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In spring 2012, the muddy seafloor at Station M was literally covered with the silvery bodies of dead salps (gelatinous midwater animals that feed on microscopic algae). This debris provided food for seafloor animals such as sea cucumbers. Image © 2012 MBARI
Animals living on the abyssal plains, miles below the ocean surface, don’t usually get much to eat. Their main source of food is “marine snow” — a slow drift of mucus, fecal pellets, and body parts — that sinks down from the surface waters. However, researchers have long been puzzled by the fact that, over the long term, the steady fall of marine snow cannot account for all the food consumed by animals and microbes living in the sediment. A new paper by MBARI researcher Ken Smith and his colleagues shows that population booms of algae or animals near the sea surface can sometimes result in huge pulses of organic material sinking to the deep seafloor. In a few weeks, such deep-sea “feasts” can deliver as much food to deep-sea animals as would normally arrive over years or even decades of typical marine snow.
For over 20 years, Smith and his fellow researchers have studied animals living on the abyssal plain at Station M — a deep-sea research site about 220 kilometers (140 miles) off the Central California coast. The muddy seafloor at Station M — 4,000 meters (13,100) feet below the surface — is home to a variety of deep-sea animals, from sea cucumbers and sea urchins to grenadier fish. In addition, a myriad of smaller animals and microbes live buried within the mud.
Researchers have long wondered how all these animals and microbes get enough food to survive. The slow trickle of marine snow sinking down from above does not provide nearly enough food to support all the organisms that live down there. However, in a new paper in the Proceedings of the National Academy of Sciences, Smith and his coauthors show that occasional feasts could provide enough food to support deep-sea communities for years at a time.
Smith and his colleagues used several instruments to study the amount of marine snow arriving at Station M, as well as its impacts on life in the deep. They suspended conical “sediment traps” above the seafloor to collect and measure the amount of marine snow falling through the water. They also used automated camera systems to take time-lapse photographs of the seafloor. This allowed them to track the behavior, numbers, and sizes of larger deep-sea animals such as sea cucumbers. Finally, they used a seafloor-crawling robot, the Benthic Rover, to measure the amount of oxygen being consumed by animals and microbes in the sediment. Such oxygen measurements allowed the researchers to estimate how much food these organisms were consuming.
Using data from 1989 to 2012, Smith and his colleagues compared the amount of marine snow arriving at Station M with estimates of populations of microscopic algae observed at the surface using satellites. During most years, the amount of food arriving at the seafloor reached a yearly peak in summer and fall, but remained relatively low.
However, during 2011 and 2012, the researchers observed three dramatic events that delivered huge amounts of relatively fresh food to the deep seafloor. The first took place from June to August 2011, when large numbers of diatoms (a type of microscopic alga) bloomed near the surface, then sank rapidly to the seafloor.
The second event occurred from March to May 2012, when salps — gelatinous midwater animals that eat algae — reproduced rapidly in surface waters. These salps became so abundant that they blocked the seawater intake of the Diablo Canyon nuclear power plant, located on the California coast east of Station M. When the salps in the surface waters at Station M died, they sank so quickly that they carpeted the seafloor, four kilometers below. During the third event, in September 2012, another algal bloom created so much dead algae that it clogged the researchers’ sediment traps, but was captured by a time-lapse camera.
The excess food that arrived on the seafloor during these feasts was not wasted. Instead, it was rapidly consumed by deep-sea animals and seafloor microbes, which used it to grow and reproduce. Some of the organic carbon from the food was released into the surrounding seawater by respiration. Most of the rest was incorporated into the deep-sea sediments, where it could be recycled by animals and microbes that feed on the mud. In this way, large, intermittent pulses of food could help sustain life in the deep for years or even decades.
Smith and his colleagues are still studying the biological effects of these extreme pulses of food. They have already seen changes in the numbers and types of deep-sea animals living at Station M that appear to result from the feasts of 2011 and 2012. They will be reporting these findings in a subsequent paper.
