Sue is something of a celebrity among dinosaurs, being the best-preserved T. rex fossil ever found. But in truth, the gender of dinosaurs is rarely, if ever, known. A study in 2005 first laid claim to a new way to sex dinosaurs using a distinctive bone formation. Now paleontologists in China have found that ancient birds also had this structure, confirming that birds and dinos shared similar gender divisions and reproductive habits.
Researchers excavated the 125-million-year old birds’ feathers, organs and bones from petrified lake-bottom mud in northeastern China. These birds, called Confuciusornis sanctus, were buried by the hundreds following catastrophic volcanic eruptions in the Mesozoic era.
What’s the News: In the squid world, the body size of male spear squid determines the mating strategies they use. Small male squid, which have no chance of physically competing with their larger rivals, must try to get with the females of the species on the sly. Now, researchers in Tokyo have learned that this difference in mating behavior has resulted in the evolution of divergent sperm types, though perhaps not in the way you’d think: diminutive male squid actually produce larger sperm than big male squid.
Could Neanderthal DNA have protected our ancestors from diseases?
What’s the News: While we humans have certainly outlasted our hominin cousins, new research shows that Neanderthal and Denisovan genes may have helped us spread far and wide. By mating with the two species, our ancestors acquired genes that allowed them to adapt to diseases outside of Africa far quicker than would have been otherwise possible, according to Peter Parham, a professor of microbiology and immunology at Stanford University.
As more hospitals have begun using DNA testing to analyze babies with birth defects, doctors have occasionally discovered that a family’s little bundle of joy is also a product of incest. Since this is a new dilemma brought on by the spread of technology, doctors are now debating how to handle these incest surprises.
Geneticist Arthur Beaudet at Baylor College of Medicine addressed the issue yesterday in an article in the medical journal The Lancet. The genetic test, the single nucleotide polymorphism-based array, helps doctors identify missing genes (and can therefore help explain a child’s birth defect or disability)–but it also identifies swaths of identical DNA that a child may have inherited from two closely related parents.
In the few months that Baylor has been performing these detailed genetic tests, there have been fewer than 10 cases of consanguinity — the phenomenon of inheriting the same gene variations from two closely related people, said Dr. Arthur L. Beaudet, chairman of Baylor’s department of molecular and human genetics. However, wider use of such testing in children with disabilities is expected to identify additional cases of incestuous parentage. [ABC News]
Talk about early intervention. One day, a fetus with a genetic disease may be able to get treatment before it even leaves the womb–and that treatment will come in the form of an extra gift from mom. While this scenario will only come to pass if new mouse research can be translated to humans, the finding are exciting.
The new work solves a medical mystery. When researchers realized they could diagnose a fetus with certain genetic illnesses as early as the first trimester, they plunged into the search for in utero treatments. Ailments like sickle cell anemia and some immune disorders might be treatable with blood stem cells taken from a donor’s bone marrow, researchers thought: the transplanted cells would multiply and populate the fetus’s bone marrow with healthy blood-forming cells, and the fetus’s immature immune system wouldn’t reject the foreign entities. But when researchers tried such transplants, they didn’t work.
“The fact that fetal stem cell transplantation has not been very successful has been puzzling, especially given the widely accepted dogma that the immature fetal immune system can adapt to tolerate foreign substances,” said co-senior author Qizhi Tang…. “The surprising finding in our study is that the mother’s immune system is to blame.” [press release]
Up in the sky, under the sea, deep inside an animal society—researchers can’t go these places themselves, so they attach tracking devices to wildlife in order to gather the data. But are these gizmos invisible to the creatures themselves, and can they go about their lives the same way they would if they didn’t have a tracker stuck on their fin or wing? Or do some of these electronic devices interfere with the animals’ ways of life, and therefore send back bad data to the scientists?
This week there’s a new entry into this long-running debate, regarding one of the most-tracked animals in the world: the king penguin of Antarctica. A study published in Nature that tracked 100 penguins found that those wearing flipper bands lived different lives than those without, and less successful ones to boot.
