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CryptoCom - The CRYPTOmonad COMpanion

CryptoCom? What's that?

CryptoCom is an annotated synopsis of cryptomonad morphology, ultrastructure, taxonomy and nomenclature, hitherto available as a conventional paper-based publication only (Hydrobiologia 502: 225-270, 2003).

What is the aim of CryptoCom?

The aim of CryptoCom is to aid CRYPTOmonad identification down to whatever taxonomic level is realistically possible for any particular worker, kind of sample and equipment at hand. In an anti-elitist fashion, its aspiration is that of providing some insight into cryptomonad identification to everyone irrespective of the kind and quality of instrumentation available to them. It is based mostly on morphological criteria adopted in more recent years by several independent specialists. It is intended as a supplement to the existing taxonomic literature (a vademecum or COMpanion) rather than a self-contained identification guide. It is by no means exhaustive and it does not make it possible to identify all described cryptomonad species.

Why was CryptoCom conceived?

Most cryptomonads can be detected easily in unfixed environmental samples thanks to their characteristic swimming behaviour. However, identification at or below the generic level is notoriously complex. Here are some possible reasons:

  • An up-to-date monographic revision of the group is not available. Therefore it is necessary to have access to an abundant taxonomic literature, including many of the older, hard to find publications.

  • A range of observation methods may be indispensable. However, only some may be available to a particular investigator at any one time.

  • The quality of some of the early taxonomic descriptions is not always adequate. Because they were based necessarily on the small number of characters visible in living cells using light microscopy, it is often difficult to use those descriptions in a modern taxonomic context.

  • Cryptomonad systematics is in a state of flux, not least because molecular sequencing studies are providing a wealth of new phylogenetic information. In some cases the degree of congruence between molecular phylogenies and classifications based on ultrastructural characters such as the nucleomorph position is high, while in others the situation is still unclear and requires further investigation.

These difficulties are such that they may discourage non-specialist investigators from attempting to identify cryptomonads altogether. The situation is made worse by the existence of an authoritative viewpoint whose influence still seems to persist nowadays: namely, that cryptomonads are simply impossible to classify. As a result only a few named taxa are mentioned frequently in the non-taxonomic literature, often with little information on the actual specimens observed. However, there are several reasons why it is still important to identify unknown field specimens as far as is reasonably practicable:

  • Cryptomonad diversity may be far from having been described in full. Estimates of the total number of exisiting species range from 300 to 1200, i.e. one and a half to six times the number of currently known species. Therefore it is always possible that environmental samples will contain previously undescribed taxa, perhaps with novel morphological, ecological, physiological or other features of interest within the context of cryptomonad systematics and phylogeny.

  • Our knowledge of how diversity varies in relation to geographical and environmental variability is still very scant, and the very possibility of addressing these questions depends entirely on the ability to recognize species in the first place.

  • Cryptomonads may form nuisance blooms both in marine and freshwater ecosystems. Sound taxonomic identifications are a necessary preamble to any modelling studies of cryptomonad blooms if the models are to be sufficiently predictive.

  • There is evidence that freshwater cryptomonad species may differ considerably from one another in their physiological and ecological characteristics, and therefore they may occupy distinct, well-defined ecological niches. Although there is scant information on the subject in marine environments, a priori it cannot be excluded that the situation is analogous to that in freshwaters. Here again, the ability to address this sort of question will depend on the availability of reliable taxonomic identifications.

What is the approach followed by CryptoCom?

Although simple identification keys (be they dichotomous or not) to a selection of taxa are provided where possible, an empirical, multilateral approach is followed in order to facilitate identification by non-specialists using only what equipment is available to them at any one time. This approach is based on the fact that different degrees of taxonomic resolution can be achieved by using different combinations of observation and investigation techniques: light microscopy, scanning electron microscopy, transmission electron microscopy, freeze-fracture and spectrophotometry.

Morphology and ultrastructure? Isn't that a bit old-fashioned?

The most recently described cryptomonad genus has been separated from morphologically similar genera based on 18S rRNA sequences. Molecular sequences have also been incorporated into genus and species descriptions within a couple of other genera. Within such a scenario it is possible that in future more emphasis will be placed on using molecular sequence data for identification purposes. Far from doing away with the need for taxonomic descriptions and identifications based on "traditional" criteria, the increasing amount of molecular sequence data will need to be interpreted hand-in-hand with morphology, ultrastructure, photosynthetic pigments, physiology and ecological data if we are to build an accurate view of cryptomonad systematics, phylogeny and evolution, and ultimately understand what constitutes a cryptomonad species.

Any other basic points?

From a taxonomic viewpoint CryptoCom adopts a nominalistic philosophy, whereby taxa are considered to be acceptable as long as their names have been published in accordance with the nomenclatural rules and prevailing taxonomic practice. A number of poorly known genera whose affinities with the cryptomonads are uncertain and some genera which are taxonomically synonymous with others are also included for information purposes. Other uncertain genera are listed elsewhere. Owing to the fact that cryptomonad systematics is outside its scope, CryptoCom does not follow any particular identification system. Cryptomonads are ambiregnal protists, and therefore they are considered here to be under the dual jurisdiction of the botanical (ICBN) and the zoological (ICZN) Codes of Nomenclature.

How does it work in practice?

The web-based version is in progress. When complete it will contain several changes and improvements compared to the paper-based one, which you are welcome to try out.

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