The researchers note that deep-sea feasts may be increasing in frequency off the Central California coast, as well as at some other deep-sea study sites around the world. Over the last decade, the waters off Central California have seen stronger winds, which bring more nutrients, such as nitrate, to the ocean surface. These nutrients act like fertilizer, triggering blooms of algae, which, in turn, sometimes feed blooms of salps. The fallout from all of this increased productivity eventually ends up on the seafloor.
The authors also note that the changes in ocean conditions that provided more food for deep-sea animals at Station M might be related to global warming. Alternatively, these changes could simply reflect naturally occurring long-term cycles in the ocean.
Originally posted by the Monterey Bay Aquarium Research Institute: http://www.mbari.org/news/news_releases/2013/feast&famine/feast&famine-release.html.
Posted November 12th, 2013. Add a comment
Sep. 25, 2013 — A previously unknown genus of electric fish has been identified in a remote region of South America by team of international researchers including University of Toronto Scarborough professor Nathan Lovejoy.
The Akawaio penak. (Credit: Nathan Lujan)
The Akawaio penak, a thin, eel-like electric fish, was discovered in the shallow, murky waters of the upper Mazaruni River is northern Guyana.
Lovejoy’s team at UTSC analyzed tissue samples collected during a recent expedition by researchers led by Hernán López-Fernández at the Royal Ontario Museum. By sequencing its DNA and reconstructing an evolutionary tree, Lovejoy’s team discovered the fish is so distinct it represents a new genus, the taxonomic classification level above species.
The upper Mazaruni River is a hotspot for biological diversity, yet remains largely unexplored because of its remote location. The area contains countless rivers on top of a series of uplands that have remained isolated from the rest of South America for more than 30 million years.
“The fact this area is so remote and has been isolated for such a long time means you are quite likely to find new species,” says Lovejoy.
Like other electric knifefish, Akawaio penak has a long organ running along the base of the body that produces an electric field. The electric field is too weak to stun prey but is instead used to navigate, detect objects and to communicate with other electric fish. This trait is advantageous given the murky habitats of the fish.
The species is named in honour of the Akawaio Amerindians that populate the upper Mazaruni. The region is increasingly suffering from freshwater habitat degradation as a consequence of gold-mining in the area.
“The Mazaruni contains many unique species that aren’t found anywhere else in the world. It’s an extremely important area in South America in terms of biodiversity,” says Lovejoy.
The results of the discovery are published in the recent edition of the journal Zoologica Scripta.
Originally published http://www.sciencedaily.com/releases/2013/09/130925092233.htm
Posted September 27th, 2013. Add a comment
MANILA, PHILIPPINES – Larvae-eating guppy fish can help combat the spread of dengue, a mosquito-borne illness giving rise to hundreds of thousands of severe cases including 20,000 deaths worldwide every year, according to a trial study by the Governments of Cambodia and the Lao People’s Democratic Republic (Lao PDR) with the support of the Asian Development Bank (ADB) and the World Health Organization (WHO).
“This is a low-cost, year-round, safe way of reducing the spread of dengue in which the whole community can participate,” said ADB health specialist Gerard Servais. “It offers a viable alternative to using chemicals and can reduce the scale of costly emergency response activities to contain epidemics.”
The community-based project, conducted in two districts in Cambodia and the Lao PDR from 2009 to 2011, resulted in a sharp decline in mosquito larvae in water storage tanks after the tiny fish were introduced. Guppies eat larvae that grow into mosquitoes, which in turn bite humans and transmit dengue.
Dengue causes severe joint and muscle pain, headache, high fever and rashes and is fatal in a small proportion of cases, in particular if not diagnosed and treated early. Outbreaks of the illness not only affect families with sudden health care costs and loss of incomes for adults put out of work, but also impact health services, businesses and tourism, straining government budgets due to unplanned spending on large-scale emergency response measures. Currently there is still no vaccine or specific medicine to treat this viral disease.
Around 2.5 billion people worldwide are at risk of contracting dengue, more than 70% of whom live in Asia and the Pacific. The threat of exposure to dengue-carrying mosquitoes is rising with uncontrolled urbanization and a surge in the use of non-biodegradable packaging, which can act as a water reservoir for dengue mosquito breeding. Dengue is spread by a specific mosquito that breeds readily in standing water, such as found in storage containers, flower pots and discarded tires. The guppies are particularly effective in these settings.
