Wildlife news from around the world

Squid eyes under the knife Jun 11 2008

What has eyes the size of dinner plates, fearsome suckers that cling to its prey, razor-sharp hooks to shred its victims and two beaks to crush the remains?  It’s the colossal squid (Mesonychoteuthis hamiltoni) – an elusive “killing machine” from the dark depths of Antarctic seas.

A recent dissection has shown these squids to have the biggest eyes ever recorded in the animal kingdom.  Read the full BBC report here. 

“In the collapsed state we see here, they [the eyes] measure 25cm [almost 10in] across, but in the living animal they are probably larger, up to around 30cm [close to 12in],” said Professor Eric Warrant, an expert on animal vision at the Museum of New Zealand Te Papa in Wellington. The pupils alone are about 8cm (3in) across.

The giant eyes are thought to help the fearsome species locate prey in the dark Southern Ocean depths.

The 10m-long (34ft) specimen caught, weighing in at about 495kg (half a ton), has also turned out to be female, surprising the scientific team, which initially thought the catch was male. This sheds new light on how big the creatures can grow. Females are thought to be larger – so if this had been a 10m male, one would assume there were far bigger specimens lurking in the ocean depths.

Very little is known about colossal squid – only about 10 have ever been caught and brought to shore – but the creature’s reputation has been entangled in sea lore since the 1700s. An alleged encounter between a ferocious, man-eating squid and a French naval vessel was vividly described in Jules Verne’s book Twenty Thousand Leagues Under the Sea, which was published in 1870.

Scientists hope the latest dissection will yield new information about where and how colossal squid live and breed.

The find has also enabled researchers to study the colossal squid’s swivelling barbed clubs at the end of its tentacles. “It’s endowed with a killer arsenal: the hooks, the beak, everything about it,” said Steve O’Shea of the University of Technology in Auckland, New Zealand. 

Large squid and sperm whales have been known to engage in lethal battle – evidenced by the scars, caused by the squid’s serrated hooks, found on the heads of sperm whales.

But Professor Paul Rodhouse, head of biological sciences at the British Antarctic Survey, is more concerned about the future of the colossal squid than the fate of creatures that may encounter one. He is particularly worried about the recent flood of fishing vessels into Antarctic waters targeting Patagonian toothfish (Dissostichus eleginoides), which is a major prey species for colossal squid.

“Toothfish and these squid form part of a deepwater ecosystem that we know virtually nothing about, yet are already exploiting it through commercial fishing,” Rodhouse added.

At least the colossal squid isn’t likely to join toothfish on the seafood menu. Calamari as big as car tyres might sound tasty, but jumbo-sized squid usually contain high levels of ammonia and their meat is said to taste like floor cleaner!

Images of squid eye lens and dissection courtesy Museum of New Zealand Te Papa Tongarewa.

References:

Black, R 2008, ‘Colossal squid’s big eye revealed’, BBC News. Retrieved 6 May, 2008, from http://news.bbc.co.uk/1/hi/sci/tech/7374297.stm

Owen, J 2003, ‘Colossal squid revives legends of sea monsters’, National Geographic News. Retrieved 13 May, 2008, from http://news.nationalgeographic.com/news/2003/04/0423_030423_seamonsters.html.

Shears, R 2003, ‘Colossus of the deep’, Daily Mail, London. Retrieved 13 May, 2008, from http://www.bio.net/bionet/mm/deepsea/2003-April/000588.html.

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Spiders like what they see in UVB May 20 2008

Spiders that reflect ultraviolet B (UVB) rays are more likely to appear “sexy” to their mates, a recent study reported by Science Daily has shown. 

Professor Li Daiqin of the National University of Singapore has found the first evidence of an animal, the ornate Chinese jumping spider (Phintella vittata), using UVB rays to communicate with other members of its species.

Because it’s common knowledge that solar UVB has harmful effects on a wide range of living organisms – for example, it can cause skin cancer and damage the retinal tissues of the eyes of mammals – it has until now been assumed that animals are unable to detect UVB rays, said Li.

