Basking Sharks: Disappearing Act Of World's Second Largest Fish Explained

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ScienceDaily (May 14, 2009) — Researchers have discovered where basking sharks – the world's second largest fish – hide out for half of every year, according to a report published online on May 7th in Current Biology. The discovery revises scientists' understanding of the iconic species and highlights just how little we still know about even the largest of marine animals, the researchers said.

"While commonly sighted in surface waters during summer and autumn months, the disappearance of basking sharks during winter has been a great source of debate ever since an article in 1954 suggested that they hibernate on the ocean floor during this time," said Gregory Skomal of Massachusetts Marine Fisheries. "Some 50 years later, we have helped to solve the mystery while completely re-defining the known distribution of this species."
Using new satellite-based tagging technology and a novel geolocation technique, the researchers found that basking sharks make ocean-scale migrations through tropical waters of the Atlantic Ocean during the winter, traveling at depths of 200 to 1,000 meters. Their data show that the sharks sometimes stay at those depths for weeks or even months at a time. "In doing so, they have completely avoided detection by humans for millennia," Skomal said, emphasizing that as one of the very largest of marine animals, the sharks grow to over 10 meters and weigh as much as seven metric tons.
Skomal said they were "absolutely surprised" when they first received a signal from the tagged sharks coming from the tropical waters of the western Atlantic, in the vicinity of the Caribbean and Bahamas. After all, basking sharks were always believed to be cool-water sharks, restricted to temperate regions.
Several factors had made basking sharks a challenge to study. On top of the fact that they disappear for long periods of time, they also feed exclusively on plankton. That means they can't readily be captured with traditional rod-and-reel methods. And even when the sharks are found closer to the ocean surface, they spend their time in the cool-temperature, plankton-rich waters that limit underwater visibility and make diving difficult.
The findings could have important implications for the conservation of basking sharks, which have shown some signs of dramatic decline in the last half century and are listed as threatened by the International Union for Conservation of Nature.
"Coupled with recent genetic data, our finding indicates that the Atlantic population – and perhaps the world population – are connected and may constitute a single population," Skomal said. "Hence, the global population of basking sharks may be even smaller than previously thought." Efforts to boost basking sharks' numbers will therefore need to be coordinated at a global scale.
The authors include Gregory B. Skomal, Massachusetts Division of Marine Fisheries, Oak Bluffs, MA; Stephen I. Zeeman, University of New England, Biddeford, ME; John H. Chisholm, Massachusetts Division of Marine Fisheries, New Bedford, MA; Erin L. Summers, Maine Department of Marine Resources, Boothbay Harbor, ME; Harvey J. Walsh, Woods Hole Oceanographic Institution, Woods Hole, MA; Kelton W. McMahon, Woods Hole Oceanographic Institution, Woods Hole, MA; and Simon R. Thorrold, Woods Hole Oceanographic Institution, Woods Hole, MA.
Journal reference:
Gregory B. Skomal, Stephen I. Zeeman, John H. Chisholm, Erin L. Summers, Harvey J. Walsh, Kelton W. McMahon, and Simon R. Thorrold. Transequatorial Migrations by Basking Sharks in the Western Atlantic Ocean. Current Biology, 2009; DOI: 10.1016/j.cub.2009.04.019
Adapted from materials provided by Cell Press, via EurekAlert!, a service of AAAS.

Communal Stomach Of An Ant Colony

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ScienceDaily (May 11, 2009) — How do ant colonies manage the nutrients in their food? Audrey Dussutour from the Centre de recherche sur la cognition animale (CNRS/Université Paul Sabatier) and Steve Simpson from Sydney University have shown that an ant colony functions like a “collective mouth and gut”. The members of a colony are capable of dealing with the nutritional needs of their social structure by sharing tasks (foraging, digestion and excretion).

