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 With the increasing contribution of data from 
other fields to the systematics of ciliates and 
the growing interest of biologists of all persua-
sions in these microorganisms, we ought today 
to be familiar with a far greater range of terms 
than was required in the past. The information 
offered below not only provides, in the aggre-
gate, a “thumbnail sketch” of most aspects in the 
overall biology of ciliates, but also permits use 
of the terminology in succeeding chapters with-
out the need to reexplain it there. Our treatment 
is not exhaustive – and many commonly known 
anatomical, cytological, and ecological words are 
purposely omitted – but this compilation is longer 
than those presented for ciliates by Corliss (1959, 
1961, 1979). It is principally based on those of 
Corliss (1979) and Lee (2002). 
 An attempt has been made to keep the definitions
or explanations succinct. However, brief descriptive 
comments have been added when terms are par-
ticularly complicated or important. Almost always 
we have included information identifying the taxo-
nomic group or groups of ciliates that possess or 
show the character or trait being described. Cross-
referencing is frequently employed, either directly 
or indirectly by italicizing selected words in the 
definition. We have tried to point out controversies, 
present alternative meanings, and give synonyms. 
Furthermore, we have indicated our own preferences. 
For many words derived from Greek or Latin, we 
have provided the suggested plural. If a plural is not 
provided, it is generally acceptable to add an “s” or 
“es” to the singular, as appropriate. A number of 
morphological features are illustrated in the figures 
at the end of this chapter, and are indicated by a 
direct reference to the labelled structure in the figure 
and its part (e.g., Kd, Fig. 2.1A). 
 Aboral : away from the oral region ; in ciliatology 
almost always used in the most extreme sense, 
meaning at the opposite (usually antapical) pole 
from the (other) end (usually apical) of the body 
bearing the mouth; but – as in the case of peritrichs
– the aboral pole is not necessarily the posterior 
pole of the organism, functionally and/or morpho-
logically and/or evolutionarily (Ab, Fig. 2.8Aj). 
Abyssal : pertaining to the great depths of the ocean 
well beyond the continental shelf. 
Accessory Comb : a conspicuous ridge lying bet-
ween the oral polykinetids, especially in tintinnids.
Acellularity Concept : once popular hypothesis 
that protozoa, being individually complete (yet 
organized without tissues) cannot be cellular and 
thus must be considered noncellular or acellular 
organisms; it is now widely recognized that setting 
such eukaryotic cells as ciliates – notwithstanding 
their complex subcellular organization and extra-
cellular specializations – apart from those of the 
“higher” metazoan groups is a decision basically 
neither defensible on (ultra)structural grounds nor 
judicious from a comparative evolutionary point of 
view; “cell” and “organism” need not be thought of 
as mutually exclusive terms. 
 Chapter 2 
 Glossary of Terms and Concepts 
Useful in Ciliate Systematics 
16 2. Glossary of Terms and Concepts Useful in Ciliate Systematics
Acetabulum (pl. Acetabula ): term rarely used in 
ciliatology; see Sucker . 
Acidosome : vesicle filled with acid that fuses with 
the food vacuole to promote digestion; particularly 
used in Paramecium . 
Aciliferous : see Nonciliferous . 
Acmocyst : extrusome of rhynchodid phyllopharyn-
geans . 
Acontobolocyst : see Trichocyst . 
Actinophore : structure bearing several, a bundle 
or a fascicle of suctorial tentacles ; characteristic of 
certain suctorians . 
Adhesive Disc : thigmotactic cup-shaped organelle at 
the aboral pole of mobiline peritrichs and some other 
ciliate (e.g., some spirotrichs ) used for attachment 
to the substratum, usually the surface of another 
organism that serves as host (Fig. 2.9Bg, 2.9Bh). 
Adhesive Organelle : often restricted to a secretory 
structure responsible for or structurally involved in 
production of a substance, other than cilia or some 
ciliary derivative, allowing the organism possess-
ing it to adhere or attach to the substratum (e.g., 
the podite of dysteriid cyrtophorines ); but also see 
Holdfast Organelle (AO, Fig. 2.9Bf). 
