Difficulty: Medium
Correct Answer: Microspora (Microsporidia)
Explanation:
Introduction:
A hallmark of microsporidian parasites is a resistant spore containing a coiled polar filament (also called a polar tube). Upon germination, this tube everts to inject the infective sporoplasm into a host cell. Recognizing this structure anchors quick phylum-level identification.
Given Data / Assumptions:
Concept / Approach:
Microspora (Microsporidia) are obligate intracellular parasites of many animals, including humans. Their infectious spores show the diagnostic polar tube apparatus. This separates them from Apicomplexa (apical complex but no polar tube), Labyrinthomorpha (slime-net protists), Myxozoa (multicellular metazoan parasites with different spore architecture), and Sarcomastigophora (a broader traditional grouping lacking the polar tube hallmark).
Step-by-Step Solution:
Focus on the unique morphological clue: a coiled polar filament inside the spore.
Match that feature to Microspora/Microsporidia.
Exclude other phyla that lack this injection apparatus.
Select “Microspora (Microsporidia).”
Verification / Alternative check:
EM images and staining methods (e.g., chromotrope-based) reveal polar filament coils, confirming microsporidian identity in clinical specimens.
Why Other Options Are Wrong:
Labyrinthomorpha – gliding in mucous nets; no polar tube spores.
Apicomplexa – apical complex and gliding motility, but not polar filament spores.
Myxozoa – spores with polar capsules but belonging to metazoa; architecture differs.
Sarcomastigophora – heterogeneous, lacks this defining spore feature.
Common Pitfalls:
Confusing microsporidian polar tubes with myxozoan polar capsules; the taxa and ultrastructure differ and microsporidia are intracellular protistan parasites.
Final Answer:
Microspora (Microsporidia).
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