In an ants' nest, food is brought home by only 10% of the colony members - the foragers. This food is then regurgitated and shared among all the ants in the colony. Nutritional needs differ, however, between the young (larvae) and adults of the colony.
Audrey Dussutour and Steve Simpson have recently shown that the larvae, which cannot move or leave the nest, are capable of communicating their nutritional needs to forager ants, who adapt their gathering strategy accordingly. These researchers provided sugar- or protein-rich foods for ant colonies with and without larvae, and observed that ant behaviour differed. When a colony had larvae, high protein foods were preferentially gathered that could sustain larval growth. Inversely, when there were no larvae, the ants preferentially gathered sugar-rich foods.
In a second experiment, the researchers showed that sugar is the key nutrient regulating gathering in ants. Provided with a range of food containing varying proportions of protein and sugar, foragers are capable of harvesting the same quantity of sugar. These researchers also observed that when the food was rich in protein and poor in sugar, the excess of proteins was ejected from the nest. Ants are therefore capable of extracting sugar from food and regurgitating protein in the form of waste pellets.
However, despite this food manipulation, the colonies reared with protein-rich food had extremely high mortality due to protein toxicity and suffered losses of up to 75%. In comparison, the ant colonies reared on food of lower protein content lost less than 5% of their numbers.
The scientists noticed that the mortality was lower in colonies with larvae. They demonstrated that the ants in these colonies managed to partially escape the toxic effects of proteins by giving the work of nutrient processing to the larvae, which are better equipped for protein digestion. The researchers also confirmed the highly toxic effect of protein-rich food on ants, as they had previously demonstrated in fruit flies.
Journal reference:
Dussutour et al. Communal Nutrition in Ants. Current Biology, May 12, 2009; DOI: 10.1016/j.cub.2009.03.015
Adapted from materials provided by CNRS.

Flight Of The Bumble Bee Is Based More On Brute Force Than Aerodynamic Efficiency

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ScienceDaily (May 10, 2009) — Brute force rather than aerodynamic efficiency is the key to bumblebee flight, Oxford University scientists have discovered.

In recent years scientists have modelled how insect wings interact with the air around them to generate lift by using computational models that are relatively simple, often simplifying the motion or shape of the wings.
"We decided to go back to the insect itself and use smoke, a wind tunnel and high-speed cameras to observe in detail how real bumblebee wings work in free flight," said Dr Richard Bomphrey of the Department of Zoology, co-author of a report of the research published this month in Experiments in Fluids. ‘We found that bumblebee flight is surprisingly inefficient – aerodynamically-speaking it’s as if the insect is ‘split in half’ as not only do its left and right wings flap independently but the airflow around them never joins up to help it slip through the air more easily.’
Such an extreme aerodynamic separation between left and right sets the bumblebee [Bombus terrestris] apart from most other flying animals.
"Our observations show that, instead of the aerodynamic finesse found in most other insects, bumblebees have a adopted a brute force approach powered by a huge thorax and fuelled by energy-rich nectar," said Dr Bomphrey. "This approach may be due to its particularly wide body shape, or it could have evolved to make bumblebees more manoeuvrable in the air at the cost of a less efficient flying style."
Professor Adrian Thomas of Oxford’s Department of Zoology, co-author of the report, said: "a bumblebee is a tanker-truck, its job is to transport nectar and pollen back to the hive. Efficiency is unlikely to be important for that way of life."
Observing insects in free – as opposed to tethered – flight is a considerable challenge. The Oxford team trained bumblebees to commute from their hive to harvest pollen from cut flowers at one end of a wind tunnel. They then used the wind tunnel to blow streams of smoke passed the flying bees, to reveal vortices in the air, and recorded the results with high-speed cameras taking up to 2000 images per second. From these images the team were able to visualise the airflow over flapping bumblebee wings.
The old myth that "bumblebees shouldn’t be able to fly" was based on calculations using the aerodynamic theory of 1918-19, just 15 years after the Wright brothers made the first powered flight. These early theories suggested that bumblebee wings were too small to create sufficient lift but since then scientists have made huge advances in understanding aerodynamics and how different kinds of airflow can generate lift.
Journal reference:
Richard James Bomphrey, Graham K. Taylor and Adrian L. R. Thomas. Smoke visualization of free-flying bumblebees indicates independent leading-edge vortices on each wing pair. Experiments in Fluids, 2009; 46 (5): 811 DOI: 10.1007/s00348-009-0631-8
Adapted from materials provided by University of Oxford.

