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A 480-million-year-old parasitic spionid annelid
Karma Nanglu1,2,3, Madeleine E Waskom1, Sarah R Losso1
1Museum of Comparative Zoology and Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA.
Iscience
|November 17, 2025
Summary
Fossil bivalves from Morocco reveal ancient parasitic interactions. This discovery pushes back the known origins of spionid-like polychaete worms to the Early Ordovician period.
Area of Science:
- Paleontology
- Evolutionary Biology
- Marine Biology
Background:
- The Paleozoic fossil record offers insights into life history evolution via preserved interspecific interactions.
- Direct evidence of species interactions is rare, even in exceptional fossil sites.
- The Fezouata Shale biota in Morocco is known for exceptional preservation.
Purpose of the Study:
- To investigate evidence of parasitic organisms within the Fezouata Shale biota.
- To determine the temporal origins of specific parasitic behaviors.
Main Methods:
- Microscopic examination of seven specimens of the bivalve mollusk *Babinka*.
- Analysis of characteristic, question mark-shaped shell borings.
- Comparison of fossil borings with those produced by modern and fossil spionid polychaetes.
Main Results:
- Seven *Babinka* bivalve specimens exhibited shell borings.
- The borings are consistent with those made by parasitic spionid polychaetes.
- This indicates the presence of spionid-like parasitic behavior in the Early Ordovician.
Conclusions:
- Parasitic spionid polychaetes, or similar organisms, existed in the Early Ordovician.
- This represents a significant biostratigraphic shift from the previously accepted Devonian origin.
- Undiscovered life history strategies likely remain within the Fezouata Shale biota.
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