JCM NATURAL HISTORY LOG

Two Dartmouth biologists have found that brown anole lizards make an interesting choice when deciding which males should father their offspring. The females of this species mate with several males, then produce more sons with sperm from large fathers, and more daughters with sperm from smaller fathers. The researchers believe that the lizards do this to ensure that the genes from large fathers are passed on to sons, who stand to benefit from inheriting the genes for large size.

The male of this species can be two to three times the mass of the female, but the females seem to be in control of the genetic destiny. (Credit: Photo by Joseph Mehling '69)

The study is published in the March 4 issue of Science Express, the advance online publication of the journal Science.

“This species has figured out a clever way to pass on genes with gender-specific effects on fitness,” said Bob Cox, the lead author on the paper and a post-doctoral researcher at Dartmouth. “Usually, when natural selection pulls genes in different directions for each gender, the species faces an evolutionary dilemma. But these lizards have solved this puzzle, they’ve figured out how to get the right genes into the right gender.”

By manipulating opportunities for females to mate with males of different sizes, the researchers determined that females prefer larger males. But, when the choice of partners was limited to small males, females minimized the production of sons.

The researchers explain that the genes that make males more fit are often different from the genes that benefit females, which presents a conundrum because males and females share most of their DNA. The valuable traits for one gender are not always the same for the other. “In an evolutionary sense, what’s good for the goose is not always good for the gander,” said Cox.

In these lizards, however, mothers can enhance the fitness of their offspring by manipulating their gender depending on the size of the father. To demonstrate this, Cox and Calsbeek measured the survival rates of sons and daughters over eight months when released to their natural habitat in The Bahamas.

“As we predicted, the survival of the male offspring increased if they had large fathers,” said Calsbeek. “But, we found that the survival of the daughters was not influenced by the size of the father. This suggests that the genetic benefits of large size are specific to sons.”

How do females control the gender of their progeny? “That’s the big question at this point,” said Cox. The researchers will continue their studies to learn more about the mechanisms involved in this most fundamental of all evolutionary processes, the struggle to pass on advantageous genetic material.

On Thursday 4th March 2010, Karachi, Dr Sheh Shah, President of the Pakistan Medical Association, Dr Habib-ur-Rehman Soomro, Secretary General PMA and Dr Huma Qureshi, Executive Director Pakistan Medical Research Council launched the world’s first comprehensive snakebite protocol called ‘A2 Snakebite Management in Asia and Africa’ for use by doctors to treat snakebite in the key areas of Africa and Asia.

Snakebite has been described as a ‘neglected disease’ and yet little practical work has been done by experts to attempt to reduce the suffering caused by snakebite. The need for better guidelines has been frequently discussed but action has been conspicuously lacking. Pakistan published a National Snakebite Protocol in 2008, based on a comprehensive analysis of the conditions and infrastructure present in front line hospitals that deal with snakebite.

Above: The Malyan Pitviper (Calloselasma rhodostoma) is responsible for may envenomations in Southeast Asia. Photo: John C. Murphy.

Dr Qureshi said, “Following the success of the local protocol we decided to set ourselves the challenge of assisting with comprehensive guidelines for our African and Asian neighbours in a bid to contribute a major reduction in mortality. The use of western medical textbooks has led to sub optimal anti snake venom (ASV) dosages, ASV being given to patients who are not envenomed and too much ASV being given due to the lack of clear clinical endpoints for ASV therapy and many other problems in treatment”.

Over 95% of the world’s mortality from snakebite originates in Africa and Asia and Pakistan is ideally situated in geographical terms and in terms of it’s position in the top five countries for mortality, to provide guidance on the most effective way to approach snakebite.

The guidelines contain excellent photographs of the major medically significant snakes in Africa and Asia and recommendations for the use and dosage of anti snake venom. In addition, it includes chapters on first aid, prevention and some of the key support areas such as dealing with neurotoxic species and adverse reactions to anti venom.  There is also a unique chapter on the practical aspects of managing airway in snakebite, which has great applicability across other medical conditions.

Dr Shah stated, “The PMA has a long and distinguished history of supporting and endorsing practical solutions to medical conditions that affect the rural poor. Developed world snakebite experts do not understand the priority of snakebite in developing countries or the nature of local conditions. Many recommendations such as the routine use of mechanical ventilators are just not possible in developing country set-ups”.

There are useful guidelines on how to equip a basic medical facility to treat snakebite and methods to treat and effectively refer patients from a basic facility to a better-equipped hospital, which is crucial if significant reductions in mortality are to be secured.

