The tongue of the flowering bat A. fistulata in the test: the animal can drink sugar water from a tube that is one and a half times longer than itself. Photo: Murray Cooper
Reading The Ecuadorian flower bat Anoura fistulata can stick its tongue 1.5 times its length. So she can drink nectar from more than eight centimeters deep flower tubes. The biologist Nathan Muchhala from the University of Miami discovered this when he compared the eating habits of closely related bats. The extremely long tongue accommodates the bat in its thoracic cavity, whereby the tongue base is not as usual at the base of the oral cavity, but is located between heart and sternum. The bat A. fistulata was discovered only recently in the cloud forests of the Ecuadorian Andes, where it and two other flower bats of the same genus, A. caudifer and A. geoffroyi live. To determine the tongue length of these species, Muchhala trained the animals to drink sugar water from straws of varying lengths. While A. caudifer and A. geoffroyi did not emerge over a straw length of nearly four centimeters, A. fistulata managed to drink up to a length of about 8.5 centimeters from the tube.

Thus, the outstretched tongue is twice as long in A. fistulata as in the two related bat species, with which the bat outperforms all other mammals relative to body length. Among the vertebrates, only the chameleon is better. A. Fistulata achieves this maximum performance with a trick: The tongue is not limited to the palate and the jaw, but extends over the neck to the chest. There it is surrounded by a special tissue structure, the so-called tongue tube.

There must be a suitable flower for this long tongue, Muchhala suspected. Charles Darwin had already predicted such a connection correctly for a Malagasy butterfly. When Muchhala analyzed the pollen on the faces and fur of the three species of bats, he found only in A. fistulata pollen of the bell flower plant Centropogon nigricans, which has particularly long flower tubes of eight to nine centimeters.

As no plants have been known so far whose flowers are adapted to certain bat species, this is the first example of a plant that can be pollinated by a single species of bat alone. The researcher suspects that the long tongue and the flower tube have developed together. display

This discovery is also an example of a so-called convergent evolution. Biologists refer to the independent development of similar features in unrelated species. Even the ant-eating pangolin is under the pressure of selection to develop a tongue as long as possible - and has a tongue tube like the bat A. fistulata.

Nathan Muchhala (University of Miami): Nature, Vol. 444, p. 701 ddp / Annette Schneider


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