About Protist Image Data

Protist Image Data (PID) provides pictures and short descriptions of selected protist genera, especially those genera whose species are frequently used as experimental organisms or are important in studies of organismal evolution. As a practical matter, species upon which scientists associated with the Organelle Genome Megasequencing Project team have published are most likely to feature in PID. Our intent is to provide up-to-date online information on the morphology, taxonomy and phylogenetic relationships of these organisms.

PID was first announced on 29 July 1994, on the bionet news group hierarchy. It is written and maintained in HTML 3.2, primarily for Netscape browsers v. 3.0 and above. Formatting is kept as simple (ok, primitive) as possible to facilitate loading, recognizing that many PID users (especially in education) still have old computers and slow connections.

PID pages follow this format:

Introduction: Briefly presents the type of protist the genus describes, the approximate number of species in the genus, the presumed phylogenetic position of the genus, the places in nature in which species of the genus may be found, and the significance of the genus to humans.

Appearance: Describes what the organisms in the genus look like under the naked eye and the light microscope.

Ultrastructure: Describes what the organisms in the genus look like under the scanning and transmission electron microscopes.

Reproduction and life history: Describes cell division (mitosis and cytokinesis), asexual and sexual reproductive modes, and life history patterns in the genus.

Similar genera: Lists a selection of genera with which the subject genus can be confused.

Classification: Earlier versions of this page attempt to provide one or more classifications for the genus in tabular format, as may be used in botany (e.g. Bold HC, Wynne MJ. 1985. Introduction to the Algae 2nd edn. Prentice-Hall, Englewood Cliffs NJ), zoology (Lee JJ, Hutner SH, Bovee EC (eds.). 1985. Illustrated Guide to the Protozoa. Society of Protozoologists, Lawrence, KS), the Handbook of Protoctista (Margulis L, Corliss JO, Melkonian M, Chapman DJ. 1990. Handbook of Protoctista. Jones and Bartlett, Boston), and/or the Cavalier-Smith system (as presented in: Cavalier-Smith T. 1993. The kingdom Protozoa and its 18 phyla. Microbiological Reviews 57: 953).

More recent versions have abandoned the tabular format in favor of a narrative description of various classification schemes used in connection with the genus in question, and a summary of the history of these schemes.

The principal intent is to help the user find the genus in texts that deal with organismal morphology and taxonomy, and deal with the classification schemes they may find in such sources. The intent is not! to provide a definitive classification, unless specifically stated otherwise. Protistan classification is an active area of research and debate. At present, the only honest answer even to seemingly elementary, basic questions such as "What kingdom does it belong to?" is "We're working on it".

Why is this so? Classification systems are supposed to convey information on the evolutionary history ("phylogeny") of organisms, as well as labels (names) for the groupings that we are able to recognize. At present there is no consensus on the "true" phylogeny of protists. As research progresses, phylogenetic concepts change, and the names that are tied to these concepts change as well. Research also discovers numerous instances of wrongly applied labels, such as when two or more species are found hiding under a single species name, and identifies previously undescribed creatures and lineages for which new names are needed.

Moreover, the naming rules ("codes of nomenclature") for organisms treated as animals are separate from the rules that apply to organisms treated as plants. A protist that can be considered either a plant or an animal must therefore have separate names, one for botanists and one for zoologists. Since the vast majority of protists belong to neither the animal nor the plant lines of evolution, but represent many separate and distinctive lineages of eukaryotes that are at least as old and venerable as the "true" animals and plants, the "animal code" | "plant code" naming game is little short of bizarre.

Until there is a consensus phylogeny of protists and an improved system of organismal nomenclature (the technical and practical costs of these developments are not trivial), protist classification will be unstable.

Taxonomy and nomenclature: Briefly describes the taxonomic and nomenclatural history of the genus, emphasizing known or anticipated changes to the name of the genus, how the genus is identified, or to the number of species in the genus. Where possible and practical, keys to species are provided. Many of the problems associated with the Classification section also apply here.

Cultures: Presents data on culture availability and condition (for instance, whether or not cultures are axenic). There may be a subjective assessment of how easy they might be to grow.

Selected references: Gives a short list of books and papers relevant to morphology, taxonomy and phylogeny of the genus. Intended primarily to provide an entry to literature not accessible online.

Internet Resources: Provides pointers or access information to online resources that house further specific information on the subject genus. Pointers to resources that have information on protists, but not necessarily on the specific genus being reviewed, may be found on the PID Databases for Protistology page.