Developmental morphology of granular skin glands in pre-metamorphic egg-eating poison frogs
Developmental morphology of granular skin glands in pre-metamorphic egg-eating poison frogs
复制标题
食蛋毒蛙变态前粒状皮腺的发育形态
作者：
J. Stynoski;L. O’Connell
许多类群的父母，包括昆虫、软体动物、鱼、蛇和两栖动物，为其后代提供化学防御，如多肽、类固醇或生物碱，以减少被捕食的风险。在大多数情况下，这些防御在卵中转移到后代，并在整个幼虫时期逐渐减弱。成年毒蛙将生物碱防御节肢动物猎物的能力隔离在颗粒状皮肤腺中。在至少一种名为Oophaga umilio的毒蛙身上，母蛙会间歇性地喂食蝌蚪，直到它们变态，卵中含有含有生物碱防御系统的营养物质。然而，直到幼虫发育到中期，才能在蝌蚪中检测到生物碱。在这里，我们调查了一系列发育的小黄鼠蝌蚪的组织学，以确定它们的个体发育生物碱谱是否与颗粒腺的发育相一致。我们的发现表明，蝌蚪体内的生物碱储存是通过上皮组织中发育的颗粒状皮肤腺的分化来描述的。本种的颗粒腺分化的时间与其他无尾两栖动物一致。因此，向后代提供化学防御可能受到衍生结构的发育时机的限制，这些衍生结构可以有效地存储那些有毒或有毒的化合物。
Parents in many taxa, including insects, molluscs, fish, snakes, and amphibians provision chemical defences, such as peptides, steroids, or alkaloids to their offspring to reduce the risk of predation. In most cases, those defences are transferred to offspring in the egg and gradually diminish throughout the larval period. Adult poison frogs sequester alkaloid-based defences from arthropod prey in granular skin glands. In at least one poison frog, Oophaga pumilio, mother frogs intermittently feed tadpoles until metamorphosis with nutritive eggs containing those alkaloid-based defences. However, alkaloids are not detected in tadpoles until they reach the middle stages of larval development. Here, we investigate the histology of a developmental series of O. pumilio tadpoles to determine whether their ontogenetic alkaloid profile coincides with granular gland development. Our findings suggest that alkaloid sequestration in tadpoles is delineated by the differentiation of rudimentary granular skin glands in epithelial tissue. The timing of differentiation of granular glands in this species coincides with other anurans. Thus, provisioning of chemical defences to offspring is likely constrained by developmental timing of derived structures that can effectively store those toxic or noxious compounds.