Instituto de Diversidad y Evolución Austral (IDEAUS-CONICET), Puerto Madryn, Chubut, Argentina.
Instituto Nacional de Biodiversidad (INABIO), Quito, Ecuador.
J Morphol. 2024 Sep;285(9):e21760. doi: 10.1002/jmor.21760.
Rodents have received substantial attention in the study of olfaction. However, the rhinarium, the naked part of the nose, which plays an important role in chemical, tactile, and thermal perception, has been relatively overlooked. This study presents a comprehensive analysis of the rhinarium morphology and spatially associated structures (i.e., upper lip, and philtrum) in sigmodontines, a diverse group within the Cricetidae rodents. The research covers 483 specimens representing 145 species, accounting for 74% of genera in the clade, including all 13 recognized tribes, three incertae sedis genera, and the murid representatives Mus musculus and Rattus norvegicus. The inconsistent use of terminology in describing rhinarium traits across the literature poses a challenge for comparative analyzes. To address this issue, a standardized terminology was proposed to characterize the rhinarium. A paired complex protuberance typically with epidermal ridges (i.e., rhinoglyphics), termed here the tubercle of Hill, was identified as a distinctive feature in muroid rhinaria. Comparative assessments among tribes revealed unique sets of features defining each major clade, encompassing variations in hairiness, dorsum nasi complexity, size and positioning of the tubercle of Hill, and other key attributes. Two primary rhinarium configurations were discerned: one shared by Oryzomyalia and Sigmodontini and another specific to Ichthyomyini. The former groups display a ventrally positioned rhinarium prominently featuring the tubercle of Hill and sculptured areola circularis. In contrast, Ichthyomyini exhibit a frontally directed rhinarium characterized by an enlarged dorsum nasi fused to the tubercle of Hill, resulting in a distinctive "cherry" appearance. Convergent rhinarium structures observed in fossorial species, characterized by well-developed plica alaris and hair fringes, are presumed to mitigate potential damage during digging. Conversely, semiaquatic carnivorous sigmodontines showcase an integrated apical structure in their rhinarium, facilitating enhanced somatosensory capabilities crucial for predation activities during diving expeditions.
啮齿动物在嗅觉研究中受到了广泛关注。然而，鼻甲骨（裸露的鼻子部分）在化学、触觉和热感知中起着重要作用，却相对被忽视了。本研究对沙鼠科（Rodentia：Cricetidae）的多样化群体——叉齿鼠属（Sigmodontinae）的鼻甲骨形态及其空间相关结构（上唇和人中）进行了全面分析。研究涵盖了代表 145 种的 483 个标本，涵盖了该分支的 74%的属，包括 13 个公认的部落、三个分类地位不确定的属以及鼠科的代表物种小家鼠（Mus musculus）和褐家鼠（Rattus norvegicus）。由于文献中描述鼻甲骨特征的术语不一致，给比较分析带来了挑战。为了解决这个问题，提出了一种标准化术语来描述鼻甲骨。一个典型的带有表皮嵴的成对复杂突起（即鼻纹）被确定为鼠科鼻甲骨的一个特征。对部落之间的比较评估揭示了每个主要分支所特有的一系列特征，包括毛发密度、鼻背复杂性、丘的大小和位置以及其他关键属性的变化。发现了两种主要的鼻甲骨构型：一种由稻鼠亚科（Oryzomyalia）和沙鼠亚科（Sigmodontini）共享，另一种则是由栉趾鼠亚科（Ichthyomyini）所特有。前一组的鼻甲骨位置较低，明显具有丘和雕刻的圆形乳晕。相比之下，栉趾鼠亚科的鼻甲骨则向前指向，具有较大的鼻背与丘融合，形成独特的“樱桃”外观。在挖掘过程中可能会造成潜在伤害，因此推测穴居物种具有发达的翼褶和毛边等趋同的鼻甲骨结构。相反，半水生肉食性沙鼠亚科的鼻甲骨具有整合的顶端结构，有助于增强潜水捕食活动中的躯体感觉能力。
