MV Blog

DISPLAYING POSTS FROM: Jan 2012 (22)

Maximum rate of mammal evolution

Author
by Kate C
Publish date
30 January 2012
Comments
Comments (2)

"How fast can a mammal evolve from the size of a mouse to the size of an elephant?" This question introduces a new paper published today by a group of international researchers led by Alistair Evans of Monash University, including Dr Erich Fitzgerald, Senior Curator of Vertebrate Palaeontology at MV.

The world's largest mammal by weight, the Blue Whale, is about 61 million times heavier than the world's smallest, the Etruscan Shrew. Erich and his colleagues are interested in how such a range of body sizes evolved within the mammals, particularly the rate at which such evolution occurs.

Previous investigators have calculated rates of evolution using narrowly-defined parameters, whether within a shorter time scale or within a limited taxonomic group. This study is the first to tackle the larger picture, using data from a variety of species that lived over the last 70 million years.

The researchers found that it takes a minimum of 1.6 million generations for terrestrial mammals to increase their mass 100-fold. To increase by 5,000-fold, it takes at least 10 million generations.

In contrast, the researchers found that land mammals can decrease in size more than ten times faster than the time it takes to increase to the same degree. Hypothetically, it could take 5 million generations for a species to evolve from rabbit size to elephant size, whereas in just half a million generations it could shrink back down again if selective pressures directed it thus. Smaller body mass gives a competitive advantage under certain conditions; this phenomenon, known as insular dwarfism, is seen in the now-extinct dwarf elephants that were stranded on Mediterranean islands by rising sea levels.

Elephant and rabbit Left: Children riding on Queenie, an Indian Elephant, at Melbourne Zoo in 1917 (MM 004061). Right: Rabbit, Oryctolagus cuniculus.
Image: Unknown | Alex J.
Source: Museum Victoria | Used under CC BY 2.0 from a_jo.
 

Interestingly, aquatic mammals such as whales evolved large body mass much faster than land mammals, taking about half as many generations to achieve the same scale of increase.

Says Erich, "Whales can get bigger because the water supports their bodies and so their maximum size is not limited by gravity." He explains that a huge body can also be an advantage for aquatic mammals because it loses less heat.

"There doesn't seem to be any slowing-down in evolution of maximum body size in whales. Land mammals may have reached a plateau enforced by gravity, but it's conceivable that the Blue Whale is not the largest possible whale. Nevertheless, energetic demands of feeding a body larger than that of a blue whale may mean that, in reality, the blue whale is as large as animals get."

Large land-dwelling mammals have a variety of solutions to the problem of gravity, explains Erich. "Some of the changes we see are extreme thickening of bones, changes in locomotion and major changes to organ systems." A gigantic rabbit wouldn't just be a large version of today's feral bunny; in fact, it would probably be unrecognisable as a rabbit. Fossils of an extinct giant rabbit described in 2011 show that it had a stiff spine to support its bulk, which meant it would not have been able to hop. Accordingly, we might need to rethink the way we portray the Easter Bunny.

Links:

Evans, A.R. et al. The maximum rate of mammal evolution. Proceedings of the National Academy of Sciences, published ahead of print on January 30, 2012.

Speed limits on the evolution of enormousness (Wired Science)

Science reveals the secrets of super-sized mammals (The Age)

Dr Erich Fitzgerald

Australia Day

Author
by Katrina
Publish date
26 January 2012
Comments
Comments (0)

Your Question: What is the history of our national holiday?

The tradition of celebrating Australia Day as a national public holiday was established in Australia's first colony, Sydney, and has persevered since the early nineteenth century.

Medal - Australia's 150th Anniversary, 1938: Raising the British flag at Sydney Cove after the landing by Captain Arthur Phillip, January 26, 1788. Medal - Australia's 150th Anniversary, 1938: Raising the British flag at Sydney Cove after the landing by Captain Arthur Phillip, January 26, 1788.
Source: Museum Victoria
 

Sydney almanacs originally referred to it as First Landing Day or Foundation Day, in celebration of the arrival of Captain Arthur Phillip in Sydney on January 26, 1788. It was not until the thirtieth anniversary of European settlement, in 1818, that Governor Lachlan Macquarie officially created a public holiday in New South Wales. During this time other newly founded colonies were also celebrating their own beginnings, through sporting events, picnics and anniversary dinners.

