Cultured Gilthead Sea Bream Sparus Research Articles

Genetic variation of Sparicotyle chrysophrii (Monogenea: Microcotylidae) from the gilthead sea bream Sparus aurata (Teleostei: Sparidae) in the Mediterranean Sea.

The gill monogenean Sparicotyle chrysophrii (Van Beneden & Hesse, 1863) Mamaev, 1984 is a specific and common parasite of wild and cultured gilthead sea bream Sparus aurata Linnaeus, 1758, able to cause disease and mortality in aquaculture systems. Few molecular studies have been carried out on this monogenean, and its population structure and genetic diversity are barely known. This study provides the first contribution to the population genetic variation of S. chrysophrii, based on two molecular markers-the structural ribosomal RNA (rRNA) for the large subunit (28S) and the cytochrome c oxidase subunit I (COI) gene. Samples were collected from the gills of farmed and wild S. aurata from Italy and the Spanish Mediterranean. The analysis included previously published sequences. The 28S rDNA analysis was consistent with previous studies of specimens isolated from S. aurata and confirmed the presence of only one species on the gills of this host in the Mediterranean Sea. The COI sequences analysis suggested that the samples isolated in a previous study from a different host species, wild Boops boops (Linnaeus, 1758) in the Adriatic Sea, may represent a new undescribed sister species of S. chrysophrii. The low nucleotide diversity of S. chrysophrii isolated only from S. aurata versus the high haplotype diversity revealed small differences between haplotypes. The haplotypes shared between wild and farmed hosts from Spain provided the first molecular evidence of the possible transfer of S. chrysophrii between wild and farmed populations of S. aurata. The mtDNA COI analysis did not show a clear genetic structure, probably the result of several factors including coevolution, wild and farmed host interactions, and host population structure in space and time.

Sparicotyle chrysophrii (Van Beneden and Hesse 1863) (Monogenea: Polyopisthocotylea) parasite of cultured Gilthead sea bream Sparus aurata (Linnaeus 1758) (Pisces: Teleostei) from Corsica: ecological and morphological study

Sparicotyle chrysophrii infections were highlighted during a parasitological monitoring carried out on cultured Gilthead sea bream Sparus aurata Linnaeus 1758 from aquaculture sites in Corsica. Factors and biological mechanisms regulating parasites populations, particularly controlling the infestation and survival of monogeneans have been studied. Variations in infection support the hypotheses that the main factor determining the infection of S. chrysophrii was temperature and that the parasite life cycle could be influenced by fish size and fish age. One hundred forty-nine of 280 S. aurata studied were infected. Seasonal differences in prevalence of infection were observed in all farms studied. A similar pattern was observed for parasite abundance with maximal infection levels occurring when water temperature were lower. A statistically significant dependence between infection and host size was also observed. The study of the surface topography of S. chrysophrii with scanning electron microscopy highlighted morphological adaptations not previously described. Parasites have developed diverse mechanisms of survival within the host that facilitate the establishment of infection. We mainly studied sensory structures and the anchoring systems of the parasite, i.e., filaments of eggs and haptor, enabling it to ensure the dispersal and survival of the species.

Morphology and Ultrastructure of Cryptobia eilatica n. sp. (Bodonidae: Kinetoplastida), an Ectoparasite from the Gills of Marine Fish

A marine kinetoplastid flagellate, Cryptobia eilatica n. sp., is described from the gills of cultured gilt-head sea bream Sparus aurata L. and wild black-spot sea bream Diplodus noct (Valenciennes) in the Red Sea. The trophozoite is elongated and lacks a contractile vacuole and undulating membrane. The body averages 13.5 x 4.1 microns, anterior flagellum 9.7 microns and free portion of recurrent flagellum 15.2 microns. The ultrastructural features of the species exhibit great similarity to various previously studied Cryptobiids. Cryptobia eilatica trophozoites feed on bacteria, show a preference for the branchial interlamellar crypts, and attach to the host epithelium by means of the recurrent flagellum. Neither penetration into the epithelial cells, nor any direct damage to host tissue was observed. Cryptobia eliatica inhabits a purely marine habitat, but its trophozoite tolerates salinities as low as 10 ppt.

Aspects of the biology of Cryptocaryon irritans, and hyposalinity as a control measure in cultured gilthead sea bream Sparus aurata

The life cycle and halotolerance of Cryptocaryon im-tans were studied. Trophonts completed their growth phase on the host in 3 to 7 d. The reproductive process of the tomonts yielded tomites as early as 3 and as late as 28 d. Tomite life span was 24 to 48 h. Trophonts embedded in the fish skin withstood 18 h exposure of the host to fresh water. Tomonts withstood salinities ranging from 20 to 70 %O for 48 h without losing viability. Tomites were seen emerging only from tomonts kept in constant salinities ranging from 25 to 50 %o. All tomonts degenerated when immersed in 0 to 10 %O for 3 h. Eradication of the parasite based on these findings was achieved. Four consecutive treatments of 3 h each in 10 %O salinity 3 d apart destroyed all tomonts before tomites could excyst and were well tolerated by the fish. C. imitans life cycle was similarly interrupted by 4 consecutive transfers of fish into clean tanks at 3 d intervals. A certain degree of resistance to C. irritans invasion was observed in fish that had survived several infections.