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possibly contractile, found between 
the oral polykinetids of some tintinnid spirotrichs , 
containing curious, little understood extrusomes 
called capsules or capsules torquées , which are 
subspheroid, 200–600 nm in length. 
Tertiary Meridian : see Ciliary Meridian . 
Test : see Lorica . 
Tetrahymenal Buccal Apparatus : “tetrahyme-
nal” refers to the “four-membraned” nature of the 
ciliary organelles found in the oral region of many 
 oligohymenophoreans (e.g., members of the family 
 Tetrahymenidae ), which have a paroral or undulat-
ing membrane on the right of the buccal cavity
and three membranelles on the left; see Buccal
Apparatus (Fig. 2.7e). 
Tetrahymenium : see Tetrahymenal Buccal 
Apparatus . 
Theca : used in reference to the unusual envelope 
supporting certain operculariid peritrich species in 
particular; see Lorica . 
Thecoplasm : see mention under Spasmoneme . 
Theront : literally “hunter”; the dispersal stage in 
the polymorphic life cycle of a number of para-
sitic or histophagous ciliates (e.g., ophryoglenine 
 hymenostomes ); essentially a more or less trans-
formed tomite searching for a new host or for a 
fresh source of food; on finding food, the theront 
transforms to a trophont . 
Thigmotactic Area : see Somatic Region and 
Thigmotactic Cilia . 
Thigmotactic Cilia : generally used to denote a 
patch, area, tuft, field or zone of more or less spe-
cialized somatic ciliature functionally modified to 
serve a presumed sensory-tactile or an adhering 
function, often localized (e.g., as a group of con-
tiguous portions or segments of kineties occurring 
on the anterodorsal surface of the body in many 
 thigmotrich scuticociliates ); in certain astomes , 
and some other ciliates, the surface covered by 
the cilia may be concave and known as a sucker ; 
the scopula of many sessiline peritrichs may, in a 
broad sense, be considered to possess thigmotactic 
cilia; see Bristle and Holdfast Organelle (TC, 
Fig. 2.7c). 
Thigmotactic Zone : see Thigmotactic Cilia . 
Tissue-eating : see Histophagous . 
Tomite : a small, free-swimming, and non-feeding 
form derived by one or more fissions of a tomont
(or sometimes of a protomite ); a stage in the 
polymorphic life cycle of a number of parasitic
or histophagous ciliates; usually emerges with 
numerous others from a cyst within which the 
divisions of the tomont have typically taken 
place; the next stage is the theront or phoront
or trophont , depending on the species; the filial 
products of any binary or multiple fission could 
58 2. Glossary of Terms and Concepts Useful in Ciliate Systematics
be called tomites, but generally – by convention 
– they are not (Fig. 2.9Ah). 
Tomitogenesis : production of tomites; see also 
Palintomy (Fig. 2.9Af, 2.9Ah). 
Tomont : prefission or dividing stage in the poly-
morphic life cycle of a number of parasitic or 
histophagous ciliates (e.g., apostomes and ophryo-
glenine hymenostomes ); a large form, typically 
encysted, which may divide a number of times in 
quick succession; see Tomitogenesis . 
Tooth : see Capitulum . 
Total Conjugation : complete fusion of the 
micro - and macroconjugant ; a phenomenon 
exhibited by all peritrichs and chonotrichs , a 
number of suctorians , and a scattered few other 
ciliates; incorrectly considered to be syngamy ; 
see Conjugation . 
Toxicyst : slender tubular extrusome , located 
in the cytoplasm of predaceous, carnivorous 
 haptorians (e.g., Didinium and Dileptus ); often 
concentrated in great numbers at or near the 
apical end of the organism and in the oral 
cytoplasm; also found in the nonsuctorial 
tentacle of Actinobolina ; everting on discharge 
and apparently containing both paralytic and 
proteolytic enzymes, it penetrates, immobi-
lizes, and commences to cytolyze the prey; the 
Nesselkapseltrichocyste and, less familiarly, the 
cnidotrichocyst and the tubular trichocyst of the 
older literature (Fig. 2.9Ce). 
