Experiments were performed in goldfish to determine the effects of a short-term exposure (24 h) to atrazine or diuron (0.5, 5, 50 microgram/L) on some behavior endpoints related to swimming and social activities. Observations were also made to assess the influence of such exposure on the behavioral responses of fish to the flow of a crude skin extract solution from conspecifics, active in social chemocommunication and producing alarm behaviors. Additive tests were run to check the behavioral responses of previously unexposed goldfish to the flow of a solution of atrazine- or diuron-contaminated water, at three concentrations (0.1, 1, 10 mg/L). Significant burst swimming reactions appeared in response to a 24-h exposure to atrazine, at the lowest concentration tested (0.5 microgram/L). A 24-h exposure to 5 microgram/L atrazine or diuron was found to induce various significant behavioral alterations in fish. At this concentration, both herbicides decreased grouping behavior and atrazine also increased surfacing activity. Herbicide-exposed fish showed a decreased grouping behavior during the flow of the skin extract solution. Sheltering was also decreased during the flow of the biological solution in fish exposed to atrazine. Moreover, fish exposed to diuron clearly displayed attraction responses to the flow of the skin solution. Previously unexposed fish showed a significant increase in burst swimming reactions in response to the flow of a solution of atrazine- or diuron-contaminated water, at all concentrations tested (0.1, 1, 10 mg/L). Furthermore, the diuron-contaminated flow was found to be significantly attractive at the highest concentration. These results indicate that a short-term exposure to a relatively low concentration (5 microgram/L) of atrazine or diuron can affect various behaviors of fish not only directly but also indirectly by altering the chemical perception of natural substances of eco-ethological importance. In consideration of the basic role of olfaction in fish behavior, these results also emphasize the need for further developments on the possible effects of aquatic toxicants on olfactory-mediated behaviors.
A detergent-solubilized fraction of skin mucus of carp (Cyprinus carpio) induced ion channels after reconstitution into planar lipid bilayers. A differential extraction using a non-ionic detergent followed by electrophoretic separation led to the isolation of two hydrophobic 31 -kDa and 27-kDa proteins. In contrast to the 27-kDa protein, which was glycosylated, the 31-kDa did not bind to concanavalin A. The reconstitution of these proteins into a planar lipid bilayer restored the ionophore behavior already observed with the crude mucus. The main unit conductance levels were about 900 pS for the 27-kDa protein and 500 pS for the 31-kDa protein, and selectivity measurements gave P J P , ratios of 0.6 and 1.0, respectively. These proteins had large potent microbicidal activities (0.018 -0.1 8 pM) against different strains of gramnegative and gram-positive bacteria. This behavior can be compared with insect defensins that are known to form large ion channels in the bacterial membrane. To exclude the eventuality of bacterial origin, the bacterial flora of the crude mucus were analysed and the following were identified: Pseudomonas cepacia ; Micrococcus luteus; Micrococcus roseus; Flavobacterium sp. ; Aeromonas hydrophila. Antibacterial assays with both proteins were performed against these specific strains and revealed good growth inhibition activities. Furthermore, microsequencing analysis showed that the 31-kDa protein was protected on its N-terminal extremity in contrast to the 27-kDa protein, which had a 19-amino-acid sequence. This last sequence, when compared with sequences in protein data banks, did not reveal any significant similarities to other proteins. These results suggest that these novel proteins could be involved in antibacterial defense processes in fish.
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