In terms of survival, banded penguins had a 16 44 percent lower rate [survival rate dropped from .36 to .20, a drop of 16 percentage points, or 44 percent] over the entire 10 years, but there is a breakpoint at 4.5 years. In the first 4.5 years, banded penguins actually had a 30 percent higher mortality rate. After that, the difference in mortality between banded and unbanded birds levels off. The authors propose that flipper-banding acts as an artificial selector for the strongest penguins, creating a bias in data collected from banded birds. Over the decade, banded birds were less successful in breeding. Banded penguins produced a total of 47 chicks, while unbanded penguins had 80 chicks. [Ars Technica]
This study presents a practical problem: Studying the effects of clipped-on tracking tags means your control group must be free of them, but you have to track the group without the flipper bands somehow. So Yvon Le Maho’s team implanted small, newer-style tags that lie under the skin on all the penguins in their study. That way they could give half of the birds a dummy tracking tag clipped on the fin to see if the equipment itself changes their behavior.
To everything there is a season. Even the sexual proclivities of butterflies.
Yale researchers have found that male butterflies do not always take the lead in courting females at mating times. In some instances it’s the females that open the negotiations, and, curiously, the deciding factor seems to be the conditions in which they grew up as larvae—whether it was the dry, cool season, or the wet and warm season.
When certain caterpillars are raised in warm, moist conditions they grow into what some would consider traditional roles — males pursuing demure females. But new research has found that when they are raised in dry, cool conditions, it’s the ladies that become aggressive adults, actively courting the guys. [AP]
Among squinting bush brown butterflies, the species tracked in this study, both male and female sport what look like eye spots on their wings. The white spots in the center (the pupil of the eye) reflect light in the ultraviolet range, which appears to be the key to the butterflies‘ mating behavior.
“Cool temperatures increase the UV reflectance of female sexual ornaments, warmer temperatures increase the UV reflectance of male sexual ornaments. These changes are not visible to humans because we do not see UV,” explains postdoctoral fellow Dr Kathleen Prudic. However butterflies can see UV, so by developing more attention-grabbing eye spots, females born in the dry season are able to attract males. [BBC News]
This week in bizarre new forms of mammal reproduction: mice who have genetic material from two fathers but nary a mother, the next step in a progression of scientific efforts to get more creative with sex and reproduction.
“It has been a weird project, but we wanted to see if it could be done” in mice, says Richard Behringer, lead author of the study and a developmental geneticist at M.D. Anderson in Houston. [Wall Street Journal]
Weird, and also complex: The process requires several generations and some creative genetic trickery. To make it happen, Behringer’s team started with a single male mouse. Let’s call him Fred. Scientists took cells from Fred and transformed them into a line of induced pluripotent stem cells, which can grow into any kind of cell in the body. Normally, of course, a male’s sex chromosomes are X and Y. But when the researchers created these stem cells, some of them—about 1 percent—lost the Y chromosome through ordinary mistakes that happen in cell division.
Thus, the scientists had a batch of Fred-derived stem cells that had no Y, and thus were labeled XO cells. The next step was to take ordinary mice blastocysts—early stage embryos that had been conceived in the traditional fashion—and inject the XO cells into them. When this XO-injected embryo was implanted into a normal female mouse, she gave birth to offspring called chimera—what we call animals with two or more genetically distinct populations of cells. In this case the mouse possessed, in addition to the normal cells from its mother and father, some XO cells derived from Fred.
It’s no surprise that a chemical as potent as methylmercury harms wildlife when it enters an ecosystem in high concentration. In the case of wetland birds, researchers have found, it can even change sexual orientation, causing males to pair off with other males.
“We knew mercury could depress their testosterone (male sex hormone) levels,” explained Dr Peter Frederick from the University of Florida, who led the study. “But we didn’t expect this.” [BBC News]
Frederick and Nilmini Jayasena examined white ibises from South Florida for their study in the Proceedings of the Royal Society B. They gathered 160 of the birds and broke them up into four groups that ate food laced with different concentrations of methylmercury. Some ate 0.3 parts per million of mercury, some 0.1, some 0.05, and some none at all.
Birds exposed to any mercury displayed courtship behaviour less often than controls and were also less likely to be approached by females when they did. As the level of mercury exposure increased, so did the degree and persistence of homosexual pairing. Males that engaged in homosexual parings were also less likely to switch partners from year to year, which Frederick says ibises tend to do if they have been unsuccessful in mating during their first breeding season. [Nature]