Transpodial Kinety (pl. Kineties ): somatic kine-
ties posterior to the podite or adhesive organelle; 
found in cyrtophorine phyllopharyngeans (TR, 
Fig. 2.4O). 
Transverse Fibers : see Transverse Microtubules . 
Transverse Fibrous Spur : dense (micro)fibrillar 
material associated with the proximal end of the 
kinetosome, arising near Triplet Number 3 (see 
Numbering Conventions ) and extending a short 
distance to the left and upward into the nearby pel-
licular ridge (TFS, Fig. 2.1Ee). 
Transverse Fission : see Fission and Homo-
thetogenic Fission . 
Transverse Microtubules : microtubular ribbon
arising at the left anterior side of the kinetosome 
close to Triplet Numbers 3, 4, and sometimes 5 
(see Numbering Conventions ); the ribbon, which 
may be composed of 4–6 (occasionally more?) 
cross-linked microtubules, may originate tangen-
tially or radially to the kinetosomal perimeter, 
first extends upward toward the pellicle and then 
continue to the left; in the oral region of litostomes , 
extensions of transverse microtubules are involved 
in the composition of the cytopharyngeal appara-
tus and/or rhabdos (T, Figs. 2.1, 2.2). 
Transversodesma (pl. Transversodesmata ): a 
complex set of overlapping transverse microtubular 
ribbons; characteristic of the Class COLPODEA ; 
also called the LKm fiber (Td, Fig. 2.2). 
Trichite : term used in at least two senses: (1) as an 
older and once highly popular, but now preferably 
discarded, name for a nematodesma, so promi-
nent especially in the cyrtos and rhabdos ; and (2) 
to describe the unique, rod-like, proteinaceous 
extrusome found in abundance in certain oligot-
richs (e.g. Strombidium ), usually radially arranged 
beneath the pellicle. 
Trichocyst : in the past, term used to embrace 
nearly all extrusomes found in ciliates; now prop-
erly limited to the rather prominent, spindle-shaped, 
non-toxic, explosive extrusome of peniculines , like 
Paramecium ; in the mature stage, consisting of an 
apical tip, shaped like an inverted golf tee, and a 
long, fusiform, fibrous shaft; on ejection, following 
an appropriate stimulus, acquiring a characteristic 
periodic structure; their function is often defensive; 
the fibrocyst of microthoracid nassophoreans is 
considered a special case; see Extrusome (Fig. 
Trochal Band : synonym for locomotor fringe
(TBd, Fig. 2.11B). 
Trochal Girdle : see Trochal Band . 
Trophic Nucleus : see Macronucleus . 
Trophont : mature, vegetative, adult form as an 
interfissional or feeding or growing stage in the life 
cycle of any ciliate; the term is most often used, 
however, in reference to the specific stage between 
tomite (or theront ) and tomont in the polymorphic 
life cycle of parasitic or histophagous species (e.g., 
as found among apostomes and hymenostomes ); a 
term with identical meaning is trophozoite (but see 
remarks under that word, below). 
Glossary 59
Trophozoite : typically used for the “feeding” stage 
of truly parasitic species of protozoa, such as 
apicomplexans; see Trophont , the preferred syno-
nym for ciliates. 
Tubercle : variously used; see Papilla . 
Tubicolous : tube-dwelling; used now and then with 
reference to loricate species (e.g. some folliculinids 
and a few spirotrichs ), which may only temporarily 
occupy their loosely fitting, tube-shaped, often 
gelatinous housing, in a manner reminiscent of 
some of the true tube-dwellers among the polycha-
ete annelids (Fig. 2.8Ak, 2.8Al). 
Tubular Trichocyst : see preferred term, Toxicyst . 
Tubulin : specific class of globular protein serving 
as the principal macromolecular constituent of all 
microtubules . 
Type-genus : nominal genus designated as the type 
of a family-group taxon and not to be removed from 
that taxon; the familial name must be formed from 
the stem of this generic name plus the appropriate 
suffix (-idae for family, -inae for subfamily). 

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