Baboons Benefit From Strong Social Networks, Expert Says

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ScienceDaily (May 9, 2009) — Monkey communication expert Robert Seyfarth began his lecture on May 5, the kick-off of the University of Delaware's Year of Darwin celebration, with a true story, documented in 1961, about a female baboon that herded goats in an African village.

The baboon knew all of the relationships between the goats so well that at night she would carry a bleating kid from one barn directly to its mother in another barn.
“For all the centuries we've bred dogs, no dog has exhibited this knowledge of kids and mothers,” said Seyfarth, who is a psychology professor at the University of Pennsylvania. “The question is where does this mind come from?”
Seyfarth transported an audience of about 200 people into the fascinating world of the baboons of Botswana's Okavanga Delta, which he and Dorothy Cheney, his research partner, fellow Penn professor, and spouse, studied from 1992 to 2008.
Based on their research, Seyfarth said, he and Cheney argue that the baboon's ability to recognize social relationships is due to natural selection. This is the process in nature, according to Darwin's theory of evolution, in which only the organisms best adapted to their environment tend to survive and reproduce.
The baboons that Seyfarth and Cheney studied live in groups of 80-90 individuals. Males leave the group in which they are born, while females stay in the group for their entire lives, with close bonds to female relatives.
The females are arranged in a matrilineal hierarchy of families, with ranks maintained for years. Although once in a while a coup is attempted, such moves are not often successful.
“Families stick together,” Seyfarth said. “The rules are, like in a Jane Austen novel, be nice to your relatives and get in with the high-ranking relatives.”
In their experiments, Seyfarth and Cheney observed baboons with names such as Sylvia, Champagne, and Helen, and recorded their language, which consists of no more than 18 sounds, and the interactions of their families.
They found that baboons use certain calls only in certain contexts. Screams and fear barks are only given from a lower-ranking to a higher-ranking baboon, while threat grunts are given only from a higher-ranking to a lower-ranking baboon.
By recording the various calls and then playing them in situations that “break the rules,” the scientists determined from the animals' behavior that baboons are able to put together the discrete elements of identity, kinship, and rank.
“The animals somehow see this world in all of its complexity,” Seyfarth said.
“It's an innate property of the baboon mind -- done instantly and unconsciously,” he noted.
What social factors stress baboons? Seyfarth and Cheney were able to measure the animals' stress levels by analyzing fecal samples for gluccocorticoid stress hormones.
They found that pregnancy and incidences of predation are major stressors. Ninety-five percent of baboon deaths are caused by predators, mostly lions, Seyfarth said.
Also, some high-ranking males practice infanticide, targeting infants by rank. Mothers may form relationships with lower-ranking males who will help look after their babies.
And just as in humans, the loss of a close relative is high on the list, Seyfarth said.
“Females respond to stress by associating with their closest grooming relationships,” Seyfarth said. “They turn to their support network if they lose someone. They broaden and extend to replace old relationships with new ones. Female baboons with strong social bonds survive better,” he said.
This work is highlighted in the award-winning book Baboon Metaphysics: The Evolution of a Social Mind, published by the University of Chicago Press in 2007.
Additional support for the series is being provided by the Provost's Office, the College of Agriculture and Natural Resources, the Science Ethics and Public Policy Program, and the following departments: Biological Sciences, English, Geography, Geological Sciences, Linguistics and Cognitive Science, and Philosophy.
Adapted from materials provided by University of Delaware.

Ultrasonic Communication Among Frogs

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ScienceDaily (May 9, 2009) — UCLA scientists report on the only known frog species that can communicate using purely ultrasonic calls, whose frequencies are too high to be heard by humans. Known as Huia cavitympanum, the frog lives only on the Southeast Asian island of Borneo.

