They trashed a pool that serves as the only remaining home for the world’s rarest fish: the Death Valley pupfish. Photo credit: Olin Feuerbacher / National Wildlife Service
All it takes is one bad decision. And when people have been drinking, there’s ample opportunity.
On April 30, three men broke into Devil’s Hole, an ecologically fragile area of Death Valley National Park. They trashed a pool that serves as the only remaining home for the world’s rarest fish: the Death Valley pupfish.
While these charming creatures have no natural predators, they tend to be slow-moving and easygoing—which makes them extremely vulnerable to vandalism. At least one of the fish died while the men trampled their home.
The story behind these tiny fish is fascinating. In addition to their rarity—population numbers fluctuate between 115 in winter and 500 in summer—the Death Valley pupfish were at the center of the first Endangered Species Act-related litigation to go all the way to the Supreme Court.
At issue was a question of water rights, a common dispute in California. In 1976 infuriated developers wanted access to water that environmental activists claimed was critical to the survival of the pupfish. The case set a precedent: when it comes to the Endangered Species Act, the protection of endangered and threatened wildlife will be taken seriously.
Concerned about the potential for retaliatory vandalism, the National Parks Service has fenced off Devil’s Hole, adding cameras to monitor the area. The three men who broke in attempted—and failed—to disable the cameras. Instead, the men ensured that they, along with their vehicle, were caught on film.
The drunken adventure included wading in the pool, clambering around the rocks, firing at least 1 rounds of bullets and tossing beer cans into the desert.
When the men finished, they left behind a pair of boxer shorts, vomit and discarded trash. The National Parks Service swept into gear, publishing stills—and later a full video.
The National Park Service offered a $5,000 reward to anyone who could help identify the culprits. The Center for Biological Diversity later sweetened the deal, upping it to a $15,000 reward. That extra incentive turned out to be enough to entice the public into naming those responsible.
The tipping point, it turned out, was the men’s vehicle, which was extremely distinctive thanks to its unique customizations. While the men hadn’t been arrested as of May 10, the National Parks Service was gathering material to build a case for arrest and prosecution.
Death Valley is an incredibly important and unique natural area, hosting more than 50 types of mammals, more than 300 bird species and a huge variety of fish, reptiles and amphibians. The park’s range of elevations creates distinct bands of habitat in which very unique species thrive, but disruptions to that habitat can prove devastating.
In Devil’s Hole, a truly special spot, trampling and skinny-dipping meant not just disrupting the fish, but also potentially destroying their eggs. If the summer pupfish population dips too low, it will be difficult for the fish to recover through the winter, when a small number of individuals becomes the stock required to keep the species alive.
Incidents like these are a stark reminder of the incredible fragility of so many endangered species. With a little more damage, the men could have wiped out the Death Valley pupfish species forever.
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Using a multigenerational experiment UTS research has shown for the first time that when reef fish parents develop from early life at elevated temperatures they can adjust their offspring gender through non-genetic and non-behavioural means.
The study, published in Global Change Biology, demonstrates that the mechanisms involved in restoring offspring sex ratios across generations are switched on during early development of the parents and do not simply occur as a result of adults being exposed to higher temperatures.
“Understanding the ability of species to respond and cope with rising environmental temperature is key to predicting the biological consequences of global warming,” said lead author and UTS Chancellor’s Postdoctoral Research Fellow Dr Jennifer Donelson.
The ability to compensate for the gender bias caused by rising temperatures is an important trait that could help constrain the impacts of ocean warming on reef fish populations and other species. However the research also suggests that when developmental temperature is too hot there is a limit to this “transgenerational plasticity”.
“The research findings are significant because global warming poses a threat to species with temperature-dependent sex determination (TSD), such as reptiles and fish, potentially skewing the sex-ratio of offspring and, consequently, breeding individuals in a population,” Dr Donelson said.
“It’s well known that gender bias away from the optimal sex ratio of juveniles, that is roughly equal numbers of males and females, can have significant consequences for population success.
“A reduction in the proportion of females in the population could be especially damaging because population growth rate is often constrained by female fertility.”
The researchers showed that even relatively small increases in developmental temperatures, just 1.5 degrees Celsius above average summer temperatures, can reduce the proportion of female offspring by more than 30 per cent. However the female sex ratio of offspring was restored when parental fish were reared at this temperature for their entire life and for two generations.