Ian Simpson, the author stated, “The guidelines are specifically targeted at rural doctors in Africa and Asia who are based at basic health facilities and contain chapters of specific interest to health officials and administrators. It is vital that health officials ensure the right drugs and simple equipment are available in the correct quantities and that they can determine if their doctors are treating snakebite using the most effective methods”.

In order for doctors to be able to freely download the guidelines locally, the guidelines are available online at:

http://www.pmrc.org.pk/index_2.htm

This enables doctors to print out those sections specific to their area.

Dr Qureshi said, “These guidelines will also help to more efficiently use currently produced anti snake venom and enable useful epidemiology data to be gathered with consistent and rational processes. Recent snakebite mortality assessments for Pakistan have been heavily overstated and effective protocols such as this will enable more accurate reporting”.

Giant plankton-eating fishes roamed the prehistoric seas for over 100 million years before they were wiped out in the same event that killed off the dinosaurs, new fossil evidence has shown.

An international team describe how new fossils from Asia, Europe and the US reveal a previously unknown dynasty of giant plankton-eating bony fishes that filled the seas of the Jurassic and Cretaceous periods, between 66-172 million years ago.
The team report their findings in this week’s Science.

Illustration of Bonnericthys by Robert Nicholls

‘Today’s giant plankton-feeders – such as baleen whales, basking sharks and manta rays – include the largest living vertebrate animals, so the fact that creatures of this kind were missing from the fossil record for hundreds of millions of years was always a mystery,’ said Dr Matt Friedman of Oxford University’s Department of Earth Sciences, an author of the report.

‘We used to think that the seas were free of big filter feeders during the age of dinosaurs, but our discoveries reveal that a dynasty of giant fishes filled this ecological role in the ancient oceans for more than 100 million years.’

Diagram showing reconstruction of Bonnericthys and position of bones Several of the most important new fossils came from deposits in Kansas in the USA, with other remains from as far afield as Dorset and Kent in the UK, and Japan. Some members of this filter-feeding fish group are estimated to have been up to 9 metres long, a similar size to modern plankton-eating giants such as the basking shark.

‘One of the reasons these big fishes were overlooked or misidentified lies in their anatomy,’ said Dr Friedman. ‘Over their evolutionary history, these fishes reduced the amount of bone in their skeletons, probably to save weight, with the consequence that most of their hard parts were easily scattered after death. As it turns out, the only parts you routinely find in the fossil record are their well-developed forefins.’

With few clues to go on, palaeontologists had argued that the owner of these isolated fins looked something like the modern-day swordfish. This changed when some of Dr Friedman’s colleagues began cleaning a fossil that preserved skull bones along with the fins.

Dr Friedman said: ‘Instead of finding a head with a long sword-like snout and jaws lined with predatory fangs, they found something completely different: long, toothless jaws supporting a gaping mouth, and long, rod-like bones that contributed to the huge gill arches needed to filter out enormous quantities of tiny plankton.’ The team named this fish Bonnerichthys, honouring the Kansas family who discovered the fossil.

Remains of similar giant plankton-eating fishes had been known from much older rocks, but they were thought to be a short-lived and unsuccessful evolutionary experiment. ‘As soon as we recognised that these animals had a longer history than anyone thought, I started examining museum collections and found more examples that had been overlooked or misidentified,’ explained Dr Friedman. Revisiting previously collected fossils netted the team evidence that these fishes thrived for millions of years and colonised many parts of the globe.

Intriguingly the ancestors of large modern filter-feeders such as baleen whales and whale sharks only appeared after the extinction of Bonnerichthys and its relatives, suggesting that today’s filter-feeders evolved to fill the ecological niche left behind by these plankton-eating contemporaries of the dinosaurs.

he research team consisted of scientists from Oxford University (UK), DePaul University, Chicago (US), Fort Hays State University, Kansas (US), University of Kansas (US), University of Glasgow (UK), and Triebold Paleontology Inc & Rocky Mountain Dinosaur Resource Centre, Colorado (US).

A report of the research, entitled ‘100-Million-Year Dynasty of Giant Planktivorous Bony Fishes in the Mesozoic Seas’, is published in this week’s Science.

By Robert Sanders | 1 March 2010

BERKELEY —Atrazine, one of the world’s most widely used pesticides, wreaks havoc with the sex lives of adult male frogs, emasculating three-quarters of them and turning one in 10 into females, according to a new study by University of California, Berkeley, biologists.

Above: An atrazine-induced female frog (a genetic male) is shown (bottom) copulating with an unexposed male sibling. This union produced viable eggs and larvae that survived to metamorphosis and adulthood. Yet, because both animals were genetic males, the offspring were all males. (Tyrone Hayes photo)

The 75 percent that are chemically castrated are essentially “dead” because of their inability to reproduce in the wild, reports UC Berkeley’s Tyrone B. Hayes, professor of integrative biology.