Adoral Ciliary Fringe : see Frange . 
Adoral Ciliary Spiral : often applies to the spiral-
ling pattern of the oral haplokinety and polykinety of 
 peritrichs ; see Adoral Zone of Oral Polykinetids
(Fig. 2.6b; ACS, Fig. 2.11B). 
Adoral Zone of Membranelles : see Adoral Zone 
of Oral Polykinetids . 
Adoral Zone of Oral Polykinetids : orderly arrange-
ment of three or more oral polykinetids serially 
arranged typically along the left side of the oral 
region ; this arrangement has evolved by convergence 
in different groups of ciliates (e.g. heterotrichs , 
 spirotrichs , colpodeans ) (Opk, Fig. 2.5Aa). 
Adult Form : generalized term; depending on the 
situation, the mature form, the parental form , the 
interfissional form, the sessile or sedentary form, 
the trophont . 
Afferent Canal : one of usually several cytoplas-
mic channels transporting excreted fluid from the 
spongioplasm to a contractile vacuole ; also called 
a pulsating, nephridial, collecting, or radial canal; 
see Secretory Ampulla . 
Aire Sécante : see Secant System . 
Akontobolocyst : a synonym of spindle trichocyst; 
see Trichocyst . 
Algivorous : feeding on algae; see also Macro-
phagous and Microphagous . 
Alpha Membranoid : see Membranoid . 
Alveolate(s) : protists whose pellicle is characterized
by pellicular alveoli ; includes at least apicomplexans , 
ciliates, dinoflagellates , and colpodellids . 
Alveolocyst : an extension of the pellicular alveolus
into the underlying cortex; particularly characteristic 
of nassulids . 
Alveolus (pl. Alveoli ), Pellicular : flattened vesicle 
or sac, bounded by a unit membrane , lying just 
beneath the surface or plasma membrane of the cell 
(organism) and above the epiplasm ; may occur in 
pairs in a given kinetosomal territory ; also known 
as a cortical vesicle (PA, Fig. 2.1B). 
Amacronucleate : without a macronucleus ; rare, 
unnatural, unstable condition, realizable only 
experimentally (e.g., in Paramecium ). 
Ambihymenium (pl. Ambihymenia ): condition 
of having oral ciliary “membranes” completely 
surrounding the mouth-area; claimed by some 
workers to be the situation obtaining in a number 
of the cyrtophorine phyllopharyngeans. 
Amicronucleate : without a micronucleus , whether 
the loss has been brought about naturally or experi-
mentally (e.g., in Tetrahymena ). 
Amitosis : nuclear division that results in the irregular 
distribution of chromosomes; a pathological kind of 
mitosis; however, unequal distribution of “chromo-
somal” elements in the polyploid macronucleus of 
ciliates might be considered a kind of amitosis. 
Amphiparakinetal : parakinetal stomatogenesis in 
which the curved oral anlage intersects many pos-
toral somatic kineties at two sites, enclosing few 
to many, short, non-proliferating kinetofragments ; 
found in some heterotrichs . 
Ampliploid : the nuclear condition in which there 
are numerous replicates of fragments of chromo-
somes, sometimes as small gene-sized pieces, 
Glossary 17
produced by an amplification process and not by 
mitosis; characteristic of the ciliate macronucleus ; 
see Polyploid . 
Ampule : small, ovoid extrusome in the dorsal 
cortex of hypotrich spirotrichs (e.g. Euplotes ), and 
associated in clusters with kinetids of the dorsal 
bristle kinety ; may be involved in sexual interactions. 
Ampulla (pl. Ampullae ), Secretory : glandular 
organelle, generally multiple in number, which pro-
duces a thigmotactic substance or structure in some 
cyrtophorines (see Adhesive Organelle ); also used 
for the collecting canal (or