Haas A, Richards S J
Institut für Spezielle Zoologie und Evolutionsbiologie, Friedrich-Schiller-Universität Jena, Germany.
J Morphol. 1998 Nov;238(2):109-41. doi: 10.1002/(SICI)1097-4687(199811)238:2<109::AID-JMOR1>3.0.CO;2-#.
Suctorial anuran larvae are highly specialized for living in fast-flowing waters, using their oral disks as adhesive organs to attach to the substrate. The cranial musculoskeletal structure of suctorial larvae of Litoria nannotis, L. rheocola, and Nyctimystes dayi (Hylidae: Pelodryadinae) were compared with congenerics with pond-type larvae (L. caerulea, L. genimaculata, L. xanthomera). Data from two other neobatrachian species with suctorial larvae (Boophis sp., Hyla armata) as well as published descriptions were taken into account. Suctorial tadpoles evolved several times independently in the Neobatrachia and share various features, irrespective of their phylogenetic position. These include the following. Cornua trabeculae are expanded anteriorly and sometimes fused. The lower jaws are robust. The greatest width of the skull is at the level of the jaw articulation. The upper jaw cartilages are partially or fully fused. The palatoquadrate is robust and connected to the skull by a wide commissura quadratocranialis anterior, processus oticus, processus basalis (in some species), and processus ascendens (vestigial or absent in some species). A processus ventralis quadrati provides an extended area of origin for the m. orbitohyoideus. The m. rectus abdominis inserts far anterior and acts on the cranium. The insertion of the epaxial musculature is shifted anteriorly to the anterior parts of the otic capsule. The mm. diaphragmatobranchialis and rectus cervicis cross at their origins. The origin of the m. levator mandibulae anterior has shifted posteriorly. The branchial basket is relatively small and the ceratohyal area is large. Multiple convergent evolution of these features suggests that they may be causally associated with the suctorial mode of larval life. Aside from these characters, however, the suctorial and pond-type neobatrachian species are remarkably similar in their jaw musculature and hyobranchial musculoskeletal composition. In some features, Ascaphus truei differs significantly from the neobatrachian suctorial species, indicating the influence of the historically distant separation of the two taxa. A novel modification of the upper jaw abduction mechanism has evolved in L. nannotis, L. rheocola, and N. dayi. It involves an adrostral cartilage as a pushing-rod element. This mechanism and unique structural similarities of the cartilago labialis superior gives support to the preliminary assumption that the nannotis species group is more closely related to the suctorial Nyctimystes dayi than it is to other Litoria species with pond-type larvae. Suctorial larvae presumably were present in the most recent common ancestor of the Litoria nannotis group and Nyctimystes dayi.
吸附型无尾目幼体高度特化，适应生活在水流湍急的水域，它们利用口盘作为附着器官附着在基质上。将纳氏姬蛙（Litoria nannotis）、溪流姬蛙（L. rheocola）和达氏夜蛙（Nyctimystes dayi，雨蛙科：姬蛙亚科）的吸附型幼体的颅骨肌肉骨骼结构与具有池塘型幼体的同属物种（绿姬蛙L. caerulea、眼斑姬蛙L. genimaculata、黄斑姬蛙L. xanthomera）进行了比较。还考虑了另外两种具有吸附型幼体的新蛙类物种（博普蛙属Boophis sp.、武装雨蛙Hyla armata）的数据以及已发表的描述。吸附型蝌蚪在新蛙亚目中多次独立进化，且具有各种共同特征，无论它们的系统发育位置如何。这些特征包括：小梁角向前扩展，有时融合；下颌粗壮；头骨最宽处位于颌关节水平；上颌软骨部分或完全融合；腭方骨粗壮，通过宽的方颅前连合、耳突、基底突（在某些物种中）和上升突（在某些物种中退化或不存在）与头骨相连；方形腹突为眶舌肌提供了一个扩展的起始区域；腹直肌插入靠前并作用于头骨；轴上肌的插入点向前移至耳囊前部；膈鳃肌和颈直肌在起始处交叉；下颌前提肌的起始点向后移；鳃篮相对较小，角舌骨区域较大。这些特征的多次趋同进化表明，它们可能与幼体的吸附生活方式有因果关系。然而，除了这些特征外，吸附型和池塘型新蛙类物种在颌部肌肉和鳃弓肌肉骨骼组成方面非常相似。在某些特征上，粗皮渍螈（Ascaphus truei）与新蛙类吸附型物种有显著差异，这表明这两个分类单元在历史上长期分离所产生的影响。纳氏姬蛙、溪流姬蛙和达氏夜蛙进化出了一种新的上颌外展机制的变体。它涉及一块前吻软骨作为推杆元件。这种机制以及上唇软骨独特的结构相似性支持了一个初步假设，即纳氏姬蛙物种组与吸附型的达氏夜蛙的亲缘关系比它与其他具有池塘型幼体的姬蛙物种更近。吸附型幼体可能存在于纳氏姬蛙组和达氏夜蛙的最近共同祖先中。