“These male frogs are missing testosterone and all the things that testosterone controls, including sperm. So their fertility is as low as 10 percent in some cases, and that is only if we isolate those animals and pair them with females,” he said. “In an environment where they are competing with unexposed animals, they have zero chance of reproducing.”

The 10 percent or more that turn from males into females – something not known to occur under natural conditions in amphibians – can successfully mate with male frogs but, because these females are genetically male, all their offspring are male.

“When we grow these guys up, depending on the family, we will get anywhere from 10 to 50 percent females,” Hayes said. “In a population, the genetically male females can decrease or wipe out a population just because they skew sex ratios so badly.”

Though the experiments were performed on a common laboratory frog, the African clawed frog (Xenopus laevis), field studies indicate that atrazine, a potent endocrine disruptor, similarly affects frogs in the wild, and could possibly be one of the causes of amphibian declines around the globe, Hayes said.

Hayes and his UC Berkeley colleagues report their results in this week’s online early edition of the journal Proceedings of the National Academy of Sciences. In last week’s issue of the Journal of Experimental Biology, Hayes and colleagues published a review of the possible causes of a worldwide decline in amphibian populations, concluding that atrazine and other hormone-disrupting pollutants are a likely contributor because they affect recruitment of new individuals and make amphibians more susceptible to disease.

“These kinds of problems, like sex-reversing animals skewing sex ratios, are much more dangerous than any chemical that would kill off a population of frogs,” he said. “In exposed populations, it looks like there are frogs breeding but, in fact, the population is being very slowly degraded by the introduction of these altered animals.”

Some 80 million pounds of the herbicide atrazine are applied annually in the United States on corn and sorghum to control weeds and increase crop yield, but such widespread use also makes atrazine the most common pesticide contaminant of ground and surface water, according to various studies.

More and more research, however, is showing that atrazine interferes with endocrine hormones, such as estrogen and testosterone – in fish, amphibians, birds, reptiles, laboratory rodents and even human cell lines at levels of parts per billion. Recent studies also found a possible link between human birth defects and low birth weight and atrazine exposure in the womb.

As a result of these studies, the Environmental Protection Agency (EPA) is reviewing its regulations on use of the pesticide. Several states are considering banning atrazine, and six class action lawsuits have been filed seeking to eliminate its use. The European Union already bars the use of atrazine.

Hayes’s studies in the early 2000s were the first to show that the hormonal effects of atrazine disrupt sexual development in amphibians. Working with the African clawed frog, Hayes and his colleagues showed in 2002 that tadpoles raised in atrazine-contaminated water become hermaphrodites – they develop both female (ovaries) and male (testes) gonads. This occurred at atrazine levels as low as 0.1 parts per billion (ppb), 30 times lower than levels allowed in drinking water by the EPA (3 ppb).

Subsequent studies showed that native leopard frogs (Rana pipiens) collected from atrazine-contaminated streams in the Midwest, including from areas up to 1,000 miles from where atrazine is applied, often had eggs in their testes. And many males had lower testosterone levels than normal females and smaller than normal voice boxes, presumably limiting their ability to call mates.

Hayes’ research also established that many frogs in Midwestern streams contaminated by atrazine and other pesticides have compromised immune systems, leading to increased mortality from bacterial disease.

Those early studies were hampered by the inability to easily distinguish genetically male from genetically female frogs. Male frogs have two identical sex chromosomes (ZZ) while females have both a Z and a W – the opposite of XX female and XY male humans. But because all frog chromosomes look the same under a light microscope, it’s not simple to distinguish male from female.

To overcome this, Hayes’ colleague Roger Liu developed a line of all-male frogs so that the genetics would be unequivocal.

“Before, we knew we got fewer males than we should have, and we got hermaphrodites. Now, we have clearly shown that many of these animals are sex-reversed males,” Hayes said. “We have animals that are females, in the sense that they behave like females: They have estrogen, lay eggs, they mate with other males. Atrazine has caused a hormonal imbalance that has made them develop into the wrong sex, in terms of their genetic constitution.”

Coincidentally, another lab in 2008 discovered a sex-linked genetic marker in Xenopus, which has allowed Hayes to confirm the genetic sex of his frogs.

In Hayes’ study, where 40 frogs lived for about three years after hatching in water with 2.5 ppb atrazine, about 10 percent of the frogs appeared to be resistant to the effects of the pesticide. In ongoing studies, Hayes is investigating whether this apparent resistance is inherited, as well as whether the sex-reversed males have more susceptible offspring.

