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Protozoan and Secondary article Article Contents . Introduction John O Corliss, University of Maryland, College Park, Maryland, USA . Historical Considerations . Major Groups of Taxonomy and systematics of major groups of the Protozoa, an assemblage of so-called . The Old ‘ Protozoa’ lower , refer basically to the classification of such groups, that is, their . Modern Options Concerning the Place of Protozoa in arrangement into a hierarchy of evolutionary interrelated groups (taxa) of scientifically the Biotic World . named phyla, classes, orders, etc. The New ‘ Protozoa’

Introduction ently, a goodly number of -possessing algal The classification of protozoa and other groups were included in the phylum), phagotrophic, and above the organizational level of the has always capable of independent locomotion. It is now abundantly been dependent on because the body sizes clear that this classical definition of protozoa is at best involved generally range from only one micrometre to one misleading and incomplete, and that it requires consider- or two millimetres in length. Any structures these able refinement. possess, useful in comparative studies of their morphology In former times, zoologists were the principal investiga- and thus their taxonomy and systematics, are at the cellular tors – and namers and claimers – of such microorganisms; and subcellular levels, and invisible to the naked eye. The and they often worked with taxonomic disregard for physiological properties of protozoa (and the neighbour- studies of what might actually be the same group, ing )have also played a role in the classification of sometimes even the same species, by the botanists these ubiquitous eukaryotic microorganisms; and of (phycologists and mycologists). Thus, unfortunately, growing significance are the findings made possible by territoriality and authoritarianism also played major roles research using molecular biological approaches. in determining the early systematic status of the protozoa, Because we are continuing to learn more and more about algae and lower fungi (Corliss, 1986). such minute , protozoan systematics – that is, Advances in our knowledge of the protozoa in general the taxonomy (classification)and the evolutionary inter- have followed progress in microscopy, as mentioned relationships of major groups of protozoa – remains a above. As early as a century ago, novel improvements in topic of debate and change, still today. Some of the rather methods of light microscopy and related techniques of large and unwieldy taxonomic groupings of past years are fixing and staining were already beginning to make particularly subject to revision with expansion of and possible the revelation of morphological cellular charac- refinement in our knowledge about the members of those – teristics that would have remained totally unrecognized and related – assemblages. Paradoxically, the protozoa before the appearance of such technological advances. themselves are becoming more difficult to define with Then, at mid-twentieth century, the use of electron precision as our information about them and other microscopical approaches in opened up a microbial assemblages increases. Thus, presenting a single whole new epoch of exploration in protozoology and satisfactory circumscribed definition for them is not an related fields. During the ‘Age of Ultrastructure’ (as it has easy task. It is attempted towards the end of this article; been called), a myriad of previously unknown subcellular but, for sake of clarity, further background information is structures were revealed that became of immense value in first supplied. the comparative taxonomy of the lower eukaryotes (especially protozoa and algae). Even more recently, the exciting development of molecular biological approaches, particularly in study of genealogical and phylogenetic Historical Considerations relationships within all groups of organisms, large and small, or , has offered a refinement in Until well beyond the middle of the twentieth century, taxonomic investigations that is without parallel in past protozoa were widely treated taxonomically as a (mere) decades. subset of the kingdom Animalia, retaining their ‘first- Here an attempt is made to review and understand the animal’ definition dating from 150 years earlier. As a systematics of protozoa both from the more traditional phylum of unicellular , they were thought to exhibit point of view, keeping in mind that many are still major characteristics typical of that kingdom: colourless familiar mostly with older, conventional classifications of (i.e. no photosynthetic pigments present; yet, incongru- these minute organisms, and from more modern ap-

