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

CRISTIÁN ITUARTE; FLORENCIA CREMONTE; DIEGO G. ZELAYA

INVERTEBRATE BIOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Año: 2005 vol. 124 p. 220 - 229

1077-8306

 New data on shell reactions elicited by larval digeneans in bivalves from Recentsub-Antarctic populations and late Holocene Patagonian deposits are reported. Shell alter-ations, which are traces of digenean trematode infections, were found affecting intertidalbivalve populations from Malvinas (Falkland) Islands, Burdwood Bank, Beagle Channel,and from Holocene deposits at Tierra del Fuego (Argentina). The bivalve species involvedbelonged to the families Nuculanidae, Cyamiidae, and Neoleptonidae. Such reactions con-sisted of quite unusual dome or igloo-shaped calcifications on the inner shell surface; thesimilarities and uniqueness of this reaction in different bivalve species reported here suggestthat the invasive agent is the same. Based on previous findings of morphologically identicalshell alterations in Gaimardia trapesina (Bivalvia, Gaimardiidae) from Magellanic and sub-Antarctic waters, it is suggested that the parasites responsible for the traces reported herebelong to a digenean platyhelminth species of the Gymnophallidae genus Bartolius. The hostbivalves reported here belong to three different superfamilies, and share a similar crystallineshell microstructure: aragonite with homogeneous structure. After a review of the availableinformation dealing with bivalve shell-mantle reactions against digeneans, it is hypothesizedthat parasites are responsible for the modeling of the host response they elicit. However, al-though the specific characteristics of the reaction depend on the parasite, they would prob-ably be constrained by some characteristics of the host shell structure.