The newts were chosen because they are a good model organism for the study of microgravity. They are a good model organism because of the female's ability to retain live sperm in her cloaca for up to five months, allowing her to be inseminated on Earth, and later (in space) have fertilisation induced through hormonal stimulation. Another advantage to this species is their development is slow, so all the key stages of ontogenesis can be observed, from the oocyte to swimming tailbud embryos or larvae.