Australia Day celebrations in Melbourne, 1916: the car in the foreground won first prize for the most decorated car. Australia Day celebrations in Melbourne, 1916: the car in the foreground won first prize for the most decorated car.
Image: Mrs C.M. Chisholm
Source: Museum Victoria
 

January 26 in 1888 marked the centenary of European settlement, however attitudes towards the celebration were mixed. The date was primarily associated with New South Wales rather than all the colonies. Nevertheless, the celebrations across Australia assisted to create a greater sense of cohesion between the separate colonies as they attempted to forget Australia's 'convict stain' and focus on the future. From the 1880s this was signified with a movement towards a national holiday, perhaps made easier by the achievement of Federation in 1901. However it was not until 1935 that all Australian states and territories used the name 'Australia Day' to mark the date.

Badge – South Australia Public Service Australia Day, 26 July 1918. Badge – South Australia Public Service Australia Day, 26 July 1918.
Image: Heath Warwick
Source: Museum Victoria
 

For Indigenous Australians, for whom the date represented invasion and an irrevocable impact upon their culture, land and population, there was no cause for celebration. During the sesquicentenary events in 1938, approximately 100 Aboriginal protesters gathered in Sydney to present a different view of the celebrations. For the protestors and those represented, Australia Day was instead 'a day of mourning', highlighting the loss of life, land and language that was a cause of the European occupation of Australia.

Badge – ‘White Australia has a Black History,’ Australia, 1988 Badge – ‘White Australia has a Black History,’ Australia, 1988
Image: Heath Warwick (photographer)
Source: Museum Victoria
 

The protest demanded new laws that would ensure equality for Aboriginal people in the wider Australian community, such as citizenship rights. From this time, new voices were arising to question the celebratory status of Australia Day. This gained impetus during the 1988 Bicentenary with numerous protests staged across Australia including both Indigenous and non-Indigenous people declaring Australia Day a commemoration rather than a celebration of Australia's history.

Bicentenary display, <i>Window’s on Victoria</i> exhibition, Melbourne Museum, 2000-2007. Bicentenary display, Windows on Victoria exhibition, Melbourne Museum, 2000-2007.
Image: Benjamin Heally
Source: Museum Victoria
 

Material objects, such as badges, coins and t-shirts, have often been disseminated to commemorate Australia Day. Many of these are in Museum Victoria's collection and can be viewed on Collections Online. These items remind us of the different meanings that Australia Day can have for Australia's diverse population. They also provide us with an understanding of the various circumstances leading up to Australia Day's consistent recognition by all States and Territories on January 26 for the first time in 1994, and as we know it today.

Got a question? Ask us!

Links:

Australia Day: History

Australia Day Student Resources: Indigenous Australians

Moles of many colours

Author
by Kate C
Publish date
25 January 2012
Comments
Comments (2)

Golden moles are burrowing mammals native to southern Africa that are completely blind. Yet, their fur produces "a rainbow of colours when viewed from various angles, much like the surface of a compact disc," according to Dr Kevin Rowe, Senior Curator of Mammals. This raises the question: why would an animal that lives in the dark, and can't see anyway, be brightly coloured? Kevin and his colleagues, including MV Research Associate Dr Karen Rowe, have published a new study in Biology Letters that considers the implications of how and why iridescence evolved.

Golden mole specimen from the Museum Victoria collection. Golden mole specimen from the Museum Victoria collection.
Source: Museum Victoria
 

Many insects, reptiles and birds use iridescence to attract mates, but this depends on keen eyesight on the part of the viewer. Analysis under scanning electron microscopy and transmission electron microscopy showed that the golden mole's colourful sheen is produced by the same mechanism as other animals: microscopic surface structures that refract light. The minute layers of scales on the surface of each hair are "most likely to reduce drag and damage while the moles swim through sand and soil," explains Karen. "The colours they produce are merely a by-product."

