Lubricated earthquakes

It’s well known that tectonic plates can slip underneath another plate in subduction zones and that violent earthquakes occur when the plates stick and release. Research is revealing the frequency of potential earthquakes. If it weren’t for ‘lubricated’ sliding, British Columbia would have a major earthquake every fourteen months and Japan every six. I’m not sure whether the lubrication is from melting rock or from seawater or a bit of both.

 

A map of British Columbia's seacoast shows where earthquakes occur

Cascadia subduction zone

Neanderthals evolved greater intelligence independently

A rare find of Neanderthal fossils or subfossils shows that early Neanderthals were small-brained and developed larger brains independently of the line that led to us.

As best we can tell, humans and Neanderthals diverged from a common ancestor about 500,000 years ago, a species called Homo heidelbergenesis. Modern humans appeared in Africa some 300,000 years later, a time when Neanderthals were already romping around Europe and Asia.

These skulls are 430,000 years old. They have a small  braincase but in other respects have Neanderthal characteristics.

…the Neanderthal trait of an elongated and rounded brain case came later.

Invasive species old and new

The Winnipeg Free Press reports on six species that have moved out of their home grounds and become a nuisance in Canada or the U.S., doing ecological damage: the Asian carp, the American bullfrog, Burmese python, killer bees, zebra mussels, and purple loosestrife.

Mammograms: when and how often?

At what age should we start getting mammograms and how often should we get them? It’s necessary to balance the dangers of ionizing radiation against the benefits of detecting cancer early. Read “Mammography’s Limits are Becoming Clear.”

“Stars hung suspended” — robot camera finds ice-dwelling anemones

A robot camera in the Antarctic Ocean found something that no one was looking for: bloodless sea anemones anchored to the underside of the Ross Ice Shelf. The researchers, from the University of Nebraska, dropped their camera-robot through the 270-metre-thick ice to explore sea currents and test their machine. The team did not include any biologists but they preserved some of the tiny animals for later study. These are the first anemones found that live in or on ice: ANDRILL team discovers ice-loving sea anemones in Antarctica. They are only a couple of centimetres high.

“The white anemones have been named Edwardsiella andrillae, in honor of the ANDRILL program.” I guess we’ll have to look at PLoS One to discover why they were placed in Edwardsiella so quickly. (the anemones, not the bacteria): Edwardsiella andrillae, a New Species of Sea Anemone from Antarctic Ice.

The large-scale image of the discovery is stunning.

Ice-dwelling anemones

What is squalene, anyway?

The short answer is given here, in the organic molecule directory, alkenes page:

Squalene is found in shark liver oil, and is also a major component of the lipids on the surface of human skin. Although it is not obvious from the way the structure above is drawn, squalene is a precursor for the biosynthesis of cholesterol. Through a complex series of enzymatically controlled reactions, squalene is converted into an intermediate called lanosterol, which undergoes a number of subsequent reactions to become cholesterol.

Here is what the molecule looks like. Every angle or terminus has a carbon atom, with enough hydrogen atoms to fill the unused bonds up to carbon’s complement of four per atom. A double line indicates a double bond.

squalene_01

Placoderms evolved penetrative sex

Placoderms are an extinct class of armoured fishes containing several orders. Placoderm comes from Greek words for “plate” and “skin.” They are jawed fishes, but so ancient that they precede both sharks & rays and bony fishes: some elements of the skeleton are cartilaginous while others are bony and there are bony elements in their skin armour. Yes, bones and teeth are derived from skin tissue. They appeared in the fossil record about 420 Ma in the Early Silurian and by 400 Ma in the Devonian all major placoderm orders were present. (See “Australia: The Land Where Time Began: Placoderms“.}

402px-Dunkleosteus_terrelli_2 (From Wikipedia)

Before placoderms, all fertilization of eggs by sperm occurred outside the body, as females released eggs and males released sperm into the water. They might hover near each other, but if sperm found egg it was partly by chance. Female fishes release their eggs through a cloaca, an opening for both eggs and bodily wastes. As the fish that were closest had the most success, eventually males began to position themselves at the cloaca. One group of placoderms, the ptyctodontids, have these external claspers to hold the female, as do sharks. The pelvic fin perhaps developed a tube shape to funnel the male’s sperm into the female’s cloaca. Some modern fish mate in this way. What is known is that some placoderms gave birth to live young, which means that that at the very least, eggs were fertilized while still in the female. In short, these early fishes invented internal fertilization.

Two prehistoric fish swimming

Rhamphodopsis threiplandi, a placoderm with claspers (from Wikipedia)

There are two pathways after internal fertilization. One is ovivipary, where eggs are retained and hatch inside the mother, who then expels the young. Some sharks still do that. In fact, in some sharks the first young to hatch eat the other eggs to nourish themselves until birth. Females may develop areas of nourishing skin that the young can scrape off. The other main path is for the young & the female to cooperatively grow a placenta, which attaches to the her and extracts nourishment from her blood. (Placentas could  not have happened without a retrovirus inserting itself into the genome, but that’s another topic.)

At first, scientists thought that young placoderms inside larger fossils could have been evidence of predation; but at last a tiny fossil placoderm was found with a tiny umbilical cord, still attached to the mother.

In memoriam: Frederick Sanger

250px-Frederick_Sanger2Frederick Sanger, the only Briton to have won two Nobel prizes, has died. He worked in biochemistry, studying DNA and proteins. His first Nobel prize was awarded for being the first to sequence a protein, insulin. At the time, it required years of work to do so.  He found that it was made up of two peptide chains: all proteins are one or more peptide chains. He spent nearly ten years removing one amino acid at a time from the end of the protein and identifying it, then going on to the next.

Winning the prize enabled him to afford better facilities and gather bright students around him. His second prize was for an ingenious and efficient way of discovering the sequence of nucleotide bases in a molecule of DNA or RNA. The linking of base pairs gives the molecule its ladder structure. The Sanger method cuts the molecules at different places, sorts them by weight (and therefore length) and identifies the base on the end using fluorescent dyes of different colours. According to Wikipedia, he used the method sequence human mitochondrial DNA (16,569 base pairs) and bacteriophage λ (48,502 base pairs). His method was used to sequence the human genome and many others.

His work allowed us to understand the genetic basis of mutations and diseases and was important for the development of better vaccines. Frederick Sanger was also honoured with the Order of Merit for distinguished service in science as well as several other awards.

The Telegraph has quite a nice obituary: Frederick Sanger.

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