Parasite-mediated shell alterations in Recent and Holocene sub-antarctic bivalves: the parasite as modeler of host reaction

ITUARTE C., F. CREMONTE Y D. G. ZELAYA

INVERTEBRATE BIOLOGY

The American Microscopical Society

Lugar: Kansas; Año: 2005 vol. 124 p. 220 - 229

1077-8306

New data on shell reactions elicited by larval digeneans in bivalves from Recent sub-Antarctic populations and late Holocene Patagonian deposits are reported. Shell alterations, which are traces of digenean trematode infections, were found affecting intertidal bivalve populations from Malvinas (Falkland) Islands, Burdwood Bank, Beagle Channel, and from Holocene deposits at Tierra del Fuego (Argentina). The bivalve species involved belonged to the families Nuculanidae, Cyamiidae and Neoleptonidae. Such reactions consisted of quite unusual dome or igloo-shaped calcifications on the inner shell surface. The similarities and uniqueness of this reaction in different bivalve species reported here suggest that the invasive agent is the same. Based on previous findings of morphologically identical shell alterations in Gaimardia trapesina (Bivalvia, Gaimardiidae) from Magellanic and sub-Antarctic waters, it is suggested that the parasites responsible for the traces reported here belong to a species of the Gymnophallidae genus Bartolius. The bivalves in which the reaction reported here was observed, belong to three different superfamilies; they share a similar crystalline shell microstructure: aragonite with homogeneous structure. After a review on the available information dealing with bivalve shell-mantle reactions against digeneans, it is hypothesized that parasites are responsible for the modeling of the host response they elicit. The similarity in shell mineralogy and crystalline structure of bivalves involved would be indicative that, although the specific characteristics of the reaction depend on the parasite, they would be probably constrained by some characteristics of the host shell structure.