Four golden mole specimens Hairs from these four golden mole specimens were analysed with scanning electron microscopy and transmission electron microscopy in this study.
Source: Museum Victoria
 

The only other known example of mammal iridescence is the 'eye shine' seen when torchlight reflects from the retina of nocturnal animals, a useful trick for spotting animals in trees. With more investigation, the researchers may find other species with true iridescence and thus piece together the story of its evolution.

Links:

Holly K. Snyder, Rafael Maia, Liliana D'Alba, Allison J. Shultz, Karen M. C. Rowe, Kevin C. Rowe and Matthew D. Shawkey (2012) 'Iridescent colour production in hairs of blind golden moles (Chrysochloridae)' Biology Letters

World's first iridescent mammal discovered

Media release

Hydrothermal vents

Author
by Kate C
Publish date
24 January 2012
Comments
Comments (1)

Collection Manager David Staples has recently returned from a six-week voyage with a team of British scientists studying the marine life on seamounts and hydrothermal vents in the southern Indian Ocean.

Hydrothermal vents are associated with active spreading centres of tectonic plate boundaries and are often referred to as black (or white) smokers because of the mineral-rich, super-heated fluids they spew into the water column.

A diverse and unique fauna lives in association with the vents and a short clip of what was seen on one of these vents at about 3km depth can be viewed here. Yeti crabs, sea spiders, scaly-foot gastropods, mussels, worms and shrimp can be seen moving quickly at the periphery of these high temperature plumes.

 

Video used with the kind permission of Dr Jon Copley, National Oceanography Centre, Southampton.

Links:

Mountain life beneath the sea

Black smoker in Dynamic Earth

Five things about dragons

Author
by Dr Andi
Publish date
23 January 2012
Comments
Comments (2)

Happy Chinese New Year! In 2012 it's the Year of the Dragon. I've been stalking Wally the Gippsland Water Dragon in the Forest Gallery for days but couldn't get decent photo. I figured he should be the notional poster boy for this year's Chinese horoscope. Alas I am hopeless paparazzo because every time a customer service officer called me to say he was out and about and ready for his close-up, he would flee at the sight of me.

So I wandered down to the Live Exhibits lab to try get some tips on reptile whispering or to see if Wally had a stunt double, dead or alive. The staff responded by saying things like "oh, here I have a picture of Wally on my phone," and another said "here is a snap of another type of water dragon I took while bushwalking." You gotta love our museum staff.

1. Wally the Water Dragon only poses for visitors and Live Exhibits staff.

Wally's scientific name, Phisygnathus lesueurii howittii, has a connection to Museum Victoria. Our founding director Frederick McCoy named this species after "that excellent geologist, magistrate, and bushman, my accomplished friend Mr. A. Howitt... willing to aid in any scientific investigation of the natural products of Gippsland, and who with infinite difficulty succeeded in procuring three specimens for me of this River-Lizard."

McCoy also reported that that these lizards must have given rise to the rumours of crocodiles in Gippsland.

Wally the Gippsland Water Dragon Wally the Gippsland Water Dragon.
Image: Caitlyn Henderson
Source: Caitlyn Henderson
 

Eastern Water Dragon Wally's stunt double cousin, Eastern Water Dragon Physignathus lesueurii lesueurii.
Image: David Holmes
Source: David Holmes
 

2. Chinese dragons have four claws and Japanese dragons have three.

Next time you find yourself in a dragon-slaying situation, take a moment to count the claws on the foot of the dragon. That way you will know the its origin; if it has four claws it is Chinese but if it has three claws it is characteristically Japanese.

Japanese wood carving of dragon Japanese dragon carving in wood with articulated body, limbs and tongue. (ST 018385)
Source: Museum Victoria
 

3. Some dragons have fire in their bellies that sounds the passage of time.

Some dragons may breathe fire, but this Chinese dragon has fire in its belly; it's a reproduction of a Chinese fire clock. The dragon is boat-shaped with wires that support a burning incense stick or taper. This gradually ignites cords that then drop metal balls into a brass dish below.

