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Like many insects, beetles can walk upside down without falling due to the extremely sticky structures of their foot pads. Scientists James Bullock and Walter Federle from the University of Cambridge recently published a study in the journal Naturwissenschaften (The Nature of Science) that found different hair structures have different levels of stickiness. Their study is the first to measure the adhesive strength of a single seta, the adhesive hairs that are responsible for the “stickiness” of the beetle’s feet.
The researchers found there were three different structures of setae on the foot pads: pointed, flat (spatula-tipped) and disk-like. The three structures have different functions depending on the specific pattern they are arranged in. Each of these structures is made up of thousands of microscopic hairs and prior to this study there was no way to determine the adhesiveness of one individual hair due simply to their microscopic size.
By using an extremely fine glass cantilever and measuring the deflection of the cantilever with a microscope, the exact force needed to detach each hair was calculated. By use of this novel technique the researchers were able to calculate the exact stickiness of each hair, which are only 5 micrometers across.
Of the three different seta structures the disk like hairs had the greatest level of stickiness, followed by the spatula shaped hairs, with the pointed hairs coming in least sticky. The most sticky hairs were also the most stiff, most likely providing stability to the foot-pad. The researchers hypothesize it is these disk-like hairs that are particularly responsible for the strong adhesion the beetles have to smooth surfaces, such as the underside of a leaf.
This adhesion is also important during mating so that males can attach themselves to a female’s back. The other hair structures which aren’t as sticky are probably used for adhesion while running because they are quicker and easier to unstick.
This new understanding of the beetle’s sticky feet may one day lead to the creation of bio-inspired synthetic adhesives, such as extra sticky super glue.
Researchers from Sussex University have found that there may be some truth to the old saying “listen to your elders”, or at least in elephants there is. When comparing the leadership skills of matriarch elephants it seems that wisdom really does come with age.
In simulated crises, matriarchs over the age of 60 tended to assess threats more accurately than their younger counterparts. Researchers led by Karen McComb played recordings of various lion roars to 39 wild elephant families in Ambseli National Park in Kenya and judged how defensive they became after hearing the threatening lion calls.
Both the young and old matriarch elephants reacted more defensively to the calls of three lions than to the call of only one lion, showing that they could both accurately make threat assessments based on quantity. However, only the older matriarchs reacted more defensively to the calls of male lions than those of female lions. This strong reaction to male lions is an important awareness that can only be gained from experience. Although male lions do not often attach elephants, when they do the results can be devastating. It only takes a single male lion to bring down an elephant calf.
You can watch a video here to see the defensive behaviour of the elephants after a lion call is sounded.
In the wild elephant herds can remain together for decades, so having a matriarch that can provide leadership as well safety is invaluable.
There seems to be a trade-off between old and young matriarchs. With a young matriarch the herd gains the strength and fitness of a young leader who can defend the group, but an older matriarch offers experience and wisdom to accurately assess danger to the herd. Given the choice wild elephants value experience over youth.
The original article can be found here.
What is powerful enough to spark a decade long health care crisis, create epidemics of fear and guilt, bring about the resurrection of a nearly eradicated deadly disease and globally motivate parents to boycott vaccinating their children?
The answer: the power of the press.
Last month the aftermath of a huge scandal in medicine finally came to a conclusion when the British Medical Journal published two articles (here and here) in response to the scandal surrounding the measles, mumps and rubella (MMR) vaccine.
The scientific article responsible for the onset of all the panic was written by Dr Andrew Wakefield in 1998 and focused on a group of 12 anonymous participants that reportedly presented with autism after receiving the MMR vaccine. The article was backed by a press conference and a video-news release to support the findings that the MMR vaccine was linked with causing childhood autism. The press storm that followed attacked the MMR vaccine and warned parents to keep their children away. This led to a collapse of public confidence in the vaccine that prior to the article had been given almost universally to children, and had almost eradicated measles and mumps.
In the UK and the US vaccine rates decreased below those needed to keep measles and mumps at bay and children began to present with cases of measles. In the US a ferocious anti-vaccine movement gained ground after Wakefield appeared on the CBS program 60 Minutes in November 2000. All vaccines became suspect in the public eye, either due to their content or the increased rate at which they were being given to children. Despite the results of Wakefield’s original study never being replicated, the public was for the most part convinced by the media that the MMR vaccine led to autism.
While most journalists were interviewing scared and irate parents over the vaccine, Brian Deer in the UK set out the investigate Wakefield and his results. In doing so Deer unearthed one of the largest scandals the medical community has seen in decades. You can read an account of all the details here, but the bottom line is that the public vaccine crisis had zero scientific basis and Wakefield was motivated not by scientific inquiry but a corrupt payroll.
In 2010 Wakefield was discredited and his medical license was removed, however public opinion is still clouded about the MMR vaccine and autism link. It just goes to show how powerful the press can be in lending tinder to the fire of public outcry and how carefully the public should scrutinize what is presented to them in the media without apparent evidence or fact.
As we continue to release anthropogenic carbon into our atmosphere the earth warms. The ocean however is actually fighting to combat these changes by absorbing some of the heat. This sounds like an answer to our problems, but there is a catch: the oceans are becoming more acidic. As carbon dioxide concentrations increase in the seawater, the carbonate concentrations decrease. Carbonate is a key building block of the shells of many aquatic organisms and the decreased concentration is having negative effects.
An in depth case study was done on one Arctic mollusc, Limacina helicina, to test the effects of increasingly acidic waters. The full research paper can be found here, or you can check out the news article for a condensed version here. These “sea butterflies” or pteropods, were kept in a controlled environment for 5 days to see how well their shells grew under different pH values. A pH value of 8.09 (which was recorded in the Arctic in 1900) and a pH value of7.78 (the projected value for 2100) were used. The results were a startling 28% decrease in linear shell growth for those kept at the acidic pH compared to those kept in the normal ocean pH.
So what does this mean with respect to ocean ecosystems? Decreased shell growth may not seem immediately fatal to thepteropods an associated ecosystems but the associated decrease in shell density has some larger effects.
In the Arctic pteropods form the base of the food chain and are eaten by many larger organisms. As the oceans become more acidic the pteropods can’t grow or mature as quickly. They also can’t swim away as quickly from their prey and are eaten more often. With a diminishing population of pteropods, organisms that rely on them for food will also be at risk.
Pteropods also play an important role in the geochemical cycle, namely transferring carbon to the deep. However, with decreased shell density pteropods do not sink as well and so they are not transferring carbon. Without carbon cycling in the ocean the effects of global warming would be much worse.
These results are not specific to just pteropods; similar studies have been done on other shellfish and corals which found similar results. Ocean acidification is causing global effects and the scariest part is that most of them are still unknown. At this point we can only predict how acidic the ocean will get due to global warming and how strongly shellfish and their respective ecosystems will be affected.