Ultrasounds are high-pitched sounds more than 20 kilohertz (kHz) in frequency, which exceeds the upper limit of sounds detectable by humans and is far higher than the 5 to 8 kHz frequencies most amphibians, reptiles and birds are capable of hearing or producing. Key parts of the ear must be specially adapted to detect ultrasounds.
The frogs can hear sounds up to 38 kilohertz, the highest frequency any amphibian species has been known to hear, the scientists report. Humans can hear up to about 20 kHz and typically talk at 2 or 3 kHz.
While most of the more than 5,000 frog species worldwide have eardrums that are flat on the side of the head, Huia cavitympanum has eardrums recessed in the side of the skull, similar to mammals.
Peter Narins, UCLA distinguished professor of physiological science and of ecology and evolutionary biology, and Victoria Arch, a UCLA graduate student in ecology and evolutionary biology, spent several nights in the remote area where the frogs live.
"We had very little information suggesting that they would be in this location," said Arch, lead author of the study. "We found them our first night out."
Huia cavitympanum produces some audible calls and others that are entirely ultrasonic.
"You look at the frog and can see it is vocalizing — you can tell because their vocal pouches pulsate — but you don't hear any sound. It's amazing," Arch said. "Then you look down at the recording equipment and see the lights flashing, indicating sound. I have never seen that before. In a frog, it's unprecedented to have purely ultrasonic vocalizations."
Narins and Arch have an idea about why the frogs, which live along a noisy stream, use both ultrasonic communication and calls that are audible to humans.
"Our hypothesis is that these frogs have shifted to use higher frequencies in their communication to avoid the interference of sound produced by rushing water in the lower-frequency range," Arch said. "However, high-frequency sounds do not transmit as far. By producing some lower-frequency calls, they can transmit calls over a greater distance, so they can communicate with frogs that are farther away. But by also producing some calls that are high-frequency — all ultrasonic — they may be able to communicate better over that background noise.
"Producing both types of calls might be a bet-hedging strategy to be heard," Arch said. "This is how males attract females, communicate with one another and establish territorial boundaries."
The research may have implications for improving human hearing aids and addressing hearing loss. Most hearing aids, Narins said, simply amplify sound, including unnecessary background noise. Better hearing aids that are directional, for example, could result from the research.
In 1998, Kraig Adler, a professor of neurobiology and behavior who had been Narins' professor at Cornell University, told Narins he should go to China to see "a frog with an ear canal like a human," Narins recalled.
Narins took the advice. Along with colleagues, including Albert Feng from the University of Illinois, Urbana-Champaign, he discovered a frog species that lives in rushing streams and waterfalls in east-central China called Odorrana tormota (formerly known as Amolops tormotus). Odorrana tormota, Narins found, could detect and produce ultrasounds due to the highly unusual presence of an ear canal. That research was published March 16, 2006, in the journal Nature.
The frogs in China produce very loud calls that are, at the same time, both audible and ultrasonic. In Borneo, however, Huia cavitympanum produces some sounds that are purely ultrasonic.
"That was unique — and the first time that has been found in any frog species," said Narins, who has studied dozens of frog species. "We are reporting this for the first time."
"With the Chinese frog species, every time you see the vocal sac pulsate, you will hear a sound," Arch said. "With the Bornean frog, sometimes you will see it is calling and you don't hear anything; it's all outside of our hearing range."
The frogs in China and Borneo's Huia cavitympanum are the only two frog species known to have recessed ear drums, Narins said.
In China, the scientists had set up a loudspeaker in the frogs' natural habitat near a river, then played frog calls and recorded the frogs' vocal responses with a microphone and very high-frequency equipment.
Later, they learned of this second species in Borneo with similar ear morphology. Narins and Arch went to Borneo in 2007, and Arch went back last summer.
In Borneo, they lived in a camp with a roof and three walls, with one side open. They slept on a wood floor, protected by mosquito nets. Narins was bitten by leeches and woke up several mornings soaked in blood. They ate noodles and peanut butter.
"It was a huge adventure, and so exciting to study the animals in their habitat," Arch said. "You feel like you're eavesdropping on them."
"There are not many places on the planet left that are so pristine and untouched by humans," Narins said. "It's exciting to go there and wonderful to have a sense of discovering something brand-new. We were there a week and saw only two other people."
Arch and Narins studied male frogs. In the majority of frog species, the females do not vocalize, and when they do, they do so less frequently than males, Arch said.
The research was funded by the National Geographic Society's Committee for Research and Exploration, the Paul S. Veneklasen Research Foundation, the National Institute on Deafness and Other Communication Disorders (NIDCD) of the National Institutes of Health, and the National Science Foundation (through a doctoral dissertation improvement grant to Arch).
Co-authors are T. Ulmar Grafe, a faculty member in the biology department at Borneo's University Brunei Darussalam, and Marcos Gridi-Papp, a UCLA postdoctoral scholar in Narins' laboratory.
Journal reference:
Arch et al. Pure Ultrasonic Communication in an Endemic Bornean Frog. PLoS ONE, 2009; 4 (4): e5413 DOI: 10.1371/journal.pone.0005413
Adapted from materials provided by University of California, Los Angeles.

