Mixing Coca Cola and Milk: What Happens?

A reflection on simple chemistry

Here is a fun experiment you can do at home. Take a bottle of Coca Cola and add some milk. Wait for a while and you will get a strange mixture in the bottle. The bottom is covered by a snot-like substance, while the remaining liquid becomes transparent. What is happening here?

Because I have a (short) history as a chemistry teacher, I wanted to find out what reaction is taking place. And it turns out to be quite simple. The phosphoric acid in the Coca Cola reacts with a protein in milk called casein. The phosphoric acid molecules attach to the protein and become more dense. That is why they sink to the bottom and form a snot-like substance. You can trigger the same reaction if you mix milk with other acidic liquids, such as vinegar or lemon juice.

Mannelijke onderzoekers bezorgen muizen stress

I also write articles for the Dutch popular science website scientias.nl. Today I send in an article based on a paper that appeared today in Nature Methods. Unfortunately, the editor of the site (a sweet lady named Caroline) already wrote a piece on it. Since I put some work (not too much though) in it, I will publish it here. It is, however, in Dutch, but I guess most visitors of this blog are Belgian or Dutch.

Mannelijke onderzoekers veroorzaken stress bij knaagdieren

Ratten en muizen vertonen verhoogde stress wanneer zij gehanteerd worden door mannen in vergelijking met vrouwen. Dit kan mogelijk onderzoeksresultaten beïnvloeden.

Knaagdieren voelen minder pijn als zij door mannelijke onderzoekers gehanteerd worden in vergelijking met vrouwelijke onderzoekers. Een team rond Jeffrey Mogil (McGill University) kwam tot deze verrassende conclusie tijdens experimenten naar pijn bij knaagdieren. Muizen en ratten kregen een injectie in de enkel, waarna het ervaren pijnniveau aan de hand van de gezichtsexpressie van de muis (zogenaamde mouse grimace scale) bepaald werd. De resultaten lieten zien dat de pijnrespons 40% minder was wanneer er een man in de kamer was in vergelijking met een vrouw. Het experiment werd uitgebreid en het bleek dat hetzelfde effect opgewekt werd door een T-shirt dat gedragen de vorige nacht door een man werd. Ook de geur van mannelijke oksels resulteerde in een daling in pijnrespons.

Stress

De auteurs ontdekten dat de mannelijke stimuli geen directe invloed uitoefenden op de pijnrespons van de muizen en ratten. De dieren hadden verhoogde concentraties van het stresshormoon corticosterone in hun bloed. Dit duidt aan dat stress de pijnrespons tijdelijk onderdrukte. Niet enkel mensen veroorzaakten dit effect, ook de aanwezigheid van mannelijke dieren, zoals hamsters, ratten, katten en honden zorgde voor een toename in stress. Mogil geeft aan dat alle experimenten erop wijzen dat blootstelling aan mannelijke stimuli stress veroorzaakt bij muizen. Daarenboven blijkt deze vorm van stress veel sterker in vergelijking met andere vormen.

Gevolgen

Deze ontdekking is niet zo maar een curiositeit, aangezien deze stressrespons een belangrijke invloed kan hebben op resultaten van andere studies. Een analyse van een oudere studie (pijn veroorzaakt door heet water) toonde aan dat muizen die getest werden door mannelijke onderzoekers een lagere gevoeligheid voor pijn vertoonden. Hoe moeten onderzoekers nu omgaan met deze onverwachte factor? “Eén optie”, grapt Mogil, is alle mannen ontslaan, of zorgen dat er altijd een vrouw aanwezig is.” Een andere mogelijkheid is het melden van het geslacht van de onderzoeker in publicaties. Op die manier kan deze factor in de statistische analyses opgenomen worden.

Bronmateriaal

Sorge, R. E. et al. Nature Meth. http://dx.doi.org/10.1038/nmeth.2935 (2014).

Species Spotlight: Forest Robin

Time to put another bird in the Species Spotlight. 

An African species popped up: Forest Robin (Stiphrornis erythrothorax). This small passerine is the only species in the genus Stiphrornis. Its taxonomic position is not entirely clear, but generally you can find it in the Muscicapidae, the family comprising Chats and Old World Flycatchers. Most taxonomists consider it a single species, but some recommend to split it into five species (now subspecies). 

Do Lobsters Feel Pain?

A reflection on pain reception of invertebrates

Big riot in Belgium today. The television station VIER showed how chef Piet Huysentruyt threw a live lobster on the grill after slicing it in half and tearing its limbs off. Here is the clip in Dutch (well, West-Vlaams...).

This raises a question that biologists have been looking at for years: Do lobsters feel pain? There does not seem to be a consensus on this issue at the moment. A quick literature search shows that opinions vary.

Robert Elwood, Stuart Barr and Lynsey Patterson (Queens University, Northern Ireland) reviewed studies specifically aimed at welfare concerns in invertebrates and concluded "some animals show a cognitive ability that is comparable with that of some vertebrates". Hence, some invertebrates might feel pain. In another review, however, Lauritz Somme (University of Oslo, Norway) states that "most invertebrates probably are unable to feel pain".

The difficulty in assessing whether invertebrates (including lobsters) feel pain boils down (pun intended) to the issue whether they also experience the pain, mostly called suffering. The problem is that suffering is a private and emotional experience. It is not possible to quantify such a (possible) emotional state. One cannot simply ask a lobster if the water if too hot.

A completely different question is if this should be shown on television. Honestly, I see no real problem. If one can look at documentaries where lions kill a little zebra, one should be able to watch a lobster being cooked... But that is just my opinion.

Species Spotlight: Hoopoe Starling

A nice coincidence for this Species Spotlight. My previous post was about a giant extinct swan, and now another extinct species was randomly chosen. 

