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Fish Thinking

Zebra danio. Photograph by Oliver Lucanus.

Scientists have just observed a thought swimming through the brain of a live fish, and that thought concerned getting something good to eat.

Fish and other wild animals appear to think a lot about food: how to obtain it and what to consume.

The finding, published in the journal Current Biology, also reminds that thoughts can be isolated and monitored.

Source: Discovery News

Posted February 1st, 2013.

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Faster Than Tuna?

Bluelined wrasse. Photo credit: Sally Pollack.

Tiny coral reef wrasses can swim as fast as some of the swiftest fish in the ocean – but using only half as much energy to do so, Australian scientists working on the Great Barrier Reef have found.

By flapping their fins in a figure-eight pattern, bluelined wrasses can travel at high speeds while using 40 per cent less energy than tunas of the same size.

“For a long time, people thought the best high-speed swimmers were the fishes cruising in open waters, like mackerel and tunas,” says Dr Chris Fulton from the ARC Centre of Excellence for Coral Reef Studies and The Australian National University.

“Our study shows that these coral reef wrasses, by virtue of their unique wing-like fins, can maintain very similar speeds at a dramatically lower energetic cost,” he says.

The researchers’ discovery could help revolutionise robot submarine technology by reducing how much energy is needed to propel objects underwater.

Current Autonomous Underwater Vehicles (AUVs) use propellers or jets at the back. “By replacing these with fins at the front to mimic how the bluelined wrasses flap their fins, we could propel robots with less power, saving on batteries and increasing their range,” Dr Fulton says.

Dr Fulton explains that fish like tunas and mackerels move their bodies and tails to propel themselves through the water. While this method enables them to swim fast, it can come at a high energetic cost.

“Another way fish swim is to use their pectoral fins, those at the front of their body, to produce thrust,” says Dr Fulton. “Fishes that do this with rounded fins tend to paddle their fins back and forth, almost like how we row a boat: they hold their fins out and pull back in a power stroke, then collapse their fins and bring them forward for a recovery stroke. This means they are producing thrust only half the time.”

Bluelined wrasses, however, flap their tapered fins in a figure eight pattern that produces thrust on every stroke, making it far more energy efficient.

“This figure-eight fin sweep allows the bluelined wrasse to create a lift force as the water flows over their fins, in a very similar way to how birds fly through the air. This means the fish are literally flying underwater.

“They also hold their body rigid while swimming to make it as streamlined as possible. They only flap their fins, slightly adjusting the angle so as to cruise along without burning up a lot of energy.”

The study shows that bluelined wrasses stand out as the highest performing swimmers for their size with respect to optimum swimming speed and energy consumption, Dr Fulton says.

Such extreme performance appears to be linked with the fish’s habitat, he says. Unlike many tail-swimmers that dwell in the open ocean, these wrasses live on shallow coral reefs where they experience some rough treatment from waves breaking over the reef.

“Most people think that coral reefs are idyllic places for fish to live, but dwelling in these shallow waters means they often experience extreme water flows generated from waves,” Dr Fulton says.

“It’s almost like living with constant winds from a cyclone – you can just imagine what it’d be like to try and find food and get home in that sort of weather!”

Having a smart swimming technique has ensured these small reef fish have an evolutionary advantage in the marine environment, Dr Fulton says.

“Fish use up to half of their energy on swimming. So if they can save even just a fraction of this, they can spend it on growing bigger, holding larger territories and producing more offspring,” he says.

“Just imagine if you could save 40 per cent on the petrol bill for your car – how good would it be to spend that spare cash on other things?”

“We know fish with these wing-like fins dominate shallow reefs around the world, where in some cases they can be about 10 times more abundant than fishes with paddle-shaped fins.”

Source: Arc Center of Excellence for Coral Reef Studies. The study “Energetic extremes in aquatic locomotion by coral reef fishes” by Christopher J. Futon, Jacob L. Johansen and John F. Steffensen is published in the latest issue of PLoS ONE. See:http://dx.plos.org/10.1371/journal.pone.0054033

Posted January 15th, 2013.

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Tadpole’s Tail May Hold Secrets for Human Healing

It is generally appreciated that frogs and salamanders have remarkable regenerative capacities, in contrast to mammals, including humans. For example, if a tadpole loses its tail a new one will regenerate within a week. For several years Professor Enrique Amaya and his team at The Healing Foundation Centre in the Faculty of Life Sciences have been trying to better understand the regeneration process, in the hope of eventually using this information to find new therapies that will improve the ability of humans to heal and regenerate better.

