Department of Ecology and Evolutionary Biology, Brown University, Providence, RI 02912, USA.
Proc Natl Acad Sci U S A. 2013 May 28;110(22):8852-7. doi: 10.1073/pnas.1222726110. Epub 2013 May 6.
Nectarivorous birds and bats have evolved highly specialized tongues to gather nectar from flowers. Here, we show that a nectar-feeding bat, Glossophaga soricina, uses dynamic erectile papillae to collect nectar. In G. soricina, the tip of the tongue is covered with long filamentous papillae and resembles a brush or mop. During nectar feeding, blood vessels within the tongue tip become engorged with blood and the papillae become erect. Tumescence and papilla erection persist throughout tongue retraction, and nectar, trapped between the rows of erect papillae, is carried into the mouth. The tongue tip does not increase in overall volume as it elongates, suggesting that muscle contraction against the tongue's fixed volume (i.e., a muscular hydrostat) is primarily responsible for tip elongation, whereas papilla erection is a hydraulic process driven by blood flow. The hydraulic system is embedded within the muscular hydrostat, and, thus, intrinsic muscle contraction may simultaneously increase the length of the tongue and displace blood into the tip. The tongue of G. soricina, together with the tongues of nectar-feeding bees and hummingbirds, which also have dynamic surfaces, could serve as valuable models for developing miniature surgical robots that are both protrusible and have highly dynamic surface configurations.
食蜜鸟和蝙蝠进化出了高度特化的舌头，以便从花朵中吸取花蜜。在这里，我们展示了一种食蜜蝙蝠——墨西哥兔唇蝠（ Glossophaga soricina ），它利用动态勃起的乳头来采集花蜜。在墨西哥兔唇蝠中，舌头的尖端覆盖着长而丝状的乳头，形状类似于刷子或拖把。在吸食花蜜时，舌头尖端的血管会充满血液，乳头会勃起。肿胀和乳头勃起会一直持续到舌头缩回，被困在一排排勃起的乳突之间的花蜜会被带进嘴里。当舌头伸长时，其总体积不会增加，这表明肌肉收缩对舌头的固定体积（即肌肉静压）起着主要作用，而乳头勃起是一个由血流驱动的液压过程。液压系统嵌入在肌肉静压中，因此，内在的肌肉收缩可能会同时增加舌头的长度并将血液推向尖端。墨西哥兔唇蝠的舌头，以及具有动态表面的食蜜蜜蜂和蜂鸟的舌头，可以作为开发微型手术机器人的有价值模型，这些机器人既具有可伸出性，又具有高度动态的表面结构。
