform with both ends rounded, laterally slightly to distinctly (2:1) flattened. Macronucleus globular, in posterior half to quarter of cell, contains roundish nucleoli. Micronucleus globular, in indentation of macronucleus. Contractile vacuoles subequatorial, with single excretory pore underneath buccal cavity. Cytopyge in median of cell between excretory pore of contractile vacuole and posterior end of cell, often underlain by bright, seemingly empty vacuole. Cortex thick, glassy, distinctly furrowed by ciliary rows, in one population colonized by epibiontic bacteria. Exrusomes recognizable neither in vivo nor in silver carbonate of protargol stained cells. Cytoplasm colourless, contains many 1-2 um sized, brightly shining fat droplets, mainly in posterior half of body; no crystals. Food vacuoles 5-10 um in diameter, usually containing only few bacteria and/or food residues. Swims rapidly by rotation about longitudinal body axis. Somatic cilia about 10 um long and rather stiff, single except for few pairs at anterior end of postoral kineties 2, 3, 4. Silver carbonate impregnations show each kinetid composed of a large granule, which bears the cilium and short kinetodesmal fibre extending obliquely anteriad, and of a small granule, possibly a parasomal sac or an alveolocyst. Distances of kinetids increase within kineties from anterior to posterior, those of first kinety right of oral apparatus especially closely spaced in anterior portion. Ciliary rows bipolar on dorsal side, those on ventral surface form long and narrow preoral suture, because anterior left kineties abut obliquely on anterior right kineties which gradually shorten from anterior end of cell to oral apparatus. Four postoral kineties: first kinety commences very close to anterior end of paroral membrane, second in buccal cavity very near pharyngeal opening, third at distal end of adoral organelle, fourth left of excretory pore of contractile vacuole. No elongated caudal cilia. Oral apparatus slightly above mid-body, with conspicuous tube-shaped buccal cavity containing single, large adoral organelle and anterior end of postoral kinety 2. Adoral organelle in posterior vertex of buccal cavity, slightly curved, composed of 3 rows of ciliated basal bodies. Paroral membrane at right margin of buccal cavity, slightly curved, composed of distinctly inclined dikinetids having only anterior basal bodies ciliated; distances between dikinetids increase from anterior to posterior. Cytopharyngeal basket large but delicate, thus not recognizable in vivo and also faintly stained with protargol, composed of about 10 thin nematodesmal bundles; commences in upper vertex of buccal cavity, which appears more intensely stained at this site, and extends as wide, somewhat irregular tube almost to anterior end of cell where it curves dorsally and posteriorly. Silverline system tightly and irregularly meshed in somatic and oral cortex, meshes within ciliary rows often filled with argyophilic substance. (ref. ID; 4861)
Morphogenesis: A few middle, late and very late dividers were found in the preparations. The middle and late stages show 2 very small adoral organelles ahead of the large adoral organelle and reorganization of the parental paroral membrane and cytopharyngeal basket. In very late dividers a small (5x2.5 um), distinctly stained cytopharyngeal basket is appearent in both proter and opisthe; the 2 small adoral organelles disappear or are at least no more recognizable. (ref. ID; 4861)
Remarks
I have no doubt about the identification, although my observations differ in many significant details from those of Wilbert (1982), who obviously observed superficially, at least the living cells, and misinterpreted the silver nitrate preparations. These show paired granules (cilia according to Wilbert) which are not recognizable in his micrographs from protargol impregnated specimens. Obviously, one of the two granules is a parasomal sac or an alveolocyst. I checked very carefully the absence of paired cilia in vivo, in silver carobonate preparations, and in protargol slides. Furthermore, Wilbert (1982) described an "upper ciliary field" (membranelle) deep in the buccal cavity. Such a field is lacking in my specimens. Very likely, Wilbert (1982) misinterpreted the pharyngeal fibres (entrance) as a membranelle, because he figured this structure exactly at the site where the pharyngeal basket commences in my specimens. A third difference concerns the location of the contractile vacuole, which Wilbert drew rather far to the rear in his Figure 1 (living aspect), while it is located subequatorially in my specimens and in Wilbert's Figure 3a, which shows a silver nitrate impregnated cell. Obviously, Wilbert (1982) drew the oral apparatus and the contractile vacuole too near to the posterior end in Figure 1. Next, Wilbert (1982) stated that C. caudatum lacks a silverline system. In fact, I was also unable to impregnate it with the Chatton-Lwoff technique but it stains well with Klein's dry silver method. Finally, Wilbert (1982) claimed that C. caudatum divides in cysts. This is obviously not the case. Colpodidium caudatum was also redescribed by Dragesco & Dragesco-Kerneis (1986). However, their species differs greatly from the populations investigated by Wilbert (1986) and myself, especially in the size of the paroral membrane. In fact and as the authors suppose, it is a new species which I also found recently in several African soils. It has not only a much larger paroral membrane but also very peculiar extrusomes, which were overlooked by Dragesco & Dragesco-Kerneis (1986), who apparently did not study the species in vivo. (ref. ID; 4861)
Type specimens deposited
Slides with type and voucher specimens have been deposited in the Oberosterreichische Landesmuseum in Linz (LI), Austria. Relevant specimens are marked by a black ink circle on the cover glass. (ref. ID; 4861)