Long-term preservation of echinoderm sperm under non-cryo condition for ecotoxicological bioassay

The preservation of sea urchin gametes was examined to make them more convenient material for research and education, especially on the embryology and ecotoxicology field. The possibility of egg preservation for enough period, two weeks to one month, were reported (Epel et al., 2004; Kiyomoto et al., 2014). The sperm storage is usually done without seawater (dry sperm) for several days. This storage period is lengthened by the addition of antibiotics up to 10 days (Hata, 1998). To maximize the preserved period, we examined the dilution or replacement of seminal plasma with seawater containing antibiotics. Because the activation of sperm is induced by dilution, the condition to inhibit flagella motility was also investigated. Neither high potassium nor low pH improved the period of sperm preservation. The dilution of dry sperm around 100 times with normal seawater containing antibiotics was enough to keep the motility and fertilization ability for longer period, where sperm motility was prevented possibly by the effect of carbon dioxide.