The rise of the 'Dino-Chickens'

The first Archaeopteryx fossil was unearthed from a limestone quarry in Bavaria, in the early 1860s. This relatively small (Raven size as an adult), feathered, broad winged dinosaur is believed to have glided like a bird through the forests of the Jurassic period 145 million years ago, leading many palaeontologists name it the ancestor of modern birds. Phylogenetic study is never so clean-cut however. Therefore it is unsurprising that other species similar to archaeopteryx; Aurornis xui, and the four winged Anchiornis huxleyi for example, are also contenders for the title of the first bird. But why are our winged dinosaur friends relevant? Well in May 2015 scientists were able to 'alter' chicken embryos to produce a dinosaur-like snout, which was an amazing breakthrough given the lack of clarity in the evolution of dinosaurs into birds; there is no single physical feature that defines this phylogenetic change. One important phenotypical transition evidenced by fossils was the alteration of the premaxilliae in the reptilian snout, growing longer and fusing together to form the beak structure present in birds today. The research team from Harvard then looked at gene expression domains in the face of multiple bird and reptile species; the earlier frontonasal ectodermal zone (FEZ) and the later midfacial WNT-responsive region (they sound incredibly intellectual but rather arbitrary at the same time). From this the researchers reasoned that reptile and dinosaur snouts develop from premaxillae in a similar way, and that the developmental pathways that form the snout were altered in the course of the evolution of Aves. 2 proteins; FGF and Wnt, were found to be essential in the differing developmental process of reptile and bird faces, due to differential gene expression and therefore differential translation of these proteins. The proteins worked differently also, as in reptiles they were active across 2 small regions of the embryo's 'face', whereas in birds they were expressed across a larger band, but in the same region as in reptiles. This may be evidence that evolutionary alteration of expression of these proteins contributed to beak formation. To test this theory and the mechanism of the snout to beak transformation, the autapomorphic median gene expression region found in birds (the area of the genome coding for the beak) was altered in developing chicken embryos. Biochemical inhibitors were added to the chicken eggs to block the 2 vital proteins, thus reverting the chicken's beak to its ancestral reptilian snout, with the premaxillae formed showing a resemblance to fossil specimens, rather than beaked birds. If you're like me though, the term 'biochemical inhibitors' is far too vague. So what do they do exactly? I believe they alter the epigenome of the chicken embryo, perhaps removing methyl groups from CpG regions of long silenced genes, or they may involve acylation of the tails of histones (perhaps using histone acetyltransferase enzymes) to alter transcription rates of genes (See my previous posts for more on epigenetics, it's my favourite thing ever). Back on the Dino-Chickens; let's not get overexcited about a potential Jurassic World situation happening where we reverse engineer dinosaurs and splice them all together into ridiculously improbable 'combosaurs'. The team from Harvard was only seeking the mechanism behind ancestral amniote snout transformation. But perhaps in the future... My army of squid, poison dart frog, chameleon ankylosaurs will become a reality!

Zombie Apocalypse anyone?

"Brains..." That is what most of us Western World dwellers think of when the topic of the undead is broached, however most of us are clueless as to the origin story of our beloved halloween staple; the Zombie. I would like to dispel this ignorance, but at the same time give a real world example of where zombification (It's a word now, deal with it) is an all too real occurrence, but also how it can even happen. Our story begins in Haiti, where rural folklore describes necromancers, who supposedly used magic to commune with or summon the dead, and had possibly the most epic job title ever. These Zombies would become mind-slaves of the necromancers (but they were not called Steve weirdly), and had no will of their own. The root of such folklore lies in Africa, and was likely exported to Haiti via slavery. The African slaves believed that Vodou deities would resurrect them and take them to the heavenly afterlife in their home continent. Western Zombies just seem uncultured and dull compared to the Haitian legends, you might say they pale in comparison... (I'm not entirely sure that made sense). That's enough history for today, let's get our biology on! The real world Zombie-esque paradigm we shall confront involves the sophisticated predator that is the Ladybird, and a wasp of a parasitic persuasion. Did you know Ladybirds use their antennae to detect chemicals that plants release when under attack by herbivorous insects like aphids (the Ladybird's main prey), and they can bleed poison from their legs to dissuade predators? The fact that they are so effective within their niche was why it came as a shock to me that they are vulnerable to zombification. The parasitic wasp in question, Dinocampus coccinellae, uses its stinger to inject an egg into the Ladybird's underside, along with a venom. Once the larva emerges, it feeds on the fluids that fill the Ladybug's thorax cavity. Externally, the insect is still behaving normally, eating aphids with its usual fervour, which in turn feeds the parasite growing within it. This is where it starts to get upsetting, so please if you have a weak heart or a particularly irrational attachment to the Ladybird, stop reading now. After 3 weeks of 'gestation', the larva squirms out through a weakness in the Ladybird's exoskeleton, and creates a silk cocoon for itself below its host. The Ladybird remains under the control of the parasite though, and so stays perfectly still during this process, apart from when the wasp larva's predators approach. The Ladybird acts as an insect shield for the D. Coccinellae by spasming its limbs to scare off Lacewing larvae for example. This continues for a week, until the adult wasp cuts itself free of the cocoon with newly formed mandibles and flies away, finally deigning its enslaved protector to die... But why did such mind controlling, zombie-making parasites even come to evolve? The answer, like just about everything on this blog, lies within the genome of the organisms. Genes use organisms as vehicles to increase their own replication success, and the phenotype created by the genes is vital in this process. The phenotype is not just limited to dictating the appearance of an organism. It can profoundly alter the organism's environment, as the phenotype extends to structures in the brain which produce specific behaviours. So if a gene is powerful enough to alter a physical environment, then could it manipulate another living creature? The fact that parasites can manipulate their hosts is because of transcription of genes and resultant translation into necessary proteins, and if a mutation changes the base structure of the genome, the way in which the parasite influences its host's behaviour will change, and those parasites that produce the most offspring have developed a mutation that changes the host's behaviour in a favourable way. For example the parasitic wasp genome that codes for venom molecules that cause the Ladybird to act as a bodyguard for the growing larva will be more successful, and so the genes which dictate this will be found in higher frequencies in offspring and therefore in the gene pool of the species as a whole. In this way the need for genes to preserve themselves and increase their chances of wider replication affects the behaviour of another organism... So there you have it; the genetics behind the development of such extra-ordinary mind controlling (zombifying) powers. It was never necromancy, just egomaniacal genes. Biology wins over popular culture and mythology once again! (In my head at least)