For sea squirts the key to a long and happy life is to be fertilised not by a fast sperm, but by one that stands the test of time, a study has revealed.The research by Dr Angalea Crean, of the UNSW School of Biological, Earth and Environmnetal Sciences also shows for the first time that the influence of sperm extends well beyond the moment of conception. If further studies demonstrate the same effects occur with human sperm, the finding will change some of the assumptions used in IVF practice.