Taxonomy
Tip of Buddenbrockia worm with fluorescent-stained musculature (green). © A Gruhl
Morphology
The worms consist of an outer and an inner epithelial tissue layer. Sandwiched between these layers are four longitudinal muscle blocks which consist of numerous muscle cells (Okamura et al. 2002).
The multicellular spores consist of valve cells that form the spore wall, capsulogenic cells that produce polar capsules, and two infective sporoplasm cells (Canning et al. 2002).
Polar capsules are intracellular organelles in spores of all myxozoans and which share a common ancestry with nematocysts found in the stinging cells of cnidarians.
Diagnostic description
Colourless, whitish worms, in mature state with grainy mass of internal ovoid spores. The latter, with two sporoplasms and four polar capsules.
Lookalikes
The worms can be confused with nematodes.
Evolution
The anatomy of the spores, the ultrastructure of the polar capsules and DNA sequence data support a myxozoan affinity. Within the Myxozoa the genera Buddenbrockia and Tetracapsuloides are united in the Malacosporea.
Malacosporean characters include the production of soft spores, the utilisation of freshwater bryozoans as primary hosts, and the development of true tissues.
All other myxozoans occur as purely plasmodial or unicellular stages in their hosts. Molecular phylogenetic studies have given support for the cnidarian affinity of the Myxozoa (Jiménez-Guri et al. 2007a; 2007b).