Syngenta, which manufactures atrazine, disputes many of these studies, including Hayes’, that show adverse effects of the pesticide. But Hayes said that “when you have studies all over the world showing problems with atrazine in every vertebrate that has been looked at – fish, frogs, reptiles, birds, mammals – all of them can’t be wrong.”

“What people have to realize is that, just as with taking pharmaceuticals, they have to decide whether the benefits outweigh the costs,” he said. “Not every frog or every human will be affected by atrazine, but do you want to take a chance, what with all the other things that we know atrazine does, not just to humans but to rodents and frogs and fish?”

Hayes’ long-term studies of the effects of atrazine on frogs have been assisted by many UC Berkeley students, including co-authors on the current paper: undergraduates Vicky Khoury, Anne Narayan, Mariam Nazir, Andrew Park, Lillian Adame and Elton Chan; and graduate students Travis Brown, Daniel Buchholz, Sherrie Gallipeau and Theresa Stueve.

The work was funded by the Park Water Co., Mitch Kapor, Freada Klein, the Mitch Kapor Foundation, the David Foundation, the Cornell-Douglas Foundation, the Wallace Foundation, the UC Berkeley Class of ‘43 endowed chair and the Howard Hughes Biology Fellows Program.

Spanish scientists have studied interactions between the loggerhead turtle (Caretta caretta) and fishing gear such as longline hooks used at the water surface, mass beachings, and the effects of climate change on these animals. In order to reduce captures of this marine species without causing economic losses for fishermen, the scientists are proposing that fishing in the summer should only be carried out by night and in areas more than 35 nautical miles from land.

Above: How can accidental captures of loggerhead turtles be reduced? Photo Credit: Salvador García-Barcelona

Populations of loggerhead turtles (Caretta caretta) are in decline all over the world, and particularly in the Mediterranean Sea, where more than 20,000 animals are accidentally caught each year. Finding responsible and sustainable fisheries solutions was one of the prime objectives of this research study, published in the latest issue of the Journal of Applied Ichthyology.

Researchers from the Spanish Institute of Oceanography (IEO) in Malaga, the University of Malaga (UMA) and the Sea Classroom, also in Malaga, tested whether using different kinds of animal bait would reduce captures of loggerhead turtles, and how these changes could impact on fishing yields.

The scientists used real commercial fisheries data taken by scientific observers on board fishing boats. The results were clear. “Using fish as bait could greatly reduce incidental catches of loggerhead turtles, but could also severely affect catches of swordfish”, José Carlos Báez, lead author and a researcher at the IEO, tells SINC.

The research team also showed that stopping using small molluscs such as squid as bait could not ensure that incidental catches of loggerhead turtles would be prevented, since “as an opportunistic predator it also preys on hooks baited with fish, and can find these more easily when molluscs are used”, explains the expert.

The study proposes other measures that, the researchers say, would not involve modifying the equipment used in any way that “could result in low economic yields because of a decline in fish catches”, says Báez. These techniques would reduce the number of turtles caught while maintaining fishermen’s profits.

“Most accidental catches happen during the day, more than 35 nautical miles from the coast, and in the summer, meaning that it would be enough to limit longline fishing at these times and places in order to drastically reduce captures of this species”, says Báez, who adds that these measures should be tested before being adopted.

Longline fishing is practised by 356 vessels in Spanish waters, and provides employment for many coastal towns. However, accidental captures of species such as the loggerhead turtle are also damaging to fishermen’s interests, because of the economic losses caused and the time spent in freeing the turtles.

Citation: Báez, J.C.; Real, R.; Macias, D.; de la Serna, J.M.; Bellido, J.J.; Caminas, J.A. 2010. “Captures of swordfish Xiphias gladius Linnaeus 1758 and loggerhead sea turtles Caretta caretta (Linnaeus 1758) associated with different bait combinations in the Western Mediterranean surface longline fishery” Journal of Applied Ichthyology 26(1): 126-127, febrero de 2010.

A team of paleontologists has discovered a new dinosaur species they’re calling Abydosaurus, which belongs to the group of gigantic, long-necked, long-tailed, four-legged, plant-eating dinosaurs such as Brachiosaurus.

Above: Artist Michael Skrepnick’s depiction of Abydosaurus mcintoshi.

In a rare twist, they recovered four heads – two still fully intact – from a quarry in Dinosaur National Monument in eastern Utah. Complete skulls have been recovered for only eight of more than 120 known varieties of sauropod.