Chinese fire clock replica Chinese fire clock replica, made by J. Bishop, Melbourne, 1959. (ST 024869)
Source: Museum Victoria
 

4. Dragon's blood was once used to stain violins and treat diarrhoea.

Dragon's blood is a red resin prepared from the fruits of a climbing palm (Daemonorops draco). It is used for colouring mahogany, varnishes, for staining marble and in the preparation of lacquers and dentifrices. It was also used medicinally for the treatment of diarrhoea and severe syphilis!

Dragon's blood Glass jar containing Dragon's Blood used in the pharmacy of a mental health hospital, Victoria, Australia, circa 1900 (SH 850502).
Source: Museum Victoria
 

5. Dragons are from mythical lands and Victorian coastlines.

The Victorian marine emblem is the Weedy Sea Dragon (Phyllopteryx taeniolatus). These wonderful fish are residents of Westernport and Hobsons Bays as well as Geelong and Portland.

Like most fish, sea dragons swim horizontally rather than in a vertical position, like seahorses. However, like seahorses, male seal dragons do the egg-carrying duty.

  Seagrass habitat with Sea Dragons. Seagrass habitat with two sea dragons.
Image: Mark Norman
Source: Museum Victoria
 

So in the tradition of Chinese New Year, forget all grudges, wish peace and happiness to all, and sweep away ill fortune to make way for incoming good luck.

Links:

Gippsland Water Dragon

Frederick McCoy's debunking of the Gippsland crocodile myth

Question of the Week: Dragon's den

The science of poo

Author
by Nicole K
Publish date
22 January 2012
Comments
Comments (5)

Your Question: Why do scientists study animal poo?

Poo is truly fascinating stuff. Each deposit contains a minefield of information about its owner and the environment it lives in.

Animal poos (scats) come in a multitude of different shapes and sizes. Each species produces its own unique parcels. You can therefore discover which species are present in an area (and how abundant they are) by looking at what they leave behind.

The square droppings of a Common Wombat, <i>Vombatus ursinus</i> The square droppings of a Common Wombat, Vombatus ursinus
Image: Alan Henderson
Source: Minibeast Wildlife
 

The relative size of a deposit can also give you an idea of the age/size of he/she who dunnit. Sometimes, it's even possible to determine the sex and reproductive receptivity of the animal (by the smell).

The condition of the scat (taking recent weather conditions into account) will tell you how recently the animal was there – if it's still fragrant and sticky, you know you're fresh on the trail.

An animal's poo can also reveal the diet of the depositor. Long-term studies of scats can provide information about how animals' diets change over time and the seasonal abundance of their food sources.

A broken-up scat of a Thorny Devil <i>Moloch horridus</i>, revealing that  it has fed exclusively on ants. A broken-up scat of a Thorny Devil Moloch horridus, revealing that it has fed exclusively on ants.
Image: Alan Henderson
Source: Minibeast Wildlife
 

The scats of carnivorous (meat-eating) animals can be an invaluable source of information about the presence and abundance of their prey species. Fur, teeth and bones are not usually digested as they pass through the digestive system and come out relatively intact. As foxes and owls are far better at finding small animals than we are, scats can contain crucial records for scientists studying endangered species.

The scat of a European Red Fox <i>Vulpes vulpes</i> The scat of a European Red Fox Vulpes vulpes
Image: Karen Rowe
Source: Museum Victoria
 

Poo is also a useful indicator of animal health. Scats contain parasites, hormones and DNA (in the animal's own skin and hair cells). Scientists can therefore use the clues in poos to monitor infections, perform genetic analyses and gather information on stress levels and reproductive state, all without touching or even seeing the animal.

Got a question? Ask us!

Links:

Square Poo

About this blog

Updates on what's happening at Melbourne Museum, the Immigration Museum, Scienceworks, the Royal Exhibition Building, and beyond.

Categories