ENCYCLOPEDIA OF SCIENCES / & 2001 Publishing Group / www.els.net 1 Protozoan Taxonomy and Systematics proaches. The latter are complicated by the relatively protozoa (Table 1). Although this popular arrangement – in recent advent of the ‘protistological perspective’ – lumping comparison with the long-followed classical one of protozoa, algae and some other eukaryotic microorgan- Bu¨ tschli of 80 years earlier – contained nearly four times isms together as Protista – and by their usage of more the number of taxonomic units above the level of , it sophisticated data. For more detailed information con- showed few novelties of great significance. For an out- cerning protozoan–protistan overlapping relationships, standing example of its conservatism, the classification still the reader is referred particularly to comprehensive papers retained several major groups of algae, all treated as by Cavalier-Smith (1993, 1998)and Corliss (1994, 1998) comprising a single , the Phytomastigophorea, of and to the insightful textbooks by Sleigh (1989)and flagellated protozoa (the Mastigophora). A subsequent Hausmann and Hu¨ lsmann (1996). revision supported by the international Society of Proto- zoologists, the ‘Levine Report’ of 1980, recognized seven separate phyla (in a subkingdom Protozoa)and increased the number of taxa above the familial level to 229 (Table 2). Major Groups of Protozoa But, fundamentally, it followed the arrangement of its predecessor (Table 1). Five years later, the well-known and For many decades (commencing with the perceptive widely used Illustrated Guide to the Protozoa (Lee et al., schemes of Otto Bu¨ tschli, published in the 1880s), it has 1985)appeared, with its classification scheme mainly that been convenient to assign species known as protozoa to just of the Levine Report. By then, the ‘ revolution’ had four major categories or assemblages, as has been done in already been going strong for a full decade (see accounts in numerous textbooks of biology and as well as Corliss, 1986, 1998)and many findings were indicating the protozoology. Despite advances and improvements in our pressing need for a fresh look at the old persisting problems knowledge of eukaryotic microorganisms in general, it is of how to treat the systematics of the conventional/ still often rather helpful, for sake of discussion under diverse traditional protozoan, algal and fungal assemblages of circumstances, to arrange protozoa taxonomically in such a microorganisms. way. The categories generally recognized are: (1)the One reason for including the above discussion here, amoeboid forms (the Sarcodina, in a broad sense); (2) the besides the fact that those classifications of 20–40 years ago flagellated forms (the Mastigophora, including groups of are still accepted by many biologists, is to help bridge the autotrophic – or photosynthetic – as well as heterotrophic gap between such neoclassical systems and the suggested species); (3) the ciliated forms (the Ciliophora, the most recent arrangements of the 1990s (see below). The stable and perhaps most circumscribed of all protozoan organisms involved, and often their common group names assemblages); and (4) the various totally symbiotic or as well, have not changed over the decades, but our ideas parasitic forms (primarily -forming species that are concerning their most likely interrelationships at the higher typically endoparasites, some highly pathogenic to their taxonomic levels have done so, primarily by fresh analyses hosts, once assigned to a very broad group called the of the continuing accumulation of data of high phyloge- Sporozoa, a high-level that subsequently became netic and evolutionary significance from precise ultra- divided into the Sporozoa and the Cnidosporidia). structural and molecular biological investigations One of the pedagogically oft-regretted but inevitable (Coombs et al., 1998). changes, especially during the busy second half of the twentieth century (even before the ‘protist revolution’: see Corliss, 1986), was the tremendous expansion in the total numbers of high-level taxonomic groups (subphyla, Modern Options Concerning the Place classes, orders)of protozoa, while generally still recogniz- ing the four major top divisions mentioned above. The of Protozoa in the Biotic World discovery of new and unique differentiating characteristics There are a number of ways in which modern biologists are useful in classification – and in evolutionary and phyloge- viewing the overall placement of the protozoa with respect netic studies as well – required such a multiplication and to other major groups of organisms. Several of these are fragmentation of taxa even though it placed/places greater not truly taxonomic in their approach: for example, demands