Specialized bat tongue is a hemodynamic nectar mop

Abstract

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.

Bayesian hierarchical models suggest oldest known plant-visiting bat was omnivorous

“…Similar to those of extant nectarivorous phyllostomids, these molars are narrow, and their cusps are reduced lingually and flattened labially [1,8]. The two primarily nectarivorous phyllostomid subfamilies, Glossophaginae and Lonchophyllinae, share adaptations for acquiring nectar including an elongated rostrum and palate, reduced dentition and elongated tongues [8][9][10]. These phyllostomids compose a phenotypic optimum that prevents eating hard foods such as beetles or figs [11][12][13].…”

Erection pattern and section-wise wettability of honeybee glossal hairs in nectar feeding

“…The drinking patterns of animals such as cats (Reis et al, 2010), dogs (Crompton and Musinsky, 2011), bats (Harper et al, 2013) and hummingbirds (Kim et al, 2012;Rico-Guevara and Rubega, 2010) have been observed and analysed explicitly to varying degrees in previous studies. The dynamic surfaces, categorized as the erectable hairs, setae and filamentous papillae, play an important role in improving the ability of trapping liquid food (Harper et al, 2013).…”

“…The dynamic surfaces, categorized as the erectable hairs, setae and filamentous papillae, play an important role in improving the ability of trapping liquid food (Harper et al, 2013). A honeybee is a typical insect whose proboscis has been studied widely, for instance, in relation to gustation preferences (Heyneman, 1983;Tan et al, 2014) and nectar lapping strategies .…”

“…The glossa resembles a mop covered by bushy hairs, which helps it transport nectar more efficiently . Recently, Harper et al (2013) discovered that a nectar-feeding bat, Glossophaga soricina, uses dynamic erectile papillae driven hemodynamically to collect nectar. Inspired by this, we speculate that the glossa of the honeybee might erect hairs in a specific pattern for nectar dipping.…”

“…Inspired by this, we speculate that the glossa of the honeybee might erect hairs in a specific pattern for nectar dipping. However, characteristics of the erection pattern of glossal hairs have been a highly controversial issue until now, which is not clearly defined because of the relatively small mouthpart sizes and/or high intake rates of the honeybees (Harper et al, 2013;Snodgrass, 1956).…”