In an earlier study, Professor Amaya’s group identified which genes were activated during tail regeneration. Unexpectedly, that study showed that several genes that are involved in metabolism are activated, in particular those that are linked to the production of reactive oxygen species (ROS) – chemically reactive molecules containing oxygen. What was unusual about those findings is that ROS are commonly believed to be harmful to cells.

Professor Amaya and his group decided to follow up on this unexpected result and their new findings will be published in the next issue of Nature Cell Biology.

To examine ROS during tail regeneration, they measured the level of H2O2 (hydrogen peroxide, a common reactive oxygen species in cells) using a fluorescent molecule that changes light emission properties in the presence of H2O2. Using this advanced form of imaging, Professor Amaya and his group were able to show that a marked increase in H2O2 occurs following tail amputation and interestingly, they showed that the H2O2 levels remained elevated during the entire tail regeneration process, which lasts several days.

Talking about the research Professor Amaya says: “We were very surprised to find these high levels of ROS during tail regeneration. Traditionally, ROS have been thought to have a negative impact on cells. But in this case they seemed to be having a positive impact on tail re-growth.”

To assess how vital the presence of ROS are in the regeneration process, Professor Amaya’s team limited ROS production using two methods. The first was by using chemicals, including an antioxidant, and the second was by removing a gene responsible for ROS production. In both cases the regeneration process was inhibited and the tadpole tail did not grow back.

Professor Amaya says: “When we decreased ROS levels, tissue growth and regeneration failed to occur. Our research suggests that ROS are essential to initiate and sustain the regeneration response. We also found that ROS production is essential to activate Wnt signalling, which has been implicated in essentially every studied regeneration system, including those found in humans. It was also striking that our study showed that antioxidants had such a negative impact on tissue regrowth, as we are often told that antioxidants should be beneficial to health.”

The publication of Professor Amaya’s study comes just days after a paper from the Nobel Prize winner and co-discoverer of the structure of DNA, James Watson, suggested antioxidants could be harmful to people in the later stages of cancer.

Professor Amaya comments: “It’s very interesting that two papers suggesting that antioxidants may not always be beneficial have been published recently. Our findings and those of others are leading to a reversal in our thinking about the relative beneficial versus harmful effects that oxidants and antioxidants may have on human health, and indeed that oxidants, such as ROS, may play some important beneficial roles in healing and regeneration.”

The next step for the team at the Healing Foundation Centre will be to study ROS and their role in the healing and regenerative processes more closely. With a better understanding, Professor Amaya and his team hope to apply their findings to human health to identify whether manipulating ROS levels in the body could improve our ability to heal and regenerate tissues better. Thus these findings have very important implications in regenerative medicine.

Photograph courtesy of The University of Manchester.

Source: The University of Manchester and The Healing Foundation Centre

Posted January 14th, 2013.

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New Miniature Fish Discovered

A number of incredible species have been discovered in Southeast Asia’s Greater Mekong Region, one of them being a miniature fish: Borarus naevus. The  fish, which measures just 2cm in length, was spotted off the coast of Surat Thani in Southern Thailand. It is one of a host of new creatures found in the Greater Mekong region during the course of 2011. The tiny fish was named for the large dark blotch on the side of its body; “neavus” is the latin word for blemish.

Source: Iconocast
Photo: AFP/Getty Images

Posted December 21st, 2012.

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Coral Reefs Could Be Decimated by 2100

Nearly every coral reef could be dying by 2100 if current carbon dioxide emission trends continue, according to a new review of major climate models from around the world. The only way to maintain the current chemical environment in which reefs now live, the study suggests, would be to deeply cut emissions as soon as possible. It may even become necessary to actively remove carbon dioxide from the atmosphere, say with massive tree-planting efforts or machines.

The world’s open-ocean reefs are already under attack by the combined stresses of acidifying and warming water, overfishing, and coastal pollution. Carbon emissions have already lowered the pH of the ocean a full 0.1 unit, which has harmed reefs and hindered ability to grow. The historical record of previous suggests that acidified seas were accompanied by widespread die-offs but not total extinction.

Source: Wired
Photo: Jim Maragos/U.S. Fish and Wildlife Service

Posted December 21st, 2012.