'Gecko Vision': Key To Future Multifocal Contact Lens?

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ScienceDaily (May 8, 2009) — Nocturnal geckos are among the very few living creatures able to see colors at night, and scientists' discovery of series of distinct concentric zones may lead to insight into better cameras and contact lenses.

The key to the exceptional night vision of the nocturnal helmet gecko is a series of distinct concentric zones of different refractive powers, according to a new study.
This multifocal optical system is comprised of large cones, which the researchers calculated to be more than 350 times more sensitive than human cone vision at the human color vision threshold.
"We were interested in the geckos because they – and other lizards – differ from most other vertebrates in having only cones in their retina," said project leader Lina Roth, PhD, from the Department of Cell and Organism Biology at Lund University in Sweden. "With the knowledge from the gecko eyes we might be able to develop more effective cameras and maybe even useful multifocal contact lenses."
The nocturnal geckos' multifocal optical system gives them an advantage because light of different ranges of wavelengths can focus simultaneously on the retina. Another possible advantage of their optical structure is that their eyes allow them to focus on objects at different distances. Therefore the multifocal eye would generate a sharp image for at least two different depths. Geckos that are active during the day do not possess the distinct concentric zones and are considered monofocal, Roth said.
The scientists also developed a new method to gather optical data from live animals without harm with their modifications to the Hartmann-Shack wavefront sensor.
"Studies of animals with relatively large eyes, such as owls and cats, have included surgery and fixation of the head," the article states. "In this study, we demonstrate that it is possible to obtain high-resolution wavefront measurements of small, unharmed gecko eyes without completely controlling the gaze or the accommodation of the animal eyes."
Journal reference:
Lina S. V. Roth et al. The pupils and optical systems of gecko eyes. Journal of Vision, Volume 9, Number 3, Article 27, Pages 1-11 DOI: 10.1167/9.3.27
Adapted from materials provided by Association for Research in Vision and Ophthalmology, via EurekAlert!, a service of AAAS.

Ants In Southern Hemisphere Richer And More Diversified Than Northern Hemisphere Ants

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ScienceDaily (May 6, 2009) — There are fewer species of ants in the northern hemisphere than in the southern hemisphere. This is the conclusion drawn by an international team of scientists that have studied 1,003 local ant assemblages on five different continents. According to the study, ant communities in the northern hemisphere may have suffered more extinctions as a result of the climate changes that occurred between 53 and 54 million years ago.

