The Nopili rock-climbing goby (Sicyopterus stimpsoni) is known to inch its way up waterfalls as tall as 100 meters by using a combination of two suckers; one of these is an oral sucker also used for feeding on algae. In this study, the researchers filmed jaw muscle movement in these fish while climbing and eating, and found that the overall movements were similar during both activities. The researchers note that it is difficult to determine whether feeding movements were adapted for climbing, or vice versa with the current data, but the similarities are consistent with the idea that these fish have learnt to use the same muscles to meet two very different needs of their unique lifestyle.
Footage of climbing abilities of the goby (source: LiveScience)
We found it fascinating that this extreme behaviour of these fish, climbing waterfalls with their mouth, might have been coopted through evolution from a more basic behaviour like feeding. The first step in testing this was to measure whether the two behaviours really were as similar as they looked.(Richard Blob, lead author, Clemson University)
(Source: PLoS One, 04.01.2013)