Convincing communities to accept fish in their water containers was a key element of the project. The trial showed that guppies do not harm water quality and can survive on microscopic organic material in the absence of mosquito larvae. At the project close in Cambodia, about 88% of the storage containers contained guppies, with the figure at 76% in Lao PDR.
“The project was successful in mobilizing communities with widespread grassroots participation, and high levels of acceptance of fish as an effective way of reducing the spread of dengue,” said Dr. Eva Christophel, a WHO specialist in vectorborne diseases. “This project was an important contribution to WHO’s efforts to develop a toolkit of different community-based methods to prevent and reduce the magnitude of dengue transmission.”
ADB provided financing of $1 million for the project.
– See more at: ResearchSea
Posted September 13th, 2013. Add a comment
Photo by Thomas P. Quinn.
SEATTLE – Sept. 12, 2013 – How and why fish swim in schools has long fascinated biologists looking for clues to understand the complexities of social behavior. A new study by a team of researchers at Fred Hutchinson Cancer Research Center may help provide some insight.
To be published online in the Sept. 12 issue of Current Biology, the study found that two key components of schooling – the tendency to school and how well fish do it – map to different genomic regions in the threespine stickleback, a small fish native to the Northern Hemisphere.
That’s important, said lead author Anna Greenwood, Ph.D., because it suggests that if researchers can identify the genes that influence the fishes’ interest in being social, they may be closer to understanding how genes drive human social behavior.
“The motivation to be social is common among fish and humans,” said Greenwood, a staff scientist in the Human Biology Division at Fred Hutch. “Some of the same brain regions and neurological chemicals that control human social behavior are probably involved in fish social behavior as well.”
‘Some kind of genetic factor’ controlling behavior
Greenwood and several colleagues in the Peichel Labat Fred Hutch have been studying sticklebacks for several years to understand the genesis of natural variation. In a previous study, they found that a group of marine sticklebacks from the Pacific Ocean in Japan schooled strongly, while a second group from a lake in British Columbia preferred hiding out and were less able to maintain the precisely parallel formation required for schooling.
Though both groups were raised in identical lab conditions, they behaved differently from each other when placed together in a schooling situation.
“That really suggests that there’s some kind of genetic factor controlling this difference,” Greenwood said.
This time around, the researchers used lab-raised hybrids of the strongly schooling, saltwater-dwelling marine sticklebacks and the schooling-averse sticklebacks that live in freshwater.
Alison Bell, Ph.D., an associate professor of animal biology at the University of Illinois, Urbana-Champaign, said the linking of behaviors to different genomic regions in the same species – and in particular, social behavior that depends on the behavior of others – makes the study especially compelling.
“I think that’s very significant,” she said. “It’s been hard to find regions of the genome that are associated with any kind of behavioral traits in natural populations. Behavior is very plastic and it’s subject to environmental influences, so it’s been really tricky to do that.”
Hans Hofmann, Ph.D., a professor of integrative biology at the University of Texas at Austin, said the study also refutes the assertion that human behavior is too complex to understand.
“I think it shows that even such complex behaviors associated with other individuals in a very rigid and organized manner can be dissected genetically,” he said. “Studies like this tell us that we might get there eventually.”
Old bicycle wheel and lab motor used in experiment
Fish school primarily for protection from predators, and also to make swimming and foraging more efficient. Schools of fish in the wild are dynamic and fluid, but for both studies the Fred Hutch researchers had to create an environment in which they could observe the fish in unchanging conditions.
Building the device used for both experiments proved a challenge. The researchers suspended an old bicycle wheel above a circular acrylic tank and found a motor from an old lab shaker that could turn the wheel, but were stumped about how to connect them.
Greenwood and co-author Abigail Wark scoured craft shops and hardware stores looking for a suitable part, trying everything from plastic bra straps to necklaces before finding some silicone tubing that worked.
“It was a few weeks of going around to shops,” Greenwood said.
They made a mold to create model fish from resin tinted with grey pigment, dabbing on eyes with black paint to make them look more realistic. The eight models (they found that eight is the minimum number to get fish to school in a lab setting) were suspended from the bike wheel with wire.
