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
Posted December 4th, 2012. 1 comment
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. 1 comment
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. Add a comment
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. Add a comment
S.E.A. Aquarium—the world’s largest aquarium—opened on November 22, 2012. It will be home to 100,000 marine animals of over 800 species in 45 million litres of water. Comprising 10 different zones with 49 habitats, the aquarium takes guests on an underwater voyage beginning from Southeast Asia, and continues through the Arabian Gulf and the Open Ocean. Along the way, guests can expect to meet majestic manta rays, hammerhead sharks, bottlenose dolphins and other marine creatures.
S.E.A. Aquarium Senior Curator Grant Willis said: “S.E.A. Aquarium offers not only a stunning display of habitats, but also education and conservation programmes in which families and guests can participate. Younger guests will be thrilled to know that we have specially-designed exhibits such as the Discovery Touch Pool, the Lens Aquarium and Floor Aquarium, to provide them up-close encounters with our marine residents.” The centerpiece of the Aquarium is the Open Ocean habitat, seen through the world’s largest viewing panel, at 36 metres wide by 8.3 metres tall; Guests viewing the habitat could experience the feeling of being on a cavernous ocean floor. The habitat is flanked by an Ocean Dome—an all-round viewing area and the Ocean Restaurant, an outlet propagating sustainable seafood principles. Eleven Ocean Suites occupy the opposite site of the habitat, offering a twist to the proposition of sea-view by providing guests the experience of waking to an under-the-sea vista.
Posted November 27th, 2012. Add a comment
New findings from the partial skull of an extinct shark species show that the great white shark likely descended from the mako-like Carcharodon hubbelli rather than the massive Carcharocles megalodon.
The evolutionary history of the great white has been contested by paleontologists for 150 years. They were originally classified as direct relatives of megatooth sharks such as the extinct Carcharocles megalodon, the largest carnivorous shark that ever lived.
Fossils of a newfound species of shark, Carcharodon hubbelli, suggest the modern great white actually may have descended from broad-toothed mako sharks. Researchers say the newfound species represents a possible midway point in the evolution from one to the other.
Photo: Jeff Gage/Florida Museum of Natural History
Posted November 19th, 2012. Add a comment
Metabolomics, the study of molecules involved in an animal’s metabolism, has been successful in determining the health of whale sharks when traditional blood chemistry tests have failed. A study, led by Dr. Alistair Dove, Director of Research & Conservation at Georgia Aquarium and an adjunct professor at Georgia Tech, found that the major difference between healthy and unhealthy sharks was the concentration of homarine in their in serum, indicating that homarine is a useful biomarker of health status for the species.
Previous research and observations showed that traditional veterinary blood chemistry tests were not as useful with whale sharks; most likely because such tests are designed for mammals and comparatively less is known about shark and ray blood. Dr. Dove and six colleagues from Georgia Tech set out to significantly increase knowledge of whale shark biochemistry by examining the metabolite composition of all six whale sharks which have been cared for at Georgia Aquarium. By using metabolomics, the researchers were able to determine which chemical compounds were present in the shark blood, without knowing ahead of time what they are.
Source: Science Daily
Photo: DJ Mattaar/Shutterstock
Posted November 19th, 2012. Add a comment
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. Add a comment
By John Toon
Corals under attack by toxic seaweed do what anyone might do when threatened – they call for help. A study reported this week in the journal Science shows that threatened corals send signals to fish “bodyguards” that quickly respond to trim back the noxious alga – which can kill the coral if not promptly removed.
Scientists at the Georgia Institute of Technology have found evidence that these “mutualistic” fish respond to chemical signals from the coral like a 911 emergency call – in a matter of minutes. The inch-long fish – known as gobies – spend their entire lives in the crevices of specific corals, receiving protection from their own predators while removing threats to the corals.
This symbiotic relationship between the fish and the coral on which they live is the first known example of one species chemically signaling a consumer species to remove competitors. It is similar to the symbiotic relationship between Acacia trees and mutualist ants in which the ants receive food and shelter while protecting the trees from both competitors and consumers.
“This species of coral is recruiting inch-long bodyguards,” said Mark Hay, a professor in the School of Biology at Georgia Tech. “There is a careful and nuanced dance of the odors that makes all this happen. The fish have evolved to cue on the odor released into the water by the coral, and they very quickly take care of the problem.”
The research, supported the National Science Foundation, the National Institutes of Health and the Teasley Endowment at Georgia Tech, was reported November 8 in the journal Science. The research was done as part of a long-term study of chemical signaling on Fiji Island coral reefs aimed at understanding these threatened ecosystems and discovering chemicals that may be useful as pharmaceuticals.
