Departamento de Morfologia, Laboratório de Morfologia Funcional, Universidade Federal do Amazonas, Manaus, Brazil.
Departamento de Ciências Pesqueiras, Laboratório de Ictiologia, Universidade Federal do Amazonas, Manaus, Brazil.
J Morphol. 2024 Sep;285(9):e21772. doi: 10.1002/jmor.21772.
Neotropical freshwater stingrays of the subfamily Potamotrygoninae exhibit aplacental viviparity with uterine trophonemata. In this reproductive mode, females nourish and provide oxygenation to the embryo via the mucosa of the uterine wall. The aim of this study was to describe and histologically quantify the tissue components of the gravid uterus in an Amazonian freshwater stingray. Adult females of Potamotrygon wallacei were studied in different reproductive periods: resting stage, pregnant, and postpartum. During reproductive rest, the left ovary has numerous follicles compared to the right side. Therefore, uterine fertility is usually higher on the left side. The presence of an embryo in the right uterus suggests that the right ovary is also functional, although this only occurs in larger females. In females at reproductive rest, the wall of the uterus is formed by a mucosal layer (without the trophonemata) that contributes 16.7% to the thickness, while the myometrium accounts for 83.3% of the thickness. The mass-specific volume of the mucosal layer, inner circular, and outer longitudinal smooth muscle sheets tend to increase in the gravid uterus, indicating hypertrophy and hyperplasia of these components. During pregnancy, the trophonemata undergo marked tissue remodeling. Epithelial cells are organized into glandular acini and have apical secretory vesicles; furthermore, peripheral blood vessels proliferate and become dilated. These characteristics demonstrate that the gravid uterus of P. wallacei presents intense uterolactation activity and provides oxygenation to the fetus. Tissue remodeling occurs only in the uterus with the presence of an embryo. During postpartum, females have low body condition factor indicating a high reproductive cost. This study contributes to the knowledge of the reproductive biology of this species and will help us understand the impacts of climate change on the breeding areas of potamotrygonids.
新热带淡水𫚉科中的尖吻鲼亚科表现出有胎盘的胎生方式，具有子宫滋养体。在这种生殖方式中，雌性通过子宫壁的黏膜为胚胎提供营养和氧气供应。本研究旨在描述和组织学量化亚马逊淡水𫚉的妊娠子宫的组织成分。研究了处于不同生殖期的成年雌性亚马逊淡水𫚉：休息期、怀孕期和产后。在生殖休息期间，左侧卵巢的卵泡数量比右侧多。因此，左侧子宫的生育能力通常较高。右侧子宫中存在胚胎表明右侧卵巢也具有功能，尽管这种情况仅发生在较大的雌性中。在生殖休息的雌性中，子宫壁由黏膜层（无滋养体）组成，占厚度的 16.7%，而平滑肌层占 83.3%。黏膜层、内环和外环平滑肌层的比质量体积倾向于在妊娠子宫中增加，表明这些成分发生了肥大和增生。在怀孕期间，滋养体经历了明显的组织重塑。上皮细胞被组织成腺泡，具有顶分泌小泡；此外，周围血管增殖并扩张。这些特征表明，P. wallacei 的妊娠子宫表现出强烈的子宫泌乳活性，并为胎儿提供氧气供应。只有在有胚胎存在的子宫中才会发生组织重塑。在产后期间，雌性的身体状况系数较低，表明生殖成本较高。本研究有助于了解该物种的生殖生物学，并将有助于我们了解气候变化对尖吻鲼类繁殖区的影响。
