Here is a slowed-down high-speed video of the lunge behaviour of Drosophila males, used when they fight. The movement is too fast to observe at normal speed. The behaviour is described in [Hoyer et al. (2008)](http://www.cell.com /current-biology/fulltext/S0960-9822(07)02483-9?large_figure=true)
Very interesting. Many dinosaur 'species' could be actually individuals of the same species at different ages.
The basic assumption is that extreme differences in sculls appear late in life, as in birds, instead of modern reptiles.
While the talk seems to go on for a while, the delivery makes it interesting throughout.
These animations are very impressive. They show how the molecular machinery in each cell is thought to work.
They are brilliant because of their detail: you will probably see something new, with repeated viewings. They are also amazing because they are scientifically accurate and put in motion processes you may have only been reading about. So they are particularly revealing to a biologist.
Drosophila melanogaster males may fight over females.
Here is a video showing their 'boxing' behaviour.
I remember seeing high speed camera footage in a conference, it was even more exciting because they move too fast for the human eye to appreciate the full extent of the fight.
The image (from here) shows genetic diversity of Europeans summarised in two axes. It is obvious that genetic variation mirrors geography within Europe, but at the same time there is no obvious distinction between countries.
Another way to think about it is that the variation within a country is comparable to variation between countries.
Similarly, clusters of points (genetic groups) are visible from within countries. So the 'race' attribute provides no obvious information on genetic similarities or differences.
Nevertheless, long range patterns are obvious. That is why the overall groups are similar to the geographically defined countries of Europe.
The study is already 2 years old. I find the image to be a strong example of the power of modern molecular genetics.
The image is so information dense that every time I look at it, I find something new to think about. For example the position of Finland is further away than any other from a nordic country cluster. Or Switzerland has obvious subgroups related to language (panel b of the figure, viewable from the reference). Unfortunately the sample size was too small for the Southern countries and the Balkans (I think 4 for Greece and Turkey for example), so the clusters are not trustworthy.
A spider decided to commit suicide by jumping in a bowl of water and soap left overnight to soak in our sink. I think the soap reduces the surface tension so a small object that would float without soap, like a spider, sinks.
Not that the spider wanted to float, I guess. It was just stupid, bored or drunk, and was naturally selected not to contribute to the gene pool of the local population.
My wonderful housemates left it for me so that I can see it, because the suicide happened while I was away in Sheffield.
And here it is.
As with all small critters, they are much more cute when viewed from closeup. So I got curious and started researching spiders. Here are some random interesting facts:
The easy one is that they are not insects, but arthropods (which include insects). Insects have their body divided into three sections, as well as antennae and, usually, wings.
Spiders have 4, 6 or 8 eyes, depending on the species. Jumping spiders have very good eyesight (as expected): they are only millimetres long but can see in detail objects 20 cm away. Still, the most important sense to a spider is touch (actually vibrations). They can differentiate wind, prey or other spiders walking on their web by the vibrations each produces.
The leg muscles can only be used to contract the legs. Leg extension is achieved by fluid being pumped into them.
Spiders measure distance by counting footsteps, as ants do. We know about ants because researchers artificially made their legs longer by sticking paintbrush hairs on them, and they overshot their nest!
Web building is too complicated to describe. Richard Dawkins has 3/4 of a book chapter on it, and it was not enough. I will just mention that there are many types of silk (including sticky and non sticky, with the spider walking on the non sticky) and spider silk is stronger per unit weight than steel. Webs can be built across lengths that seem impossible because the spider relies on the wind to stick a piece of silk somewhere distant, and then it can cross to weave the remaining web.
The silk comes from a special organ, but some spiders, like tarantulas, have minimal silk on all their legs so they can attach themselves better on various surfaces.
The most obvious mouth detail are the fangs with which they bite their prey (all spiders are predators). The fangs inject venom which paralyses or kills the prey. Spiders cannot chew internally, usually they just drink the liquids of their prey. Most spiders are harmless to humans because their fangs are too weak to penetrate human skin. The highest concentration of deadly spiders is, as with most deadly stuff, in Australia. At least in the closest contact with a large population of humans.
Small mouth (only the fangs are shown), but overall a cute face, no?
Mating is usually the last action in male spider's life. The idea is that a male is smaller than a female, but still easily 10x larger than most prey, so the energy given away by a female letting a male survive is significant, and thus males often do not survive the process.
The front of any spider head has two leg-like structures, the pedipalps. They are used to handle prey, but in males they are also modified as sperm storage organs. Sperm is produced in the male abdomen and transferred to the female using the pedipalps. The female may bite these off, so a male uses one at a time during mating. If a male loses both, it effectively becomes sterile, so it may as well sacrifice by being eaten, to provide resources for its offspring with the particular female.
For the end I left the best. Spider courtship can be very elaborate, as you can see from these peacock spiders, and one of the many videos you can find online on spider courtship. Turn the sound on!
