(Press-News.org) New research from New Zealand's University of Otago is providing the most comprehensive picture of the evolutionary history of baleen whales, which are not only the largest animals ever to live on earth, but also among the most unusual.
Most other mammals feed on plants or grab a single prey animal at a time, but baleen whales are famous for their gigantic mouths and their ability to gulp and filter an enormous volume of water and food.
In a paper appearing in the UK journal Royal Society Open Science, Otago Geology PhD graduate Dr Felix Marx and Professor Ewan Fordyce present a comprehensive family tree of living and extinct baleen whales stretching back nearly 40 million years.
The pair says that similar family trees have been constructed before, but theirs is by far the largest and, crucially, the first to be directly calibrated using many dated fossils.
The research shows which whales are related and exactly how long ago every branch of the tree--whether extinct or still alive--first arose.
This new family tree allows the researchers to estimate: (1) how many species of baleen whale have existed, (2) similarities and differences between different lineages in terms of overall body shape, and (3) how fast baleen whales evolved at any chosen time over the last 40 million years.
"We find that the earliest baleen whales underwent an adaptive radiation, or sudden 'evolutionary burst', similar to that of 'Darwin's finches' on the Galapagos Islands," says Professor Fordyce.
Dr Marx adds that this early phase of whale evolution coincided with a period of global cooling. At the same time, the Southern Ocean opened, and gave rise to a strong, circum-Antarctic current that today provides many of the nutrients sustaining the modern global ocean.
The researchers found that during their early history, whales branched out into many different lineages, each with a unique body shape and feeding strategy.
"Rather surprisingly, many of these early whales were quite unlike their modern descendants: Although some had baleen, others had well-developed teeth and actively hunted for much bigger prey than is taken by modern species," says Professor Fordyce.
Yet, after a few million years of co-existence, the toothed 'baleen' whales disappeared, leaving behind only their filter-feeding cousins, he says.
That extinction occurred between 30 and 23 million years ago and was about the time that the circum-Antarctic current reached its full strength, providing more nutrients that made filter feeding a more viable option.
The researchers say that the toothed 'baleen' whales disappeared perhaps because of increasing competition from other newly evolved toothed marine mammals, such as dolphins and seals.
They found that filter-feeding whales remained successful and diverse until about 3 million years ago, when the number of lineages suddenly crashed.
"This decline was driven mainly by the disappearance of small species of baleen whale, which left behind only the giants--ranging from 6 to as much as 30 metres--that plough the ocean today," says Dr Marx.
He says the disappearance of small whales likely resulted from the onset of the ice ages, which altered the distribution of available food, caused shallow water habitats to shift or sometimes disappear, and created a need for long-distance migration between polar feeding grounds and equatorial breeding grounds.
"This behaviour--long distance-migration--is still one of the hallmarks of all baleen whales alive today," notes Professor Fordyce.
INFORMATION:
New York, NY--April 15, 2015--A research team led by Shree K. Nayar, T.C. Chang Professor of Computer Science at Columbia Engineering, has invented a prototype video camera that is the first to be fully self-powered--it can produce an image each second, indefinitely, of a well-lit indoor scene. They designed a pixel that can not only measure incident light but also convert the incident light into electric power. The team is presenting its work at the International Conference on Computational Photography at Rice University in Houston, April 24 to 26.
"We are in the middle ...
UNIVERSITY OF CALIFORNIA, BERKELEY'S HAAS SCHOOL OF BUSINESS -CEOs make a lot of money from incentive pay tied to stock performance. Although such schemes help align executives' interests with shareholders, they are not necessarily the best schemes as compared to schemes that rely on trust between board and executives.
"Ironically, the necessary trust is easier to establish when the alternative of using stock-based pay is less powerful. Our research found that government-imposed limits on contingent compensation make stock-based pay a worse alternative, facilitating superior ...
Thermoluminescence is used extensively in archaeology and the earth sciences to date artefacts and rocks. When exposed to radiation quartz, a material found in nature, emits light proportional to the energy it absorbs. Replicating the very low dose of background radiation from natural sources present in quartz is a key precondition for precise and accurate dating results. Italian scientists have now developed a method to control the accuracy of the dose calibrations delivered to the samples during laboratory irradiation with heavy particles, replicating natural radiation ...
According to the World Health Organization, breast cancer is the most common cancer in women both in the developed and less developed world, and in the long term the scientists hope that the new method will lead to better prevention and early treatment of the disease.
"The method is better than mammography, which can only be used when the disease has already occurred. It is not perfect, but it is truly amazing that we can predict breast cancer years into the future," said Rasmus Bro, a professor of chemometrics in the Department of Food Science at University of Copenhagen. ...
Today it is not possible to predict spreading from malignant melanomas. Melanoma metastases are furthermore extremely difficult to eliminate as traditional treatment such as chemotherapy and radiotherapy is mostly ineffective. Only ten per cent of the patients survive once they reach an advanced stage with distant metastases.
New research now demonstrates that the presence of the protein megalin in a malignant melanoma is an indicator of cancer cells that are particularly aggressive. The protein improves the ability of the cancer cells to divide and to survive. Accordingly, ...
COLLEGE STATION, TX - The bedding plants sold in retail outlets are typically grown in greenhouse production environments where professionals can monitor irrigation, light, and temperature. When the greenhouse-grown plants reach the retail market, however, they are often subjected to a range of less-than-ideal light levels, temperatures, and irrigation schedules that can be detrimental to plant quality and vigor. Researchers are looking for ways to increase bedding plants' shelf life to offset the negative impacts of postharvest handling.
A new research study of the popular ...
Light must travel in a straight line and at a constant speed, or so the laws of nature suggest. Now, researchers at the University of the Witwatersrand in Johannesburg have demonstrated that laser light traveling along a helical path through space, can accelerate and decelerate as it spins into the distance.
This is the first time that angular acceleration has been observed with light, and is therefore likely to lead to new applications using these structured light fields.
The results are contained in a research paper by Professor Andrew Forbes from the Wits School of ...
E-cigarettes are not without health risks for people who vape or for bystanders. This is one of the conclusions from a new risk assessment report from the Norwegian Institute of Public Health (NIPH).
The report has only considered e-cigarettes with nicotine since there has been very little research about e-cigarettes without nicotine.
In summary
Since e-cigarettes supply nicotine in the same quantities as cigarette smoking, the same harmful effects from nicotine can be expected.
The vapour from e-cigarettes contains so much nicotine that bystanders can ingest ...
Health surveys may underestimate the number of poisonings in the United States by 60 percent to 90 percent, according to a report in the journal Clinical Toxicology by University of Illinois at Chicago researchers.
As of 2009, poisonings became the leading cause of fatal injury in the U.S., surpassing transportation-related deaths and gun-related deaths.
The researchers analyzed hospital billing records, patient demographics, exposure information, and outcomes for Illinois hospital visits related to poisonings in 2010. They also looked at poisoning incidence data from ...
AMES, Iowa - It was a discovery that changed what researchers knew about the hunting techniques of chimpanzees. In 2007, Jill Pruetz first reported savanna chimps at her research site in Fongoli, Senegal, were using tools to hunt prey. That alone was significant, but what also stood out to Pruetz was the fact that female chimps were the ones predominantly hunting with tools.
It was a point some dismissed or criticized because of the small sample size, but the finding motivated the Iowa State University anthropology professor to learn more. In the years following, Pruetz ...