“However, only partial improvement in the sex ratio occurred at 3.0 degrees Celsius above average conditions, even after two generations, suggesting a limitation to transgenerational plasticity when the developmental temperature is too hot,” Dr Donelson said.
“Previous research has focused on the changes to the timing of breeding and mothers behaviourally altering the location of their nest to compensate for warming. The novelty of our study was using a multigenerational (three generations) rearing design to ask questions about non-genetic and non-behavioural parental effects to sex determination,” Dr Donelson added.
“Just precisely how our study species, the Spiny Chromis coral reef fish, engineer these amazing adjustments is unknown and is something we are now investigating. What we do know however is that oceans are warming and emerging research is showing the importance of transgenerational plasticity in reducing the negative impacts of climate change on species with TSD.”
The Jurassic fish, Dapedium, known from the Lower Lias rocks of the Dorset coast around Lyme Regis, was one of many new groups of fishes that came on the scene 200 million years ago. These included ancestors of the modern teleost fishes – the group of 30,000 species of salmon, cod, seahorses, and perch – that dominate the waters today.
This distinctive fish was also one of a number of ancient animals first discovered by the pioneering nineteenth century fossil collector Mary Anning, and fascinated early palaeontologists such as Henry De la Beche and Louis Agassiz.
Dapedium was a deep-bodied fish, shaped like a dinner plate in side view, which could grow to over half a metre in length. It had a tiny mouth with jutting front teeth and masses of pebble-shaped teeth further back.
In his research, Bristol undergraduate Fiann Smithwick applied a new lever-based mechanical model, developed to understand the jaw mechanics of modern fishes, to reconstruct the feeding behaviour of this extraordinary ancient fish.
“My work indicates that Dapedium was well adapted to crush shells,” said Fiann, “feeding on bivalves and other hard-shelled creatures that it could scrape from the sea floor.”
He examined 89 specimens of Dapedium in the Natural History Museum, Bristol City Museum, and the Philpot Museum in Lyme Regis, and measured the positions and lengths of the jaw bones. He calculated the positions and orientations of jaw muscles and varied these to include all possible models.
“Every time he ran the model, the result was the same,” explained Professor Mike Benton, Fiann’s supervisor. “The outputs showed that Dapedium was a shell crusher. Its jaws moved slowly, but strongly, and so it could work on the hard shells of its prey. Other fishes have fast-moving, but weaker jaws, and those are adapted for feeding on speedy, slippery fish prey.”
In comparisons with modern fishes, Dapedium matches closely the modern sea breams. These fishes are also flat-sided and deep-bodied, and they crush shells in their small mouths, armed with blunt-topped teeth.
Dapedium lived side-by-side with the great sea reptiles of the Jurassic, such as the dolphin-shaped ichthyosaurs, long-necked plesiosaurs, and even some marine crocodilians. Dapedium probably escaped being caught by these reptiles because it was so thin-bodied it might be hard to see head-on, and it probably lurked close to reefs and the seabed.
“We are delighted to see such an excellent piece of work carried out by an undergraduate,” said Professor Benton. “Fiann was funded by a Summer Research Bursary from the Palaeontological Association, and he devised the project himself, learned the numerical techniques, and wrote it up himself. It’s rare for an undergraduate to be able to do all this and pass the scrutiny of one of the world’s leading scientific journals.”
Archerfish hunt by shooting jets of water at unsuspecting insects, spiders, or even small lizards on leaves or twigs above, knocking them into the water below before gobbling them up. Now, a study in the Cell Press journal Current Biology on September 4 finds that those fish are much more adaptable and skillful target-shooters than anyone had given them credit for. The fish really do use water as a tool, the researchers say, making them the first known tool-using animal to adaptively change the hydrodynamic properties of a free jet of water.
It’s rather easy to see the usefulness of their impressive skill.
“The predominant impression from our field work in Thailand over several years is that there is very little to actually shoot at, so it’s important for the fish to be efficient,” says Stefan Schuster of the University of Bayreuth in Germany. “It pays to be able to powerfully hit prey over a wide range of distances.”
Schuster and Peggy Gerullis made the discovery by first training fish to hit targets ranging in height from 20 to 60 centimeters from a precise location. They then monitored various aspects of jet production and propagation as the fish did their thing.
