CONICET | Buscador de Institutos y Recursos Humanos

The relative size of the Aristotle´s lantern of most sea urchins varies in relation to the food availability and it is often used to infer the availability of food of the environment that the sea urchins inhabit. The aim of the present study was to evaluate the Aristotle´s lantern morphology plasticity of Arbacia dufresnii in populations with different environmental characteristics, either mussel beds or disturbed areas by the invasive alga Undaria pinnatifida along the Patagonian Atlantic coast. The test diameter of the sea urchins along with the weight and high of the lanterns, the jaw lenght and rotula lenght were measured. Classic and geometric morphometric analyses were performed to test differences among populations. The length of the jaw was the best indicator to describe the relative changes in size of the Aristotle´s lantern. The largest length of the jaw was measured in individuals from disturbed areas dominated by the invasive algae U. pinnatifida. The rotula shape changed with the increase of the diameter of the sea urchins, it tends to be more elongated with larger sea urchins.