see also Secant System . Longitudinal Microtubule(s) : a single microtu- bule or ribbon or band in the pellicle subjacent to the plasma membrane , running longitudinally down the body between the kineties; found in some oligohymenophorean ciliates. Lorica (pl. Loricae ): secreted and/or assembled test, envelope, case, shell, or theca; may be calcare- ous, composed of some proteinaceous or mucopoly- saccharide secretion, including chitin, pseudochitin, or tectin, or made up of foreign matter (e.g., sand grains, diatom frustules, coccoliths, debris); found most commonly in peritrichs , folliculinids , and tin- tinnines , with the important properties of fitting the body loosely, opening at one (anterior) end (or occa- sionally both ends), and being either attached to the substratum or carried about by the freely-swimming organism (e.g., by tintinnines); may occur in a mul- tiple (arboroid-tree) state; such a “house” or “tube” may be occupied only temporarily (e.g., as is true in the case of some stichotrichs) (Figs. 2.4S, 2.8A). Loricastome : specialized opening or aperture, sur- rounded by thickened but movable lips, in the rigid lorica of lagenophryid peritrichs ; the buccal cilia- ture may be extended through the aperture when it is open, the migratory larval form exits through it, and microconjugants can enter through it. Lysosome : cytoplasmic organelle bounded by a unit membrane and containing hydrolytic enzymes; see Golgi Apparatus . 36 2. Glossary of Terms and Concepts Useful in Ciliate Systematics M Macroconjugant : larger member of a pair in con- jugation , and the only surviving conjugant in cases of total conjugation , such as in peritrichs ; a little- used synonym is macrogamont . Macrogamont : see Gamont , Macroconjuant . Macronuclear Anlage (pl. Anlagen ): nucleus that begins development from one of the diploid division products of the synkaryon and finishes development as the typically highly polyploid macronucleus . Macronuclear Evolution Hypothesis : origin of the complex, nearly autonomous, polyploid macro- nucleus typical of the great majority of contemporary ciliates from a preceding diploid and non-dividing form (stage 2), which, in its turn, supposedly arose – concomitant with the first micronucleus – from a single nucleus (i.e., homokaryotic stage 1), before the differentiation that led to nuclear dualism ; appli- cation of this idea to ciliate systematics is enhanced by recognition of the actual existence today of sup- posed karyological relicts assignable to the first two postulated stages as well as to the last, stage 3, which is today the predominant condition. Macronucleus (pl. Macronuclei ): so-called veg- etative, trophic or transcriptionally active nucleus; controls the organism’s phenotype; may be multi- ple, but even then is typically much larger than the micronucleus ; most often compact, spherical or ellipsoidal, but sometimes of diverse other shapes (e.g., reniform, moniliform, filiform, dendritic, halteriform, C- or E-shaped); typically ampliploid or polyploid , but diploid or paradiploid in the karyorelicteans , with respect to its genomic con- tent; commonly contains numerous small nucleoli ; may be homomerous or heteromerous ; divides by amitosis , though totally incapable of division in the karyorelicteans; has regenerative powers, but normally is resorbed during sexual phenomena and replaced by products of a synkaryon , itself derived from fusion of gametic nuclei (Ma, Fig. 2.9Aa, 2.9Af, 2.12). Macrophagous : feeding on relatively large par- ticles of food; see Algivorous , Carnivorous , and Microphagous . Macrostome : a stage in the polymorphic life cycle in which the oral apparatus undergoes morphogenesis to become enlarged and capable of ingesting larger prey items, typically other ciliates, and sometimes conspecifics; see Microstome (Fig. 2.4B). Macrozooid : see Zooid . Marginal Cilia : circumferential band of long, stout cilia located above the aboral locomotor fringe of many mobiline peritrichs ; sometimes called cirri because of their stoutness. Marsupium : see Brood Pouch . Maternal Form : see Parental Form . Mating Type : a physiological state of the mature stage in the clonal life cycle of a ciliate enabling it to engage in conjugation with other individuals of different or so-called complementary mating type; can be developmentally determined either geneti- cally or epigenetically (e.g., by cytoplasmic factors or environmental factors). Maxillary Armature : see Capitulum . M-band : see Myoneme . Meganucleus : see Macronucleus , the preferred word. Membrana Quadripartita : see Quadrulus . Membrane : generalized term with a variety of par- ticular meanings depending on its specific modifier: (e.g., see Cystic Membrane, Nuclear Membrane, Paroral Membrane, Plasma Membrane , Undulating Membrane ); in ciliate systematics, often understood, to mean a ciliary membrane, such as the paroral . Membranelle : one of the several serially arranged oral polykinetids , often known as the adoral zone of membranelles ( AZM ) or adoral zone of oral poly- kinetids (AZOPk), typically found on the left side of the buccal cavity or peristomial field ; its cilia , sometimes seemingly fused or partially coalesced, if only hydrodynamically, may be used in food-getting or locomotion; the generally rectangular infracili- ary base is commonly composed of two, three or more rows of densely set kinetosomes , which may or may not be associated with parasomal sacs and may be linked by microtubular or micro fibrillar structures in specific patterns not necessarily iden- tical for each row of the base or for the similar- appearing “membranelle” in a different taxonomic group; membranelle sensu stricto may be used to refer to the left-hand oral ciliary organelles of the tetrahymenine hymenostomes ; membranelle sensu Glossary 37 lato includes organelles very likely not homologous (e.g., see Heteromembranelle, Membranoid, Paramembranelle, Peniculus, Polykinety, and Quadrulus ) (M1, M2, M3, Fig. 2.7e). Membranoid : an oral polykinetid , including either the definitive membranellar fields or some stage in their development, in species belonging to the oligohymenophorean scuticociliates ; at one time, alpha, beta, gamma and zeta types were differen- tially defined, the first three referring to the oral polykinetids on the left side of the buccal area, from anterior to posterior, and the fourth to the paroral on the right; the zeta membranoid or paro- ral in some scuticociliate species may consist of three, more or less separable, segments (“a”, “b” and “c”), with terminal fragmentation (probably of “b”, in this case) into a dozen additional pieces in the genus Schizocalyptra and with “a” most anteriad and “c” (= scutico-vestige ) at the posterior end, sometimes far to the left (e.g., in Pleuronema ). Meridian : see Ciliary Meridian . Merotelokinetal : telokinetal stomatogenesis in which the oral anlage is derived by proliferation of kinetofragments from a limited number of somatic kineties ; found in colpodeans , cyrtophorians , and prostomes (Fig. 2.11Db, 2.11Dc). Mesocyst : see Cyst . Mesosaprobic : see mention under Polysaprobic . Metacyst : a “granular layer” between the ciliate cell surface and the endocyst ; see Cyst . M Fibers : see Myoneme . Microbiocenosis : restricted natural community of interacting microorganisms, including ciliates, with a stability of limited duration, but temporary equilibrium may be repeatedly regained. Microconjugant : smaller member of a pair in conjugation ; completely absorbed by the macro- conjugant in cases of total conjugation (e.g., in chonotrichs and peritrichs ); a little-used synonym is microgamont. Microfibril : generalized term, perhaps better