Tokita Masayoshi, Hasegawa Yuya, Yano Wataru, Tsuji Hiroshi
1 Department of Biology, Faculty of Science, Toho University, 2-2-1 Miyama, Funabashi, Chiba 274-8510, Japan.
2 Department of Oral Anatomy, Asahi University School of Dentistry, 1851 Hozumi, Mizuho, Gifu 501-0296, Japan.
Zoolog Sci. 2018 Feb;35(1):99-108. doi: 10.2108/zs170099.
The order Anura (frogs and toads) is a group of amphibians and contains over 6500 extant species living in a variety of environments. Each frog species evolved body form adaptive for living and breeding in their own habitats. In Japan, four taxa of Bufo are living: Western-Japanese common toad (Bufo japonicus japonicus), Eastern-Japanese common toad (B. japonicus formosus), Miyako toad (B. gargarizans miyakonis) and Japanese stream toad (B. torrenticola). The former three taxa breed in still water as many other species of Bufo do. In contrast, B. torrenticola breeds in running water such as streams in mountainous area. Corresponding to their breeding in a stream environment, both adult and larva of B. torrenticola acquired unique morphological characters. However, few study have explored differences in the body form between B. torrenticola and closely-related Bufo species quantitatively, remaining the details about the morphological adaptation to a stream environment in this toad species poorly understood. In this study, we quantitatively compared the shape of the foot and skull between the adult male of B. torrenticola and its close relative B. j. formosus using landmark-based geometric morphometrics. Our analyses revealed that B. torrenticola has relatively longer toe phalanges with relatively larger foot webs and relatively shorter metatarsals and a narrower and more streamlined skull, compared to closely-related B. j. formosus. These morphological characteristics are considered adaptive for their breeding in mountain torrents.
无尾目（青蛙和蟾蜍）是两栖动物的一个类群，包含6500多种现存物种，生活在各种环境中。每个青蛙物种都进化出了适应其自身栖息地生存和繁殖的身体形态。在日本，有四种蟾蜍生活着：日本西部普通蟾蜍（Bufo japonicus japonicus）、日本东部普通蟾蜍（B. japonicus formosus）、宫古蟾蜍（B. gargarizans miyakonis）和日本溪蟾（B. torrenticola）。前三个类群像许多其他蟾蜍物种一样在静水中繁殖。相比之下，日本溪蟾在山区溪流等流动水中繁殖。与其在溪流环境中的繁殖方式相对应，日本溪蟾的成体和幼体都具有独特的形态特征。然而，很少有研究定量探索日本溪蟾与其近缘蟾蜍物种在身体形态上的差异，导致对该蟾蜍物种对溪流环境的形态适应细节了解甚少。在本研究中，我们使用基于地标点的几何形态测量学方法，对日本溪蟾成年雄性及其近缘物种日本东部普通蟾蜍的足部和头骨形状进行了定量比较。我们的分析表明，与近缘的日本东部普通蟾蜍相比，日本溪蟾的趾骨相对较长，蹼相对较大，跖骨相对较短，头骨更窄且更流线型。这些形态特征被认为有利于它们在山间急流中繁殖。
