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anterior to the 
rosette during tomitogenesis in many apostomes ; 
this pointed, arch-shaped patch of specialized cilia 
facilitates attachment of the tomite to a new substra-
tum, generally a crustacean integument. 
Oligomerization : postulated evolutionary process 
of reduction or diminution, but not necessarily sim-
plification, in the usual numbers of some organelle 
(e.g., in numbers of kineties over a ciliate’s body); 
see Polymerization . 
Oligoploidy : see Polyploid . 
Oligosaprobic : see mention under Polysaprobic . 
Oligotrichous : having sparse somatic cilia ; 
typically of ciliates in the spirotrich Subclasses 
 Oligotrichia and Choreotrichia , but also found in 
some stichotrichs (e.g., Halteria ) and haptorians 
(e.g., Didinium ); see Holotrichous . 
Oligotrophic : see Eutrophic . 
Omikron : Gram-negative bacterial endosymbiont
 in the cytoplasm of the hypotrich Euplotes ; often 
indispensable to their hosts’ life; see Xenosome . 
Omnivorous : eats everything(!); such ciliates are 
not at all “fussy” in their feeding habits. 
Ontogeny (pl. Ontogenies ; adj. Ontogenetic ): history 
of an individual, from egg to adult; by analogy, in 
the case of a ciliate, it is the growth and development 
from a filial product , the tomite , to the mature 
trophont or tomont , ready for another fission, in 
the full life cycle of the organism; comparative 
study of the patterns revealed in the morphogenesis
associated with such ontogenetic development may 
throw light on the phylogeny of the group concerned 
(phylembryogenesis); see also Biogenetic Law . 
Operculum (pl. Opercula ): literally, lid or cover-
ing flap; used variously (e.g., as the cover of the 
emergence pore of some cysts), but mostly for 
two quite different structures both in sessiline 
 peritrichs : (1) the stalked epistomial disc present 
in many of the operculariids ; and (2) the organelle 
attached to the anterior end of the body, as a stalked 
“cap” at an oblique angle to the epistomial disc, 
which may wholly or partially cover the opening of 
the lorica on retraction of the organism into its case 
in some of the loricate vaginicolids (e.g., Pyxicola ) 
(Opr, Figs. 2.8A, 2.9Ad). 
Ophryobuccokinetal : buccokinetal stomatogen-
esis in which the opisthe’s oral anlage derives 
from one to several ophyrokineties and the paroral ; 
found in some peniculians . 
Ophryokinety (pl. Ophyrokineties ): literally 
“brow” kinety ; one of three or more somatic 
kineties, often with dikinetids and single associ-
ated parasomal sac forming a triangular group as 
revealed in silver-impregnated material; on the 
ventral surface near the anterior end of the body 
and located immediately to the right of the buccal 
cavity proper (e.g., in the peniculine Frontonia ); 
generally, but inappropriately called vestibular 
kineties, may represent a legitimate part of the 
buccal ciliature sensu lato in the organisms bearing 
them, and hence be considered perioral ciliature
(OK, Fig. 2.7h). 
Opisthe : posterior filial product of a regular binary 
fission of the parental form ; the anterior ciliate 
resulting from such a division is the proter (Fig. 
Oral Anlage : see Anlage and Oral . 
Oral Apparatus (pl. Apparati ): the entire com-
plex of structures and organelles involved in or 
directly related to the cytosome and functionally 
integrated for the acquisition and ingestion of food; 
multiple in suctorians and absent in astomatous 
ciliates (OA, Fig. 2.11Aa). 
Oral Area : see Oral Region . 
Oral Atrium (pl. Atria ): see Atrium . 
Oral Cavity : an indentation or depression that 
contains part or all of the oral apparatus ; see 
Buccal Cavity (OC, Fig. 2.5c). 
Oral Ciliature : simple or compound cilia that are 
directly associated with the oral apparatus ; associated
with it would be the bases of all such structures, the 
42 2. Glossary of Terms and Concepts Useful in Ciliate Systematics
oral infraciliature (as opposed to kinds of somatic
ciliature ). 
