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 good exemplars for students that want to understand basic biological phenomena. The common sea urchin Paracentrotus lividus is a familiar animal that students can frequently observe in nature and represents a good didactic model for teaching various biological concepts in schools. Its simple body structure and anatomy allow easily recognition of the main external and internal organs, including spines, tube feet, feeding apparatus (Aristotle's lantern), digestive tract and reproductive organs, providing several practical cues for interactive discussions on animal physiology and ecology. Additionally, this organism is an optimal model for in vitro observation of major reproductive processes, including release of gametes, fertilization and recognition of various embryonic stages. In fact, this species produces millions of spermatozoa and thousands of large, transparent eggs which can be easily collected; these can be used for in vitro fertilization and observation of basic biological processes such as mitosis, cell migration and differentiation and of early developmental stages.