Ichthyosporea
Parasitic opisthokonts bridging the gap between fungi and animals.
The Ichthyosporea (also known as the DRIP clade or Mesomycetozoea) are a small group of Opisthokonta within Eukaryota, formerly classified as protists. They are mostly parasites of fish and other animals, and are not particularly distinctive morphologically, appearing in host tissues as enlarged spheres or ovals containing spores. Most were originally classified in various groups as fungi, protozoa, or colorless algae, but they form a coherent group on molecular trees, closely related to both animals and fungi, making them of interest to biologists studying the origins of these kingdoms.
- classification
- Class Ichthyosporea (Opisthokonta, Eukaryota)
- also_known_as
- DRIP clade, Mesomycetozoea
- morphology
- Enlarged spheres or ovals containing spores
- habitat
- Parasites of fish and other animals
- notable_member
- Rhinosporidium seeberi (infects birds and mammals, including humans)
- evolutionary_position
- Sibling-group of the Filozoa (which includes animals)
Lore & Background
In a 2008 study, the Ichthyosporea emerged robustly as the sibling-group of the clade Filozoa, which includes animals. Huldtgren et al., following x-ray tomography of microfossils from the Ediacaran Doushantuo Formation, interpreted certain structures as mesomycetozoan spore capsules, suggesting an ancient lineage. The name Mesomycetozoa (without a third 'e') is also used, but Mendoza et al. employ it as an alternate name for basal Opisthokonts.
Reader's Guide
The Ichthyosporea hold significance primarily as a key group for understanding the evolutionary origins of animals and fungi. Their position on molecular trees as the sibling-group of Filozoa places them at a critical branching point in opisthokont evolution. Despite their morphological simplicity and historical misclassification, they form a coherent clade that informs studies of multicellularity and parasitism. The interpretation of Ediacaran microfossils as mesomycetozoan spore capsules hints at their deep evolutionary history. Their inclusion of parasites affecting fish and even humans (e.g., Rhinosporidium seeberi) also gives them medical and ecological relevance. The ongoing taxonomic refinements, including the addition of former fungal orders, underscore the group's dynamic classification and its role in clarifying the boundaries between traditional kingdoms.
Did You Know?
- The name DRIP is an acronym for the first protozoa identified as members: Dermocystidium, the rosette agent, Ichthyophonus, and Psorospermium.
- One species, Rhinosporidium seeberi, infects birds and mammals, including humans.
- The name Mesomycetozoea refers to their evolutionary position in the middle ('Meso-') of fungi ('-myceto-') and animals ('-zoea').
- Huldtgren et al. interpreted microfossils from the Ediacaran Doushantuo Formation as mesomycetozoan spore capsules.
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