Sunday, March 22, 2009

Sex bias is entirely controlled by the females in Gouldian Finches

The birds, which have either red or black heads, prefer to mate with males with the same head colouring, as this signifies a better genetic match. A report in the journal Science says that the birds compensate for this by having more male chicks in their brood. Colourful Gouldian finches can judge if a mate is genetically compatible just by looking at its head.

This new study has found that, when the female finches mate with a male that has a different head colour, they select the sex of their offspring - giving their chicks a better chance of survival.
Two male Gouldian finches

In birds, the sex of an egg is already determined before it is fertilised by the male.
Sarah Pryke, a biologist from Macquarie University in Sydney, led this study. She found that when female finches mate with mismatched males, 70% of their chicks are male.

Dr Pryke's team disguised some of the male finches to show that this "sex bias" is entirely controlled by the females. They blackened the head feathers of red males, using a non-toxic dye, and paired them to both red and black females to allow them to breed.

The birds were fooled, and the team found that black females that mated with the "disguised" red males produced an equal ratio of male and female chicks. "This is the clearest and perhaps most extreme example of sex biasing that has been found," said Dr Pryke. "It's really black and white - or in this case black and red."

"It is pretty amazing to think that the female herself has so much control - subconsciously of course - over this basic physiology," said Dr Pryke.

The results were particularly striking because colour-matched matings, which result in much healthier broods, always produce roughly equal numbers of male and female chicks. "Females really don't want to mate with a male with a different head colour. But there simply aren't enough compatible males, so later in the mating season they seem to use this control to make the best of a bad situation."

From BBC News

Thursday, March 19, 2009

The Fish-Tetrapod Transition

With the vertebrate comparative anatomy lab quickly approaching in my Animal Diversity class, I was excited to fall upon a paper that appears well-tailored to the content of my own teaching schedule (for once! geesh). This is spankin' new, published March 17, 2009, from the journal Evolution: Education and Outreach.

This paper is paricularly interesting because it outlines both the history of tetrapod evolution and the history of human's perception of the animal transition from aquatic to terrestrial habitats. It highlights the helpful fossils unearthed that helps us trace this vertebrate history, such as Icthyostega spp., and those fossils, such as the Eryops cephalus, that hindered the pursuit. In the case of the latter organism (pictured below), despite its anatomy being characteristic of an early trasitional tetrapod, its ancestral origin was found to exist much later in tetrapod evolution.

This paper also describes the reason for the recent fame of the Tiktaalik transitional fossil, as it is known from several nearly complete specimens. Its excellent preservation and diagnostic transitional tetrapod features have made it an important tool for understanding the origin of the phylogenetic tree of Tetrapoda.

"In a nutshell, the 'fish–tetrapod transition' usually refers to the origin, from their fishy ancestors, of creatures with four legs bearing digits (fingers and toes), and with joints that permit the animals to walk on land. This event took place between about 385 and 360 million years ago toward the end of the period of time known as the Devonian. The Devonian is often referred to as the 'Age of Fishes,' as fish form the bulk of the vertebrate fossil record for this time."

This paper is a great read for eager young biologists like myself searching for readable scientific papers on phylogenetics and evolution. I recommend it!

The Fish–Tetrapod Transition: New Fossils and Interpretations

Monday, March 16, 2009

More Coleopterans Coitus

Seed Beetle 1.jpg

A new study has revealed the painfully scandalous anatomy of C. maculatus seed beetles. The C. maculatus have a series of spikes and barbs on their members that, during sex, become embedded in their mates, acting as anchors of sorts.

Seed beetle 3.jpg

"They literally injure females internally in their copulatory duct. They're pretty mean," Goran Arnqvist, the lead author of the study, said to National Geographic.

After looking at a large group of diverse, virgin beetles after copulation the study concluded that the beetles with the "largest and most damaging" phalluses had the most reproductive success. The injury to the females was simply an "unfortunate side effect" of the process.

At this point, I will use what little class I have to bite my tongue.

Seed beetle 2.jpg

Seed beetle 5.jpg
Above: a seed beetle's jaw-like spine structure on its appendage.

Tuesday, March 10, 2009

A Sea Biscuit's Life

I'm teaching about Echinoderms this week in Animal Diversity lab. They exhibit pentaradial symmetry as adults, but are actually born with bilateral symmetry. Put a beat to that concept, and you have a dance party (below).

