Leubner Fanny, Hörnschemeyer Thomas, Bradler Sven
Department of Morphology, Systematics & Evolutionary Biology, J-F-Blumenbach Institute for Zoology & Anthropology, Georg-August-University Göttingen, Göttingen, Germany.
BMC Evol Biol. 2016 Feb 18;16:39. doi: 10.1186/s12862-016-0612-5.
Secondary winglessness is a common phenomenon found among neopteran insects. With an estimated age of at least 140 million years, the cave crickets (Rhaphidophoridae) form the oldest exclusively wingless lineage within the long-horned grasshoppers (Ensifera). With respect to their morphology, cave crickets are generally considered to represent a `primitive' group of Ensifera, for which no apomorphic character has been reported so far.
We present the first detailed investigation and description of the thoracic skeletal and muscular anatomy of the East Mediterranean cave cricket Troglophilus neglectus (Ensifera: Rhaphidophoridae). T. neglectus possesses sternopleural muscles that are not yet reported from other neopteran insects. Cave crickets in general exhibit some unique features with respect to their thoracic skeletal anatomy: an externally reduced prospinasternum, a narrow median sclerite situated between the meso- and metathorax, a star-shaped prospina, and a triramous metafurca. The thoracic muscle equipment of T. neglectus compared to that of the bush cricket Conocephalus maculatus (Ensifera: Tettigoniidae) and the house cricket Acheta domesticus (Ensifera: Gryllidae) reveals a number of potentially synapomorphic characters between these lineages.
Based on the observed morphology we favor a closer relationship of Rhaphidophoridae to Tettigoniidae rather than to Gryllidae. In addition, the comparison of the thoracic morphology of T. neglectus to that of other wingless Polyneoptera allows reliable conclusions about anatomical adaptations correlated with secondary winglessness. The anatomy in apterous Ensifera, viz. the reduction of discrete direct and indirect flight muscles as well as the strengthening of specific leg muscles, largely resembles the condition found in wingless stick insects (Euphasmatodea), but is strikingly different from that of other related wingless insects, e.g. heel walkers (Mantophasmatodea), ice crawlers (Grylloblattodea), and certain grasshoppers (Caelifera). The composition of direct flight muscles largely follows similar patterns in winged respectively wingless species within major polyneopteran lineages, but it is highly heterogeneous between those lineages.
次生无翅现象在新翅类昆虫中很常见。洞穴蟋蟀（穴蟋科）估计至少有1.4亿年的历史，是长角蚱蜢（直翅目）中最古老的完全无翅谱系。就其形态而言，洞穴蟋蟀通常被认为是直翅目的一个“原始”类群，目前尚未报道其具有任何衍生特征。
我们首次对东地中海洞穴蟋蟀Troglophilus neglectus（直翅目：穴蟋科）的胸部骨骼和肌肉解剖结构进行了详细研究和描述。T. neglectus拥有其他新翅类昆虫尚未报道过的胸侧肌。一般来说，洞穴蟋蟀在胸部骨骼解剖方面表现出一些独特特征：外部退化的前胸腹片、位于中胸和后胸之间的狭窄中骨片、星形的前胸背板以及三叉形的后叉骨。将T. neglectus的胸部肌肉结构与灌丛蟋蟀Conocephalus maculatus（直翅目：螽斯科）和家蟋蟀Acheta domesticus（直翅目：蟋蟀科）的进行比较，揭示了这些谱系之间一些潜在的共衍征。
基于观察到的形态，我们认为穴蟋科与螽斯科的关系比与蟋蟀科的关系更密切。此外，将T. neglectus的胸部形态与其他无翅多新翅类昆虫的进行比较，可以得出与次生无翅相关的解剖学适应的可靠结论。无翅直翅目的解剖结构，即离散的直接和间接飞行肌肉的减少以及特定腿部肌肉的加强，在很大程度上与无翅竹节虫（叶足亚纲）的情况相似，但与其他相关无翅昆虫，如足跟虫（螳䗛目）、冰爬虫（蛩蠊目）和某些蚱蜢（蝗亚目）的情况明显不同。直接飞行肌肉的组成在主要多新翅类谱系中有翅和无翅物种中大致遵循相似模式，但在这些谱系之间高度异质。