Beyond its findings connecting specific behaviors with genomic regions, the study also found that the same regions of the genome appear to control both the stickleback’s ability to school as well as the anatomy of its lateral line, a system of organs that detect movement and vibration in water, and contain the same sensory hair cells found in the human ear.
That suggests a single gene could cause fish to detect their environment differently, Greenwood said, and supports the long-held notion that schooling behavior is controlled in part by the lateral line.
It provides a promising starting point in trying to locate the gene involved, and Fred Hutch researchers are now working on manipulating the gene they think causes changes in the stickleback’s lateral line to see if that alters the fishes’ schooling behavior.
Research on schooling behavior in fish may seem an odd fit for a cancer research center, but Greenwood said natural variation can influence not just behavior, but also susceptibility to illness and disease.
“If we can understand the process by which evolution works and the genes that tend to be affected during evolution in these other model systems, we can apply that to humans,” she said.
Source: Fred Hutchinson Cancer Research Center
Posted September 12th, 2013. Add a comment
Tackling the risks of infection and other illnesses remains a challenge. Might the solution come from the sea?
The life that inhabits the world’s oceans has almost infinite variety. It remains an untapped source of diversity. “The oceans can be deep or shallow, they can be more or less tidal, and they can include unique environments such as volcanic vents,” says Brian McNeil of Strathclyde University in Scotland, UK. “That means that the life that lives there has huge diversity. We have only very limited knowledge of it, and especially of the microbial life forms that are found in the ocean,” he adds.
The SeaBioTech project, started in 2012, is intended to close some of these knowledge gaps by looking in the seas and oceans around the globe for life forms with novel properties. The aim is to find raw material for the world’s biotechnology industry, with a particular emphasis on antibiotics and other medical compounds. “Think about marine sponges,” says McNeil, who is coordinator for the project. “They are vulnerable to predators and to attack by fungi and bacteria, but they don’t seem to suffer much from their attacks. This is partly because they have an internal coating, the biofilm, which contains protective microbial species. We think that these microbes make compounds which deter fungi and bacteria.”
The plan is for the project to sample organisms from a wide range of marine environments, ranging from the cold Atlantic sea off Scotland to the volcanically-active region near the Mediterranean island of Santorini. The sea there is so deep that a remotely-operated submarine will be used to gather samples. “Enzymes and microbes that can survive temperatures of over 70˚C, and high levels of toxicity, could be of interest to biotechnology, perhaps for detoxifying land or water,” McNeil tells youris.com.
He adds that the less romantic phase of the project, the lab work that will follow the sample-gathering, will also be the difficult part. The approach is to search for interesting gene sequences as well as for antibiotic activity. Antibiotics are an especially important target for the project, because of growing bacterial resistance to existing antibiotics. In addition, there could be compounds of interest as additives for cosmetics, or for wound healing. There could also be new vaccines for the fast-growing global fish industry. At the moment, farmed fish are plagued by sea lice and other parasites. The project could lead to fish vaccines that are less polluting than those used today.
Some experts perceive the project as an original initiative and praise its unprecedented scale. “While we have appreciated the importance of marine organisms, genetics and biochemistry since the 1970s,” says Frank Koehn, research fellow for natural products and world-wide medicinal chemistry at the pharmaceutical corporation Pfizer, based in Groton, Connecticut, USA, “we now recognise more clearly that microbes and larger organisms are an untapped source of genetic diversity, and of compounds that can be important to human and animal health.” He adds that there are already anticancer drugs in use that were discovered in the marine environment.
What is more, “many species of marine microorganisms, algae and invertebrates have been shown to produce interesting small molecules,” says Camila Esguerra, lecturer at the laboratory for molecular biodiscovery at the University of Leuven in Belgium. She is involved in a completely separate EU-funded project in marine biodiscovery, calledPharmaSea. She points out that SeaBioTech is designed to discover how these molecules might work as pharmaceuticals. But it could be 10-15 years before the findings of this project turn into usable drugs or treatments.
