Research findings to be published in June 6 issue of Science
Animals incorporate a number of unique methods for detecting prey, but for the Japanese sea catfish, Plotosus japonicus, it is especially tricky given the dark murky waters where it resides.
John Caprio, George C. Kent Professor of Biological Sciences at LSU, and colleagues from Kagoshima University in Japan have identified that these fish are equipped with sensors that can locate prey by detecting slight changes in the water's pH level.
A paper, "Marine teleost locates live prey through pH sensing," detailing the work of Caprio and his research partners, will be published in the journal Science on Friday, June 6. This is the first report of any fish using pH to find live prey.
"What makes this so interesting is that the discovery was unexpected, quite serendipitous," Caprio said.
The study was an offshoot of work initiated in 1984 when Caprio, a specialist in aquatic vertebrate taste and smell systems, began a collaborative investigation at Kagoshima University examining the physiology of the taste system of the Japanese sea catfish. While performing electrical recordings from the fish barbells, or "whiskers," he noticed that every so often some new sensory nerve fibers would respond at a much larger amplitude than the others.
"Immediately I knew that there was something different about those nerves, but I was working on a different project funded by the National Science Foundation and had to put my curiosities on the back burner," Caprio said.
In 1986, Caprio's curiosities got the best of him, and he asked his friends in Japan to ship him some of the catfish so that he could examine what was triggering such huge responses in the fish.
"I suspected the response was due to a change in pH caused by some of the tested stimuli," he said. "It was obvious that there were sensory nerve fibers in these fish that were responding to transient lowering of the pH of the seawater; however, what I did not know was what function this response served."
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' sensitivity was highest in natural seawater of pH 8.2, but decreased dramatically at pH less than 8. These findings imply that the food-locating abilities of Japanese sea catfish could be compromised by ocean acidification, the ongoing decrease in the pH of the Earth's oceans due to uptake of carbon dioxide from the atmosphere caused in great part by man-made activities.
Studies show that prior to the industrial revolution, carbon dioxide levels were approximately 280 parts per million. Today, it is 390 parts per million, and scientists predict that the levels could increase to 900 parts per million by the year 2100. According to the National Oceanic and Atmospheric Administration, the oceans absorb about a quarter of the carbon dioxide released in the atmosphere each year, resulting in increasing acidified seawater.
"Once the pH of the ocean drops much below 8, shell producing invertebrates can no longer produce their shells," Caprio said. "Our work could possibly be an indicator of the possible effects of ocean acidification on marine vertebrates. If ocean acidification continues at its same rate, we do not know if marine life will be able adapt to such a rapid alteration in pH. It is possible that the sensors could adapt to such a change, but we are not certain that this will happen. As of today, what we know is that these sensors work optimally in the vicinity of pH of 8.2, that of normal seawater. If ocean pH drops much below 8, a number of deleterious events are likely to occur."
Aaron Looney | Eurek Alert!
A new potential biomarker for cancer imaging
05.02.2016 | Universiti Putra Malaysia (UPM)
NIH researchers identify striking genomic signature shared by 5 types of cancer
05.02.2016 | NIH/National Human Genome Research Institute
Automobiles increase the mobility of their users. However, their maneuverability is pushed to the limit by cramped inner city conditions. Those who need to...
Advance in biomedical imaging: The University of Würzburg's Biocenter has enhanced fluorescence microscopy to label and visualise up to nine different cell structures simultaneously.
Fluorescence microscopy allows researchers to visualise biomolecules in cells. They label the molecules using fluorescent probes, excite them with light and...
NASA's follow-on to the successful ICESat mission will employ a never-before-flown technique for determining the topography of ice sheets and the thickness of sea ice, but that won't be the only first for this mission.
Slated for launch in 2018, NASA's Ice, Cloud and land Elevation Satellite-2 (ICESat-2) also will carry a 3-D printed part made of polyetherketoneketone (PEKK),...
In the last decades, sea level has been rising continuously – about 3.3 mm per year. For reef islands such as the Maldives or the Marshall Islands a sinister picture is being painted evoking the demise of the island states and their cultures. Are the effects of sea-level rise already noticeable on reef islands? Scientists from the ZMT have now answered this question for the Takuu Atoll, a group of Pacific islands, located northeast of Papua New Guinea.
In the last decades, sea level has been rising continuously – about 3.3 mm per year. For reef islands such as the Maldives or the Marshall Islands a sinister...
The ‘Internet of Things’ is growing rapidly. Mobile phones, washing machines and the milk bottle in the fridge: the idea is that minicomputers connected to these will be able to process information, receive and send data. This requires electrical power. Transistors that are capable of switching information with a single electron use far less power than field effect transistors that are commonly used in computers. However, these innovative electronic switches do not yet work at room temperature. Scientists working on the new EU research project ‘Ions4Set’ intend to change this. The program will be launched on February 1. It is coordinated by the Helmholtz-Zentrum Dresden-Rossendorf (HZDR).
“Billions of tiny computers will in future communicate with each other via the Internet or locally. Yet power consumption currently remains a great obstacle”,...
02.02.2016 | Event News
26.01.2016 | Event News
26.01.2016 | Event News
05.02.2016 | Life Sciences
05.02.2016 | Materials Sciences
05.02.2016 | Physics and Astronomy