on (the memories of)teachers, students and arrangement of species of protozoa based solely on their researchers alike. nutritional preferences or requirements, or considering protozoan groups as representing simply an or level of cellular organization between the The Old ‘Phylum Protozoa’ anucleate (essentially the bacteria)and the well-known ‘higher’ (nucleated)eukaryotic forms of life Basically, the classification scheme of the widely accepted (particularly the multicellular and multitissued and ‘Honigberg Report’ of 1964 may be used to illustrate the animals). And popular today, especially among workers conventional situation concerning the systematics of the employing cladistic approaches in their investigation of

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Table 1 Taxonomic classification of the single phylum Protozoa according to the Report published by Honigberg et al. (1964), but omitting ordinal and subordinal names. The total number of suprafamilial categories reached 140, nearly four times the number in vogue among earlier protozoologists well into the twentieth century. (Modified and abbreviated from Corliss, 1998.) I. Subphylum II. Sporozoa Superclass 1. Mastigophora Class 1. Teleosporea Class 1. Phytomastigophorea Subclass (1) Gregarinia Class 2. Zoomastigophorea (2) Superclass 2. Opalinata Class 2. Toxoplasmea Superclass 3. Sarcodina Class 3. Haplosporea Class 1. Rhizopodea Subclass (1) Lobosia Subphylum III. (2) Filosia Class 1. Myxosporidea (3) Granuloreticulosia Class 2. Microsporidea (4) Mycetozoia (5) Labyrinthulia Subphylum IV. Ciliophora Class 2. Piroplasmea Class 1. Ciliatea Class 3. Actinopodea Subclass (1) Holotrichia Subclass (1) (2) Peritrichia (2) Acantharia (3) Suctoria (3) Heliozoia (4) Spirotrichia (4) Proteomyxidia

phylogenetic interrelationships of life forms, is the idea of This five-kingdom arrangement represents a pragmatic , distinct evolutionary lines or lineages but ones often one that is quite attractive pedagogically (easy to teach at with unknown or nonpostulated possible taxonomic all levels in the educational hierarchy)and is convenient for relationships with other lines of organisms (microorgan- general nonspecialist usage and for information retrieval isms or macroorganisms)(see Patterson, 1999). systems. But it is becoming evident that, as our store of The only true taxonomic options today are the inclusion relevant data continues to expand, the ‘single kingdom of the protozoa with other eukaryotic microorganisms in a Protista’ hypothesis lumps together lines of microscopic single kingdom called Protista or the recognition of a organisms that are proving to be not very closely related number of kingdoms (one called the Protozoa)within the evolutionarily and includes still other lines that are being overall assemblage of the Eukaryota. These two ap- shown to have closer affinities with forms assigned to one proaches require further discussion. of the other three eukaryotic kingdoms. And the protozoa Recognition of a single kingdom to contain all are not sufficiently given their own identity as an eukaryotic microorganisms (and some of their larger but independent high-level taxonomic assemblage. yet basically unicellular or single-tissued relatives)is a The second major alternative available to us today is to choice, first voiced more than 120 years ago by E. Haeckel consider the , overall, as best assignable to a and others, still popular today among a number of number of separate kingdoms, one of which has now been biologists. In this option, a neoHaeckelian kingdom labelled with the familiar name Protozoa (Cavalier-Smith, Protista (or ‘Protoctista’)contains commingled phyla, 1993; Corliss, 1994). The composition of this protozoan divisions and classes of organisms formerly representing assemblage – distinctly separated from the four other the protozoa, the algae and taxa of lower fungi. It is given eukaryotic assemblages or kingdoms recognized, the equal standing with the neighbouring kingdoms of the (taxonomic home for most lines of algae), prokaryotic Bacteria, on the one hand, and of the (other) Plantae, Fungi and Animalia (see Cavalier-Smith, 1998; eukaryotic moieties known as the Fungi, Plantae and Corliss, 1998, 2000)– is considered below in further detail. Animalia, on the other hand (Margulis et al., 1990; Two points need emphasis here. (1)A formal high-level Margulis and Schwartz, 1998). taxonomic category called ‘Protista’ is no longer needed or

