Analysis of early developments in a viviparous fish Xenotoca eiseni

本文以活体硬骨鱼Xenotoca eiseni为研究对象，分析了非哺乳动物胎生系统的机制。胎生鱼不具有哺乳动物的胎盘和脐带所对应的明确的类似胎儿器官。它们有独特的带状结构，从肛周延伸而来。这种结构被认为是哺乳动物胎儿器官的功能类似物，它起着吸收母体营养物质的作用。我发现胎儿鱼苗的带状结构在围产期被程序性细胞死亡所破坏。这种退化机制在哺乳动物中尚未见报道。这被认为是胎生鱼类特有的系统。

I analyzed a mechanism of non-mammalian viviparous system using a live-bearer teleost Xenotoca eiseni. The viviparous fish doesn't possess defined analog of fetal organs corresponding to a placenta and an umbilical cable of mammals. They have unique ribbon-like structure elongated from a perianal. This structure is presumed to be a functional analog of the fetal organ of mammals, which plays a role for absorption of maternal nutrients. I found that the ribbon-like structure of the fetal fry is disrupted by programed cell death in perinatal stage. Such regression mechanism has not reported in mammals. It was presumed to be a unique system in viviparous fish.