An international team of more than 26 researchers - including scientists from the Autonomous University of Barcelona (AUB) and the Doñana Biological Station - has studied the global patterns that govern the biological diversity of ant communities. They conclude that latitudinal asymmetry is due to climatic and historical differences between hemispheres, which have led to there being a larger number of species of ants in the southern hemisphere than in the northern hemisphere.
"There is a latitudinal gradient in local ant species richness. However, there is latitudinal asymmetry around the equator and, therefore, sites in the southern hemisphere are more diverse than sites in the northern hemisphere", co-author of the study and a researcher at the Ecology Unit and Centre of Ecological Research and Forestry Applications (CREAF) at the AUB, Xavier Arnan explained to SINC.
The study, which was published recently in Ecology Letters, examines species richness in 1,003 local ant assemblages on five different continents. Researchers attribute the differences between hemispheres to climate-related and historical variables such as regional history, disturbance history and the history of climate change itself.
Results suggest that contemporary climatic conditions explain this difference, along with the Eocene climate changes (between 53 and 54 million years ago). "It appears that a greater change in climate since the Eocene (when temperatures were 10ºC warmer than today) in the northern hemisphere than in the southern hemisphere led to a larger number of extinctions in the north with the subsequent effect on ant species richness on a local scale", Arnan indicated.
Australia has more ants than the entire northern hemisphere
Ant species richness ranges from 0 to 184 different species, variations being caused by temperature and rainfall, the levels of which are higher in the southern hemisphere for one same latitude. Almost half (49%) of the variation in the number of species between the different locations studied is due to climate differences.
In 1845, English naturalist Charles Darwin explained that the greater diversity of life forms in the southern hemisphere was related to a more equable climate, a theory this international study supports.
There is such a large difference between the two hemispheres that Australia alone has greater ant species richness than the entire northern hemisphere. Unlike birds, amphibians or plants, ant species richness is greater in dry habitats, particularly in the warmest regions of the planet. "In warm and dry environments, ants are diverse", the ecologists clarify.
The researchers, from eight different countries, contributed to the study with regional data and their own field work. This information was used to create the Global Ant Community Database, "a database that contains information on the diversity and abundance of ant communities in more than 3,000 sites around the world", Arnan informed SINC Arnan.
This is the second study using this database that has been published and one of the first large-scale studies of local communities, in this case between hemispheres, which jointly considers the impact of both historical and contemporary factors on hemispheric diversity asymmetries," the scientist concludes.
Journal reference:
Dunn et al. Climatic drivers of hemispheric asymmetry in global patterns of ant species richness. Ecology Letters, 2009; 12 (4): 324 DOI: 10.1111/j.1461-0248.2009.01291.x
Adapted from materials provided by Plataforma SINC, via AlphaGalileo.

Two Brown Bear Populations In Spain In Danger of Extinction Have Been Isolated For Past 50 Years

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ScienceDaily (May 6, 2009) — The situation of bears in the Iberian Peninsula is critical. Researchers from the University of Oviedo (UO) and the Superior Council of Scientific Research (SCSR) have performed a genetic identification based on the analysis of stools and hair of brown bears (Ursus arctos) from the Cantabrian mountain range, gathered between 2004 and 2006.

The non-invasive analysis of 146 samples has allowed for the identification of 39 bears in the western sub-population, and 9 in the eastern one, so as to show the genetic structure of the population. In order to obtain the individual genotypes of the bears, scientists have employed 18 micro-satellite markers in a joint fashion, and a sex marker with high-class genetic technology.
"The level of genetic diversity was 45% in the western sub-population, and 25% in the eastern population¨, explain Trinidad Pérez and Ana Domínguez Sanjurjo to SINC, authors of the study and researchers at the Department of Functional Biology (Genetics) at the UO.
According to Pérez, these levels of gene variation (which allow for adaptation, survival and evolution of the species) are ¨among the lowest of those described in scientific literature for this species¨.
The study, which appears in the latest edition of the magazine Conservation Genetics, points out that the difference between the two Cantabrian sub-populations is ¨extreme¨, around 41%. This value is comparable, for example, to that of the chamois (Rupicapra), which are considered a different species.
For Domínguez Sanjurjo, this phenomenon ¨can only be explained by an absolute isolation between both sub-populations, joined with an extremely reduced size in the eastern¨. From this differentiation data between sub-populations, ¨it can be inferred that there has been no genetic flow between them for at least 50 years¨, affirm the scientists.
In this fashion, we know that in the eastern population, the endogamy rate (reproduction of individuals from the same lineage) per generation is approximately 10%, ¨a value with amply exceeds the maximum tolerable rate given for domestic animals, which is 1%¨, asserts Pérez to SINC.
The sub-population has a number of around 20 individuals, a number which ¨is very far from the size considered as a viable minimum, which means its short-term conservation is seriously compromised¨, adds the biologist.
On the other hand, the western sub-population presents moderated levels of diversity, ¨probably due to an important reduction in the number of bears which would have begun 300 years ago¨, highlights Pérez. Although at the end of the 90s, the estimated size of this sub-population was between 50 and 60 members, ¨this number should be situated around 200 individuals for the bear population to be viable short-term¨, declare the scientists.
Connecting populations, a solution
In spite of the fact that the eastern population has less individuals, the western one possesses ¨a great risk of extinction in the near future¨, points out Domínguez. To this end, the researchers explain that ¨the connectivity between the two sub-populations is priority if we want to maintain the eastern nucleus, which would be at risk of immediate extinction¨.
The genetic analysis has allowed for the identification of a macho individual in Palencia belonging to the western sub-population. ¨In theory, if one migrant from one sub-population managed to reproduce with another every 10 years, it would reduce the differentiation between the two bear populations by 20%¨, confirm Pérez and Domínguez. The genetic difference would diminish by 11% if they were two bears. ¨This migration would increase diversity in the eastern sub-population, considerably increasing their possibilities of survival¨, points out Pérez.
In order for the brown bears to be out of danger long-term, ¨it would be necessary to control the population as a whole, estimate size and tendency, procure connectivity between the two sub-populations and avoid losses of habitat¨, conclude the researchers.
Journal reference:
Pérez et al. Non-invasive genetic study of the endangered Cantabrian brown bear (Ursus arctos). Conservation Genetics, 2009; 10 (2): 291 DOI: 10.1007/s10592-008-9578-1
Adapted from materials provided by Plataforma SINC.

