Smithsonian Science » entomology

Heliconius butterfly genome explains wing pattern diversity

John Barrat — Thu, 17 May 2012 01:25:58 +0000

Pooling funds and putting their heads together, more than 70 scientists from 9 institutions including the Smithsonian Tropical Research Institute, sequenced the entire genome of the butterfly genus Heliconius, a brightly colored favorite of collectors and scientists since the Victorian era. Their results are published in the prestigious journal, Nature.

Image right: Based on the new sequence, scientists found that different species copy each other’s wing patterns by exchanging genes, a process thought to be very rare, especially in animals. (Photo by Mathieu Joron)

The genome of the Postman butterfly, Panama’s Heliconius melpomene, helps scientists understand how the stunning diversity of wing color patterns in tropical butterflies evolved. Heliconius species are highly distasteful. Their vivid wing patterns warn predators not to eat them. How have different butterfly species evolved similar wing patterns?

Based on the new sequence, scientists found that different species copy each other’s wing patterns by exchanging genes, a process thought to be very rare, especially in animals. Although many different species interbreed in the wild, their hybrid offspring often cannot reproduce successfully. But sometimes hybrids gain useful genes that help them adapt to changing conditions. Heliconius hybrids gain wing patterns that help them survive.

Kanchon Dasmahapatra, the a lead author of the study and a former Smithsonian fellow who worked with Jim Mallet at University College London notes: “What we discovered is that one butterfly species can gain its protective colour pattern genes ready-made from a different species by hybridizing with it–a much faster process than having to evolve one’s colour patterns from scratch.”

Some of the other genes in the sequence also surprised researchers. These butterflies, typically regarded as primarily visual insects, apparently have a rich array of genes for smelling and sensing chemicals in their environment, raising new questions about the links between perception and the origins of new species. Indeed, analysis carried out at the University of California by co-author Adriana Briscoe showed that butterflies have an even greater array of genes involved in chemical communication than moths, which depend on chemical signals for finding mates and host plants.

The study heralds a new era in genome biology and an important step in the Smithsonian’s goal to understand and sustain a biodiverse planet. Low-cost genetic sequencing opens doors to small research groups and individuals to sequence entire genomes, a technique formerly accessible only to labs with major government funding.

“Assembling a genome from scratch is still hard work: think Humpy-Dumpty,” said Owen McMillan, geneticist and Academic Dean at the Smithsonian Tropical Research Institute, “but it is getting easy, inexpensive, and is transforming how we do science. At the core, having a reference genome opens up new research possibilities and reveals previously unimagined connections.

First ever record of insect pollination captured in 100 million-year-old amber

John Barrat — Tue, 15 May 2012 13:24:47 +0000

Amber from Cretaceous deposits (110-105 million years ago) in Northern Spain has revealed the first-ever record of insect pollination. Scientists have discovered several specimens of tiny insects covered with pollen grains in two pieces of amber, revealing the first record of pollen transport and social behavior in this group of animals. The results are published in the Proceedings of the National Academy of the Science (PNAS) dated 14-18 May 2012.

Image right: Gymnosperm pollen attached to the abdomen and wing of a thysanopteran from the Alava amber (Credit: Enrique Peñalver, IGME).

The international team of scientists comprises: Enrique Peñalver and Eduardo Barrón from the Instituto Geológico y Minero de España in Madrid; Xavier Delclòs from the University of Barcelona; Andre and Patricia Nel from the Muséum national d’histoire naturelle in Paris; Conrad Labandeira from the Smithsonian’s National Museum of Natural History in Washington D.C.; and Carmen Soriano and Paul Tafforeau from the European Synchrotron Radiation Facility in Grenoble, France. The amber samples were from the collection of the Museo de Ciencias Naturales de Álava in Spain.

Today, more than 80 percent of plant species rely on insects to transport pollen from male to female flower parts. Pollination is best known in flowering plants but also exists in so-called gymnosperms, seed-producing plants like conifers. Although the most popular group of pollinator insects are bees and butterflies, a myriad of lesser-known species of flies, beetles or thrips have co-evolved with plants, transporting pollen and in return for this effort being rewarded with food.

Image left: An artist’s conception of of Gymnospollisthrips with pollen attached to the body over an ovulate organ of a gingko (Credit: Enrique Peñalver, IGME).