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Table 2 Taxonomic classification of the animal subkingdom Protozoa according to the Report published by Levine et al. (1980), but here omitting all categories below the rank of class. The total number of suprafamilial categories reached 229, nearly double the number endorsed in the preced- ing Honigberg Report of 1964 (see Table 1). (Modified and abbreviated from Corliss, 1998.) Phylum I. Sarcomastigophora Phylum II. Labyrinthomorpha Subphylum 1. Mastigophora Class (1) Labyrinthulea Class (1) Phytomastigophorea (2) Zoomastigophorea Phylum III. Subphylum 2. Opalinata Class (1) Class (1) Opalinatea (2) Sporozoea Subphylum 3. Sarcodina Superclass 1. Rhizopoda Phylum IV. Microspora Class (1) Lobosea Class (1) Rudimicrosporea (2) Acarpomyxea (2) Microsporea (3) Acrasea (4) Eumycetozoea Phylum V. Ascetospora (5) Plasmodiophorea Class (1) Stellatosporea (6) Filosea (2) Paramyxea (7) Granuloreticulosea (8) Phylum VI. Superclass 2. Actinopoda Class (1) Class (1) (2) Actinosporea (2) Polycystinea (3) Phylum VII. Ciliophora (4) Heliozoea Class (1) Kinetofragminophorea (2) (3) Polyhymenophorea

recognized; all former protists (spelled with a lower case Protozoa. The first person to do this systematically and in ‘p’)can be reassigned to various of the five kingdoms some detail was T. Cavalier-Smith, starting in the 1980s mentioned immediately above. (2)The (new)kingdom (see full discussions in Cavalier-Smith, 1993, 1998). The Protozoa, while containing many conventional groups of kingdom Protozoa may be briefly described (after Corliss, protozoa, is purged of others and thus is not identical in 1994, 2000)as follows. overall taxonomic composition to the old phylum Proto- The kingdom comprises predominantly unicellular, zoa embraced in very popular classifications of both plasmodial or colonial protists (eukaryotic microorgan- distant and more recent past years (for example, see isms)that are mostly phagotrophic or osmotrophic, preceding sections of this article; see also Honigberg et al., colourless, lacking cellulosic cell walls, and microscopic 1964, and Levine et al., 1980; and contrast the contents of in body size. Included species that are capable of Table 1 and Table 2 with that of Table 3). (but some are nutritionally mixotrophic) typically possess unique cytosolic with stacked thylakoids, no stored starch, and surrounded by three membranes. Nearly universally present are tubular mito- The New ‘Kingdom Protozoa’ chondrial cristae; when mitochondria are absent, they are typically replaced by . Golgi bodies and Of the two options briefly described above, many biologists peroxisomes are widely present. Flagellar mastigonemes, if now favour the second one, the concept of dividing up present, are never rigid or tubular. Free-living (typically major taxa of former protozoa (and of algae and lower independently motile via , flagella, or cilia) fungi, too), with new assignments to several different and symbiotic species are numerous from a great of kingdoms, one of which is identified as the kingdom habitats. As one of the two (of five)eukaryotic kingdoms

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Table 3 The 14 phyla, including authorships and dates of their names, comprising the kingdom Protozoa Goldfuss, 1818, with an indication of the kinds and numbers of protists included in each phyletic taxon (based on abbreviated characterization data from Corliss, 1994, 1998, 2000) Cavalier-Smith, 1983 Large, benthic, microaerobic amoebae, amitochondriate, allegedly primitive forms, with endosymbiotic bacteria; species few in number, all free-living in fresh water Neomonada Cavalier-Smith, 1997 Often small, free-living, marine heterotrophic flagellates and amoeboflagellates; small group, still ill-defined Rhizopoda von Siebold, 1845 Typically amoeboid, with differing kinds of pseudopodia, some flagellated forms; naked or with tests or thecae; 4 5000 species found in , fresh- or saltwater habitats de Bary, 1859 Plasmodial slime moulds (cellular and acellular), some very large; aerial (stalked) fruiting bodies produce ; c. 850 species, mostly in decaying vegetation; a few symbiotic forms d’Orbigny, 1826 Amoeboid forms in tests (usually calcareous), with alternation of haploid sexual and diploid asexual generations; shells of extinct species reach 15 cm in diameter; reticulate pseudopodia for feeding and locomotion; mostly marine, with some 45 000 species (largest phylum in the kingdom)of which c. 90% are fossil forms Haeckel, 1866 Mostly freshwater group of the classical ‘actinopod sarcodinids’, with slender radiating axopodial type of pseudopodia used in food capture; c. 100 species, many stalked Radiozoa Cavalier-Smith, 1987 Marine, spherical forms, typically planktonic, often with elaborate symmetrical shell pierced by stiff axopodia; three major subgroups, with total of nearly 12 000 species (c. 65% fossil forms), second largest phylum in the kingdom Cavalier-Smith, 1991 Small heterotrophic flagellates or