How Social Insects Recognize Dead Nestmates

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ScienceDaily (May 6, 2009) — When an ant dies in an ant nest or near one, its body is quickly picked up by living ants and removed from the colony, thus limiting the risk of colony infection by pathogens from the corpse.

The predominant understanding among entomologists – scientists who study insects – was that dead ants release chemicals created by decomposition (such as fatty acids) that signal their death to the colony's living ants.
But now UC Riverside entomologists working on Argentine ants provide evidence for a different mechanism for how necrophoresis – the removal of dead nestmates from colonies – works.
In a research paper recently published online in the early edition of the Proceedings of the National Academy of Sciences, the researchers report that all ants, both living and dead, have the "death chemicals" continually, but live ants have them along with other chemicals associated with life – the "life chemicals." When an ant dies, its life chemicals dissipate or are degraded, and only the death chemicals remain.
"It's because the dead ant no longer smells like a living ant that it gets carried to the graveyard, not because its body releases new, unique chemicals after death," said Dong-Hwan Choe, the lead author of the research paper and a graduate student working towards his doctoral degree with Michael Rust, a professor of entomology at UCR.
Choe explained that the research paper's results resolve a conundrum of long-standing in animal behavior and correct a misinterpretation of previous results that has become both popular and widespread in literature.
"There is no mistaking that it is the dissipation of chemical signals associated with life rather than the increase of a decomposition product 'death cue' that triggers necrophoric behavior by Argentine ants," he said.
Along with Rust and UCR's Jocelyn Millar, a professor of entomology, Choe used analytical chemistry techniques to identify the "signals of life" in the Argentine ant: the chemicals dolichodial and iridomyrmecin.
"These chemicals, or compounds similar to them, are found in numerous ant species that display necrophoresis," Choe said. "Therefore, these ant species also are likely to have necrophoric behavior triggered by the decrease or absence of chemical signs of life, rather than by cues associated with death. We plan to research this next."
He added that dolichodal, iridomyrmecin, or similar compounds are found also in other insects, such as thrips, stick insects, aphids and rove beetles.
"Understanding the exact mechanism of ant necrophoresis will help researchers develop a more environmentally friendly pest management strategy by which we can achieve results with smaller amounts of insecticide," Choe said. "A recent study on Argentine ants that we did in the lab indicated that nestmates can efficiently distribute slow-acting and non-repellent insecticides among themselves via necrophoresis. When an ant exposed to an insecticide dies in the nest, other ants carry its body around, with the insecticide transferring easily from the corpse to healthy ants."
Choe's coauthors on the research paper are Millar and Rust. The Carl Strom/Western Exterminator Scholarship, a Pi Chi Omega Scholarship and a Bayer Young Scientist of the Year 2008 Scholarship to Choe funded the three-year study.
Choe, who expects to graduate this summer, received his bachelor of science degree in agriculture from Korea University, Seoul (2002), and his master's degree in entomology from UCR (2005).
Journal reference:
Dong-Hwan Choe, Jocelyn G. Millar, and Michael K. Rust. Chemical signals associated with life inhibit necrophoresis in Argentine ants. Proceedings of the National Academy of Sciences, 2009; DOI: 10.1073/pnas.0901270106
Adapted from materials provided by University of California - Riverside.