During the last 20 years, amber from the Lower Cretaceous found in the Basque country in Northern Spain has revealed many new plant and animal species, mainly insects. Here, the amber featured inclusions of thysanopterans, so-called thrips, a group of minute insects of less than 2 millimeters long that feed on pollen and other plant tissues. They are efficient pollinators for several species of flowering plants.

Two amber pieces revealed six fossilized specimens of female thrips with hundreds of pollen grains attached to their bodies. These insects exhibit highly specialized hairs with a ringed structure to increase their ability to collect pollen grains, very similar to the ones of well known pollinators like domestic bees. The scientists describe these six specimens in a new genus (Gymnopollisthrips) comprising two new species, G. minor and G. major.

The most representative specimen was also studied with synchrotron X-ray tomography at the European Synchrotron Radiation Facility to reveal the pollen grain distribution over the insect’s body in 3D and at very high resolution. The pollen grains are very small and exhibit the adherent features needed so that insects can transport them. The scientists conclude that this pollen is from a kind of cycad or ginkgo tree, a kind of living fossil of which only a few species are known to science. Ginkgos are either male or female, and male trees produce small pollen cones whereas female trees bear ovules at the end of stalks which develop into seeds after pollination.

Image right: Synchrotron tomography image of Gymnospollisthrips minor showing pollen. (Credit: ESRF).

Why did these tiny insects collect and transport gingko pollen 100 million years ago? Their ringed hairs cannot have grown due to an evolutionary selection benefiting the trees. The benefit for the thrips can only be explained by the possibility their larvae ate pollen. This suggests that this species formed colonies with larvae living in the ovules of some kind of gingko for shelter and protection, and female insects transporting pollen from the male gingko cones to the female ovules to feed the larvae and at the same time pollinate the trees.

More than one hundred million years ago, flowering plants started to diversify enormously, eventually replacing conifers as the dominant species. “This is the oldest direct evidence for pollination, and the only one from the age of the dinosaurs,” says Carmen Soriano, who led the investigation of the amber pieces with X-ray tomography at the ESRF. “The co-evolution of flowering plants and insects, thanks to pollination, is a great evolutionary success story. It began about 100 million years ago, when this piece of amber fossil was produced by resin dropping from a tree, which today is the oldest fossil record of pollinating insects. Thrips might indeed turn out to be one of the first pollinator groups in geological history, long before evolution turned some of them into flower pollinators.” –Source: European Synchrotron Radiation Facility

Meet the 125-million-year-old pollinator “Jeholopsyche liaoningensis”

John Barrat — Mon, 19 Mar 2012 18:45:23 +0000

What: Jeholopsyche liaoningensis is a new genus and species of flying insect from northeastern China, recently revealed in two new fossil specimens. Moderate in size, adults have a remarkably long, straw-like, ridged proboscis (or “tongue”) covered with well-developed, dense hairs that ended in a fleshy tip. Other characteristics included large separated eyes, long antennae and long wings.

When: J. liaoningensis lived some 125 million years ago alongside the dinosaurs just as flowering plants (angiosperms) were beginning to appear. This species has long been extinct. It is the first member of the Aneuretopsychidae, a prehistoric family of insects, to be discovered so exquisitely preserved that scientists can see and study the anatomical detail of its body parts, including the abdomen, antennae, thorax, forewings, legs and the head and mouthparts, especially the proboscis. This new specimen also reveals previously unknown ancient relationships between plants and these spectacular insects.

Image above: J. liaoningensis gen. et sp. n. Holotype, specimen CNU-M-LB-2005-002-2, counterpart. Image below: Close-up of the proboscis of J. liaoningensis accompanied by a scientific illustration of the proboscis as well. (Click photos to enlarge)

How: This insect lived by sucking nectar-like fluid from deep funnels or similar tubular structures that were part of the reproductive features of seed-producing plants such as certain conifer, cycad and ginkgo-like hosts, collectively known as gymnosperms. J. liaoningensis was one of a diverse guild of long-proboscis insects that fed upon these plants, including flies, lacewings and possibly moths. Scientists know that it “nectared” gymnosperms and not angiosperms because at that time the most primitive angiosperms did not have deep-throated, tubular flowers whereas some gymnosperm hosts did have reproductive structures that would accommodate the proboscis of J. liaoningensis.