“Their heads are built lighter than mammal skulls because they sit way out at the end of very long necks,” said Brooks Britt, a paleontologist at Brigham Young University. “Instead of thick bones fused together, sauropod skulls are made of thin bones bound together by soft tissue. Usually it falls apart quickly after death and disintegrates.”

Britt is a co-author on the discovery paper scheduled to appear in the journal Naturwissenshaften. The lead author is Daniel Chure, a paleontologist at Dinosaur National Monument, who has no trouble boiling down the significance of the discovery.

“We’ve got skulls!” he shouted with sweeping hand gestures during a recent visit to the site.

BYU geology students and faculty resorted to jackhammers and concrete saws to cut through the hardened 105-million-year-old sandstone containing the bones. At one point the National Park Service called in a crew to blast away the overlying rock with explosives.

The skulls are temporarily on display at BYU’s Museum of Paleontology, where visitors can also watch BYU students prepare other bones from Abydosaurus.

“The hardest bone I personally have worked on is a vertebra that was half-eroded before discovery and is so fragile that it crumbles if you look at it wrong,” said Kimmy Hales, a geology major studying vertebrate paleontology at BYU. “The funnest project I have worked on was a set of five toe bones. Each toe bone was larger than my hand.”

Analysis of the bones indicates that the closest relative of Abydosaurus is Brachiosaurus, which lived 45 million years earlier. The four Abydosaurus specimens were all juveniles.

Most of what scientists know about sauropods is from the neck down, but the skulls from Abydosaurus give a few clues about how the largest land animals to roam the earth ate their food.

“They didn’t chew their food; they just grabbed it and swallowed it,” Britt said. “The skulls are only one two-hundredth of total body volume and don’t have an elaborate chewing system.”

All sauropods ate plants and continually replaced their teeth throughout their lives. In the Jurassic Period, sauropods exhibited a wide range of tooth shapes. But by the end of the dinosaur age, all sauropods had narrow, pencil-like teeth.

Abydosaurus teeth are somewhere in between, reflecting a trend toward smaller teeth and more rapid tooth replacement.

The fossils were excavated from the Cedar Mountain Formation in Dinosaur National Monument near Vernal, Utah. The site is just a quarter of a mile away from the condemned visitor center that displays thousands of bones that remain in place on an uplifted slab of sandstone.

University of Michigan researchers John Whitlock and Jeffrey Wilson are also co-authors on the study.

What’s in the name Abydosaurus mcintoshi?

The generic name refers to Abydos, the Greek name for the city along the Nile River (now El Araba el Madfuna) that was the burial place of the head and neck of Osiris, Egyptian god of life, death and fertility. Abydos alludes to the type specimen, which is a skull and neck found in a quarry overlooking the Green River. Sauros is the Greek word for lizard.

The specific name mcintoshi honors the American paleontologist Jack McIntosh for his contributions to the study of sauropod dinosaurs. In 1975 McIntosh debunked the myth of Brontosaurus, exposing it as a mixed-up skeleton with an Apatosaurus body and a Camarasaurus skull.

 An extremely small RNA molecule created by a University of Colorado at Boulder team can catalyze a key reaction needed to synthesize proteins, the building blocks of life. The findings could be a substantial step toward understanding “the very origin of Earthly life,” the lead researcher contends.

The smallest RNA enzyme ever known to perform a cellular chemical reaction is described in a paper published in the Proceedings of the National Academy of Sciences. The paper was written by CU graduate student Rebecca Turk, research associate Nataliya Chumachenko and Professor Michael Yarus of the molecular, cellular and developmental biology department.

Cellular RNA can have hundreds or thousands of its basic structural units, called nucleotides. Yarus’ team focused on a ribozyme — a form of RNA that can catalyze chemical reactions — with only five nucleotides.

Tom Blumenthal, a professor and chair of the MCDB department, noted that Tom Cech, a Nobel laureate and distinguished professor of chemistry and biochemistry at CU, and Professor Norman Pace of MCDB, independently discovered that RNA can act as an enzyme, carrying out chemical reactions. That “pioneering work” has been carried on further by Yarus, Blumenthal said.

Because proteins are complex, one vexing question is where the first proteins came from, Blumenthal said. “It now appears that the first catalytic macromolecules could have been RNA molecules, since they are somewhat simpler, were likely to exist early in the formation of the first life forms, and are capable of catalyzing chemical reactions without proteins being present,” he said.

“In this paper the Yarus group has made the amazing discovery that even an extremely tiny RNA can by itself catalyze a key reaction that would be needed to synthesize proteins,” Blumenthal said. “Nobody expected an RNA molecule this small and simple to be able to do such a complicated thing as that.”

