The role of models in science : a multicomprehensive experience with the sea urchin Paracentrotus lividus

Model organisms are frequently used in science teaching as they provide support and suggestions to help student understanding of basic biological phenomena. The common sea urchin Paracentrotus lividus is a good didactic model for the teaching of different biological concepts at school and, in addition, is a familiar animal that students can frequently observe in nature. Its simple body structure and anatomy allow an easy recognition of the main external and internal organs, such as spines, tube feet, feeding apparatus (Aristotle’s lantern), digestive tract and reproductive organs, thus providing several practical cues for interactive discussions on animal physiology and ecology. Additionally, this organism is an optimal model for the in vitro observation of the main reproductive processes, including release of gametes, fertilization and embryonic stages. In fact, this species can produces millions of spermatozoa and thousands of large, transparent eggs which can be easily collected; these can be used for the in vitro fertilization and the observation of the first developmental stages and of fundamental biological processes such as mitosis, cell migration and differentiation.