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Burrowing worms that belong to Polydora spp. infest marine mollusks cultured worldwide, causing problems for production and marketing. The clam Chione fluctifraga is semi-cultured in Bahı´a Falsa, Baja California, NW Mexico, and some clams harbor burrowing worms. The present study was carried out to determine the identity of the worm species infesting the clam, the infesting process by cohabitation of infested and non-infested clams in aquaria with a variety of substrates (fine sand, gross sand, plastic bag used for clam culture, and aquarium without substrate) and turbulence conditions, and the occurrence of architomy phenomena in connection with infestation of the clam. The burrowing worm was considered as a nova species due to its singular limbate neurosetae and notosetae in the setiger 5, hooks in the setiger 6, eyes not present, and general pigmentation, among other characteristics. Infestation was similar in all substrates and turbulence conditions, but it was more abundant on clams previously infested than on those free of worms, showing a preferential settlement of worm infesting stages on pre-infested clams. Regeneration was observed in all segments of the worm: anterior (metastomium), medium, and posterior (prostomium); the complete regeneration time occurred in 40 days. This is the first record of architomy in a species of Polydora and this phenomenon could account for the increase of infestation intensity in pre-infested clams at the end of the study period. Infestation of clams by settling polichaete in the conditions studied, and the architomy process in this worm species, shows its great infesting capacity. [Copyright &y& Elsevier]

The copepod Pseudomyicola spinosus infests marine mussels and other commercial bivalve species. There is a lack of information on the infestation process and on its relationship to size, density, and health of the host. To obtain this information, an infestation study of the copepod in Mytilus galloprovincialis in field conditions was carried out. Results showed that the intensity of infestation is closely related to host size [F((2,810))=198.33; p<0.001], but not to density [F((2,810))=0.96; p<0.38]. After an initial colonization of the host by the infested copepodite stages, an equilibrium between the intensity of the infestation and host size is maintained; mean intensity in small mussels was 1.57, in medium mussels it was 4.23, and in large mussels it was 9.86. Adult stages were observed after a period of 30 days, and ovigerous females were observed after a period of 45 days. Copepods may be found on the branches and mantle (89.5%) and inside the digestive tract (10.5%); in this last case and at the end of the study period some histological disorders were found such as obstruction of the intestine, rupture of the digestive epithelia, and encapsulations around digestive tissues. Most infested mussels showed the lowest meat weight in relation to shell weight; however, the reproductive stage may affect this observation., ((c) 2002 Elsevier Science (USA).)