The finding adds weight to the “RNA World” hypothesis, which proposes that life on Earth evolved from early forms of RNA. “Mike Yarus has been one of the strongest proponents of this idea, and his lab has provided some of the strongest evidence for it over the past two decades,” Blumenthal said.

Yarus noted that the RNA World hypothesis was complicated by the fact that RNA molecules are hard to make. “This work shows that RNA enzymes could have been far smaller, and therefore far easier to make under primitive conditions, than anyone has expected.”

If very simple RNA molecules such as the product of the Yarus lab could have accelerated chemical reactions in Earth’s primordial stew, the chances are much greater that RNA could direct and accelerate biochemical reactions under primitive conditions.

Before the advent of RNA, most biologists believe, there was a simpler world of chemical replicators that could only make more of themselves, given the raw materials of the time, Yarus said.

“If there exists that kind of mini-catalyst, a ’sister’ to the one we describe, the world of the replicators would also jump a long step closer and we could really feel we were closing in on the first things on Earth that could undergo Darwinian evolution,” Yarus said.

“In other words, we may have taken a substantial step toward the very origin of Earthly life,” he said. “However, keep well in mind that the tiny replicator has not been found, and that its existence will be decided by experiments not yet done, perhaps not yet imagined.”

“Dr. Yarus has brought an innovative approach to bear on the key question of how complex processes originated,” said Michael Bender, a biologist who oversees protein synthesis grants at the National Institutes of Health’s National Institute of General Medical Sciences. “By showing that a tiny segment of RNA can perform a key step of protein synthesis, this study has provided evidence that fundamental, protein-mediated cellular processes may have arisen from RNA-based mechanisms.”

An extremely small RNA molecule created by a University of Colorado at Boulder team can catalyze a key reaction needed to synthesize proteins, the building blocks of life. The findings could be a substantial step toward understanding “the very origin of Earthly life,” the lead researcher contends.

The smallest RNA enzyme ever known to perform a cellular chemical reaction is described in a paper published in the Proceedings of the National Academy of Sciences. The paper was written by CU graduate student Rebecca Turk, research associate Nataliya Chumachenko and Professor Michael Yarus of the molecular, cellular and developmental biology department.

Cellular RNA can have hundreds or thousands of its basic structural units, called nucleotides. Yarus’ team focused on a ribozyme — a form of RNA that can catalyze chemical reactions — with only five nucleotides.

Tom Blumenthal, a professor and chair of the MCDB department, noted that Tom Cech, a Nobel laureate and distinguished professor of chemistry and biochemistry at CU, and Professor Norman Pace of MCDB, independently discovered that RNA can act as an enzyme, carrying out chemical reactions. That “pioneering work” has been carried on further by Yarus, Blumenthal said.

Because proteins are complex, one vexing question is where the first proteins came from, Blumenthal said. “It now appears that the first catalytic macromolecules could have been RNA molecules, since they are somewhat simpler, were likely to exist early in the formation of the first life forms, and are capable of catalyzing chemical reactions without proteins being present,” he said.

“In this paper the Yarus group has made the amazing discovery that even an extremely tiny RNA can by itself catalyze a key reaction that would be needed to synthesize proteins,” Blumenthal said. “Nobody expected an RNA molecule this small and simple to be able to do such a complicated thing as that.”

The finding adds weight to the “RNA World” hypothesis, which proposes that life on Earth evolved from early forms of RNA. “Mike Yarus has been one of the strongest proponents of this idea, and his lab has provided some of the strongest evidence for it over the past two decades,” Blumenthal said.

Yarus noted that the RNA World hypothesis was complicated by the fact that RNA molecules are hard to make. “This work shows that RNA enzymes could have been far smaller, and therefore far easier to make under primitive conditions, than anyone has expected.”

If very simple RNA molecules such as the product of the Yarus lab could have accelerated chemical reactions in Earth’s primordial stew, the chances are much greater that RNA could direct and accelerate biochemical reactions under primitive conditions.

Before the advent of RNA, most biologists believe, there was a simpler world of chemical replicators that could only make more of themselves, given the raw materials of the time, Yarus said.

“If there exists that kind of mini-catalyst, a ’sister’ to the one we describe, the world of the replicators would also jump a long step closer and we could really feel we were closing in on the first things on Earth that could undergo Darwinian evolution,” Yarus said.

“In other words, we may have taken a substantial step toward the very origin of Earthly life,” he said. “However, keep well in mind that the tiny replicator has not been found, and that its existence will be decided by experiments not yet done, perhaps not yet imagined.”

