Friday, March 12, 2010

The Sucker-Footed Bat (Myzopoda aurita)

Myzopoda aurita ready to cling! - photo by Daniel Riskin

This is the sucker-footed bat, or Myzopoda aurita - myzo meaning "suck," poda meaning "foot." Though contrary to its name and what was previously thought, it does not adhere to surfaces by means of suction but rather by wet adhesion, as research by Daniel Riskin and Paul Racey has discovered.

These little guys (and girls) are two inches long and weigh 1/3 of an ounce. They roost head-up, way up in the furled leaves (that open at the top) of the Traveler's tree in Madagascar. Only six species (out of 1,200) of bats are known to roost in an upright position. They do so because it allows for a quick escape from predators.

Traveler's tree - photo by Daniel Riskin

These Old World bats have flat to slightly convex pads at their wrists and ankles that enable them to cling to the smooth surfaces of the leaves. Or Plexiglas.

Myzopoda aurita climbing on Plexiglas - photo by Daniel Riskin

foot pad of Myzopoda aurita - photo by Daniel Riskin

wrist pad of Myzopoda aurita - photo by Daniel Riskin

* * *

Below we have Myzopoda aurita's Neotropical buddy - Thyroptera tricolor, or Spix's disk-winged bat. (Well, I'd like to think they'd be buddies, having quite a few things in common.) These even tinier insectivorous bats are found in the New World tropics of Central and South America.

the concave discs of Thyroptera tricolor - photo by Daniel Riskin

Thyroptera tricolor also has little adhesive structures at its wrists and ankles and is also known to roost upright in rolled up leaves. However, its discs are concave and do cling to surfaces by means of suction. This gives Thyroptera tricolor the ability to cling to a surface at any angle, including head-down; whereas, Myzopoda aurita, using wet adhesion, doesn't have this ability - it can only roost head-up. Riskin believes that Thyroptera tricolor is in a later stage of evolution than Myzopoda aurita because of this ability to roost head-up or head-down.

Riskin will be joining the faculty at the City University of New York where he will head the Riskin Lab later this year. He's lookin' for grad students...

Link to Daniel K. Riskin and Paul A. Racey's recently published article:

Many many thanks to Dr. Riskin for letting me use his awesome bat photographs here and elsewhere in hey little bat!!

Tuesday, March 2, 2010

Bats & Their Bat Flowers

help...stuck... (Anoura caudifer) - photo by Nathan Muchhala

No, this nectar-feeding bat is not really stuck. (Nor what I would call a dainty eater.) Bats are known to push their heads into bat-flowers to lap up the nectar.

Anoura caudifer - photo by Nathan Muchhala

Anoura fistulata - photo by Nathan Muchhala


(I love these photos! They're so funny to me!)
A bat will insert its head into the flower - even when its tongue is longer than the flower's tube. It extends its tongue as much as it needs to, then retracts it, lapping the nectar much like a dog drinks water. By pushing its head into the flower, the bat collects lots of pollen on its head and chest, inadvertently transferring it to the next flower.

Moths are also nectar-feeders; however, when a moth drinks nectar, its tongue acts as a straw. So if a moth evolves a tongue longer than the floral tube, it could potentially partake of the flower's nectar without actually pollinating it. Therefore, the flower is always evolving a longer floral tube so that the moth has to actually push its head into the flower, thus picking up the pollen.

This is the background info of Nathan Muchhala's research on the coevolution of one bat species and its flower.

Anoura fistulata, getting that last drop - photo by Nathan Muchhala

Muchhala studied the tube-lipped nectar bat (Anoura fistulata), a bat that he and two Ecuadorian biologists actually discovered in Ecuador in 2005.

This bat has a very interesting characteristic - its tongue is 1 1/2 times the length of its body! That's twice as long as other nectar-feeding bats. In fact, relative to its body size, it's the longest tongue of any mammal! It is the perfect length (3.3 inches) to reach the nectar of the tropical plant Centropogon nigricans (seen above) for which it is the exclusive pollinator. (When not in use, the bat keeps most of its tongue inside of a structure in its ribcage.) Link to a photo of the bat's tongue on Muchhala's website.

While it's clear that a longer tongue benefits the bat because it enables it to reach the very last bit of nectar, Muchhala wanted to find out how the plant benefits from a longer floral tube. He suspected that the bat would use more force to reach the last bit of nectar of a longer-tubed flower, thus, transferring more pollen.

His research found that flowers with longer floral tubes were indeed better pollinated by the bats - more pollen grains were transferred and received - though not for the reason he thought. Read more about his research in "Going to great lengths: selection for long corolla tubes in an extremely specialized bat–flower mutualism" by Nathan Muchhala and James D. Thomson.

Many thanks to Nathan Muchhala for kindly letting me use his amazing bat photographs in hey little bat!! Link to his page "Bat Pollination in Cloud Forests" which contains more cool photos (and video snippets) of nectar-feeding bats pollinating their bat-flowers. Muchhala is a post-doctoral fellow at the University of Toronto.