Rams-Pociecha Izabela, Mizia Paulina C, Piprek Rafal P
Department of Comparative Anatomy, Institute of Zoology and Biomedical Research, Faculty of Biology, Jagiellonian University, Krakow, Poland.
Doctoral School of Exact and Natural Sciences, Jagiellonian University, Krakow, Poland.
Anat Rec (Hoboken). 2025 Sep;308(9):2490-2507. doi: 10.1002/ar.25621. Epub 2024 Dec 24.
Chameleons are a family of lizards distinguished by several unique features related to their arboreal lifestyles, such as a ballistic tongue, skin color changes, independent movement of both eyes, a prehensile tail, and cleft hands and feet. The veiled chameleon (Chamaeleo calyptratus) has been proposed as a promising model species for studying squamate biology. Despite its potential, the developmental biology of this species remains poorly understood, particularly in terms of gonadal development. This study aimed to elucidate the development of the gonads in the veiled chameleon, from the initial appearance of the gonadal ridges through the sexual differentiation into ovaries and testes, to the establishment of the gonadal structures in both sexes. The study showed the accelerated appearance of gonadal primordia compared to the soma in the veiled chameleon, which is unique and possibly influenced by a prolonged in ovo development period due to the slowed rate of embryonic development in this species. The undifferentiated gonads are characterized by a voluminous medulla and a thin cortex. The process of gonadal sexual differentiation mirrors that seen in other vertebrates. Ovarian differentiation involves the development of a cortex containing germ cells and the loss of these cells in the medulla. Differentiated ovaries are characterized by a thin cortex and early induction of meiosis, leading to the formation of ovarian follicles before hatching. In contrast, testis differentiation involves the loss of germ cells from the cortex, its transformation into a thin epithelium, and the development of germ cell-containing testis cords in the medulla. The testis cords originate from invagination and remain without forming a lumen during embryogenesis. This comprehensive examination of gonadal development in the veiled chameleon provides important insights into sexual differentiation processes in this species. Moreover, it may stimulate further, broader studies in vertebrate developmental biology.
变色龙是一类蜥蜴，其具有一些与树栖生活方式相关的独特特征，比如弹射式舌头、皮肤颜色变化、双眼可独立活动、能抓握的尾巴以及裂开的手脚。蒙面变色龙（Chamaeleo calyptratus）被认为是研究有鳞目生物学的一个很有前景的模式物种。尽管它有这样的潜力，但该物种的发育生物学仍知之甚少，尤其是在性腺发育方面。本研究旨在阐明蒙面变色龙性腺的发育过程，从性腺嵴最初出现，经过性分化形成卵巢和睾丸，到两性性腺结构的建立。研究表明，与身体其他部分相比，蒙面变色龙性腺原基出现得更快，这一现象很独特，可能是由于该物种胚胎发育速度减慢导致卵内发育期延长所致。未分化的性腺特点是髓质大而皮质薄。性腺性分化过程与其他脊椎动物相似。卵巢分化包括含有生殖细胞的皮质的发育以及髓质中这些细胞的消失。分化后的卵巢特点是皮质薄且减数分裂提前诱导，导致在孵化前形成卵巢卵泡。相比之下，睾丸分化包括皮质中生殖细胞的消失、皮质转变为薄上皮以及髓质中含生殖细胞的睾丸索的发育。睾丸索起源于内陷，在胚胎发育过程中一直不形成管腔。对蒙面变色龙性腺发育的这一全面研究为该物种的性分化过程提供了重要见解。此外，它可能会激发在脊椎动物发育生物学领域开展更广泛深入的研究。
