Passage I

Torrent frogs (Staurois guttatus) can cling to wet sur­faces, even when the surfaces are at an angle of 90° (verti­cal) or greater. Researchers conducted 2 experiments to study how surface texture and water flow over the surface affects the clinging ability of S. guttatus.

Experiment 1

An apparatus was constructed with a transparent plat­form that could have different surface textures applied to it and that could be rotated 180°. A pump could direct water from a tank to flow over the platform (see Figure 1).

Then, in each of 9 trials (Trials 1一9), each of 10 S. guttatus (identical in size) was tested as follows:

1. The water flow rate was adjusted, a surface texture was applied to the platform, and the platform was rotated to a 10° angle.

2. A frog was placed on the platform.

3. The platform was rotated from 10° to 180° at a rate of 5° per sec.

4. The angle of detachment (angle at which the frog detached from the platform) was recorded.

The average angle of detachment was determined for each trial (see Table 1).

Experiment 2

Trial 1 of Experiment 1 was repeated, but with a camera attached to the underside of the platform. At spe­cific platform rotation angles during the trial, the camera was used to determine each frog's contact area (the surface of the frog that was in contact with the platform). in millimeters squared (mm²). The average contact area was determined for each angle (see Figure 2).

Table and figures adapted from T. Endlein et al., "Sticking Under Wet Condition: The Remarkable Attachment Abilities of the Torrent Frog, Staurois guttatus." @2013 by T. Endlein et al.