Pearls in the ribbed mussel Aulacomya atra caused by polydorin polychaetes (Spionidae) infestation

What is it about?

Aulacomya atra populations of the San Jose gulf, Northern Patagonia, Southwestern Atlantic Ocean, are infested by two polydorin species, Polydora rickettsi and Dipolydora cf. giardi. The infestation by these boring polychaetes causes the formation of pearls which is evidenced by the presence of capsules containing polydorin tissue debris and the elemental composition of organic material inside the pearls. Moreover, a positive relationship between the abundance of perforations of polydorin polychaetes and abundance of pearls was found by applying generalized lineal model analysis. These results constitute the first evidence of pearls formation due to infestation by polychaete.

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Photo by Ovidiu Creanga on Unsplash

Photo by Ovidiu Creanga on Unsplash

Why is it important?

In Northern Argentine Patagonia, two polydorin species were reported: Polydora rickettsi Woodwick, 1961, boring all the exploited molluscs except the mussel Mytilus edulis, and Dipolydora cf. giardi (Mesnil, 1896) affecting only the ribbed mussel Aulacomya atra . In this region, A. atra is exploited by artisanal fishermen, who reported their concern about the presence of pearls, making this resource not suitable for the commercial market. This is important to investigate the cause of the pearl formation in A. atra populations, and what variables (sampling site, shell length, condition index and abundance of polydorin perforations) affect the bundance of pearls