The parasitizing stage (trophozoite) of the protozoan parasite Perkinsus olseni progresses to the dormant stage (prezoosporangium) immediately after the death of the host through physiologically and morphologically drastic changes. This development is reproducible in Ray's fluid thioglycollate medium (RFTM). In this study, supplementation with tissue extract from a host, the Manila clam, significantly improved the efficiency of development, as determined by the numbers and sizes of developed prezoosporangia. Similar results were seen following supplementation with boiled host tissue extract, which indicates that a thermally stable component of the host is required for the parasite's development. Subsequently, we found that a commercially available lipid concentrate significantly increased prezoosporulation without host tissue, suggesting that the lipids in host tissue enhance prezoosporangia development. Moreover, we determined that yeast extract, sodium thioglycollate, and sodium chloride were the only components of RFTM required for prezoosporulation. Based on these findings, we prepared a simple, host-free medium for P. olseni prezoosporulation—Lipid concentrate Yeast extract Medium (LpcYM)—consisting of yeast extract, lipid concentrate, sodium thioglycollate, and sodium chloride. We confirmed that the prezoosporangia developed in LpcYM produce zoospores that are infectious to Manila clams and that trophozoites of other Perkinsus species (P. marinus, P. honshuensis, and P. chesapeaki) also develop to prezoosporangia in this host-free medium. As LpcYM has the simplest composition of prezoosporulation media available thus far, it enables us to conduct molecular and biochemical studies examining the drastic transformation process of this parasite.

原生动物寄生虫Perkinsus olseni的寄生阶段（滋养体）在宿主死亡后，会通过生理和形态上的剧烈变化而进入休眠期（前孢子囊）。在Ray的液体巯基乙酸盐培养基（RFTM）中，这种发展是可重现的。在这项研究中，补充来自宿主马尼拉蛤的组织提取物，可以显着提高发育效率，这取决于发达的口孢子虫的数量和大小。补充煮沸的宿主组织提取物后，观察到相似的结果，这表明寄生虫的发育需要宿主的热稳定成分。随后，我们发现市售的脂质浓缩物可显着增加无宿主组织的前孢子形成，这表明宿主组织中的脂质可增强前孢子囊的发育。此外，我们确定酵母提取物，巯基乙酸钠和氯化钠是前孢子形成所需的RFTM的唯一成分。根据这些发现，我们准备了一种简单的无宿主培养基P. olseni prezoosporulation-脂质浓缩酵母提取物培养基（LpcYM）-由酵母提取物，脂质浓缩物，巯基乙酸钠和氯化钠组成。我们证实，在LpcYM中发育的前孢子囊产生了能感染马尼拉蛤的游动孢子，其他Perkinsus物种（P. marinus，P。honshuensis和P. chesapeaki）的滋养体也可以在这种无宿主培养基中发展为前孢子囊。由于LpcYM具有迄今为止最简单的前孢子形成培养基成分，因此它使我们能够进行分子和生化研究，检查该寄生虫的急剧转化过程。