PURPOSE:

To provide on-line documentation as to what features make up ultrastructural identities and therefore characterise lineages. This exercise may help to stabilise some of the taxonomic concepts.

INTRODUCTION:

Catalogues of organelles are critical elements in understanding the identity of major evolutionary lineages. The catalogue, combined with architectural understanding, constitutes the 'Ultrastructural Identity'. Catalogues of organelles also provide a wealth of information that can be called upon to establish synapomorphies for groups. Many of the supergroups now being developed lack any clear edges. In these cases, no synapomorphy is mentioned and a small number of taxa are selected to represent major clusters. As a result, we do not know the full composition of a group, nor can we be sure what criteria have to be met in order for an unassigned taxon to be assigned to the group, nor how to know if a group that appears close in evolutionary trees should be inside or adjacent to the reference group.

APPROACH:

Although cataloguing would seem to be a straightforward exercise, over the last few years it has become clear that ultrastructuralists 'missed' some key organelles within cells.

Examples:

Mitchondria-derived or mitochondria-like organelles in species that were previously thought to have been amitochondriate (such as in the entamoebae).

Plastids or plastid-derived organelles within some (but not all) sporozoa.

The raw material from which our understanding arises comes from a variety of microscopy techniques:

• thin sections
• whole mounts
• SEM
• Immunolocalization

Information from light microscopy also contributes to this understanding.

A draft list of the organelles has been developed, but is incomplete and needs to be expanded.

Protistiary home page top of electron microscopy exercise