Goldberg Javier, Barrasso Diego A, Agostini M Gabriela, Quinzio Silvia
Instituto de Bio y Geociencias del NOA (IBIGEO-CONICET), CCT-Salta, 9 de Julio 14, 4405 Rosario de Lerma, Salta, Argentina.
Instituto de Diversidad y Evolución Austral (IDEAus-CONICET), Bvd. Brown, 2915 Puerto Madryn, Argentina.
Zoology (Jena). 2016 Dec;119(6):489-499. doi: 10.1016/j.zool.2016.07.001. Epub 2016 Jul 2.
Sexual maturity involves the differentiation of the reproductive system, the maturation of germ cells, and the development of secondary sexual characteristics. Even though this topic has received much attention, little is known about the sequence of events that encompass reproductive maturation in anurans and what it could reveal about the developmental basis of life cycle evolution. The discovery of froglets of Pseudis minuta with incipient vocal sacs calling in breeding pools alongside several larger adult specimens with fully developed vocal sacs raised the question of the timing of sexual maturity in this species. Here we describe the sequence and timing of differentiation, development and maturation of the vocal sac apparatus and the testes in P. minuta (Anura, Hylidae), in order to establish a timeline of events leading to sexual maturity. Differentiation of the vocal sac apparatus begins at the final metamorphic stages, earlier than reported for other species, and the vocal sac acquires its final shape during the early postmetamorphic period. These modifications occur after gonadal differentiation, which begins early during the larval period and proceeds with a highly accelerated rate of development (e.g., secondary spermatids appear well before metamorphic climax), a situation reported previously for other anuran species only in the genus Pseudis. These results, together with a skeletochronological analysis showing that some calling specimens presented no lines of arrested growth, indicate acceleration in the timing of sexual maturity in Pseudis, and raise questions about the interdependence/decoupling during the development of the different components involved in reaching the adult stage.
性成熟涉及生殖系统的分化、生殖细胞的成熟以及第二性征的发育。尽管这个话题已经受到了很多关注，但对于无尾两栖动物生殖成熟所包含的一系列事件的顺序以及它能揭示的生命周期进化的发育基础，我们知之甚少。在繁殖池中发现了带有初始声囊的小伪蛙幼体与几只声囊完全发育的较大成年标本一起鸣叫，这引发了该物种性成熟时间的问题。在这里，我们描述了小伪蛙（无尾目，雨蛙科）声囊器官和睾丸的分化、发育和成熟的顺序及时间，以便确定导致性成熟的事件时间表。声囊器官的分化始于最终变态阶段，比其他物种报道的时间更早，并且声囊在变态后早期获得其最终形状。这些变化发生在性腺分化之后，性腺分化在幼体期早期开始，并以高度加速的发育速度进行（例如，次级精细胞在变态高潮之前就出现了），这种情况以前仅在伪蛙属的其他无尾两栖动物物种中报道过。这些结果，连同骨龄分析表明一些鸣叫标本没有生长停滞线，表明伪蛙的性成熟时间加速，并引发了关于达到成年阶段所涉及的不同组成部分发育过程中的相互依存/解耦的问题。