A Sea Biscuit's Life from Bruno Vellutini on Vimeo.

Friday, March 6, 2009

Sand lizards find excuse for being lazy lovers

Sand lizards engage in what are called serial copulation events. A single female copulates with multiple males in a sequence: male one, male two, male three, etc. In response to selective pressure exerted by mating with more than one male, the first male will insert a copulatory plug to serve as a barrier so the next male's sperm does not fertilize his female. We see this elsewhere in Animalia - namely, in humans! (Think "flowback")

Scientists noticed something peculiar was resulting from the serial copulation events. Sand lizards yield a disproportionate number of offspring that are sired by the multiple partners with whom the female mates. We would expect that the first male sire the majority of offspring, but that was not the case. There appeared to be something going on with the sperm or reproductive tract, but what?

Mats Olsson of University of Wollongong observed the male lizards exerting variable amounts of effort when copulating with a female. The amount of effort was positively correlated with clutch size (Figure 1 and 2, above). He sought to find what determined the time investment.

He and his team studied the second male and his ejaculation tactics. The second male would approach a female and obtain information about the prior male's relationship to her. If his rival was more genetically similar to the female than the second male was to the female, the second male stands a better chance of passing on his genetic material. The male sand lizards are able to sense an MHC (major histocompatibility compex)- related odor of the copulatory plug. With this information, the second male could ascertain the relatedness of the first male and female, and would spend more time in copula with the female if the first male was more related to her than he was to her. (Figure 3, below)

If his nemesis was less related to the female than the second male, the second male would engage in an informal "quickie" and then move on.

Olsson, M., T. Madsen, B. Ujvari, and E. Wapstra. 2004. Fecundity and MHC affects ejaculation tactics and paternity bias in sand lizards. Evolution 58: 906-909.

Pepto-Bismol-Pink Dolphin in Louisiana

This is a peculiar find. (Thanks to Dr. Melissa Palmer for the tip)

Pink the albino dolphin: Pink dolphin appears in US lake

The pink color and reddish eyes indicate albinism, an inherited condition that results in individuals lacking normal pigmentation. This special aquatic mammal drew quite a crowd when it first surfaced in Lake Calcasieu, an inland saltwater estuary north of the Gulf of Mexico in Louisiana.

The dolphin was first identified by charter boat captain Erik Rue, who said it was swimming with a pod of four other dolphins. I hope this special critter makes it despite its strange coloration.

Is this first pink dolphin observed in nature?

Actually, there are pink dolphins that reside in South America in the Amazon. The boto is the largest of the river dolphins. They have different color patterns, varying from bright pink to deep grey, depending upon their age and the geographical area where they are found. In the Arauca River in Colombia, dolphins are very pink (pictured below) and very active at the surface. They tend to become more "pink" with age because their skin becomes more translucent and the blood circulating beneath their skin becomes visible. These Amazon River Botos are close relatives to the dolphins with which we are familiar from the states. However, there are a few significant morphological differences.

In addition to the higher frequency of pink coloration among populations, the Amazon River Botos have specialized teeth that are used to crush fish and heavily armored benthic organisms such as crustaceans. They also have a big hump on their head and a ridge on their back in place of a defined dorsal fin.

da Silva V (1994) Aspects of the biology of the Amazonian dolphins Genus Inia and Sotalia fluviatilis. PhD Dissertation, University of Cambridge, Cambridge, 327 pp.

Tuesday, March 3, 2009

Science Fare

A student introduced me to this fine tribute to science. Bad Astromony guy, you inspire!

In April, I was asked to give a short speech to a group of local students who participated in a science fair. I wasn’t sure what to say to them, until I saw a newscast the night before the fair. The story was some typically inaccurate fluff piece giving antiscience boneheads “equal time” with science, as if any ridiculous theory should have equal time against the truth.

I sat down with a pad of paper and a pencil and scribbled down this speech. I gave it almost exactly as I wrote it.

I know a place where the Sun never sets.

It’s a mountain, and it’s on the Moon. It sticks up so high that even as the Moon spins, it’s in perpetual daylight. Radiation from the Sun pours down on there day and night, 24 hours a day — well, the Moon’s day is actually about 4 weeks long, so the sunlight pours down there 708 hours a day.

