Sebastes schlegelii is a commercially important fish with a special viviparous reproductive system that is cultured in near-shore seawater net cages in East Asia. In the gonadal development of the species, the gonad of males mature before those of females, which mature after mating. Mating in male/female fishes occurs in October of each year. Then, females undergoing oocyte maturation complete fertilization using stored sperm in March of the following year. The pregnancy is completed when larvae are produced in the ovary. It has been reported that embryonic nutrient supply originates entirely from the female viviparous reproductive systems. However, until now, the nutritional patterns and the processes of nutrient provision in S. schlegelii before parturition have not been clear. The goal of this research was to study the embryos, larvae and juveniles of S. schlegelii during pregnancy. Anatomical observations, light microscopy and scanning electron microscopy were used to study the developmental characteristics of early embryos and larvae and the connecting structures between the mother and the fetus. The results showed the following: (1) Placental-like structures were found during the process of embryonic development in S. schlegelii, and these placental-like structures proliferated after fertilization. (2) The embryos of S. schlegelii were encased by a saclike structure composed of blood vessels, connective tissue, and surface epithelial cells. The vessels near the embryo existed in the thecal layer. Vascularized proliferation was detected following embryonic development. (3) Starting in the gastrula stage, connections between the embryo and surrounding cells loosened, and ovarian fluid became abundant. In addition, a large number of small holes and cristae were observed on the surface of the embryo. We speculate that embryos may be able to absorb nutrients from the ovarian fluid. (4) Yolk was present throughout embryo development. (5) Two types of nutritional modes were observed, lecithotrophic and matrotrophic during embryonic development. Three forms of placental analogs may exist in S. schlegelii: (1) external epithelial absorptive surfaces; (2) trophonemata, with modifications of the ovarian epithelia for absorbing the histotroph; and (3) a follicular pseudoplacenta, with close apposition between follicle cells and embryonic absorptive epithelia.

中文翻译：

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胎生鱼 Sebastes schlegelii 分娩前的多种胎儿营养模式 (Hilgendorf, 1880)

Sebastes schlegelii 是一种具有特殊胎生生殖系统的具有重要商业价值的鱼类，在东亚近海海水网箱中养殖。在该物种的性腺发育过程中，雄性性腺先于雌性成熟，雌性性腺在交配后成熟。雄鱼/雌鱼的交配发生在每年的 10 月。然后，经历卵母细胞成熟的雌性在次年 3 月使用储存的精子完成受精。当幼虫在卵巢中产生时，妊娠就完成了。据报道，胚胎营养供应完全来自雌性胎生生殖系统。然而，直到现在，S. schlegelii 在分娩前的营养模式和营养供应过程尚不清楚。这项研究的目的是研究胚胎，S. schlegelii 怀孕期间的幼虫和幼虫。通过解剖观察、光镜和扫描电镜研究早期胚胎和幼虫的发育特征以及母胎之间的连接结构。结果表明：（1）S. schlegelii胚胎发育过程中发现胎盘样结构，受精后这些胎盘样结构增殖。(2)S. schlegelii的胚胎被血管、结缔组织和表面上皮细胞组成的囊状结构包裹着。胚胎附近的血管存在于鞘层中。在胚胎发育后检测到血管化增殖。(3) 从原肠胚阶段开始，胚胎与周围细胞之间的连接松动，和卵巢液变得丰富。此外，在胚胎表面观察到大量小孔和嵴。我们推测胚胎可能能够从卵巢液中吸收营养。(4) 蛋黄在整个胚胎发育过程中都存在。(5)在胚胎发育过程中观察到两种营养模式，卵形营养型和营养型。S. schlegelii 中可能存在三种形式的胎盘类似物：(1) 外上皮吸收表面；(2) trophonemata，为了吸收组织营养而改变卵巢上皮；(3)卵泡假胎盘，卵泡细胞与胚胎吸收性上皮细胞紧密并置。我们推测胚胎可能能够从卵巢液中吸收营养。(4) 蛋黄在整个胚胎发育过程中都存在。(5)在胚胎发育过程中观察到两种营养模式，卵形营养型和营养型。S. schlegelii 中可能存在三种形式的胎盘类似物：(1) 外上皮吸收表面；(2) trophonemata，为了吸收组织营养而改变卵巢上皮；(3)卵泡假胎盘，卵泡细胞与胚胎吸收性上皮细胞紧密并置。我们推测胚胎可能能够从卵巢液中吸收营养。(4) 蛋黄在整个胚胎发育过程中都存在。(5)在胚胎发育过程中观察到两种营养模式，卵形营养型和营养型。S. schlegelii 中可能存在三种形式的胎盘类似物：(1) 外上皮吸收表面；(2) trophonemata，为了吸收组织营养而改变卵巢上皮；(3)卵泡假胎盘，卵泡细胞与胚胎吸收性上皮细胞紧密并置。(1) 外部上皮吸收表面；(2) trophonemata，为了吸收组织营养而改变卵巢上皮；(3)卵泡假胎盘，卵泡细胞与胚胎吸收性上皮细胞紧密并置。(1) 外部上皮吸收表面；(2) trophonemata，为了吸收组织营养而改变卵巢上皮；(3)卵泡假胎盘，卵泡细胞与胚胎吸收性上皮细胞紧密并置。