Caprio tabled the investigation again, as other research activities took precedence, and resumed his analysis in 2005 with support from the National Institutes of Health and LSU. Caprio traveled to Japan six times between 2005 and 2013, staying at least a month each visit. During this time, he focused his attention on the fishes' nervous system, while colleagues conducted behavior experiments.
For the physiological experiments, the fish were outfitted with electrodes that allowed the recording of the fishes' responses to water of varying pH. It was during this time that they determined that the function of the sensitivity of the fishes' barbells to minor changes in water pH was due to the respiration of small sea worms, polychaetes, a primary prey of the sea catfish.
The sea worms live in tubes or burrows in the mud. As the worms breathe, they release tiny amounts of carbon dioxide and acid, producing a slight decrease in the pH of the seawater that the nocturnal sea catfish detects.
"These fish are like swimming pH meters. They are just as good as a commercial pH meter in the lab," Caprio said.
For the behavioral experiments, the researchers placed the fish in aquariums filled with seawater, along with the sea worms, which were placed into glass tubes within the coral substrate of the aquarium. The researchers used infrared photography to show that the nocturnally active fish spent significantly more time in the vicinity of the worms than in other locations in the aquarium. The researchers also confirmed that the catfish were attracted to a location in the aquarium where seawater of a slightly lower pH was being emitted from a small tube even when no worms were present. In addition, the fish became extremely active, searching for food and even bit repeatedly at the end of the tube.
The research indicates that the catfishes' sensitivi
|Contact: Aaron Looney|
Louisiana State University