Dietary saponins and phytosterols do not affect growth,intestinal morphology and immune response of on‐growing European sea bass (Dicentrarchus labrax)

This study was the first to investigate the effect of soy antinutrients, saponins and phytosterols, in on‐growing sea bass. Seven diets were formulated: a control diet (fishmeal and fish oil based) and six diets containing 1 or 2 g kg^?1 levels of soya saponins, 5 or 10 g kg^?1 levels of phytosterols or a combination of 1 g kg^?1 saponins + 5 g kg^?1 phytosterols or 2 g kg^?1 saponins + 10 g kg^?1 phytosterols. After a 59 days feeding trial fish were weighed, faeces collected for digestibility studies and plasma sampled for cholesterol quantification. At day 15 and 59, distal intestine (DI) samples were collected for histological evaluation and quantification of maltase (Malt), alkaline phosphatase (AlP) and leucine aminopeptidase (LAP) activities. At day 59, DI was collected for gene expression of AlP, Malt and immune related genes. Antinutrients had no effect on fish performance, digestibility, plasma cholesterol levels and digestive enzymes activities and gene expression. Only mild morphological changes were present in groups fed high levels of saponins + phytosterols. Expression of immune related genes showed no differences between groups. Overall, on‐growing sea bass showed high tolerance to dietary antinutrients up to the levels tested.     

The influence of Gyrodactylus salaris Malmberg 1957 (Monogenea) on the epidermis of Atlantic salmon,Salmo salar L., and brook trout,Salvelinus fontinalis (Mitchill): experimental studies

The effect of Gyrodactylus salaris on the epidermal structure of hatchery-reared brook trout parr and Norwegian Atlantic salmon parr was evaluated. Both species were initially susceptible to this parasite, but whereas populations on salmon increased until the host died, brook trout responded to, and eventually eliminated, their infections. Salmon skin samples taken 14 days p.i. showed a reduced mucous cell concentration (less than 1500 cells mm^–2 on the head compared with 2000 cells mm^–2 in controls; the same trend was also seen in other sites) and the epidermis was thinner (48 μm compared with 60 μm on pectoral fins; similar trend seen in other sites) than in uninfected controls kept under identical conditions. Brook trout skin samples were taken 50 days p.i., when the hosts had responded to, and almost eliminated, their infections. No change was then observed in mucous cell density, while the number of epidermal cell layers and the epidermal thickness of brook trout had increased slightly following infection. These results are related to the nature of the host response, and the thinning of the epidermis and loss of mucous cells may in some way be related to the inability of Norwegian salmon parr to respond to the parasite.     

Mycobacterium avium in pygmy rabbits (Brachylagus idahoensis): 28 cases.

The Columbia basin subpopulation of pygmy rabbit Brachylagus idahoensis was listed as endangered by the United States Fish and Wildlife Service in November 2001, and no pygmy rabbits have been seen in the wild since spring 2002. Captive propagation efforts have attempted to increase population size in preparation for reintroduction of animals into central Washington. Disseminated mycobacteriosis due to Mycobacterium avium has been the most common cause of death of adult captive pygmy rabbits. Between June 2002 and September 2004, mycobacteriosis was diagnosed in 28 captive adult pygmy rabbits (representing 29% of the captive population), in contrast to 18 adult pygmy rabbits dying of all other causes in the same time period. Antemortem and postmortem medical records were evaluated retrospectively to describe the clinical course of mycobacteriosis in pygmy rabbits, physical examination findings, and diagnostic test results in the diagnosis of mycobacteriosis in pygmy rabbits. Various treatment protocols, possible risk factors for mortality, and recommendations for prevention of mycobacteriosis were evaluated also. Compromised cell-mediated immunity appears to be the best explanation at this time for the observed high morbidity and mortality from mycobacterial infections in pygmy rabbits.     

Prevalence and dispersal of a facultative bacterial symbiont associated with an endemic metazoan host

Co-dispersal is of primary importance in symbiotic relations between macro- and micro-organisms. Obligate symbionts generally follow the same dispersal pattern as their host, while it still remains unresolved whether hosts and their facultative symbionts follow the same dispersal patterns. Here we addressed the question of symbiont and host co-dispersal by analyses of the earthworm Lumbricus terrestris, and its facultative bacterial symbiont Verminephrobacter. We analyzed co-dispersal by direct sequence-based typing of the earthworm mitochondrial ND4, and the symbiont adk genes, respectively. A total of 96 earthworms from Norwegian (n = 20), German (n = 20), English (n = 31) and Canadian (n = 25) populations were analyzed. We found that the earthworms were mainly endemic, while the symbiont showed a more complex dispersal pattern. The symbiont showed a significant difference in prevalence between the geographic regions. In addition, we found a low degree of co-evolution between host and symbiont, with some of the symbiont sequence types being globally distributed. Future research, however, is needed to resolve whether the symbiont is truly globally distributed, in contrast to its endemic host.