Tissue Parameters of the Sea Urchin ( Paracentrotus Lividus ): The Effects of Magnesium and Transport Stress

The present study investigates some biochemical and biological variables in sea urchins (Paracentrotus lividus) that were stressed in the course of collection, transportation and laboratory conditioning and the effect thereon of pre-treatment with a test compound; magnesium chloride (MgCl₂). Handling and transportation for 5h resulted in significantly decreased gonadal indices due to unplanned spawning. The pre-treatment of sea urchins with 5 mmol l⁻¹ MgCl₂ reduced unplanned spawning during all of the experiments. Protein content and humidity were significantly higher (p < 0.05) in sea urchins treated with Mg than in the control group, these differences between groups were maintained throughout the experimental period. The analyses of gonad mineral compounds (Na⁺, K⁺, P, Ca²⁺ and Mg²⁺) showed a significantly higher (p < 0.05) Na⁺ and K⁺ tissue contents in the Mg-treated group than the control group throughout the conditioning period. Phosphorus with initial similar levels in both groups, however, showed a significantly higher gonad level (p < 0.05) in the Mg-treated group towards the end of the experiment (> 9 days).