Seasonal abundance and growth of the scyphomedusa Aurelia aunta were studied during 1991 and 1992 In the Inner part of a small shallow fiord, Kertinge Nor, Denmark Uunng both years, mass occurrence of A aunta was observed, and a maximum value of ca 300 ind m-3 was measured In Apnl 1992 Growth was poor in the fiord and the maximum mean umblella diameter of medusae was only 54 i 12 mm and 37 + 15 mm In 1991 and 1992 respectively Growth, clearance, lngestlon and resplratlon were measured at different prey concentrations in the laboratory, and an energy budget was estabhshed Ephyrae (4 mm in diameter] were offered rotiferas (Brachjonus plicatllls) in concentrations ranging from 7 to 13000 ind I ' Clearance of ephyrae decreased 30 to 5 0 % with increasing prey concentration, and a curved relationship between prey concentration and lngestlon was found A maximum speclflc growth rate of 0 2 d ' was measured In the laboratory at 400 B plicatilis 1 ', correspondlng to 60 pg C 1. ' In Kertinge Nor, the growth rate never exceeded 0 1 d ' The average zooplankton concentration In Kertinge Nor was only 5 p g C I ' and it could therefore be concluded that A aunta was food hmited in the fiord

With the aim of studying molecular mechanisms of virulence and immunogenesis of Egtved virus, monoclonal antibodies (MAbs) were produced against 4 dominant virus proteins (G, N, M, and M2). The reactivity of each MAb was determined by ELISA, immunoblotting, immunofluorescence and plaque neutralization. Antibodies specific for each of the 4 proteins, as demonstrated by immunoblotting, gave characteristic reactions in ELISA as well as immunofluorescence. None of the MAbs were able to neutralize virus in vitro. When analysed in immunofluorescence using cell cultures fixed at different times after inoculation with live virus, the N-protein was first to be detected followed by M,, G and M2. G-specific MAbs reacted with either a 'reticular', or a 'Go1gi'-form of the G-protein. Results are consistent with published information on the protein compositon and cellular appearance pattern of other rhabdovimses studied in vitro.

ABSTRACT. The humoral immune response to Egtved virus, the causative agent of viral haemorrhagic septicaemia (VHS) in rainbow trout Oncorhynchus mykiss, was investigated by means of the enzymelinked immunosorbent assay (ELISA), immunofluorescence (IF), a n d the 50 'X plaque neutralization test (50°/"PNT). Sera from fish immunized with virus under aquarium conditions as well a s sera collected from fish in farms with different VHS status were included In the experiments. ELISA proved to b e more sensitive and less time-and material-consuming than either IF or 50°/~PNT Using Elisa, antibody to Egtved virus was found in 54 %I of fish from infected trout farms examined w h~l e only 16 % were positive by 50°/r,PNT The IF test had a sensitivity close to that of ELISA, but was less suitable for examination of large numbers of sera. Non-neutralizing antibodies tend to perslst longer after VHS infection than neutralizing antibodies. The kinetics of the antibody response was close to that prev~ously published. No anamnestic immune response was observed with any of the tests. We conclude that our ELISA is well suited for VHS surveillance.

No abstract

The concentration of serum immunoglobulin in different groups of rainbow trout Salrno gairdneri was measured by means of a single radial immuno&ffusion test. The normal IgM concentration was 3.3 mg ml-' in a group of free-living trout. Hypergamrnaglobulinaemia was found in PKDinfected fish and in fish from a trout farm with VHS and ERM, while the IgM concentration was low in sera from fish living under aquarium con&tions. Inhvidual variations were very pronounced. The purity of reference preparations and the specificity of antisera used were examined by crossed in~munoelectrophoresis.