The sea bream, Diplodus vulgaris, is a marine teleost widely distributed in the Mediterranean and eastern Atlantic coastal waters. The larvae colonize shallow waters along rocky shores where, after a short period spent in the water column, they settle. Such habitat transition is characterized by important shape changes, mostly related to their swimming capacity and feeding behavior. In this study, geometric morphometrics has been used to characterize shape changes during early juvenile life. All specimens were collected in a single locality in the Gulf of Tigullio (Ligurian Sea), and data relative to their position in the water column and to the habitat selected were recorded. A total of 14 landmarks were collected on 82 specimens (range of standard length 11.2-82.8 mm). Landmark configurations were superimposed, and residuals were modeled with the thin-plate spline interpolating function: shape changes were visualized as splines. Growth trajectories were computed using relative warp analysis. Shape changes in the observed size range concern an overall broadening along the dorsoventral axis, a displacement of the mouth position, and a negative allometry of the head region. The growth trajectory resembles a theoretical saturating growth curve: shape change is fast for small sizes and slows down at standard lengths of approximately 28 mm, where an increase in size is not accompanied by a change in shape. This size value corresponds roughly to the size at which the settlement and the successive phase of dispersion of D. vulgaris have been observed in the area of study. This approach provides quantitative descriptors of shape changes and allows for the visualization of allometry. This method implies the definition of a new space for biological shapes in which shape trends and clusters can also be identified in relation to nonmorphological variables. As such it might contribute to the definition of the morphospace in the context of ecomorphology.

For a toxicity assessment of substances entering the marine environment, it is preferable to carry out ecotoxicological tests on a base-set of taxa utilizing target species belonging to different trophic levels. In this study a battery composed of Vibrio fischeri (bacteria), Dunaliella tertiolecta (algae), Tigriopus fulvus (crustacea), Paracentrotus lividus (echinodermata), and Dicentrarchus labrax (pisces) was used for acute toxicity testing of sodium dodecyl sulfate (SDS). SDS is an anionic surfactant widely employed in industry, agriculture, and domestic usage and therefore is found in abundance in the environment, particularly in the sea. The mean values of EC50 obtained were 2.6, 4.8, 7.4, 3.2, 7.3 mg L(-1), respectively, for V. fischeri, D. tertiolecta, T. fulvus, P. lividus, and D. labrax. The results indicate the high acute toxicity of SDS with respect to all the trophic levels represented by the target species. In addition, they highlight the usefulness of employing a base-set of taxa rather than a single species in toxicological tests, in order to obtain more reliable information for the evaluation of toxicity and potential hazards to the marine environment of selected substances.

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