RESUMEN
We define co-introduced parasites as those which have been transported with an alien host to a new locality, outside of their natural range, and co-invading parasites as those which have been co-introduced and then spread to new, native hosts. Of 98 published studies of co-introductions, over 50% of hosts were freshwater fishes and 49% of parasites were helminths. Although we would expect parasites with simple, direct life cycles to be much more likely to be introduced and establish in a new locality, a substantial proportion (36%) of co-introductions were of parasites with an indirect life cycle. Seventy-eight per cent of co-introduced parasites were found in native host species and can therefore be classed as co-invaders. Host switching was equally common among parasites with direct and indirect life cycles. The magnitude of the threat posed to native species by co-invaders will depend, among other things, on parasite virulence. In 16 cases where co-introduced parasites have switched to native hosts and information was available on relative virulence, 14 (85%) were more virulent in native hosts than in the co-introduced alien host. We argue that this does not necessarily support the naïve host theory that co-invading parasites will have greater pathogenic effects in native hosts with which they have no coevolutionary history, but may instead be a consequence of the greater likelihood for parasites with lower virulence in their natural host to be co-introduced.
RESUMEN
Physiological parameters and growth performance of Huso huso fingerlings fed with diet supplemented with herbal plants were studied in this study. Dietary treatments were 0 g (= control), 1.0 g (garlic) and 1.0 g (ginger) of 100 g(-1) feed for 60 days. Specific growth rate, body weight gain and condition factor were significantly increased in ginger treatment at the end of the trial. Highest levels of erythrocyte and hematocrit were observed in fingerlings ginger group after 60 days. Globulin increased significantly in ginger group, and the highest level of albumin was observed in garlic group. To sum up, it seems that herbal diet can improve some growth and physiological parameters in this species.