amoeboflagellates, c. 100 species, some poorly known Cavalier-Smith, 1981 The old ‘Euglenophyta’, mainly free-living, freshwater ‘phytoflagellates’, 4 1000 species, plus Kinetoplastidea (parasitic trypanosomes plus free-living bodonids), 4 600 species; commonly with discoidal mitochondrial cristae and a paraxial rod in their main flagellum Dinozoa Cavalier-Smith, 1981 Dinoflagellates, unique biflagellated protists, mostly marine planktonic, one-half pigmented forms; some thecate; a few colonial; cortical alveoli; about half found as fossils; total species c. 4500, with some 100 described as parasites; many orders Metamonada Grasse´ , 1952 Biflagellated to multiflagellated forms, typically digestive tract parasites (insects to humans); c. 300 species; hydrogenosomes in place of mitochondria Parabasala Honigberg, 1973 Parasitic multiflagellated forms, amitochondriate and with prominent parabasal (Golgi)apparatus; 4 400 species, in intestines of woodroaches to humans Apicomplexa Levine, 1970 Essentially the ‘Sporozoa’ of old; unique complex of apical ; all symbiotic, with many minute species as harmful endoparasites (e.g. in birds, livestock, humans: outstandingly, ); cortical alveoli; 4 5000 species in three major classes Ciliophora Doflein, 1901 All heterokaryotic (micro- and macronuclei); usually multiciliate, phagotrophic, relatively large protists found mostly free-living in diverse fresh-/saltwater/soil habitats; others symbiotic or epibiotic, mostly in or on hosts; often complex oral ciliature; cortical alveoli; many exhibit sexual phenomenon of conjugation; asexual by transverse fission; third largest protozoan phylum: c. 8000 species in 8–10 classes, many orders composed purely of protistan forms, the Protozoa – As characterized above, the refined kingdom Protozoa, counting fossil as well as extant species – embrace nearly large though it is, is considerably more discriminating and 40% of all protists (numbering some 213 000 species) more restricted in its boundaries than was the ‘old’ phylum described to date. Protozoa. The latter, traditionally, contained a number of

ENCYCLOPEDIA OF LIFE SCIENCES / & 2001 Nature Publishing Group / www.els.net 5 Protozoan Taxonomy and Systematics major taxa (e.g. at class and ordinal levels)that have now Fungi, while the complex Myxozoa are better classified in been eliminated. For example, purged from the ‘new’ the Animalia (perhaps close to the cnidarians). kingdom have been half a dozen algal groups, the curious Until rather recently, the Archamoebae (with labyrinthomorphids, the , the opalinids, the and possibly others such as the important myxozoa, and most recently, the . All species parasite of humans, )were considered as very of these taxa fail to possess major distinguishing features of primitive protists in a kingdom of their own. Latest studies the kingdom Protozoa listed above and/or have unique (see references in Cavalier-Smith, 1998; Corliss, 2000) morphological, physiological or molecular characteristics suggest that, while probably composed of very ancient of their own beyond discussion here. Supported by recent species (now without mitochondria or hydrogenosomes), molecular (e.g. rRNA sequencing information)as well as the phylum belongs more appropriately in the revised morphological and biochemical findings, these other kingdom Protozoa, as seen in Table 3. protists have been placed in one or another of the The unique Choanozoa, collar-celled, loricate, colour- neighbouring kingdoms Chromista, Fungi, Plantae or less flagellates with flattened mitochondrial cristae, pre- Animalia (Corliss, 1998, 2000). The 14 phyla (containing sumably at the crossroads of origins of both kingdoms nearly 83 000 species, about 60% of which are fossil and Animalia and Fungi, have been removed from the 12% symbiotic forms)that then remain in the refined Protozoa and tentatively placed in the Animalia (Corliss, kingdom Protozoa are listed, with abbreviated descrip- 2000), where another protistan group and former proto- tions, in Table 3. Representative genera are not mentioned, zoan phylum, the Myxozoa, is also now located (see above). for sake of brevity within the table, but names of many such genera are included in the long papers by Cavalier-Smith (1993)and Corliss (1994). Several additional observations might be helpful con- References cerning some of the major differences between this new classification of the Protozoa and the older, more Cavalier-Smith T (1993)Kingdom Protozoa and its 18 phyla. Micro- biological Reviews 57: 953–994. conventional ones discussed on preceding pages. Cavalier-Smith T (1998)A revised six-kingdom system of life. Biological Two distinctive eukaryotic algal lines – the Reviews 73: 203–266. and the dinoflagellates – are