Perhaps the project’s biggest problem may be the public acceptability of new compounds from the sea, according to Yvonne Armitage, sector lead for biosciences at the UK government’s biosciences knowledge transfer network, based at the Roslin Institute in Scotland. However, chemicals from the marine environment are already used in cosmetics, foods and nutraceuticals, so this issue should be manageable.
Finally, the political issue of intellectual property in the wild environment is another possible problem for a project of this type. Esguerra says that “an uncoordinated and complex mixture of legal domains” has jurisdiction over these resources… This includes theUN Convention on the Law of the Sea, the Convention on Biological Diversity, and a range of intellectual property rights law. In the past, universities and companies collected and used soil and water samples without payment, and without proper contracts to control the use that was made of them.
But Koehn, who is also an unpaid member of the scientific advisory board for the project, contends that more recently, progress has been made in this area. He concludes: “Nations now regard biodiversity as part of their wealth, and there is an understanding that it has to be paid for.”
Photo courtesy of Sean Nash
Posted September 9th, 2013. Add a comment
Photograph by Radim Blazek, Matej Polacik and Martin Reichard.
African annual fish take the adage ‘live fast, die young’ to a whole new level with the discovery that their short lifespan is accompanied by the most rapid sexual maturation of any vertebrate species. The find, reported in the open access journal EvoDevo as part of a series on extreme environments, adds to our knowledge of extremophile lifestyles.
Extreme environments can give rise to extreme adaptations. The tiny annual fish of Africa live in temporary puddles created by seasonal rainfall, and so must grow and reproduce quickly in order to lay their hardy eggs before the waters dry up.
African annual fish can grow up to 23% of their body length in a day, report Martin Reichard and colleagues, who studied wild-caught fish in captivity. One species, Nothobranchius kadleci started reproducing at 17 days old, at a size of just 31 mm, with a related species, N. furzeri maturing only one day later. The fish then produced eggs that developed to the hatching stage in as few as 15 days, making the time from one generation to the next as little as month – the most rapid sexual maturation time and minimum generation time of any known vertebrate species.
When the pools dry up, dormant embryos can survive in the dried mud for months, until the next rains come and the life cycle begins again. In the lab, half of embryos skipped dormancy when incubated on a peat substrate in a Petri dish. In the wild these individuals would populate secondary pools produced within a single rainy season after the primary pool desiccated. The findings suggest that rapid growth and maturation do not compromise subsequent fecundity.
Animals with a long life span can afford to take things slow. The tiny cave-dwelling salamander, olm (Proteus anguinus), which lives for over 100 years, takes 16 years to reach sexual maturity. But when the risk of mortality is high or lifespan shorter, animals reach sexual maturity earlier. The tiny goby, Schindleria, and females of house mouse lab strains (Mus musculus) become sexually mature at just 23 days old.
Earlier studies of a laboratory strain of an African annual fish suggested that it took the fish four weeks to mature, but this may have been an over-estimate. Previous reports of early maturation were based on anecdotal evidence, but this study is based on quantitative data and demonstrates that the rapid growth rate in the lab is still an underestimate compared to that in the wild.
Source: BioMed Central
Posted September 6th, 2013. Add a comment
Small prey fish can grow a bigger ‘eye’ on their rear fins as a way of distracting predators and dramatically boosting their chances of survival, new scientific research has found.
Researchers from Australia’s ARC Centre of Excellence for Coral Reef Studies (CoECRS) have made a world-first discovery that, when constantly threatened with being eaten, small damsel fish not only grow a larger false ‘eye spot’ near their tail – but also reduce the size of their real eyes.
The result is a fish that looks like it is heading in the opposite direction – potentially confusing predatory fish with plans to gobble them up, says Oona Lönnstedt, a graduate student at CoECRS and James Cook University.
For decades scientists have debated whether false eyespots, or dark circular marks on less vulnerable regions of the bodies of prey animals, played an important role in protecting them from predators – or were simply a fortuitous evolutionary accident.
The CoECRS team has found the first clear evidence that fish can change the size of both the misleading spot and their real eye to maximise their chances of survival when under threat.