Oral Disc : specialized name for the apically 
located oral region of a ciliate when it is conspicu-
ously separated from the rest of the body (e.g. in 
the hourglass-shaped spirotrich Licnophora ). 
Oral Groove : generalized term for a depression 
leading to a buccal cavity or a cytostome ; widely 
used in the past for Paramecium to indicate what 
was more recently termed vestibulum and now 
considered to be a kind of prebuccal area in that 
organism; see Vestibulum . 
Oral Infraciliature : see Oral Ciliature . 
Oral Polykinetid : general term for organellar 
complexes in the oral region that are composed 
of many, usually ciliferous kinetosomes; see 
Polykinetid (OPk, Figs. 2.5Aa, 2.5Ab, 2.7a, 2.7b, 
2.7i; 2.4G, 2.4R, 2.7k, 2.7l). 
Oral Primordium : synonym of oral anlage . 
Oral Region : that part of the ciliate’s body bearing 
the oral apparatus ; convenient to use in a non-specific 
way; to be contrasted with the somatic region (the 
rest or bulk of the body); buccal area , a more restric-
tive term, is not to be considered a synonym. 
Oral Replacement : see Stomatogenesis . 
Oral Ribs : argentophilic pellicular ridges of a 
non-naked ribbed wall ; appearing, under light 
microscopy, to represent lines coursing inwardly 
in a one-to-one ratio from the kinetosomal bases 
of the right-hand paroral ; found in many oligohy-
menophoreans (OR, Fig. 2.7e). 
Organellar Complex : consistently recognizable 
subcellular structures responsible for subsidiary 
cell functions and composed of a specific associa-
tion of unit organelles ; see Organellar System . 
Organellar System : an organization of organel-
lar complexes integrated to perform a major (i.e., 
systemic) cellular function (e.g., locomotion, 
osmoregulation, feeding and ingestion, digestion). 
Organelle of Fixation : see Attachment Organelle . 
Organic Pollution : see Polysaprobic and Saprobity 
System . 
Orthogenetic Line : supposed evolutionary series
that has allegedly followed a predetermined pathway 
and has not invoked nor been subject to the laws of 
natural selection; such proposed phylogenetic lines 
are rejected by modern evolutionary theory. 
Orthography : correct or conventional spelling. 
Orthomere : DNA-rich karyomere of a heteromer-
ous macronucleus ; to be contrasted with the para-
mere , the other kind of karyomere in that type of 
nucleus (Om, Fig. 2.12r, 2.12bb). 
Orthonematocyst : extrusome in which the mate-
rial to be extruded appears as a capped, straight 
tubular filament embedded in a matrix whose outer 
portion appears to be composed of myelin-like 
sheets; the ciliate organelle is unlikely homologous 
to the nematocyst of the cnidarians; found in the 
 karyorelictean Remanella . 
Osmotrophic : see Saprozoic
Palintomic (adj.): see Palintomy . 
Palintomy (adj. Palintomic ): rapid sequence of 
binary fissions , typically within a cyst and essentially 
without intervening growth, resulting in production 
of numerous, small-sized filial products or tomites ; 
characteristic of various parasitic ciliates, including 
some apostomes, the hymenostome Ichthyophthirius , 
and a few others; the net result is similar to that of 
polytomic divison (Fig. 2.9Af, 2.9Ah). 
Palp : variously used, often for a protuberance of 
the body with an alleged sensory function. 
Papilla (pl. Papillae ): variously used; often referring 
to the pellicular or extrapellicular wart-like bumps 
or small protuberances on the surface of an organism 
(e.g., on the bell of some sessiline peritrichs and on 
the body of certain chonotrichs ); in a broad sense, 
tubercle may be considered a synonym. 
Paradiploid : condition of ploidy of the macronu-
cleus of karyorelicteans ; very close to the diploid 
DNA amount, hence “para”-diploid; see Diploid
and Polyploid . 
Parakinetal : type of stomatogenesis in which 
the anarchic field of kinetosomes