The difference between UVA and UVB light is a matter of wavelength. UVA rays come in longer wavelengths (320 to 400 nanometres), so they pass through the outer layer of skin rather than burning it, which the shorter UVB rays (290 to 320 nanometres) do. 

Many animals, particularly butterflies, have body parts that reflect UVB light but no past studies have been carried out to investigate the adaptive significance of UVB vision.

Mate-choice experiments have now shown that male Chinese jumping spiders are drawn more to their female counterparts when they aren’t behind a filter that blocks UVB rays. Similarly, females are more aroused by males that reflect UVB.

“This selection process could be related to survival of the species as products of such unions are more fertile,” Li said.

Jumping spiders are known to have uniquely complex eyes and acute eyesight but it’s still unclear how their eyes detect UVB.

Jumping spiders make their homes in among grassy patches and low shrubs in gardens and rural areas. Females measure 4-5mm (about 0.2in) and males 3-5mm (0.1-0.2in). The species occurs in Singapore, Malaysia, Indonesia, the Philippines, Vietnam, India and southern China.

“Most research has been based on observing animals through human eyes but we have to realise that animals see things differently to us. We don’t have UV vision but jumping spiders do. The way animals are studied should be reassessed,” added Li.

Image courtesy Professor Li Daiqin

Sources:

‘Female jumping spiders find ultraviolet B rays sexy’ 2008, ScienceDaily, 6 May. Retrieved 6 May, 2008, from http://www.sciencedaily.com/releases/2008/05/080501125508.htm
Morelle, R 2008, ‘Study sheds light on spider sex’, BBC News, 2 May. Retrieved 7 May, 2008, from http://news.bbc.co.uk/go/pr/fr/-/2/hi/science/nature/7378196.stm
Koh, JKH 2000, ‘A guide to common Singapore spiders’, BP Guide to Nature Series, Singapore Science Centre. Retrieved 14 May, 2008, from http://habitatnews.nus.edu.sg/guidebooks/spiders/text/Phintella_vittata.htm
Jingjing Li, Matthew LM Lim, Zengtao Zhang, Qingqing Liu, Fengxiang Liu, Jian Chen, Daiqin Li 2008, ‘Sexual dichromatism and male colour morph in ultraviolet-B reflectance in two populations of the jumping spider Phintella vittata (Araneae: Salticidae) from tropical China’,
Biological Journal of the Linnean Society 94 (1) , pp 7–20. Retrieved 14 May, 2008, from http://www.blackwell-synergy.com/doi/abs/10.1111/j.1095-8312.2008.00968.x

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Robotic aircraft to track marine mammals Apr 17 2008

Robotic aircraft or unmanned aerial vehicles (UAVs) may soon take to the Australian skies in the name of marine mammal research, if a project to test the technology succeeds.

Science Alert reports that researchers working through the University of Queensland and the Australian Centre for Applied Marine Mammal Science will conduct UAV surveys of dugongs (Dugong dugon) and humpback whales (Megaptera novaeangliae) to test whether the robotic aircraft can improve the safety, cost-effectiveness and accuracy of marine mammal population checks.

In the medium to long term, smaller UAVs could reduce the cost of flights to just a few dollars an hour, while better imaging software could obviate the need for any human analysis.

Dugongs and humpback whales are being targeted by UAVs as they live in different environments, are sighted using different cues from the air, and have very different movement habits and socialisation patterns.

“Dugongs can congregate in large herds of up to 300 individuals, and need to be circled to be counted,” Dr Michael Noad of the University of Queensland says. These ocean dwellers are highly migratory.

Noad adds that migrating humpback whales usually travel singly or in pairs. Often observers can only see their blows before they submerge again. “They’re spread out on a long migratory path, so you have to cover quite a bit of ocean to find them.”

The habitat of humpback whales comprises polar to tropical waters, including the waters of the Arctic, Atlantic and Pacific Oceans, as well as the waters surrounding Antarctica. The whales are divided into several populations which are mostly isolated.

Image of humpback whale courtesy Wikipedia

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Darwin and the jungle fowl gene Apr 14 2008

Evolution theorist Charles Darwin believed the domesticated chicken descended from the red jungle fowl (Gallus gallus) only, but new research shows there’s more to the story.