“Dr. Yarus has brought an innovative approach to bear on the key question of how complex processes originated,” said Michael Bender, a biologist who oversees protein synthesis grants at the National Institutes of Health’s National Institute of General Medical Sciences. “By showing that a tiny segment of RNA can perform a key step of protein synthesis, this study has provided evidence that fundamental, protein-mediated cellular processes may have arisen from RNA-based mechanisms.”

Citation: Rebecca M. Turk, Nataliya V. Chumachenko, and Michael Yarus. 2010. Multiple translational products from a five-nucleotide ribozyme. PNAS published online before print February 22, 2010, doi:10.1073/pnas.0912895107

New research on lizards supports an old idea about how species can originate. Morphologically distinct types are often found within species, and biologists have speculated that these “morphs” could be the raw material for speciation. What were once different types of individuals within the same population could eventually evolve into separate species.

Side-blotched lizards have three color morphs with different mating strategies, but in some populations only one morph occurs. This male lizard is from an all-orange population in the Warner Mountains in northeastern California. Photo by Ammon Corl.

A new study conducted by researchers at the University of California, Santa Cruz, supports this idea. The study documents the disappearance of certain morphs of the side-blotched lizard in some populations. The researchers reported their findings in a paper published this week in the online early edition of Proceedings of the National Academy of Sciences (PNAS).

The side-blotched lizard, Uta stansburiana, has three morphs differing in color and mating behavior. Barry Sinervo, a professor of ecology and evolutionary biology at UCSC, has studied a population of side-blotched lizards near Los Banos, Calif., for over 20 years. Ammon Corl, now a postdoctoral researcher at Uppsala University in Sweden, led the new study as a graduate student at UCSC and is first author of the paper.

Previous work by Sinervo and his colleagues showed that competition among male side-blotched lizards takes the form of a rock-paper-scissors game in which each mating strategy beats and is beaten by one other strategy. Males with orange throats can take territory from blue-throated males because they have more testosterone and body mass. As a result, orange males control large territories containing many females. Blue-throated males cooperate with each other to defend territories and closely guard females, so they are able to beat the sneaking strategy of yellow-throated males. Yellow-throated males are not territorial, but mimic female behavior and coloration to sneak onto the large territories of orange males to mate with females.

“My goal when starting my Ph.D. thesis research was to understand how this fascinating mating system evolved,” Corl said. “We studied lizard populations from California to Texas and from Washington State down to Baja California Sur in Mexico.”

Corl found the three color morphs in many places, but not everywhere. Some populations were missing some of the color morphs. For example, populations in the northwest only have orange-throated lizards, while only orange- and blue-throated morphs are found on Anacapa Island in the Channel Islands. In the field, the researchers captured lizards to collect tissue samples for DNA analysis and then released them back into the wild. In the lab, they used the tissue samples to get DNA sequences from all of the lizard populations in the study.

“Based on these sequences, we reconstructed the ‘family tree’ of the lizard populations and figured out which populations were more closely related to one another. This let us figure out how the mating strategies evolved,” Corl said.

The results showed that all three color morphs existed millions of years ago and have persisted since then in many populations. Over time, however, some branches of the lizard family tree lost some of the color types.

“What was particularly interesting was the pattern in how color morphs were lost,” Corl said. “Any time there was a loss, the yellow type–the sneaky males that mimic females–was the first to go. Thus, the rock-paper-scissors game can break down on an evolutionary timescale. Something about the game must change so that, for instance, both the rock and scissors strategies are able to beat paper.”

Sinervo has documented the cycling of the rock-paper-scissors game at his main study site for 22 years, with the dominant morph in the population changing every four to five years. “It’s like an evolutionary clock ticking between rock, paper, scissors then back to rock,” he said. “Ammon’s research indicates that the game has been cycling for millions of years at some sites, and yet at other sites it collapses on one or two strategies and begins to create new species. It is simply mind-boggling to think about deep time and these evolutionary cycles.”

Many aspects of the evolutionary history of these lizards are consistent with the theory that morphs can be involved in speciation, Corl said. Evolutionary theory predicts that new species could arise from particular morphs originally found in a population containing multiple morphs. Side-blotched lizards started off with three color morphs. If just one or two types occur in a population, they look just like the original morphs.

The theory was also supported by patterns in the formation of subspecies, which are the precursors to new species. Two subspecies of side-blotched lizard that originated from populations with three morphs now have only a single color morph. Thus, populations that lose morphs are not transitory, but can persist and eventually become a different species.

The study also found evidence to support the hypothesis that rapid evolutionary change occurs when particular morphs are lost from the system. “Imagine the three lizard morphs playing rock-paper-scissors,” Corl explained. “They have very specific adaptations for fighting one another. Now imagine that some morphs are lost, leaving a population of all rock morphs. Their adaptations for fighting the paper and scissors morphs are no longer useful. Therefore, rapid evolutionary change is expected in a population of rock morphs as they adapt to a new game in which they only fight other rock morphs.”