Where: Discovered recently in China’s Yixian Formation, near Beipiao City of Liaoning Province, China. The Yixian Formation is a geological formation holding deposits that span several millions of years during the Early Cretaceous Period. It is well known for the abundant fossils of plants, animals, such as feathered dinosaurs, and insects that have been discovered there, broadly known as the Jehol Biota.

Image left: J. liaoningensis gen. et sp. n. Holotype, specimen CNU-M-LB-2005-002-1, part.

Who: These specimens were described and named in the journal Zookeys recently by Dong Ren and ChungKun Shih of the Capital Normal University, Beijing, and Conrad Labandeira of the Smithsonian’s National Museum of Natural History. Article link: “A well-preserved aneuretopsychid from the Jehol Biota of China (Insecta, Mecoptera, Aneuretopsychidae)”

Fancy footwork and non-stick leg coating helps spiders not stick to their own webs

John Barrat — Thu, 01 Mar 2012 13:21:19 +0000

Researchers at the Smithsonian Tropical Research Institute and University of Costa Rica studying why spiders do not stick to their own sticky webs have discovered that a spider’s legs are protected by a covering of branching hairs and by a non-stick chemical coating. Their results are published online in the journal, Naturwissenschaften.

Image right: This mature female golden silk spider had just contacted the sticky line with her right leg IV and was about to extend this leg, thereby pulling additional line from her spinnerets. (Photo by C. Frank Starmer)

They also observed that spiders carefully move their legs in ways that minimize adhesive forces as they push against their sticky silk lines hundreds to thousands of times during the construction of each orb.

The web-weaving behavior of two tropical species, Nephila clavipes and Gasteracantha cancriformis, was recorded with a video camera equipped with close-up lenses. Another video camera coupled with a dissecting microscope helped to determine that individual droplets of sticky glue slide along the leg’s bristly hair, and to estimate the forces of adhesion to the web. By washing spider legs with hexane and water, they showed that spiders’ legs adhered more tenaciously when the non-stick coating was removed.

( “Spiders avoid sticking to their webs: clever leg movements, branched drip-tip setae, and anti-adhesive surfaces” by R.D. Briceño and W.G. Eberhard. 2012. Naturwissenshaften. DOI 10.1007/s00114-012-0901-9. Published online: 1 March 2012.)

“Anastrepha conflua,” new fruit fly species

John Barrat — Mon, 13 Feb 2012 18:46:19 +0000

Anastrepha conflua, one of seven new fruit fly species of the genus Anastrepha Schiner described in a new paper by USDA entomologist Allen Norrbom, Systematic Entomology Laboratory of the Smithsonian’s National Museum of Natural History, and Cheslavo Korytkowski, University of Panama. This is the most diverse genus of fruit flies in the American tropics and subtropics, with 230 described species, a number of which are major fruit pests. A. conflua is from Costa Rica. Its host plants and other aspects of its biology are unknown.

Male spider’s sexual organs work fastest only when a female breaks them off

John Barrat — Tue, 07 Feb 2012 15:50:44 +0000

Even after the sexual organs of the male orb web spider Nephilengys malabarensis have broken off during copulation, they continue to do the work of transferring sperm to the female, a new study published in the journal Biology Letters has revealed. In fact, researchers have learned, the detached male pedipalps transfer more sperm faster after copulation is ended by the female than when it is ended by the male.

N. malabarensis females normally end copulation (which lasts an average of 8.3 seconds) by grabbing and devouring the much-smaller male or by yanking him off. Scientists have long known that during copulation the palps (males have two, one located on each side of their heads) snap off entirely inside the female’s genitals, effectively plugging them to prevent her from mating again. Males will end copulation by deliberately severing their own palps. As the eunuch male is being eaten or fleeing the female’s jaws, sperm transfer continues from his severed organs into the female’s genitals, a previously unknown process newly coined as “remote copulation.”

Image right: An Nephilengys malabarensis female with a severed male palp (red box) lodged in her epigynum after copulation, and a half-cannibalized male at her side. (Photo by Daiqin Li)

“Frankly, we don’t know” the physics behind this process, says Matjaž Kuntner, co-author of the recent paper in the journal Biology Letters and a research associate at the Smithsonian’s National Museum of Natural History and the Slovenian Academy of Sciences and Arts. When connected, “a palp usually pumps out sperm through the hydraulic action of the membranes, but in the case of remote copulation, the mechanism is unknown.”