“It’s an amazing feat of cunning for a tiny fish,” Ms Lonnstedt says. “Young damsel fish are pale yellow in colour and have this distinctive black circular ‘eye’ marking towards their tail, which fades as they mature. We figured it must serve an important purpose when they are young.”
“We found that when young damsel fish were placed in a specially built tank where they could see and smell predatory fish without being attacked, they automatically began to grow a bigger eye spot, and their real eye became relatively smaller, compared with damsels exposed only to herbivorous fish, or isolated ones.
“We believe this is the first study to document predator-induced changes in the size of eyes and eye-spots in prey animals.”
When the researchers investigated what happens in nature on a coral reef with lots of predators, they found that juvenile damsel fish with enlarged eye spots had an amazing five times the survival rate of fish with a normal-sized spot.
“This was dramatic proof that eyespots work – and give young fish a hugely increased chance of not being eaten.
“We think the eyespots not only cause the predator to attack the wrong end of the fish, enabling it to escape by accelerating in the opposite direction, but also reduce the risk of fatal injury to the head,” she explains.
The team also noted that when placed in proximity to a predator the young damsel fish also adopted other protective behaviours and features, including reducing activity levels, taking refuge more often and developing a chunkier body shape less easy for a predator to swallow.
“It all goes to show that even a very young, tiny fish a few millimetres long have evolved quite a range of clever strategies for survival which they can deploy when a threatening situation demands,” Ms Lonnstedt says.
Their paper “Predator-induced changes in the growth of eyes and false eyespots” by Oona M. Lonnstedt, Mark I. McCormick and Douglas P. Chivers appears in the latest issue of the journal Scientific Reports.
Source: Australia’s ARC Centre of Excellence for Coral Reef Studies (CoECRS)
Photograph courtesy of the University of Toronto.
TORONTO, ON – Some males will go to great lengths to pursue a female and take extreme measures to hold on once they find one that interests them, even if that affection is unrequited. New research from evolutionary biologists at the University of Toronto shows that the male guppy grows claws on its genitals to make it more difficult for unreceptive females to get away during mating.
Genitalia differ greatly in animal groups, even among similar species – so much so that even closely related species may have very different genitalia. The reasons for these differences are unclear but sexual conflict between males and females may be a source. Sexual conflict occurs when the fitness interests of males and females differ, which is rooted in differences in egg and sperm sizes. Males invest less than females in reproduction because sperm is cheap to produce, and larger eggs are most costly to make. This difference results in a conflict in which males are interested in mating with as many females possible but females are more selective with their mates.
The researchers examined the role of a pair of claws at the tip of the gonopodium of the male guppy (Poecilia reticulata) – essentially the fish’s penis.
“Our results show that the claws are used to increase sperm transfer to females who are resisting matings,” says Lucia Kwan, PhD candidate in U of T’s Department of Ecology and Evolutionary Biology and lead author of a paper published this week in Biology Letters. “This suggests that it has evolved to benefit males at the expense of females, especially when their mating interests differ.”
The researchers tested two ideas for the function of the claws – one for their role in securing sperm in place at the tip of the gonopodium just before it is inserted into the female, the other for grasping unreceptive or resistant females during mating to aid in sperm transfer. For the latter, Kwan, former graduate student Yun Yun Cheng and faculty members Helen Rodd and Locke Rowe used a phenotypic engineering approach. They surgically removed the pair of claws from one set of males and compared the amount of sperm transferred by them with a group of males who hadn’t been declawed after they had all mated with receptive or unreceptive females.
“Clawed males transferred up to three times more sperm to unreceptive females compared to declawed males,” says Kwan. “The claw has evolved to benefit the males at the expense of females, and implicates sexual conflict between the sexes in the diversification of the genitalia in this family of fish. This provides support that this important selective force is behind an evolutionary pattern that evolutionary biologists have been trying to unravel for over a century.”
How do fish swim? It is a simple question, but there is no simple answer.
Researchers at Northwestern University have revealed some of the mechanical properties that allow fish to perform their complex movements. Their findings, published on June 13 in the journal PLOS Computational Biology, could provide insights in evolutionary biology and lead to an understanding of the neural control of movement and development of bio-inspired underwater vehicles.