Those studies showed that the time needed before water masses up at the jet tip isn’t fixed. Rather, archerfish make adjustments to ensure that a nice drop of water forms just before impact. Surprisingly, the researchers report, the fish achieve this by modulating the dynamics of changes in the cross-section of their mouth opening. The timing adjustments that archerfish must make to powerfully hit their targets over an extended range are surprisingly comparable to the “uniquely human” ability of powerful throwing, the researchers write.
“One of the last strongholds of human uniqueness is our ability to powerfully throw stones or spears at distant targets,” Schuster says. “This is really an impressive capability and requires—among many fascinating aspects—precise time control of movement. It is believed that this ability has forced our brains to become bigger, housing many more neurons to afford the precision. With the many neurons around, they could be used for other tasks apart from applying them for powerful throws. It is remarkable that the same line of reasoning could also be applied to archerfish.”
It’s possible that the mechanism the fish use to control water with such precision might also find application in human-built nozzles, he adds, noting that adjustable jets are big business in many industries, including medicine.
“The biggest problem is how to modify the abrasive properties of a jet,” Schuster says. “Usually this is done by modulating the release pressure or by varying the abrasives added to the jet. We are not aware of someone actually using a dynamically adjustable valve.”
The above story is based on materials provided by Cell Press. Note: Materials may be edited for content and length.
The European perch’s behaviour is affected by common anti-anxiety drugs
Anti-social fish in your waterway? Perhaps you shouldn’t blame their parents but trace amounts of drugs used to treat anxiety. That’s the finding of Swedish scientists who say that low levels of psychotherapeutic drugs can change the way fish behave and could be altering the balance of entire aquatic food webs.
Common pharmaceuticals like the anti-anxiety drugs benzodiazepines end up in sewers as they are excreted by the people taking them. Conventional wastewater treatment doesn’t destroy these types of drugs, however, and they are also remarkably resistant to photodegradation, meaning that they persist in rivers and streams.
As pharmaceuticals like benzodiazepines can alter human behaviour it has been suspected for some time that they might also have an effect on aquatic organisms. Surprisingly however, no investigations into whether or not these psychotherapeutic drugs have been altering the way aquatic wildlife acts has been carried out until now.
To check on whether low doses of benzodiazepines can affect aquatic life, Tomas Brodin and colleagues from Umeå University first looked at drug concentrations downstream of a sewage treatment plant on the river Fyris in Sweden. They found concentrations of up to 0.58µg/l of the common anti-anxiety drug Oxazepam. This is similar to other waterways in Europe and the US. But when the researchers looked at levels of the drug in fish from the Fyris they got a surprise. It was more than six times that found in the river, demonstrating that the drug bioaccumulates. Co-author Jerker Fick points out that the levels of the drug in the perch are still tiny though. ‘You’d need 4 tonnes of perch from the river to get just one tablet of the drug,’ he notes.
To see what effect this low-level exposure to benzodiazepines was having on the fish the team examined how personality traits, such as boldness, activity and social interaction changed when they were exposed to 1.8µg/l of Oxazepam. Activity was simply a measure of how much the fish darted about in their tank. Boldness was measured by how often the fish entered a new area of the tank, while social interaction was judged by a fish’s willingness to get in the personal space of another.
Fish exposed to the drug at similar levels to those found in Europe’s and America’s waterways were around 50% more active and significantly less social. Perch swimming in waters with a much higher drug dose of 910µg/l were also more active and less friendly, and also much, much bolder. They also found that the fish were hungrier and ate faster.
The authors describe the effects that trace amounts of a single drug can have on food webs as ‘alarming’. They point out that the sorts of behavioural changes that the fish have been experiencing could alter their evolutionary fitness by making them easy prey for predators or even put pressure on perch’s primary foodstuff, zooplankton.
They say that now that it is clear that psychoactive drugs can affect aquatic animals, new testing regimes need to be put in place to see what other effects these types of drugs might be having on these ecosystems. ‘The solution to this problem isn’t to stop medicating people who are ill but to try to develop sewage treatment plants that can capture environmentally hazardous drugs,’ Fick says.
T Brodin et al, Science, 2013, 339, 814, (DOI: 10.1126/science.1226850)