Image left: Sexual cannibalism in N. malabarensis. A big female eats a small male. (Photo by Matjaž Kuntner)

Also unknown, Kuntner says, is why the organ works faster when the female terminates copulation. “I think it is connected to sexual conflict,” he explains. “If the female is the one to terminate copulation, then it is also likely that she will attempt to remove the remotely copulating organ. There’s where transfer speed may matter.”

Both topics represent areas of further research, Kuntner says.

Image right: This scanning electron microscope image of a eunuch N. malabarensis shows its head with eyes and mouthparts, and the two broken stumps of its pedipalps. (Photo courtesy Matjaž Kuntner)

To conduct their experiment Kuntner and his co-authors collected immature N. malabarensis spiders in Singapore and raised them to maturity. Males were placed on the female’s web and the spiders were observed before and after copulation occurred. Twenty-five mating pairs of spiders were used in the experiment. Broken palps were allowed to remain in the female’s genitals for varying periods of time before they were removed by the scientists. The researchers then isolated and counted the sperm that remained in each of the palps and the sperm that had successfully entered each female’s genitals.

The study suggests “remote copulation is an additional male adaptation to sexual cannibalism and to female control of copulation duration,” the researchers write in their paper. It allows the male to maximize his reproductive potential through continuous sperm transfer after copulation, and by monopolizing the female she is unavailable to rival males.

“Remote copulation: male adaptation to female cannibalism” appeared in the journal Biology Letters and was authored by Daiqin Li, Joelyn Oh, Simona Kralj-Fiser and Matjaž Kuntner.

Jeholopsyche liaoningensis

John Barrat — Mon, 30 Jan 2012 15:46:33 +0000

This fossil represents a new genus and species of extinct aneuretopsychid, Jeholopsyche liaoningensis, recently described in a paper in the journal ZooKeys by Conrad Labandeira of the Smithsonian’s National Museum of Natural History, and Dong Ren and ChungKun Shih of the College of Life Sciences, Capital Normal University, Beijing. The aneuretopsychidae are a family of long-proboscid insects that lived in Asia from the Late Jurassic to Early Cretaceous. The paper documents the first formal record of fossil Aneuretopsychidae in China. The new fossils reveal previously unknown and detailed structure of the mouthparts, antennae, head, thorax, legs and abdomen of this distinctive insect lineage.

Halocoryza acapulcana Whitehead

John Barrat — Wed, 19 Oct 2011 18:27:23 +0000

Halocoryza acapulcana Whitehead (Acapulco Saline Catarrh Beetle), described in 1966 by Donald R. Whitehead. This image is from a recent paper by Terry L. Erwin, entomologist at the Smithsonian’s National Museum of Natural History, containing updated information on this and two other previously described species of Halocoryza Alluaud beetles (sea-side beetles of the Indian, Atlantic and Pacific Oceans) and the description of a new species from Baja California Sur, Mexico, in the journal ZooKeys.

Suitor’s gentle massage soothes aggressive, cannibalistic female spiders, researchers find

John Barrat — Fri, 14 Oct 2011 13:11:11 +0000

For male golden orb web spiders of the tropical species Nephila pilipes, few of life’s adventures present more dangers than mating. Female N. pilipes—roughly 10 times larger than the males—are known to interrupt copulation with an abrupt kick, after which they may grab the stunned male and eat him.

Video and images: To sooth the female during copulation bouts the male N. pilipes spider gently spreads fine silk upon the dorsum of the female. It is the touch of the male that soothes the female most of all a team of researchers recently learned through a series of laboratory tests. Click photos to enlarge. (Images courtesy Shichang Zhang, National University of Singapore)

To appease the female and make her more receptive to the multiple copulation sessions that are common among these spiders, the male N. pilipes spins a fine silk which he gently spreads about the female’s dorsum or backside—a behavior scientists call “mate binding.”

Now, a new study by a team of scientists from the Smithsonian’s National Museum of Natural History, the National University of Singapore, Hubei University, and the Slovenian Academy of Sciences and Arts have unlocked the secret to this little-studied behavior, and revealed just how it calms the female. Essentially, the scientists write in a recent paper, mate binding might be more descriptively termed “mate massaging,” as it is the tactile communication between the male and female N. pilipes, not the silk or chemical pheromones in the silk, that is the most important calming factor in this process.

