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Nectar uptake in bats using a pumping-tongue mechanism.

Tschapka M, Gonzalez-Terrazas TP, Knörnschild M - Sci Adv (2015)

Bottom Line: Recent molecular data indicate a convergent evolution of groove- and hair-tongued bat clades into the nectar-feeding niche.Using high-speed video recordings on experimental feeders, we show distinctly divergent nectar-feeding behavior in clades.Our results highlight a novel drinking mechanism in mammals and raise further questions on fluid mechanics and ecological niche partitioning.

View Article: PubMed Central - PubMed

Affiliation: Institute of Evolutionary Ecology and Conservation Genomics, University of Ulm, Ulm D-89069, Germany. ; Smithsonian Tropical Research Institute, Balboa, Panama.

ABSTRACT
Many insects use nectar as their principal diet and have mouthparts specialized in nectarivory, whereas most nectar-feeding vertebrates are opportunistic users of floral resources and only a few species show distinct morphological specializations. Specialized nectar-feeding bats extract nectar from flowers using elongated tongues that correspond to two vastly different morphologies: Most species have tongues with hair-like papillae, whereas one group has almost hairless tongues that show distinct lateral grooves. Recent molecular data indicate a convergent evolution of groove- and hair-tongued bat clades into the nectar-feeding niche. Using high-speed video recordings on experimental feeders, we show distinctly divergent nectar-feeding behavior in clades. Grooved tongues are held in contact with nectar for the entire duration of visit as nectar is pumped into the mouths of hovering bats, whereas hairy tongues are used in conventional sinusoidal lapping movements. Bats with grooved tongues use a specific fluid uptake mechanism not known from any other mammal. Nectar rises in semiopen lateral grooves, probably driven by a combination of tongue deformation and capillary action. Extraction efficiency declined for both tongue types with a similar slope toward deeper nectar levels. Our results highlight a novel drinking mechanism in mammals and raise further questions on fluid mechanics and ecological niche partitioning.

No MeSH data available.


Related in: MedlinePlus

Feeding behavior.(A) The amount of nectar extracted after each visit decreases steadily toward deeper levels. (B) Hovering duration in G. soricina and L. robusta increases when bats have to reach deeper into the feeder. The final decline occurs when bats abort their visit upon reaching the limit of their tongue extension capability. (C) Standardized extraction efficiency in both species decreases at a very similar slope. All figures are presented as mean ±1 SE. (D) L. robusta visiting a bromeliad flower (Werauhia sp.). Photo was taken at the Bocas del Toro Field Station of the Smithsonian Tropical Research Institute on March 2009.
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Figure 2: Feeding behavior.(A) The amount of nectar extracted after each visit decreases steadily toward deeper levels. (B) Hovering duration in G. soricina and L. robusta increases when bats have to reach deeper into the feeder. The final decline occurs when bats abort their visit upon reaching the limit of their tongue extension capability. (C) Standardized extraction efficiency in both species decreases at a very similar slope. All figures are presented as mean ±1 SE. (D) L. robusta visiting a bromeliad flower (Werauhia sp.). Photo was taken at the Bocas del Toro Field Station of the Smithsonian Tropical Research Institute on March 2009.

Mentions: At all nectar levels, the larger L. robusta individuals extracted more nectar than did the small G. soricina individuals (mean ± SE; L. robusta: 0.11 ± 0.01 g; G. soricina: 0.06 ± 0.01 g). Uptake steadily decreased in both species when bats had to extend the tongue farther down to lower nectar levels into the feeder (Fig. 2A). Both species showed a tendency to hover and feed longer at decreasing nectar levels (Fig. 2B). However, upon reaching the limit of their tongue extension capability, the bats tended to abort an unproductive feeding attempt, and hovering duration decreased. The standardized extraction efficiency declined significantly with decreasing nectar levels [general linear mixed modeling (GLMM); F4,75.014 = 50.009, P < 0.0001, Akaike information criterion = −676.452]. Even after correction for size difference, L. robusta was significantly more efficient than G. soricina (GLMM; F1,77.216 = 41.395, P < 0.0001); however, the observed decline in efficiency toward deeper nectar levels progressed similarly in both species (linear regression; L. robusta: y = 0.006 − 0.001x; G. soricina: y = 0.005 − 0.001x) (Fig. 2C). The interaction between nectar level and species had no significant influence on extraction efficiency (GLMM; F3,74.632 = 1.264, P = 0.293).


