Viviparous stingrays avoid contamination of the embryonic environment through faecal accumulation mechanisms
Viviparous stingrays avoid contamination of the embryonic environment through faecal accumulation mechanisms
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胎生黄貂鱼通过粪便积累机制避免胚胎环境的污染
DOI：
10.1038/s41598-020-64271-2
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发表时间：
2020
影响因子：
4.6
通讯作者：
Murakumo Kiyomi
中科院分区：
文献类型：
--
作者：
Tomita Taketeru;Nakamura Masaru;Kobayashi Yasuhisa;Yoshinaka Atsushi;Murakumo Kiyomi
在胎生动物中，胚胎面临着胚胎特有的排便问题：子宫内的粪便排泄会对胚胎环境造成致命的污染。我们从胎生红黄貂鱼（Hemitrygon akajei）的数据揭示了胎生板鳃类如何规避这个问题。胚胎肠的出口保持关闭，直到接近出生，这使得粪便在胚胎体内积聚。粪便积累能力通过以下方式增加：（1）大肠大小（按比例约占成人肠道的400-600%），和（2）肠内壁结构的改变，专门用于增加从粪便中摄取的水。根据文献，排泄物的积累也可能发生在板状白色鲨鱼的胚胎中。黄貂鱼和板状鲨的生殖生物学特征是出生前开始经口进食（即分别饮用子宫乳汁和食用同胞卵），预计这将导致妊娠期间产生大量粪便。因此，这些谱系的粪便积累能力很强，可能是对它们独特的胚胎营养机制的适应。
In viviparous (live-bearing) animals, embryos face an embryo-specific defecation issue: faecal eliminationin uterocan cause fatal contamination of the embryonic environment. Our data from the viviparous red stingray (Hemitrygon akajei) reveals how viviparous elasmobranchs circumvent this issue. The exit of the embryonic intestine is maintained closed until close to birth, which allows the accumulation of faeces in the embryonic body. Faecal accumulation abilities are increased by (1) the large intestine size (represents about 400–600% of an adult intestine, proportionally), and (2) the modification in the intestinal inner wall structure, specialized to increase water uptake from the faecal matter. According to the literature, faecal accumulation may occur in embryos of the lamniform white shark as well. The reproductive biology of myliobatiform stingrays and lamniform sharks is characterized by the onset of oral feeding before birth (i.e. drinking of uterine milk and eating of sibling eggs, respectively), which is expected to result in the production of large amounts of faeces during gestation. The strong ability of faecal accumulation in these lineages is therefore likely an adaptation to their unique embryonic nutrition mechanism.