In a series of laboratory experiments, the scientists—Shichang Zhang from the National University of Singapore, Daiqin Li of the National University of Singapore and Hubei University in China and Matjaž Kuntner of the Slovenian Academy of Sciences and Arts and a research associate at the Smithsonian’s National Museum of Natural History—blocked the tactile feeling on the dorsum of one group of female spiders with a thin layer of glue, and blocked the chemical receptors on the forelegs and palps (appendages near the mouth) of other females. In a third group of females they blocked both of these senses.

In addition, on a number of males they blocked the spinnerets used to spin the fine silk used in mate binding.

Next, they placed male spiders on the webs of the females and observed their mating behavior. What they learned, the scientists write, is that mate binding is not an obligatory behavior that always precedes mating, but rather, it always “occurred after females had interrupted copulations and became aggressive towards their suitors.”

Tactile communication caused by the male spider moving around the dorsum of the female with his spinnerets rubbing against her was the most important calming factor in mate binding behavior, they determined. Chemical signals embedded in the silk also appeared to have a calming influence on the females, but are secondary to the tactile feel of the male moving around the female’s dorsum. Silk production is but a by-product of the mate binding behavior.

Mate binding “enables the male to mate with the female multiply,” reducing her resistance and aggression, prolonging copulation bouts and maximizing the male’s paternity, the scientists conclude.

“Mate binding: male adaptation to sexual conflict in the golden orb-web spider (Nephilidae: Nephila pilipes)” appeared in a recent edition of the journal Animal Behaviour.

Invertebrates are ignored, overlooked by conservationists, policymakers and the public

John Barrat — Thu, 01 Sep 2011 15:22:31 +0000

When it comes to conservation, the earth’s invertebrates—insects, mollusks, worms, coral, arthropods and others—are getting a bad deal, say a team of scientists in a paper published recently in the journal Biological Conservation. Invertebrates make up more than 80 percent of all known species and provide humans with a myriad of valuable services—from crop pollination to their use as food—yet they are overlooked and underrepresented in conservation decisions and on priority lists of threatened and endangered species.

Image left: A honeybee pollinates and apple blossom.

“Invertebrate conservation is hard to justify when many people see each insect as a potential pest or each spider as a potential health threat,” write the paper’s authors, who include entomologists Terry Erwin and Pedro Cardoso of the Smithsonian’s National Museum of Natural History. In general the public is unaware of the critical role invertebrates play in the health of the ecosystem or the conservation threats that these creatures now face.

In addition, policymakers are often poorly informed about the details of invertebrate conservation, the scientists say. “Many assume that in protecting a single large animal, that animal will serve as an ‘umbrella species’ protecting all the other species—including invertebrates—in its habitat. “This view is however largely unsupported and untested,” the scientists say.

Image right: The tree-nesting tropical ant Cephalotes atratus (Stephen Yanoviak)

Remarkably, most of the world’s invertebrates remain unknown and have never been studied or described by scientists. The vast majority of species now going extinct due to human activities—about 3,000 a year—belong mainly to understudied groups of invertebrates, ‘the little things that run the world,’ the scientists write. “Because most invertebrates are undescribed, their geographic distribution is unknown as is their abundance, ways of life and sensitivities to pollution and habitat change.” Basic science for the study of invertebrates is scarce and underfunded.

Image left: Bonaire box jelly fish, St. Vincent Island, Caribbean (Photo by Ned DeLoach)

To remedy the problem the scientists offer a number of suggestions, including: More invertebrates should be placed on red lists of endangered species and in environmental impact statements; a stronger link must be made in the public imagination between invertebrate conservation and human well-being; sampling and analytical methods for biodiversity assessment and monitoring should be improved; and long-term ecological studies should be initiated to monitor ecosystem change.

“Invertebrate conservation is only possible with the preservation of ecosystems and their structure, function and processes,” the scientist’s conclude. “Only by preserving all species and guaranteeing interactions and ecosystem services may we reach the goal of overall biodiversity conservation.”

Photo right: A living colony of cupuladriid bryzoans, tiny coral-like marine organisms. (Photo by Aaron O’Dea)

“The seven impediments in invertebrate conservation and how to overcome them,” appeared in the journal Biological Conservation, and is authored by Pedro Cardoso, Terry Erwin, Paulo Borges of the Azorean Biodiversity Group, Portugal, and Tim New of La Trobe University, Australia.