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Fish on Probiotics Grow Up Healthier

BALTIMORE, MD (December 3, 2012)— Probiotics like those found in yogurt are not only good for people–they are also good for fish. A new study by scientists at the Institute of Marine and Environmental Technology found that feeding probiotics to baby zebrafish accelerated their development and increased their chances of survival into adulthood.

This research could help increase the success of raising rare ornamental fish to adulthood. It also has implications for aquaculture, since accelerating the development of fish larvae–the toughest time for survival–could mean a more efficient and safe system for bringing fish to the dinner table.

Tiny zebrafish are often used in genetic research because scientists can easily track changes in their development and the fish grow quickly. They also share many of the same genes as humans and can be used for studying cellular and physiological processes and their impact on human disease.

“This is really exciting,” said Jacques Ravel, a leading genomic scientist studying the role of the human microbiome in health and disease at the University of Maryland School of Medicine Institute for Genome Sciences. “Knowing you can colonize the gut of a zebrafish with a probiotic strain and improve its development becomes an interesting model for us to study the beneficial effect of probiotics in children and adults.” He and his colleagues are currently looking into the effect of Lactobacillus rhamnosus probiotics on the gut development of premature infants.

In the zebrafish experiment, researchers added Lactobacillus rhamnosus, a probiotic strain sometimes used in yogurt, to the zebrafish water. The fish drank the probiotic through their gills, and it landed in their gastrointestinal tract, preventing bad bacteria from taking over and promoting growth, including advancing the development of bone, vertebrae, and gonads.

“If you have increased growth and survival from each batch of hundreds of thousands of eggs, that is a huge benefit,” said study co-author Dr. Allen Place of the Institute of Marine and Environmental Technology.

Probiotics helped the zebrafish get through the touch-and-go time when their gastrointestinal tract is maturing. They are still living off yolk with which they are born, and it is during this weaning period when most mortality occurs. Adding probiotics to the water increases the survival rate of zebra fish larvae from 70% to 90%.

“We did not anticipate the enhancement in maturation,” said Place. “When you look at various molecular markers of stress, the overall stress in the fish that were treated with the probiotic were lower–which may be the reason for the development.”

The study, Lactobacillus rhamnosus Accelerates Zebrafish Backbone Calcification and Gonadal Differentiation through Effects on the GnRH and IGF Systems, was published in the September issue of PLOS ONE. Researchers include Matteo Avella and Oliana Carnevali from the Polytechnic University of Marche in Italy; Allen Place, Shao-Jun Du, Yonathan Zohar and Ernest Williams of the Institute of Marine and Environmental Technology in Baltimore, Maryland; Stefania Silvi of the University of Camerino in Italy.

Photograph courtesy of the University of Maryland Center for Environmental Science

Source: http://www.umces.edu/imet/release/2012/dec/03/new-study-shows-probiotics-help-fish-grow-faster-and-healthier

Posted December 4th, 2012.

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Zebrafish Use Color to Woo a Mate

Billy Ocean may not have been thinking of fish when he wrote “The Color of Love”, but Sophie Hutter, Attila Hettyey, Dustin Penn, and Sarah Zala from the Konrad Lorenz Institute of Ethology of the University of Veterinary Medicine, Vienna were able to show that zebrafish males and females both wear their brightest colours while wooing a mate.

Elaborate secondary sexual displays are often overlooked because many species attract mates through sensory modalities imperceptible to humans, including ultraviolet light, ultrasound, electrical signals, or pheromones. Also, sexual coloration may only be expressed briefly during courtship (ephemeral courtship dichromatisms) to avoid attracting predators. Zebrafish (Danio rerio) are a widely studied model organism, though there have been few studies on their mating behaviour. Like many schooling fish, zebrafish do not appear sexually dichromatic to humans; there are no obvious differences in the colour of males and females. Previous studies suggest that colour and stripe patterns influence their social and reproductive behaviour, but surprisingly, body colouration has not been quantitatively studied before in this fish.

The researchers studied sexually mature wild-derived zebrafish and a domesticated strain to compare the sexes and the two populations both in the morning, when mating and spawning occur, and again later in the day, when the fish only shoal. To assess the colour properties the scientists used non-invasive techniques such as digital photography, computer software and human observations and they photographed the fish in the water, while interacting with each other. The photographs allowed them to analyse hue, saturation, and brightness and to obtain numerical estimates of three colour properties. 

