Impact and residence time of oxytetracycline in the sea urchin, Psammechinus miliaris, a potential aquaculture species

Previous work has shown that it is possible to grow the sea urchin, Psammec hinus initial-is, alongside Atlantic salmon, Salmo salar, in a polyculture system. The intensive nature of salmon fam-ling demands the use of antibiot ics, such as oxytetracycline (OTC), administered with the feed, which has t he potential to accumulate within the edible part of the urchin, the gonad. There is little information on the effect and potential for accumulation o f antibiotics in echinoderms. Thus, accumulation and residue elimination of OTC in the gonads of the echinoid, P. miliaris, following oral administrat ion were evaluated in urchins of high and low nutritional status, under lab oratory conditions. A commercially prepared, medicated salmon food (29 mg O TC g(-1)) was fed to urchins ad lib for 12 days. Gonad tissue was sampled a t 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 urch ins conditioned on salmon feed. Individual urchins demonstrated considerabl e variation in amount of OTC accumulated. On day 12, mean OTC residue conce ntrations 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 7 0, mean OTC residue concentrations were above 8 mug g(-1) in both treatment s, indicating a long residence time of the drug within gonadal tissue. A li near model was used to describe OTC uptake and elimination kinetics in the gonad of P. miliaris. No significant differences in accumulation and residu e 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 'w orse case scenario' for the uptake and elimination of OTC in the gonads of P. miliaris maintained with finfish receiving medicated feed (C) 2001 Elsev ier Science B.V. All rights reserved.