A simple method for several-week sperm preservation applicable for various echinoid species

Easy, universal, and cost-effective methods of gamete preservation for echinoids are required since echinoids are important model organisms for studying fertilization and early development, and at the same time, they are valuable fishery resources, and key components of marine ecosystems. In general, cryopreservation is the common method of animal sperm preservation, but we previously reported a simple method using a chilled condition as an alternative choice, using Hemicentrotus pulcherrimus. In this study, we applied this method to various echinoid species to test whether it was effective for them, and then we determined the features of the preserved sperm in detail. The fertilization capability of preserved sperm was maintained for several weeks, though higher sperm density was needed to obtain 100% fertilization in later periods. Eggs fertilized by the preserved sperm developed normally, and the morphology of the embryos was not affected. Sperm swimming in a stable, regular manner were observed even at the end of the preservation period, though the flagellar beat frequency was substantially decreased during preservation. There was almost no change of the flagellar beat form during preservation. Here, we showed that our simple method is basically applicable to various echinoid species and provides the opportunity for effective and immediate use of competent echinoid sperm by a wide variety of users, such as people in research, fisheries and education.