They found that both males and females changed their colour (dark and light stripes) only during spawning, and that some sex differences in stripes were larger or only became apparent during this time. They also observed that individual males that appeared more colourful and conspicuous to the human eye engaged in courtship more often than less conspicuous males. These observations support the hypothesis that body colouration plays a role in the courtship and mating behaviour of zebrafish.

Both wild-derived and the laboratory strain of zebrafish showed this ephemeral dichromatism, but there were differences in the colour properties of the two populations, and reduced individual variation in the laboratory strain.

Further studies are needed to determine the underlying mechanisms and signalling functions of fleeting different colour expressions in zebrafish.  Genetic analyses could help explain individual variation in nuptial colouration and provide insights into the evolutionary functions of this sexual dichromatism.

Photograph by Oliver Lucanus.

Source: The article “Ephemeral sexual dichromatism in zebrafish (Danio rerio)” by Sophie Hutter, Attila Hettiyey, Dustin Penn, and Sarah Zala is published in the current issue of the journal “Ethology” (Vol. 118 (2012): 1208–1218).

Posted December 3rd, 2012.

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Blind Loach Species Disovered

Fauna and Flora International

Ha Long Bay in the Gulf of Tonkin, Vietnam, was inscribed as a World Heritage Site1 in 1995 and provides a spectacular seascape of some 2,000 islets and other islands. The bay is famous for its geology and scenery, especially its towering limestone pillars, magnificent arches and its vast and beautiful caves. As a result, it is visited by hundreds of thousands of tourists annually.

The largest area of coastal limestone towers in the world, Ha Long Bay’s natural beauty is complemented by its great biological diversity. Probably few visitors are aware that Ha Long Bay is home to 14 endemic plants and 60 endemic animals. Even fewer will be aware of the fascinating and unique creatures that exist there, confined to a system of subterranean caves.

In 2002, at the request of the Site’s Management Authority, Fauna & Flora International (FFI) began an extensive survey of Ha Long Bay’s biodiversity. Experts in karst limestone ecology from Slovenia joined local experts in 2003, and it was during these surveys that the new loach was discovered by University of Ljubljana biologists Boris Sket and Peter Trontelj on the tiny (1 km2) and contorted Van Gio Island2. The fish has just been described in Revue suisse de Zoologie3 by the world-renowned Swiss ichthyologist, Maurice Kottelat, not just as a new species but as a new genus to be known as Draconectes narinosus.

This inch-long fish is notable for having no eyes, no markings and no scales – all common adaptations for animals that have evolved in the total darkness of deep limestone caves.

Its relatives most typically inhabit fast-flowing rivers where they live under stones and rocks. A number of loaches are already known from caves in the region and more await description.

The name of this new fish derives from the Greek for dragon (drakon) and swimmer (nectes) – a reference to Halong which means ‘descending dragon’ (so-called because it is believed that the landscape was created by a dragon). The Latin ‘narinosus’ means ‘who has large nostrils’.

Also found in the cave was a new species of amphipod crustacean, Seborgia vietnamica, which is likely to be a major component of this fish’s diet.

The fish belongs to a family that is strictly limited to freshwater and so cannot cross seawater. This means that it is very likely to be endemic to Van Gio Island. Scientists are yet to discover whether there are other related species on nearby islands, or whether this is the only surviving species in its genus.

It is remarkable that this species has managed to evolve and survive on such a small island. The new fish appears to be restricted to the island, which has long, narrow arms with a maximum width of just 400 m. The cave’s freshwater lake (where the fish was found) is barely 200 m from the sea and at about sea level. It is therefore extremely sensitive to rainfall and climate change, as well as human activities.

Photograph courtesy of Tan Heok Hui, Boris Sket and Revue suisse de Zoologie: Kottelat, M. 2012. Draconectes narinosus, a new genus and species of cave fish from an island of Halong Bay, Vietnam (Teleostei: Nemacheilidae). Revue suisse de Zoologie 119 (3): 341-349).

Source: Fauna and Flora International

 

Posted December 3rd, 2012.

