Thigmokeronopsis

• Buccal apparatus. The membranelles are paramembranelles (as defined by Puytorac and Grain 1976) and each comprises 4 rows of kinetosomes: the first (posteriormost) and second are of equal length and are the longest rows (~40 kinetosomes), the third is shorter (~25 kinetosomes) and the fourth row is the shortest with only 3-6 kinetosomes. In general, the membranelles in the middle lapel region have longer rows than membranelles in either proximal or distal regions. A series of microfibillar units couch the proximal edge of both anterior and posterior rows of membranellar kinetosomes and extend toward the cell surface. Both inter and intramembranellar fibrillar connections are present. Nematodesmal microtubules originate near the proximal end of membranellar kinetosomes, plunging into the cytoplasm at a slight posterior angle. Groups of mitochondria are arranged between these fibers. Transverse microtubular ribbons are associated with the third and fourth membranellar rows; these originate at the middle zone of the kinetosome and extend toward the cell surface within an intermembranellar ridge that separates each membranelle. Postciliary microtubular ribbons originate from the posterior border of the first kinetosomal rows, run toward the cell surface within the intermembranellar ridge, meeting the transverse microtubules of the adjacent membranelle. The postciliary ribbon then courses left along the intermembranellar ridge, joins postciliary ribbons from other kinetosomes within the row and unites with ribbons from other membranelles to form a postmembranellar fiber. This fiber runs posteriorly along the left border of the lapel membranelles and subtends the proximal membranelles. To the right of each membranelle are found additional bundles of microtubules. These extend along the left wall of the buccal cavity and are probably the supporting elements of the ribbed wall observed in SEM. Electron opaque vesicles are found near the cell surface bordering the membranelles and within the intermembranellar ridges. These osmophilic vesicles are presumed to be the yellow-green granules observed at the light microscope level. At times they appear to be expelled from the cell surface. The single row of kinetosomes of the endoral membrane lies within the dorsal wall of the buccal cavity and continues toward the cytostome, well beyond the posterior limit of the paroral membrane and the proximal membranelles. The anterior end of the endoral membrane is oriented with the distal end of kinetosomes nearest the ventral surface of the cell; as the row desends into the buccal cavity, it rotates 180 degrees along its longitudinal axis until the proximal end of each kinetosome is nearest the cell's ventral surface. This causes the proximal microtubules of each kinetosome to appear as a clockwise chartweel. This rotation is not, however, reflected in the position of the postciliary and transverse microtubules: postciliary microtubules originate from the right and transverse microtubules arise from the left of each kinetosome. The paroral membrane is a longitudinal series of short (1-6 kinetosomes) oblique rows that lies within a pellicular grove on the right buccal overture. The rows are longer in the middle and shorter toward the anterior and posterior ends of the membrane. Postciliary microtubules originate near the right (posterior) kinetosome and transverse microtubules arise near the left (anterior) kinetosome of each oblique row. Nematodesmal microtubules plunge into the cytostome from the proximal part of the paroral kinetosomes; these fibers join with the postmembranellar fiber as it curves around the proximal membranelles and extends anteriorly. (ref. ID; 7590)
• Cirri. The midventral ciliature consist of 2 rows of parallelogram shaped cirri running along the longitudinal axis of the cell; each right midventral cirrus comprises 3 rows of 6-7 kinetosomes oriented at a 60 degrees angle to the cell's longitudinal axis, whereas each left midventral cirrus is an assemblage of three rows of 5-6 kinetosomes lying at a 75 degrees angle. These angles become less acute in cirri anterior to the cytostome. Thigmotactic cirral bases usually consist of 2 rows or 2-6 parallelogram arranged kinetosomes (although packets of 3 kinetosomes can also be found). Marginal cirri comprise 2 rows of 5-7 kinetosomes arranged at a 60 degrees angle to the cell's main axis. A closer look at a right midventral cirrus reveals each kinetosomal packet to be surrounded by an electron opaque microfibrillar matrix. A similar microfibrillar system connects neighboring kinetosomes. Four microtubular bundles originate from the microfibrillar peripheral matrix of the cirral base: an anterior bundle (7.5 um), a posterior bundle (~6 um), a right bundle (~5 um), and a left bundle (~3 um). Posterior, right, and left microtubular bundles extend toward the cell surface while the anterior microtubular bundle runs parallel to the main axis of the cell, to join with the right posterior margin of the left midventral cirrus. In this way, right and left midventral cirri are linked in an oblique, ladder-like array. Linear groups of microtubules, originating from the microfibrillar cirral matrix, border both anterior and posterior kinetosomal rows: these extend directly to the pellicle forming a basket-like framework around the cirrus base. A similar system of microtubular ribbing borders thigmotactic and marginal cirri. Transverse microtubules arise from the far left kinetosomes of each cirrus and also extend directly toward the cell cortex. Postciliary microtubules originate at the far right kinetosomes of each cirrus and also extend directly toward the cell cortex. Postciliary microtubules originate at the far right kinetosomes, then join the posterior microtubular bundle as it courses at an oblique angle toward the cell surface. Single postciliary microtubules are associated with triplet number 9 of internal cirral kinetosomes. (ref. ID; 7590)

Type locality

Measurements