The study showed clear evidence of very rapid evolution of body size when morphs are lost from a population. “Such rapid evolution could eventually cause populations to evolve into distinct species. We are the first group to provide a statistical test of this hypothesis,” Corl said.

The idea of morphs being involved in speciation is an old one. Charles Darwin conducted experiments with different reproductive morphs in flowers to try to gain insight into the process of speciation. However, the new paper by Corl and colleagues is one of the first studies to use modern techniques to tackle the problem of morphs and speciation.

“My hope is that the paper will inspire other researchers to consider a role for morphs in the evolution of the species that they study,” said Corl. “For most species, the speciation process is thought to begin only after populations are geographically separated. Our study shows that the distinctive morphs that build up within populations are important for understanding speciation. Thus, the first stages of new species may occur within and not between populations. This idea could fuel lots of interesting research for many years to come.”

In addition to Corl and Sinervo, the other coauthors of the paper are Alison Davis, a graduate student in Sinervo’s lab now at UC Berkeley, and Shawn Kuchta, a postdoctoral researcher in Sinervo’s lab now at Dartmouth University. This research was supported by a Mildred Mathias grant, a Gaige Fund award, a Sigma Xi grant, a National Geographic Society grant, and multiple grants from the National Science Foundation.

Corl, A. et al. 2010. Selective loss of polymorphic mating types is associated with rapid phenotypic evolution during morphic speciation. PNAS published online before print February 16, 2010, doi:10.1073/pnas.0909480107

Prof. Michael Gurevitz of Tel Aviv University’s Department of Plant Sciences is investigating new ways for developing a novel painkiller based on natural compounds found in the venom of scorpions. These compounds have gone through millions of years of evolution and some show high efficacy and specificity for certain components of the body with no side effects, he says.

Above: Extracting venom from a scorpion. Courtsey of American Friends of Tel Aviv University.

Peptide toxins found in scorpion venom interact with sodium channels in nervous and muscular systems — and some of these sodium channels communicate pain, says Gurevitz. “The mammalian body has nine different sodium channels of which only a certain subtype delivers pain to our brain. We are trying to understand how toxins in the venom interact with sodium channels at the molecular level and particularly how some of the toxins differentiate among channel subtypes.

“If we figure this out, we may be able to slightly modify such toxins, making them more potent and specific for certain pain mediating sodium channels,” Gurevitz continues. With this information, engineering of chemical derivatives that mimic the scorpion toxins would provide novel pain killers of high specificity that have no side effects.

In his research, Gurevitz is concentrating on the Israeli yellow scorpion, one of the most potent scorpions in the world. Its venom contains more than 300 peptides of which only a minor fraction has been explored. The reason for working with this venom, he says, is the large arsenal of active components such as the toxins that have diversified during hundreds of millions of years under selective pressure. During that process, some toxins have evolved with the capability to directly affect mammalian sodium channel subtypes whereas others recognize and affect sodium channels of invertebrates such as insects. This deviation in specificity is for us a lesson of how toxins may be manipulated at will by genetic engineering, he says.

While the use of scorpion venom to treat some body disorders seems counter-intuitive, the Chinese have recognized its effectiveness hundreds of years ago. “The Chinese, major practitioners of what we call ‘alternative medicine,’ use scorpion venom, believing it to have powerful analgesic properties,” Gurevitz says. Some studies have also shown that scorpion venom can be used to treat epilepsy. “We study how these toxins pursue their effects in the Western sense to see how it could be applied as a potent painkiller.”

Using an approach called “rational design” or “biomimicry,” Prof. Gurevitz is trying to develop painkillers that mimic the venom’s bioactive components. The idea is to use nature as the model, and to modify elements of the venom so that a future painkiller designed according to these toxins could be as effective as possible, while eliminating or reducing side effects.

Finding a new and effective pain medication could solve one of the biggest problems in the medical world today. Pain is an important physiological response to danger, physical injury and poor health, yet doctors need to reduce extreme pain in patients which aspirin could never palliate. To date, opiate-derived painkillers have been quite effective, but the medical community is eager to find other solutions due to the risks associated with their use.

Gurevitz says. “This new class of drugs could be useful against serious burns and cuts, as well as in the military and in the aftermath of earthquakes and natural disasters. Instead of running the risk of addiction, this venom-derived drug, mimicking the small peptide toxin, would do what it needs to do and then pass from the body with no traces or side-effects,” .