Parassitosi sostenuta da Diplectanum aequans (Wagener 1857) Diesing 1858 in branzino (Dicentrarchus labrax L.) di allevamento.
1983
Giavenni R.
The high incidence of trematodiasis caused by Diplectanum aequans in a one-year-old sea bass (Dicentrarchus labrax) population, reared in a 500 m('3) earth pond, led to the study of different aspects of this infestation. Monthly samplings from October 1979 to April 1981 showed a higher occurrence and intensity of trematodiasis during winter and its reduction corresponding with the highest water temperatures in summer. Observations carried out on the second and fourth gill arch of the left side led, respectively, to the following mean number of parasites: 9.1+/-0.7; 6.4+/-0.4. These results seem to confirm the hypothesis of a parasitic distribution with a decreasing gradient from external to internal gill arches. Histological examination of infested gills put into evidence a proliferative reaction of epithelial cells. One-hour formalin treatment at 375 ppm proved to be effective against juvenile stages of Diplectanum aequans, while the presence of adult trematodes was observed also after treatments at higher formalin concentrations (1000 and 1500 ppm). Experimental infestion showed that sea bass larvae and juveniles (30-130 days old) can also be affected by Diplectanum aequans; at 18 deg C the biological cycle of the parasite appears to be longer than three months.
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