Torrent Frogs Hold on Tight to Wet Surfaces Using Toes, Belly and Thighs

Torrent frogs not only use their toes but also thighs and belly to cling on tight to wet and steep surfaces, a new finding suggests.

The study led by Thomas Endlein from the Centre for Cell Engineering at the University of Glasgow in collaboration with experts from other institutions claims that torrent frogs use their toes, belly and thighs to maintain a grip on wet, rough and steep surfaces.

In the study, the researchers compared the attachment abilities of two frog species namely torrent frogs (Stauroi guttatus) and tree frogs (Rhacophorus pardalis). In order to observe the attachment methods of the two frog species they used imaging process. The researchers measured the frogs' attachment process under various conditions of roughness and fast flowing water on a platform that rotated slowly.

The researchers noticed that compared to the tree frog, the torrent frogs were better in maintaining a grip on extremely wet, steep and uneven surfaces.  But on dry and smooth surfaces both the frog species were able to hold tight to steep slopes.

With help of imaging they explored the differences in the attachment processes between the two species. The researchers discovered that the torrent frogs increase the use of their belly and thighs to maintain a grip as the surface gets steeper. On the other hand, on steeper platforms the tree frogs failed to maintain contact of their belly and thigh skin with the surface.

The team used scanning electron microscopy to identify the shape of the cells on the toe pads of both the frog species. They noticed that the toe pads of the torrent frogs were slightly more  elongated than the tree frogs' and also that these cells develop channels, which  allow the excess fluid to get drained below the pad offering a better grip.

 Endlein concluded saying, "Torrent frogs adhere to very wet and rough surfaces by attaching not only their specialised toe pads (like many tree frogs do) but also by using their belly and ventral thigh skin. In addition, torrent frog's exhibit elongated cells on their toe pads which might help to drain off excess water for close surface attachment."

The study is published in the journal PLOS ONE.