Nectar uptake in bats using a pumping-tongue mechanism.

Tschapka M, Gonzalez-Terrazas TP, Knörnschild M - Sci Adv (2015)

Feeding behavior.(A) The amount of nectar extracted after each visit decreases steadily toward deeper levels. (B) Hovering duration in G. soricina and L. robusta increases when bats have to reach deeper into the feeder. The final decline occurs when bats abort their visit upon reaching the limit of their tongue extension capability. (C) Standardized extraction efficiency in both species decreases at a very similar slope. All figures are presented as mean ±1 SE. (D) L. robusta visiting a bromeliad flower (Werauhia sp.). Photo was taken at the Bocas del Toro Field Station of the Smithsonian Tropical Research Institute on March 2009.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4643790&req=5

Figure 2: Feeding behavior.(A) The amount of nectar extracted after each visit decreases steadily toward deeper levels. (B) Hovering duration in G. soricina and L. robusta increases when bats have to reach deeper into the feeder. The final decline occurs when bats abort their visit upon reaching the limit of their tongue extension capability. (C) Standardized extraction efficiency in both species decreases at a very similar slope. All figures are presented as mean ±1 SE. (D) L. robusta visiting a bromeliad flower (Werauhia sp.). Photo was taken at the Bocas del Toro Field Station of the Smithsonian Tropical Research Institute on March 2009.
Mentions: At all nectar levels, the larger L. robusta individuals extracted more nectar than did the small G. soricina individuals (mean ± SE; L. robusta: 0.11 ± 0.01 g; G. soricina: 0.06 ± 0.01 g). Uptake steadily decreased in both species when bats had to extend the tongue farther down to lower nectar levels into the feeder (Fig. 2A). Both species showed a tendency to hover and feed longer at decreasing nectar levels (Fig. 2B). However, upon reaching the limit of their tongue extension capability, the bats tended to abort an unproductive feeding attempt, and hovering duration decreased. The standardized extraction efficiency declined significantly with decreasing nectar levels [general linear mixed modeling (GLMM); F4,75.014 = 50.009, P < 0.0001, Akaike information criterion = −676.452]. Even after correction for size difference, L. robusta was significantly more efficient than G. soricina (GLMM; F1,77.216 = 41.395, P < 0.0001); however, the observed decline in efficiency toward deeper nectar levels progressed similarly in both species (linear regression; L. robusta: y = 0.006 − 0.001x; G. soricina: y = 0.005 − 0.001x) (Fig. 2C). The interaction between nectar level and species had no significant influence on extraction efficiency (GLMM; F3,74.632 = 1.264, P = 0.293).

Bottom Line: Recent molecular data indicate a convergent evolution of groove- and hair-tongued bat clades into the nectar-feeding niche.Using high-speed video recordings on experimental feeders, we show distinctly divergent nectar-feeding behavior in clades.Our results highlight a novel drinking mechanism in mammals and raise further questions on fluid mechanics and ecological niche partitioning.

View Article: PubMed Central - PubMed

Affiliation: Institute of Evolutionary Ecology and Conservation Genomics, University of Ulm, Ulm D-89069, Germany. ; Smithsonian Tropical Research Institute, Balboa, Panama.

ABSTRACT
Many insects use nectar as their principal diet and have mouthparts specialized in nectarivory, whereas most nectar-feeding vertebrates are opportunistic users of floral resources and only a few species show distinct morphological specializations. Specialized nectar-feeding bats extract nectar from flowers using elongated tongues that correspond to two vastly different morphologies: Most species have tongues with hair-like papillae, whereas one group has almost hairless tongues that show distinct lateral grooves. Recent molecular data indicate a convergent evolution of groove- and hair-tongued bat clades into the nectar-feeding niche. Using high-speed video recordings on experimental feeders, we show distinctly divergent nectar-feeding behavior in clades. Grooved tongues are held in contact with nectar for the entire duration of visit as nectar is pumped into the mouths of hovering bats, whereas hairy tongues are used in conventional sinusoidal lapping movements. Bats with grooved tongues use a specific fluid uptake mechanism not known from any other mammal. Nectar rises in semiopen lateral grooves, probably driven by a combination of tongue deformation and capillary action. Extraction efficiency declined for both tongue types with a similar slope toward deeper nectar levels. Our results highlight a novel drinking mechanism in mammals and raise further questions on fluid mechanics and ecological niche partitioning.

No MeSH data available.


Related in: MedlinePlus