Sea urchin development

Abstract

Sea urchins (Phylum Echinodermata, Class Echinoidea) are excellent or- ganisms for demonstrating fertilization and early development. They have classically been used in embryology and developmental biology courses. Sea urchins are also an excellent choice of living material for use in general biology or general zoology labs on development. With advanced planning and prep- aration by the instructor, students should be able to observe all major stages of development in a single three-hour laboratory period. If more time is avail- able it may be advantageous to have the students set up their own embryo cultures for intermittent observations over a two to three day time span. The latter option gives the students a better feeling for the temporal aspects of developmental changes. The study of living embryos may be supplemented with models, prepared slides, and films or film loops. The purpose of this chapter will be to present information on animal avail- ability and maintenance in the laboratory, procedures required of instructors and students for the microscopic study of development, and a description of sea urchin development from fertilization to pluteus larva. Emphasis will be placed on the study of Lytechinus variegatus which may be maintained at room temperature and has exceptionally clear eggs and embryos. The description of gametes and embryonic development included in the Student Materials is a summary of the important events typically studied in embryology and developmental biology courses. This information is more ex- tensive than necessary for a general biology or general zoology laboratory on development. We suggest that the description be condensed to be compatible with the level of understanding desired for beginning students. For a complete, thorough description of sea urchin development you are referred to the many excellent references available (e.g., Harvey 1956; Tyler and Tyler 1966a, 1966b; Costello and Henley 1971; Guidice 1973; Horstadius 1973; Stearns 1974; Ishikawa 1975; Okazaki 1975; Piatigorsky 1975; Ruggieri 1975; Brook- bank 1978; Davenport 1979).