Author(s): EL MENIF Najoua Trigui, LAHBIB Youssef, LE PENNEC Marcel, FLOWER Roger, BOUMAIZA Moncef
Monthly withdrawals than 100 of the Murex Hexaplex trunculus, 40 to 60 mm in height, were conducted from January to July 2003 two stations in northern Tunisia: that of Menzel Jemil, on the edge of the lagoon Bizerte and that of the cement plant, located in the lagoon of the communication channel with the Mediterranean. The physicochemical parameters (temperature, salinity, oxygen and pH) were recorded monthly during the study period. Monitoring the relative growth of the opening of the shell, flesh and dry shell found that in individuals of the lagoon, the growth of the opening and the dry flesh is higher than in individual channel. However, the shell growth is higher in individuals canal for superior individuals to 60 mm. Comparing them females and males together, we found that the growth of the flesh and of the dry shell is greater than the cement station from some shell size. Examination of the soft part of 100 to 150 individuals collected in January, March and June showed that the rate of imposex is 100% at the cement station against 65.8% that of Menzel Jemil. The intensity of the development of the male reproductive tract in females appears to have an impact on fertility of the gastropod. Following a gamete emission held in aquarium during the spawning period (February-March to June), we found that the rate of individuals emitting capsules, and the average fertility, are more important in lagoon that channel. The excessive development of the male reproductive tract of the female of the cement plant, including the vas deferens the side of the egg hole, has a negative impact on the gamete emission.