Because they control the growth of seaweeds that damage coral, the importance of large herbivorous fish to maintaining the health of coral reefs has been known for some time. But Georgia Tech postdoctoral fellow Danielle Dixson suspected that the role of the gobies might be more complicated. To study that relationship, she and Hay set up a series of experiments to observe how the fish would respond when the coral that shelters them was threatened.
They studied Acropora nasuta, a species in a genus of coral important to reef ecosystems because it grows rapidly and provides much of the structure for reefs. To threaten the coral, the researchers moved filaments of Chlorodesmis fastigiata, a species of seaweed that is particularly chemically toxic to corals, into contact with the coral. Within a few minutes of the seaweed contacting the coral, two species of gobies – Gobidon histrio and Paragobidon enchinocephalus – moved toward the site of contact and began neatly trimming away the offending seaweed.
“These little fish would come out and mow the seaweed off so it didn’t touch the coral,” said Hay, who holds the Harry and Linda Teasley Chair in Environmental Biology at Georgia Tech. “This takes place very rapidly, which means it must be very important to both the coral and the fish. The coral releases a chemical and the fish respond right away.”
In corals occupied by the gobies, the amount of offending seaweed declined 30 percent over a three-day period, and the amount of damage to the coral declined by 70 to 80 percent. Control corals that had no gobies living with them had no change in the amount of toxic seaweed and were badly damaged by the seaweed.
To determine what was attracting the fish, Dixson and Hay collected samples of water from locations (1) near the seaweed by itself, (2) where the seaweed was contacting the coral, and (3) from coral that had been in contact with the seaweed – 20 minutes after the seaweed had been removed. They released the samples near other corals that hosted gobies, which were attracted to the samples taken from the seaweed-coral contact area and the damaged coral – but not the seaweed by itself.
“We demonstrated that the coral is emitting some signal or cue that attracts the fish to remove the encroaching seaweed,” Hay said. “The fish are not responding to the seaweed itself.”
Similar waters collected from a different species of coral placed in contact with the seaweed did not attract the fish, suggesting they were only interested in removing seaweed from their host coral.
Finally, the researchers obtained the chemical extract of the toxic seaweed and placed it onto nylon filaments designed to stimulate the mechanical effects of seaweed. They also created simulated seaweed samples without the toxic extract. When placed in contact with the coral, the fish were attracted to areas in which the chemical-containing mimic contacted the coral, but not to the area contacting the mimic without the chemical.
By studying the contents of the fish digestive systems, the researchers learned that one species – Gobidon histrio – actually eats the noxious seaweed, while the other fish apparently bites it off without eating it. In the former, consuming the toxic seaweed makes the fish less attractive to predators.
The two species of fish also eat mucus from the coral, as well as algae from the coral base and zooplankton from the water column. By defending the corals, the gobies are thus defending the home in which they shelter and feed.
“The fish are getting protection in a safe place to live and food from the coral,” Hay noted. “The coral gets a bodyguard in exchange for a small amount of food. It’s kind of like paying taxes in exchange for police protection.”
As a next step, Hay and Dixson would like to determine if other species of coral and fish have similar symbiotic relationships. And they’d like to understand more about how the chemical signaling and symbiotic relationship came into being.
“These kinds of positive interactions needs to be better understood because they tell us something about the pressures that have gone on through time on these corals,” said Hay. “If they have evolved to signal these gobies when a competitor shows up, then competition has been important throughout evolutionary time.”
Source: Danielle L. Dixson and Mark E. Hay, Corals chemically signal mutualistic fishes to remove competing seaweeds, Science (2012).
Photograph by Georgia Tech, Danielle Dixson
Posted November 9th, 2012. 1 comment
The world’s first-ever pink florescent Pterophyllum scalare, commonly known as the angelfish, were showcased in an exhibit on Wednesday prior to the Taiwan International Aquarium Expo, which opens today.
Lin Yu-ho (林育禾), president of Jy Lin Trading Co — the company that cooperated with National Ocean University and Academia Sinica on developing the fish — said this was the first time the world had seen a pink angelfish since the fish was discovered in the Amazon.
Despite the 32 colors developed worldwide for the angelfish, the fish lacked the cells to create any color resembling pink, Lin said, adding that the company had accomplished the endeavor after three years of research with the university and Academia Sinica.
Source: Taipei Times
Photograph courtesy of National Taiwan Ocean University.
Posted November 9th, 2012. 4 comments