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Sea Anemone Insecticide

Bethesda, MD—As insects evolve to become resistant to insecticides, the need to develop new ways to control pests grows. A team of scientists from Leuven, Belgium have discovered that the sea anemone’s venom harbors several toxins that promise to become a new generation of insecticides that are environmentally friendly and avoid resistance by the insects. Since these toxins disable ion channels that mediate pain and inflammation, they could also spur drug development aimed at pain, cardiac disorders, epilepsy and seizure disorders, and immunological diseases such as multiple sclerosis. This finding is described in the December 2012 issue of The FASEB Journal.

“Are toxins friend or foe? The more we understand these toxins, they are more friend, and less foe,” said Jan Tytgat, Ph.D., co-author of this study from the Laboratory of Toxicology at the University of Leuven in Leuven, Belgium. “Toxicology shows us how to exploit Mother Nature’s biodiversity for better and healthier living.”

To make this discovery, Tytgat and colleagues extracted venom from the sea anemone, Anthopleura elegantissima, and purified three main toxins present in the venom. The toxins were characterized in depth, using biochemical and electrophysiological techniques. This provided insight into their structure, functional role and mechanisms of action. The discovery of these toxins may be considered similar to the discovery of a new drug, as they are compounds which could lead to new insecticides and possibly new treatments for human diseases.

“Because these toxins are aimed at important ion channels present not only in insect cells, they form the leading edge of our new biotechnology. Discovery of this useful marine toxin should provide additional incentive to preserve the fragile coral reefs where anemones thrive,” said Gerald Weissmann, M.D., Editor-in-Chief of The FASEB Journal, “But, given current attitudes, I suspect there’s a better chance of a sea anemone killing a stink bug than for us to reverse our inroads on ocean life.”

Photograph by Natalie Jean/Shutterstock.

Source: Steve Peigneur, László Béress, Carolina Möller, Frank Marí, Wolf-Georg Forssmann, and Jan Tytgat. A natural point mutation changes both target selectivity and mechanism of action of sea anemone toxins. FASEB J 26:5141-5151, doi:10.1096/fj.12-218479 ; http://www.fasebj.org/content/26/12/5141.abstract

Posted November 30th, 2012.

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Many Marine Species Remain Undescribed

 

At least one-third of the species that inhabit the world’s oceans may remain completely unknown to science. That’s despite the fact that more species have been described in the last decade than in any previous one, according to a report published online on November 15 in the Cell Press publication Current Biology that details the first comprehensive register of marine species of the world—a massive collaborative undertaking by hundreds of experts around the globe.

The researchers estimate that the ocean may be home to as many as one million species in all—likely not more. About 226,000 of those species have so far been described. There are another 65,000 species awaiting description in specimen collections.

“For the first time, we can provide a very detailed overview of species richness, partitioned among all major marine groups. It is the state of the art of what we know—and perhaps do not know—about life in the ocean,” says Ward Appeltans of the Intergovernmental Oceanographic Commission (IOC) of UNESCO.

The findings provide a reference point for conservation efforts and estimates of extinction rates, the researchers say. They expect that the vast majority of unknown species—composed disproportionately of smaller crustaceans, molluscs, worms, and sponges—will be found this century.

Earlier estimates of ocean diversity had relied on expert polls based on extrapolations from past rates of species descriptions and other measures. Those estimates varied widely, suffering because there was no global catalog of marine species.

Appeltans and colleagues including Mark Costello from the University of Auckland have now built such an inventory. The World Register of Marine Species (WoRMS) is an open-access, online database (see http://www.marinespecies.org/) created by 270 experts representing 146 institutions and 32 countries. It is now 95% complete and is continually being updated as new species are discovered.

“Building this was not as simple as it should be, because there has not been any formal way to register species,” Costello says.

A particular problem is the occurrence of multiple descriptions and names for the same species—so called “synonyms,” Costello says. For instance, each whale or dolphin has on average 14 different scientific names.

As those synonyms are discovered through careful examination of records and specimens, the researchers expect perhaps 40,000 “species” to be struck from the list. But such losses will probably be made up as DNA evidence reveals overlooked “cryptic” species.

While fewer species live in the ocean than on land, marine life represents much older evolutionary lineages that are fundamental to our understanding of life on Earth, Appeltans says. And, in some sense, WoRMS is only the start.

“This database provides an example of how other biologists could similarly collaborate to collectively produce an inventory of all life on Earth,” Appeltans says.

Source: Appeltans et al.: “The Magnitude of Global Marine Species Diversity”

Photograph by Borisoff/Shutterstock.

Posted November 16th, 2012.

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