Protist, Vol. 150, 1, March 1999 © Urban & Fischer Verlaghttp://www.urbanfischer.de/journals/protist

EDITORIAL

What is a Protist?As an editor of a journal named 'Protist' one is fre­quently confronted with the above question posedby potential authors, apt readers of the journal, stu­dents, administrators and other paymasters, or fel­low editors of other journals.

What is a protist? An editor is tempted and per­haps well-advised not to take a too restrictive standon this matter, especially if a top-quality manuscripthas been submitted. However, unless one wants totreat protists as a formal taxon (e.g. the 'Protista'), inwhich case, when applying phylogenetic (cladistic)classification principles all eukaryotes become pro­tists, one needs to come up with a more practicalsolution to this question.

One may, of course, consult dictionaries, text­books, scholarly treatises (as e.g. referred to in thisissue's 'from the Archives' contribution by JohnCorliss), interview professional colleagues or tracethe history of the name. In doing so, it is evident thatno consensus emerges. Should we thus concludewith Mark Ragan (1998) that 'protists are what pro­tistologists study', or that a protist qualifies as suchby appearing in the pages of a journal bearing thisname? Are protists just social constructs?

The problem in defining the protists in my estima­tion stems mainly from the misconception that pro­tists should be treated as a taxonomic entity and isthus a consequence of that genuine human activity ofclassifying nature in a hierarchical manner. FromHaeckel's (1866) Protista to the 'modern' ~ '5 king­dom' concepts (e.g. Margulis and Schwartz 1998) ithas been 'convenient' to treat protists as a 'kingdom'(or a few 'kingdoms') because of the 'relative simplic­ity for information retrieval systems and for the educa­tion/edification of high school and college students,the general public, non-scientific professional people,and non-biological scientists' (Corliss 1998). Thekingdom concept apparently also serves to raise theself-confidence of scientists who study these organ­isms. After all who wants to study the 'lower', 'simple'or 'primitive' organisms when others deal with the'higher', 'complex' or 'more advanced' ones?

If one uncouples the term protist from its perpetu­ated taxonomic pervasion, protists much in thesense of Haeckel (but excluding the bacteria: part ofHaeckel's Moneres) constitute a grade of cellular or­ganization, namely single-celled (unicellUlar) eukary-

Protist

otes. This is also the concept that stimulated the in­auguration of the 'Archiv fUr Protistenkunde', thepredecessor of the journal 'Protist' (Schaudinn: 'eineSammelstelle fUr aile Forschungen zur Naturge­schichte der Einzelligen'). As in any biological defini­tion the borders are blurred: are (sometimes macro­scopic) coenocytic organisms unicellular and thusprotists? Are cell colonies, aggregates, or simple fila­ments consisting of nondifferentiated cells uni- ormulticellular and thus protists or not? What about or­ganisms that have been secondarily reduced from amulticellular to a unicellular status such as Saccha­romyces cerevisiae? It is clear that protists when de­fined as unicellular eukaryotes cut through mono­phyletic taxa (clades): Chlamydomonas is a protist,but the majority of taxa within the Viridiplantae arenot protists, the same may be said about Porphyri­dium (a red alga), Chytridium (a fungus) or Monosiga(a choanoflagellate, presumably part of the animallineage). Conversely, the brown alga Macrocystis inbeing a multicellular organism of considerable size(up to 50 m long) with differentiation of its thallus intoorgans, tissues and various cell types (thus mimick­ing the vascular plants), transcellular communicationthrough plasmodesmata, and a complex life historyinvolving specialized reproductive organs for asexualand sexual reproduction hardly qualifies as a protist.

'Protist' publishes papers that report substantialand novel findings in any area of research on pro­tists. As 'Protist' enters its second year authors andreaders will eventually decide whether 'Protist' livesup to this goal. An excellent paper will not be turneddown because it does not fit a definition!

References

Corliss, JO (1998) Haeckel's kingdom Protista and currentconcepts in systematic protistology. Stapfia 56: 85-104Haeckel E (1866) Generelle Morphologie der Organismen. 2vols. G. Reimer, Berlin

Margulis L, Schwartz KV (1998) Five kingdoms: an illustratedguide to the phyla of life on earth. 3rd ed WH Freeman, NewYork

Ragan MA (1998) On the delineation and higher-level classifi­cation of algae. Eur J Phycol 33: 1-15

Michael Melkonian, EditorCologne

1434-4610/99/150/01-1 $12.00/0