'Sobering' Decline Of Caribbean's Big Fish, Fisheries: Overfishing Deemed Most Likely Cause

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ScienceDaily (May 6, 2009) — Sharks, barracuda and other large predatory fishes disappear on Caribbean coral reefs as human populations rise, endangering the region's marine food web and ultimately its reefs and fisheries, according to a sweeping study by researcher Chris Stallings of The Florida State University Coastal and Marine Laboratory.

While other scientists working in the Caribbean have observed the declines of large predators for decades, the comprehensive work by Stallings documents the ominous patterns in far more detail at a much greater geographic scale than any other research to date.
"Seeing evidence of this ecological and economic travesty played out across the entire Caribbean is truly sobering," said Associate Professor John Bruno of the University of North Carolina at Chapel Hill, who served as the PLoS One academic editor for Stallings' new paper.
"I examined 20 species of predators, including sharks, groupers, snappers, jacks, trumpetfish and barracuda, from 22 Caribbean nations," said Stallings, a postdoctoral associate at the FSU Coastal and Marine Laboratory. "I found that nations with more people have reefs with far fewer large fish because as the number of people increases, so does demand for seafood. Fishermen typically go after the biggest fish first, but shift to smaller species once the bigger ones become depleted. In some areas with large human populations, my study revealed that only a few small predatory fish remain."
Stallings said that although several factors -- including loss of coral reef habitats -- contributed to the general patterns, careful examination of the data suggests overfishing as the most likely reason for the disappearance of large predatory fishes across the region. He pointed to the Nassau grouper as a prime example. Once abundant throughout the Caribbean, Nassau grouper have virtually disappeared from many Caribbean nearshore areas and are endangered throughout their range.
"Large predatory fish such as groupers and sharks are vitally important in marine food webs," Stallings said. "However, predicting the consequence of their loss is difficult because of the complexity of predator-prey interactions. You can't replace a 10-foot shark with a one-foot grouper and expect there to be no effect on reef communities. Shifts in abundance to smaller predators could therefore have surprising and unanticipated effects. One such effect may be the ability of non-native species to invade Caribbean reefs."
A case in point, said Stallings, is the ongoing invasion by Pacific lionfish, which were introduced by aquarium releases.
"Lionfish are minor players on their native Pacific reefs, yet they are undergoing a population explosion and overeating small fishes in the greater Caribbean region," said Professor Mark Hixon of Oregon State University, Stallings' doctoral advisor at OSU. "Preliminary evidence suggests that lionfish are less invasive where large predatory native fishes are abundant, such as in marine reserves," Hixon said.
The study also demonstrates the power of volunteer and community research efforts by non-scientists. Stallings used data from the Reef Environmental Education Foundation's (REEF) online database, which contains fish sightings documented by trained volunteer SCUBA divers, including more than 38,000 surveys spanning a 15-year period.
"Chris was completely undaunted by the lack of fisheries data and essentially adopted the 'Audubon Christmas Bird Count' approach in a marine system to find strong evidence for a native fisheries effect," said Felicia Coleman, director of the FSU Coastal and Marine Laboratory and Stallings' postdoctoral advisor.
Given that about half the world's populations live near coastlines and that the world population is growing, demands for ocean-derived protein will continue to increase, Stallings warned. He said meeting such demands while retaining healthy coral reefs may require multiple strategies, including implementation of marine reserves, finding alternative sources of protein, and increased efforts to implement family-planning strategies in densely populated areas.
Journal reference:
Stallings et al. Fishery-Independent Data Reveal Negative Effect of Human Population Density on Caribbean Predatory Fish Communities. PLoS ONE, 2009; 4 (5): e5333 DOI: 10.1371/journal.pone.0005333
Adapted from materials provided by Florida State University, via EurekAlert!, a service of AAAS.