| Summary: | Previous work has shown that it is possible to grow the sea urchin, Psammechinus initial-is, alongside Atlantic salmon, Salmo salar, in a polyculture system. The intensive nature of salmon fam-ling demands the use of antibiotics, such as oxytetracycline (OTC), administered with the feed, which has the potential to accumulate within the edible part of the urchin, the gonad. There is little information on the effect and potential for accumulation of antibiotics in echinoderms. Thus, accumulation and residue elimination of OTC in the gonads of the echinoid, P. miliaris, following oral administration were evaluated in urchins of high and low nutritional status, under laboratory conditions. A commercially prepared, medicated salmon food (29 mg OTC g(-1)) was fed to urchins ad lib for 12 days. Gonad tissue was sampled at intervals during the medication period (5th, 8th, and 12th day) and after its cessation (20th, 40th and 70th day). OTC analyses were carried out by high performance liquid chromatography (HPLC), after solid phase extraction (SPE.). OTC significantly reduced gonadal growth rates (g day(-1)) in urchins conditioned on salmon feed. Individual urchins demonstrated considerable variation in amount of OTC accumulated. On day 12, mean OTC residue concentrations were 69.9 mug g(-1) + SD 35.7 and 57.95 mug g(-1) +/- SD 26.9 in urchins conditioned on salmon food and L saccharina, respectively. At day 70, mean OTC residue concentrations were above 8 mug g(-1) in both treatments, indicating a long residence time of the drug within gonadal tissue. A linear model was used to describe OTC uptake and elimination kinetics in the gonad of P. miliaris. No significant differences in accumulation and residue depletion of OTC in the gonads were observed between urchins of different nutritional status. The OTC half-life (t(1/2)) of the elimination phase in gonad tissue was 24.6 days (at 11-13 degreesC). These results reflect a 'worse case scenario' for the uptake and elimination of OTC in the gonads of P. miliaris maintained with finfish receiving medicated feed (C) 2001 Elsevier Science B.V. All rights reserved.
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