Associated and digenean fauna of the mussel Mytilus galloprovincialis cultured on shellfish tables in the lagoon of Bizerta (Tunisia)

Abstract

1 - Shellfish tables used for the breeding in bags of the oyster Crassostrea gigas and the mussel Mytilus galloprovincialis are suitable support for rapid colonization by marine living organisms.2 - During the period, June 2008 to May 2009, monthly samples of M. galloprovincialis were collected from the mytiliculture farm situated in Menzel Jemil (Bizerta Lagoon). Specimens were analyzed to identify their associated and digenean fauna.3 - Overall samples contain 68 taxa belonging to 12 zoological classes. Crustaceans, Polychaetes and Bivalves dominated largely the associated fauna, with frequencies of 34.7%, 22.9% and 10.6% respectively. The Polychaete Myrianida pinnigera was identified for the first time in the Tunisian coast. The remaining groups of associated fauna (Ascidia, Ophiuroids, Gastropods, Actinaria, Gymnolaemata, Demosponges, Calcispongia, Turbellaria, and Echinids,) accounted for only 31.8%. Diversity indices showed a temporal variation of the taxonomic structure of listed groups related to the environmental conditions and the biological cycles.4 - The examination of ~1400 individual mussels showed the occurrence of a low number of Proctoeces maculatus sporocysts (Digenea, Fellodistomodae). Bag-shaped sporocysts containing, according to the maturation stage, germinal balls, daughter sporocysts and or cercariae colonize at the beginning of the infection, the digestive gland then gonads and totality of the mantle.