I know a place where the Sun never shines. It’s at the bottom of the ocean. A crack in the crust there exudes nasty chemicals and heats the water to the boiling point. This would kill a human instantly, but there are creatures there, bacteria, that thrive. They eat the sulfur from the vent, and excrete sulfuric acid.

I know a place where the temperature is 15 million degrees, and the pressure would crush you to a microscopic dot. That place is the core of the Sun.

I know a place where the magnetic fields would rip you apart, atom by atom: the surface of a neutron star, a magnetar.

I know a place where life began billions of years ago. That place is here, the Earth.

I know these places because I’m a scientist.

Science is a way of finding things out. It’s a way of testing what’s real. It’s what Richard Feynman called "A way of not fooling ourselves."

No astrologer ever predicted the existence of Uranus, Neptune, or Pluto. No modern astrologer had a clue about Sedna, a ball of ice half the size of Pluto that orbits even farther out. No astrologer predicted the more than 150 planets now known to orbit other suns. But scientists did.

No psychic, despite their claims, has ever helped the police solve a crime. But forensic scientists have, all the time.

It wasn’t someone who practices homeopathy who found a cure for smallpox, or polio. Scientists did, medical scientists.

No creationist ever cracked the genetic code. Chemists did. Molecular
biologists did. They used physics. They used math. They used chemistry, biology, astronomy, engineering. They used science.

These are all the things you discovered doing your projects. All the things that brought you here today.

Computers? Cell phones? Rockets to Saturn, probes to the ocean floor, PSP, gamecubes, gameboys, X-boxes? All by scientists.

Those places I talked about before? You can get to know them too. You can experience the wonder of seeing them for the first time, the thrill of discovery, the incredible, visceral feeling of doing something no one has ever done before, seen things no one has seen before, know something no one else has ever known.

No crystal balls, no tarot cards, no horoscopes. Just you, your brain, and your ability to think.

Welcome to science. You’re gonna like it here.

Parasitizing caterpillar tricks ants into service

A kind of European caterpillar can garner royal treatment from ants by mimicking the ch-ch-ch-ch of their queen, says an international research team.

Ants of the species Myrmica schencki can be fooled into carrying certain caterpillars into the colony nurseries where the fakers enjoy full care and five-star dining, explains Jeremy Thomas of the University of Oxford in England. An interloper caterpillar gains most of its body mass while luxuriating in ant care, and then turns into a Maculinea rebeli butterfly.

Chemical camouflage alone will let the caterpillars game their way into the ant colony. Now experiments show that the noises the caterpillars make get them the premium treatment, Thomas says. The rhythmic caterpillar purring has the effect of the queen ant’s noises, not those of a worker, Thomas and his colleagues report in the Feb. 6 Science.

It’s news that a queen sounds different from workers in an ant colony, Thomas says. Ants have such remarkable chemical messaging systems that their noises haven’t received much scientific attention.

“I haven’t been this excited about a paper in a long time,” says tropical butterfly ecologist Phil DeVries of the University of New Orleans. He made the first recordings of caterpillar calls, which he says occur only in groups that have some kind of relationship with ants.

M. rebeli caterpillars make a mini version of the brrrrrr of a woodcock or snipe, Thomas says. Recent work has suggested that caterpillar noises may come from repeated muscle spasms. And when caterpillars become enclosed pupae, they make noises by rubbing a scraper, or plectrum, on their abdomen against a patch of fine grooves called a file. “Actually they can wriggle their abdomen quite a bit,” Thomas says.

Adults of four of the 11 ant subfamilies also make noises by rubbing plectrum and file, Thomas says. “It’s rather like strumming a guitar.” In a quiet room of ants, he can just manage to hear “quite a scratchy sound,” he says.

Advances in miniature electronics made the new study possible. Specially built ant-scale microphones and speakers allowed researchers to record both queen and worker ants under normal conditions and then play back the noises and observe ant behavior.

To a human ear, queens and caterpillars don’t sound at all similar, Thomas warns. Yet ants perceive noises differently, picking up vibrations with sensors in the legs. “There is a debate about how well, if at all, they perceive airborne sounds,” he says.