Main Content
< Top page

The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Paraspathidium

Paraspathidium Noland, 1937

[ref. ID; 1618]
Body cylindrical; cytostome an elongate slit, bordered on one side by strong cilia and on the other by weaker cilia and a shelf-like, nonundulatory membrane; two longer cilia on dorsal edge near anterior tip; anterior one-third compressed; posterior two-thirds nearly cylindrical; two oval macronuclei, each with a micronucleus; cytoplasm filled with numerous refractile granules; about seventy rows of cilia; contractile vacuole terminal; salt water. One species. (ref. ID; 1618)
  1. Paraspathidium fuscum (Kahl, 1928) (ref. ID; 3119) reported year? (ref. ID; 1618, 1879, 2117) or (Kahl, 1928) Fjeld, 1955 (ref. ID; 2858 redescribed paper)

Paraspathidium fuscum (Kahl, 1928) (ref. ID; 3119) reported year? (ref. ID; 1618, 1879, 2117) or (Kahl, 1928) Fjeld, 1955 (ref. ID; 2858 redescribed paper)

Descriptions

The redescription is based on cultured specimens studied in live and with the scanning electron microscope as well as on protargol and silver carbonate-impregnated cells. However, P. fuscum is very difficult to stain. This is not unlikely because feeding specimens strongly contract becoming urceolate. Shape likewise fairly variable, usually, however, cylindrical or slightly bursiform and highly reminiscent of slender spathidiids (cp. Kahl, 1930); anterior mouth-bearing portion more or less distinctly widened and obliquely truncate, posterior end narrowly rounded, laterally slightly flattened. Nuclear apparatus on average slightly underneath mid-body, invariably consisting of two ellipsoidal (about 2:1) macronuclear nodules with a single micronucleus in between. Contractile vacuole in posterior end, associated with many fine and anastomosing collecting canals extending to at least mid-body; very likely, these canals were interpreted as satellite vacuoles by Dragesco (1960, 1963). Extrusomes in vivo about 10x0.5 um, concentrated around pharyngeal basket and scattered throughout cytoplasm, consist of fusiform posterior half, which stains with protargol, and filiform anterior portion having minute globule on top. This particular shape of the extrusomes, highly reminiscent of exploded toxicysts, was seen in 10 specimens and thus very likely represent the resting state. Cortex about 2 um thick, stands out as bright fringe from darkly granulated cytoplasm, distinctly punctate by deep ciliary pits, very flexible and gelatinous, contains innumerable tiny granules in small bolsters between ciliary rows; cortical granules irregularly shaped, 0.1-2 um across, stain blue with methyl green-pyronin but are not extruded when dye is added. Cells, respectively, cytoplasm conspicuously dark at x100 due to countless, highly refractive inclusions; mouth region, macronuclear nodules, contractile vacuole, and food vacuoles stand out as bright blisters; inclusions colourless ellipsoidal to roughly globular, some possible hollowed, 3-6x2-4 um in size. Slowly gliding on bottom of culture dishes or swimming by rotation about main body axis, usually, however burrowing in and under mats of sulphur bacteria ingesting small ciliates (mainly Euplotes), which break in pieces when touching mouth opening. Somatic cilia 8-10 um long, very regularly arranged in bipolar and transverse rows, originate from deep cortical pits producing curious, cross-hatched cortical pattern, as already noted by Kahl (1928) and Noland (1937). Cilia single (monokinetids), except at anterior end of kineties, where 5-10 narrowly spaced, ciliated dikinetids occur producing conspicuous perioral ciliary corona. Anterior dikinetids associated not only with the usual set of fibres (short, anteriorly directed kinetodesmata and very short transverse microtubule ribbon), but also with long nematodesma supporting cytopharyngeal basket. Dorsal brush highly complex, difficult to study because short and in deep cleft at dorsal anterior end of cell, consists of two or three rows of transversely oriented dikinetids bearing up to 25 um long, curiously vase-shaped cilia; left row with monokinetidal tail extending above mid-body and bearing 15-20 um long cilia having filiform process. Long, vase-shaped brush cilia accompanied by about 5 um long, rod-shaped cilia. Oral apparatus in widened anterior end of cell. Oral opening apical, elliptical, excavated (i.e. not closed), surrounded by inconspicuous oral dome. Circumoral kinety at base of oral dome, made of dikinetids having, like dorsal brush, about 15 um long, vase-shaped cilia. Inner wall of oral dome striated by fine fibres forming inconspicuous, campanulate cytopharyngeal basket. (ref. ID; 2858)

Measurements

About 220 um long; macronuclei 44 um long each. (ref. ID; 1618)
Length:width ratio, and shape highly variable, as also indicated by literature data (200-500 um, 8-13:1; Agamaliev 1968, 1983; Dragesco 1960; Fjeld 1955; Kahl 1928; Noland 1937). Cultured Roscoff specimens in vivo about 220-350x40-60 um, length:width ratio 4:1-9:1, on average 6.5:1 (n=11); contractile slightly during fixation, prepared specimens thus shorter than live cells (length:width ratio 3.5-6:1, on average 5:1). In vivo very flexible and about 30% contractile, especially in anterior half, as also observed by Kahl (1928) and Biernacka (1963); however, later Kahl (1930) stated that P. fuscum can contract up to 2/3 of its length. (ref. ID; 2858)