Thigmokeronopsis
Thigmokeronopsis Wicklow, 1981 (ref. ID; 7590 original paper)
[ref. ID; 7590]
Diagnosis; Somatic ciliature includes dorsal bristle rows, one left and one right marginal cirral row; frontal ciliature includes migratory, midventral, transverse, malar, and thigmotactic cirri. Thigmotactic cirri form a left, post-oral ciliary field used for adhesion to substate. Multimacronucleate. (ref. ID; 7590)
Type species; Thigmokeronopsis jahodai (ref. ID; 7590)
- Thigmokeronopsis jahodai Wicklow, 1981 (ref. ID; 7590 original paper) reported author and year? (ref. ID; 191, 3682)
Thigmokeronopsis jahodai Wicklow, 1981 (ref. ID; 7590 original paper) reported author and year? (ref. ID; 191, 3682)
Descriptions
When subjected to a current (such as water forced from a pipette) the cell adheres firmly to the substrate. Adhesion is accomplished by a thigmotactic ciliary field. Irregular groups of yellow-green granules are scattered subcortically through the cytoplasm. These structures are more numerous on the dorsal surface. A buccal cavity plunges ~50 um into the cytoplasm from the posterior buccal overture. Food vacuoles contain numerous and sundry diatoms. Over 100 oval macronuclei are dispersed throughout the cytoplasm. Hyptorichs possess 3 kinds of ciliature: buccal, frontal and somatic (Borror 1979). Buccal ciliature in Thigmokeronopsis consists of ~75 membranelles and a two part undulating membrane: an endoral membrane consisting of a single row of cilia and a paroral membrane consisting of multiple arrays of cilia. Somatic ciliature includes 4 rows of dorsal bristles; each bristle complex contains 2 kinetosomes -the anterior is ciliated, the posterior is not. One left marginal and one right marginal row of cirri are also present. Frontal ciliature comprises paroral (buccal), malar, midventral, transverse, migratory, and thigmotactic cirri. A single paroral cirrus lies just anterior to the buccal cavity and 2 malar cirri lie adjacent to the paroral membrane. Just right of the paroral cirrus and curving to the posterior end of the cell are 2 rows of ~54 midventral cirri; a U-shaped group of transverse cirri subtends this series. Two migratory cirri are present to the right of the midventral row, just posterior to the distal collar membranelles. A cirral field, located between the midventral and left marginal cirral rows, consisting of a series of ~42 transverse rows, compose the thigmotactic ciliature. (ref. ID; 7590)
Ultrastructure:
- 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)
Morphogenesis: Cortical morphogenesis in Thigmokeronopsis occurs in 2 latitudinal developmental zones: an anterior field of the future proter and a posterior field of the future opisthe. The first morphogenetic event within these zones is initiation of oral primordia (OP) by proliferation of kinetosomes from the left midventral cirri in the opisthe and from the dedifferentiated endoral membrane in the proter. Development occurs on the cell surface. An undulating membrane primordium (UMP) forms at the right edge of the OP in both the proter and opisthe. At this stage, membranelles begin to differentiate within the OP in a posteriad direction (membranellar organization in the opisthe proceeds that of the proter). Paroral and endoral membranes differentiate from the UMP and a paroral cirrus develops from the anterior end of the paroral membrane. Meanwhile, the membranelles and the endoral membrane from within, and the paroral membrane along the right side of, the new buccal cavity. Both membranes are oriented with cilia directed outwardly. As development of the buccal cavity proceeds, the endoral membrane (probably because of cortical flow) becomes twisted, resulting in the cilia being directed inwardly toward the cytostome. To the right of the proter OP, following the dedifferentiation of the paroral membrane and malar cirri, a frontal cirral primordium (FP) appears. As the FP develops, it elongates into a series of oblique streaks that lie within a newly formed cortical invagination. Two malar cirri differentiate from the anteriormost frontal streak; these eventually lie beside the paroral membrane. Three kinds of cirri differentiate from the last 10 frontal streaks; midventral, transverse and, from the last streak only, 2 additional cirri. These 2 migratory cirri are formed at the right edge of the last streak, then migrate anteriorly alongside the right midventral row until they are positioned behind the distal membranelles. The 10 transverse cirri eventually subtend the midventral rows. In addition to midventral cirri, all remaining frontal streaks differentiate thigomotactic cirri. A similar FP develops alongside the midventral cirri in the opisthe. This field becomes separated from the OP by a cortical ridge, later to become the right buccal overture. Development of this FP proceeds as in the proter. Marginal primordia (MP) and dorsal bristle primordia (DBP) appear early in the developmental process. Both originate dorsal to old marginal cirral rows; right and left MP are closely associated with the first and last DBP. Only after new sets of ciliature for both proter and opisthe have differentiated, do the remaining parental structures begin to be disassembled and resorbed. (ref. ID; 7590)
Type locality
Surface sediments (mostly gravel and crushed shell) of Great Bay near Jackson Estuarine Laboratory, Adams Point, New Hampshire. (ref. ID; 7590)
Measurements
Cell length ranges from 180-240 um (average=208 um, n=20), cell width ranges from 55-85 um (average=67 um, n=20). The ciliate is supple and slightly contractile; a 200 um individual can stretch to 400 um when feeding actively. (ref. ID; 7590)