retained as Protozoa, but they Coombs GH, Vickerman K, Sleigh MA and Warren A (eds)(1998) have strikingly different characteristics (including presence Evolutionary Relationships Among Protozoa. Dordrecht: Kluwer of three, not two, plastidic membranes and frequent Academic Publishers. exhibition of nonphotosynthetic modes of , Corliss JO (1986)Progress in during the first decade among others)from other major assemblages of algae following reemergence of the field as a respectable interdisciplinary area in modern biological research. Progress in Protistology 1: 11–63. now appearing in the separate kingdoms Chromista (e.g. Corliss JO (1994)An interim utilitarian (‘user-friendly’)hierarchical the chrysophytes, phaeophytes, haptomonads, cryptomo- classification and characterization of the protists. Acta Protozoologica nads and lesser heterokontic groups)and Plantae (e.g. the 33: 1–51. prasinophytes, chlorophytes (with such long-claimed Corliss JO (1998)Classification of protozoa and protists: the current ‘protozoa’ genera as and Chlamydomonas), ulvo- status. In: Coombs GH, Vickerman K, Sleigh MA and Warren A (eds) phytes, charophytes, rhodophytes and ). In Evolutionary Relationships Among Protozoa, pp. 409–447. Dordrecht: fact, the ‘euglenophytes’ of old are phylogenetically closely Kluwer Academic Publishers. Corliss JO (2000), classification, and numbers of species of related to the colourless kinetoplastideans (bodonids and protists. In: Raven P and Williams T (eds) Nature and Human Society: parasitic trypanosomatids), the combining single phyletic the Quest for a Sustainable World, pp. 130–155. Washington DC: name now being the Euglenozoa. National Academy Press. The dinoflagellates (Dinozoa), furthermore, are linked Hausmann K and Hu¨ lsmann N (1996) Protozoology, 2nd edn. Stuttgart: with the (Ciliophora)and the sporozoa (Apicom- Georg Thieme. plexa)in a supraphyletic assemblage often designated as Honigberg BM, Balamuth W, Bovee EC et al. (1964)A revised the Alveolata because of their common possession of classification of the phylum Protozoa. Journal of Protozoology 11: 7–20. cortical alveoli in their pellicles, a character not particu- Lee JJ, Hutner SH and Bovee EC (eds)(1985) An Illustrated Guide to the larly known in other phyla of protists. Protozoa. Lawrence, KS: Society of Protozoologists. Mostly on the basis of very recent rRNA data, but also Levine ND, Corliss JO, Cox FEG et al. (1980)A newly revised supported by other differentiating characteristics, the long- classification of the Protozoa. Journal of Protozoology 27: 37–58. linked ‘protozoan-cnidosporidian’ groups, the enigmatic Margulis L and Schwartz KV (1998) Five Kingdoms: an Illustrated Guide microsporidia and myxosporidia, turn out to be not only to the Phyla of Life on Earth, 3rd edn. New York: WH Freeman. not closely related to each other but also not members of Margulis L, Corliss JO, Melkonian M and Chapman DJ (eds)(1990) Handbook of Protoctista. Boston: Jones and Bartlett. the kingdom Protozoa. The first, the Microspora, along Patterson DJ (1999)The diversity of eukaryotes. American Naturalist with chytrids (but not with and hyphochytrio- 154 (Supplement): 96–124. mycetes, which are now in the Chromista), are probably Sleigh MA (1989) Protozoa and Other Protists, 2nd edn. London: primitive or degenerate protistan members of the kingdom Arnold.

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Further Reading Kudo RR (1966) Protozoology, 5th edn. Springfield, IL: Charles C Thomas. Andersen RA (1992)Diversity of eukaryotic algae. Biodiversity and Margulis L (1996)Archaeal–eubacterial mergers in the origin of Conservation 1: 267–292. Eukarya: phylogenetic classification of life. Proceedings of the Cavalier-Smith T (1989)The kingdom Chromista. In: Green JC, National Academy of Sciences of the USA 93: 1071–1076. Leadbeater BSC and Diver WL (eds) The Chromophyte Algae: Patterson DJ (1994)Protozoa: evolution and systematics. In: Hausmann Problems and Perspectives, pp. 381–407. Oxford: Clarendon Press. K and Hu¨ lsmann N (eds) Progress in Protistology (Proceedings of the Cavalier-Smith T (1995)Evolutionary protistology comes of age: IX International Congress of Protozoology, Berlin, July–August 1993), biodiversity and molecular . Archiv fu¨r Protistenkunde pp. 1–14. Stuttgart: G Fischer. 145: 145–154. Vickerman K (1998)Revolution among the Protozoa. In: Coombs GH, Corliss JO (1998)Haeckel’s kingdom Protista and current concepts in Vickerman K, Sleigh MA and Warren A (eds) Evolutionary Relation- systematic protistology. Stapfia 56: 85–104. ships Among Protozoa, pp. 1–24. Dordrecht: Kluwer Academic Grell KG (1973) Protozoology. Berlin: Springer-Verlag. Publishers.

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