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Jaafar Kefi F.,University of Carthage | Gargouri Ben Abdallah L.,Tunis el Manar University | Trigui El-Menif N.,University of Carthage | Mraouna R.,National Institute of science and Marine Technologies | El Bour M.,National Institute of science and Marine Technologies
Cahiers de Biologie Marine | Year: 2012

The present study was done with a view to characterize the health status of the Tunisian date mussel Lithophaga lithophaga following the detection of shell disturbances on the external and internal side of the valves. Macroscopic and microscopic observations and bacteriological analysis were carried out seasonally from 2004 to 2006 on samples from Bizerte Bay (Northern Tunisia). Burrowing annelids and sipunculids living inside galleries on the internal valve surface have been removed. Shell thinness and galleries have led to serious morphological disturbances of the lithophagid bivalves. Besides, brown-blackish or white stains appeared on the external and/or inner surfaces of the valves with the periostracal layer missing. Shell ESEM (Environmental Scanning Electron Microscopy) examination showed the presence of thick mucilage on the external valve surfaces with the microscopic tubiculous annelids stuck to them. On the internal side, the shell was perforated by minute pores of 2 urn diameter. Otherwise, no parasites were specified on the date mussel flesh. Bacteriological analysis revealed important accumulation of heterotrophic mesophyllic bacteria particularly in summer and autumn (3.107 and 2.108 CFU ml-1 respectively). Pathogen Vibrionaceaes appeared in high concentration during the study. Three kinds of bacteria (Vibrio hollisae, Pasteurella pneumotropica and Chtysomonas luteold) are suspected of being the cause of stains in L. lithophaga. Source

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