“If we could play God and create an undulatory swimmer, how stiff should its body be? At what wave frequency should its body undulate so it moves at its top speed? How does its brain control those movements?” said Neelesh Patankar, professor of mechanical engineering at Northwestern’s McCormick School of Engineering and Applied Science. “Millennia ago, undulatory swimmers like eels that had the right mechanical properties are the ones that would have survived.”
The researchers used computational methods to test assumptions about the preferred evolutionary characteristics. For example, species with low muscle activation frequency and high body stiffness are the most successful; the researchers found the optimal values for each property.
“The stiffness that we predict for good swimming characteristics is, in fact, the same as the experimentally determined stiffness of undulatory swimmers with a backbone,” said Amneet Bhalla, graduate student in mechanical engineering at McCormick and one of the paper’s authors.
“Thus, our results suggest that precursors of a backbone would have given rise to animals with the appropriate body stiffness,” added Patankar. “We hypothesize that this would have been mechanically beneficial to the evolutionary emergence of swimming vertebrates.”
In addition, species must be resilient to small changes in physical characteristics from one generation to the next. The researchers confirmed that the ability to swim, while dependent upon mechanical parameters, is not sensitive to minor generational changes; as long as the body stiffness is above a certain value, the ability to swim quickly is insensitive to the value of the stiffness, the researchers found.
Finally, making a connection to the neural control of movement, the researchers analyzed the curvature of its undulations to determine if it was the result of a single bending torque, or if precise bending torques were necessary at every point along its body. They learned that a simple movement pattern gives rise to the complicated-looking deformation.
“This suggests that the animal does not need precise control of its movements,” Patankar said.
To make these determinations, the researchers applied a common physics concept known as “spring mass damper” — a model, applied to everything from car suspension to Slinkies, that determines movement in systems that are losing energy — to the body of the fish.
This novel approach for the first time unified the concepts of active and passive swimming — swimming in which forcing comes from within the fish (active) or from the surrounding water (passive) — by calculating the conditions necessary for the fish to swim both actively and passively.
The paper, “A Forced Damped Oscillation Framework for Undulatory Swimming Provides New Insights into How Propulsion Arises in Active and Passive Swimming,” was authored by Patankar, Bhalla, and Boyce E. Griffith, assistant professor of medicine and mathematics at New York University.
The work was supported by the National Science Foundation (NSF).
Photograph by D. Ross Robertson and Carole C. Baldwin, CC-BY 3.0.
A new species of tiny blenniiform fish has been discovered in the biodiversity rich waters of the southern Caribbean. Haptoclinus dropi is only around 2 cm in length with a beautiful color pattern that includes iridescence on the fins. The proposed common name of the species is four-fin blenny, due to the division of the dorsal fin into four sections, which is a distinguishing feature of the genus and unique among blenniiform fishes. The study was published in the open access journal Zookeys.
This beautiful new species was discovered as a lucky bycatch during targeted specimen catching at 157-167 m depth off Curaçao as a part of the Smithsonian Institution’s Deep Reef Observation Project (DROP). The new species, Haptoclinus dropi, gets its name from the project’s abbreviation and is one of numerous new ray-finned fish species emerging from this project.
For DROP expeditions the Substation Curaçao‘s manned submersible Curasub was used to catch specimens. While generally used as tourist attraction because it travels at much greater depths than divers can reach, the Curasub is also used for scientific marine research. Targeted fish specimens are collected with the sub’s two flexible, hydraulic arms, but very often small non-targeted fish are also caught in the process.
“Below the depths accessible using scuba gear and above the depths typically targeted by deep-diving submersibles, tropical deep reefs are productive ocean ecosystems that science has largely missed. They are home to diverse assemblages of new and rare species that we are only just beginning to understand,” explains the lead author of the study Dr Carole Baldwin, Smithsonian Institution.
Source: Pensoft Publishers
Original Source: Baldwin CC, Robertson RD (2013) A new Haptoclinus blenny (Teleostei, Labrisomidae) from deep reefs off Curaзao, southern Caribbean, with comments on relationships of the genus.ZooKeys 306: 71–81, doi: 10.3897/zookeys.306.5198