Introducing the Hoopoe Starling (Fregilupus varius)! It was discovered in 1699 and first described by the Dutch naturalist Pieter Boddaert in 1783. This 30-cm long bird was endemic to the Island of Réunion. It could be found in swamp forests and montainous coastal regions.

Illustration of the Hoopoe Starling based on a specimen from Paris

The Hoopoe Starling became extinct in the 1830s (the last specimen was shot in 1837) because of a combination of factors: the introduction of rats on the island , the introduction of another bird species (Common Myna) to combat locusts, and hunting. Apparantly it was very tasty because it fed on coffee berries. 

An Extinct Giant Swan

A reflection on islands animals

Islands can do strange things to animals: large ones shrink (insular dwarfism) while little ones suddenly grow (insular gigantism). There are numerous examples of both phenomena, but I came across a case that interests me more because it relates to my study subject: waterfowl. 

On Sicily and Malta there lived a giant swan, known as Cygnus falconeri, with a total length (bill to tail) of more than two meters and a wing span over three meters. The nice thing is that is lived next to dwarf elephants. Imagine that, a giant swan accompanied by a dwarf elephant. How things have changed...

How One Man Changed Our Atmosphere

A reflection on the atmospheric legacy of Thomas Midley

Before photosynthesis evolved, our atmosphere was oxygen-free. When photosynthetic microorganisms started producing oxygen as a  waste product, it was first removed from the atmosphere by reduced minerals, mostly iron. This led to the deposition of banded iron formations. Later, the Great Oxygenation Event (about 2.3 billion years ago) added oxygen to the Earth's atmosphere. This series of events shows how a group of organisms dramatically changed the composition of the atmosphere. Quite impressive, right? Not if you compare it to the work of an American chemist...

Banded Iron Formation

Thomas Midley Jr. was born in Beaver Falls, Pennsylvania on the 18th of May 1889. He produced two products that have greatly altered the atmosphere. In 1923, he discovered that the addition of Tetraethyllead (TEL) prevents the "knocking" of internal combustion engines. The addition of TEL to gasoline has led to the release of large quantities of lead into the atmosphere with detrimental effects on human health. He also developed the first chlorofluorocarbons (CFCs). Three decades after his death, it became clear that CFCs deplete atmospheric ozone, leading to the well-known hole in the ozone-layer. All in all, this one man is (indirectly) responsible for increased lead concentrations in the atmosphere and the hole in the ozone-layer. Now that is impressive!

Thomas Midley Jr.

In addition, his death in 1944 is equally dramatic. Having contracted polio, he devised a system of strings and pulleys to help others lift him from the bed. Unfortunately, he became entangled in the ropes and died of strangulation.

Species Spotlight: Western Quail-thrush

Introducing a new concept! And the first species in the spotlight.

Many blogs have a daily or weekly subject. For instance, Jerry Coyne has daily dialogues with his cat Hili on his blog Why Evolution is True. As a bird watcher, I decided to add the Species Spotlight as a returning topic. Using the IOC birdlist, I randomly pick one species and briefly introduce it. Because the rich diversity of birds worldwide, this is a nice way to get to know some new species.

And the first species is ... (*drum rolls*) the Western Quail-thrush (Cinclosoma marginatum)!

This species belongs to the family Cinclosomatidae and is endemic to Australia. The habitat they occur in is stony, open acacia shrubland. Ford (1983) treats this species as a subspecies of the Chestnut-breasted Quail-thrush (C. castaneothorax), but its taxonomic position is still uncertain.

New Book by Menno Schilthuizen: Nature's Nether Regions

A new book by Menno Schilthuizen!

I promised myself not to promote anything on this blog, but today I recieved a mail from Menno Schilthuizen about his new book: "Nature's Nether Regions". And given the topic of the book and the fact that I look up to Menno as a science writer, I decided to advise you all to read (and possibly buy) the book. I plan on reading it myself in due time and maybe write a short review on the blog. I have read two other books by Menno, namely "Frogs, Flies and Dandelions" and "The Loom of Life: Unravelling Ecosystems". Two books I can also recommend. Here is the official press release:

The Cover of Nature's Nether Regions

In NATURE’S NETHER REGIONS: What the Sex Lives of Bugs, Birds, and Beasts Tell Us About Evolution, Biodiversity, and Ourselves, Menno Schilthuizen reports from the front lines of evolutionary biology, on a quest to make sense of the origins, workings and evolution of our and other species’ reproductive selves (Viking; On-sale: May 1, 2014; 978-0670785919; $28.95). In this extremely entertaining new book, Schilthuizen demonstrates that the more we learn about our animal brethren—and their underbellies—the more we understand the beauty of all life and the power of evolution to generate incredible diversity in size, shape and purpose.

What’s the easiest way to tell species apart? Check their genitals. No other organs are as diverse in the way they look and function. Animal species that look very similar on the outside are as different as night and day when one peeks between their legs. Researching private parts was long considered taboo, but scientists are now taking a serious interest in the questions of how and why genitals evolve so quickly. NATURE’S NETHER REGIONS tells the story of these intrepid researchers and the complex web of Darwinian struggle they have uncovered.

To illustrate this epic evolutionary battle, Menno describes penises that sing and have vibrators; female orgasms that sort sperm and flush out the rejects; spiders that masturbate into miniature webs; males with appendages that scoop left-behind semen from previous mates.  We learn why, when it comes to bizarre behaviors and outlandish appendages, humans are downright boring—but we fit in nonetheless.

Marrying the playful prose of a Mary Roach with the evolutionary know-how of a Jerry Coyne, Menno’s tour of the wide world of animal sex organs is a thrilling reminder of our unique place in the great diversity of life and the best way to understand the tortuous ways in which evolution works.