Instituto de Biodiversidad y Biología Experimental y Aplicada (IBBEA-CONICET) and Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina.
Department of Biological Sciences, Humboldt State University, Arcata, CA, USA.
Cell Tissue Res. 2021 Jan;383(1):289-299. doi: 10.1007/s00441-020-03330-6. Epub 2020 Nov 28.
Anuran amphibians (frogs and toads) typically have a complex life cycle, involving aquatic larvae that metamorphose to semi-terrestrial juveniles and adults. However, the anuran olfactory system is best known in Xenopus laevis, an animal with secondarily aquatic adults. The larval olfactory organ contains two distinct sensory epithelia: the olfactory epithelium (OE) and vomeronasal organ (VNO). The adult organ contains three: the OE, the VNO, and a "middle cavity" epithelium (MCE), each in its own chamber. The sensory epithelia of Xenopus larvae have overlapping sensory neuron morphology (ciliated or microvillus) and olfactory receptor gene expression. The MCE of adults closely resembles the OE of larvae, and senses waterborne odorants; the adult OE is distinct and senses airborne odorants. Olfactory subsystems in other (non-pipid) anurans are diverse. Many anuran larvae show a patch of olfactory epithelium exposed in the buccal cavity (bOE), associated with a grazing feeding mode. And other anuran adults do not have a sensory MCE, but many have a distinct patch of epithelium adjacent to the OE, the recessus olfactorius (RO), which senses waterborne odorants. Olfaction plays a wide variety of roles in the life of larval and adult anurans, and some progress has been made in identifying relevant odorants, including pheromones and feeding cues. Increased knowledge of the diversity of olfactory structure, of odorant receptor expression patterns, and of factors that affect the access of odorants to sensory epithelia will enable us to better understand the adaptation of the anuran olfactory system to aquatic and terrestrial environments.
蛙类（青蛙和蟾蜍）通常具有复杂的生命周期，包括水生幼虫和半陆生幼体及成体。然而，蛙类的嗅觉系统在非洲爪蟾（Xenopus laevis）中最为人所知，这种动物的成体是次生水生的。幼虫的嗅觉器官包含两个不同的感觉上皮：嗅上皮（OE）和犁鼻器（VNO）。成体器官包含三个：OE、VNO 和“中腔”上皮（MCE），每个都在自己的腔室中。非洲爪蟾幼虫的感觉上皮具有重叠的感觉神经元形态（纤毛或微绒毛）和嗅觉受体基因表达。成体的 MCE 与幼虫的 OE 非常相似，可感知水载气味剂；成体的 OE 则不同，可感知气载气味剂。其他（非 pipid）蛙类的嗅觉子系统多种多样。许多蛙类幼虫在口腔中暴露有一块嗅上皮（bOE），与摄食方式有关。而其他蛙类的成体没有感觉 MCE，但许多都有一个与 OE 相邻的明显上皮区域，即嗅囊（RO），可感知水载气味剂。嗅觉在幼体和成体蛙类的生活中扮演着多种多样的角色，并且已经在确定相关气味剂方面取得了一些进展，包括信息素和摄食线索。增加对嗅觉结构多样性、气味受体表达模式以及影响气味剂进入感觉上皮的因素的了解，将使我们能够更好地理解蛙类嗅觉系统对水生和陆生环境的适应。
