Investigating sperm cryopreservation in a model tunicate, Ciona intestinalis sp. A

In cryopreservation procedures, the capacity to protect the cells from freezing and thawing processes is sensitive to the choice of the cryoprotective agent (CPA) and to its optimal concentration. The advancement of research on Tunicate model species has raised interest in liquid nitrogen cryopreservation for the storage and distribution of genetic resources. Ciona intestinalis (Linnè, 1767) consists of a complex of cryptic taxa that are central to several areas of investigation, from comparative genomics to invasive biology. Here we investigated how five CPAs, three chilling rates and two freezing rates influence semen cryopreservation in C. intestinalis sp. A. By using larval morphology and motility as endpoints, we estimated that long term semen storage requires 10% dimethyl sulfoxide as a protective agent, -1°C/min chilling rate (18°C to 5°C) and -13°C/min freezing rate (5°C to -80°C), followed by immersion in liquid nitrogen.