Culture of Adult Ascidians and Ascidian Genetics

Publisher Summary This chapter describes procedures used to culture ascidians, to isolate and propagate mutant lines, and to identify markers for genomic loci of interest. Ascidians are primitive chordates that are used extensively in experimental biology. Ascidian culturing methods described include an open seawater system in use in Santa Barbara and a closed seawater system in use in Gif-sur-Yvette. Many procedures used for ascidian genetics are still in the early stages of development. Preliminary results with chemical mutagenesis and the prospects for positional cloning of mutant genes are discussed. For genetic analysis, controlled matings between individuals of specific genotypes are critical. After the larval stage, the next step is to allow and, with some species, to induce the larvae to attach to a substrate, after which most species will spontaneously undergo metamorphosis. For settlement of larvae, the embryos are first fertilized and grown in untreated petri dishes until they hatch. Once the larvae are attached, they quickly begin tail resorption, and metamorphosis is well under way within two days of fertilization. Ascidians' diet consists of an assortment of microalgae and zooplankton. A detailed N-ethyl-N-nitrosourea (ENU) mutagenesis protocol is included in this chapter.