The research by Uppsala University in Sweden was published in PLoS Genetics and reported by Science Daily.

The genes for yellow legs, which most domesticated chickens have, have been found to come from the grey jungle fowl (Gallus sonneratii). The red jungle fowl has genes for white-skinned legs.

Most of modern chickens’ other genes, however, can be traced to the red jungle fowl. It’s possible the grey jungle fowl was crossed with an early form of the domesticated chicken.

“What’s ironic is that Darwin thought that more than one wild species had contributed to the development of the dog, but that the chicken came from only one wild species, the red jungle fowl. Now it turns out that it’s just the opposite way around,” says Greger Larson, a researcher at Uppsala University.

Chickens’ yellow leg colour comes from the carotenoids in their fodder. The gene that has now been identified codes for an enzyme that breaks down carotenoids and releases vitamin A. “This gene is shut down in skin but fully active in other tissues in chickens with yellow legs,” the researchers explain. “The consequence is that yellow carotenoids are stored in the skin in these chickens. This is called a regulatory mutation since the coding sequence of the gene is intact, but its regulation is modified.”

“Our study is a clear example of the importance of regulatory mutations in the course of evolution. What we don’t know is why humans bred this characteristic,” says Professor Leif Andersson, the project director.

Scientists believe the same gene may be of significance in explaining the pink colour of the flamingo, the yellow leg colour of many birds of prey, and the reddish meat of the salmon. These characteristics are all caused by carotenoids.

As it’s known today, the red jungle fowl is native to southern Asia. The grey jungle fowl is native to evergreen forests in southern and western India.

Image of red jungle fowl courtesy Kimani Aviaries

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Bat fossil settles it: first flight, then steering Mar 24 2008

The journal Nature reports that a new bat fossil seems to have settled a debate about what came first in bat evolution: flight or echolocation.

The fossil has more primitive features than any other known species of bat and has fully developed wings, but lacks the ear morphology that goes with echolocation, which is the detection of objects using reflected sound. The bat emits a high-frequency sound, which bounces off an object and returns as an echo. Bats use echolocation to navigate. Other mammals, such as whales, use echolocation too.

The fossil bat’s legs and claws suggest it was a good climber, using all its limbs. Dating back 52-million years, it was found in Wyoming, USA.

Image of a modern-day wrinkle-lipped bat in Thailand © Earth-Touch 2008. See the video: Thousands of bats hunt at dusk.

Wildlife news from around the world

Gliders of the forest Mar 10 2008

With the help of miniature data-recording backpacks, researchers are learning more about the gliding behaviour of colugos – otherwise known as the flying lemurs of Malaysia.

The work of scientists in Singapore, the United Kingdom and at the University of California, Berkeley, was reported in Science Daily and published in Proceedings of the Royal Society B.

Although they cannot actually fly and are not true lemurs, colugos (Cynocephalus variegatus) are the champions of all gliding mammals, able to drop from the forest canopy, glide for more than 100m (328ft), execute 90-degree turns and then gently settle on a tree trunk.

What enables them to be such formidable gilders is a well-furred membrane extending from the sides of the animal’s neck to its forepaws, and from its forepaws back to its hind feet and the end of its tail.

As part of their research, scientists glued a miniature backpack fitted with an accelerometer, which measures force and speed, onto a small shaved area on the colugo’s back. The device recorded several days’ worth of data on the animal’s gliding, in particular take-offs and landings.

It’s unlikely the accelerometer bothered the colugo, as the device was about the size of half a stick of chewing gum and fell off after a few days. 

The recorded data from the accelerometer showed that colugos push off from trees more forcefully for long jumps, but that they quickly reach terminal velocity once they spread their limbs into a parachute, so their landing force remains about the same no matter how far they glide.

The landing forces increase with distance only for short leaps, probably because they land with two limbs instead of four, according to the researchers. Once all four limbs are spread out, however, the colugo may even get enough lift to land more softly the further it travels.

Colugos are native to Southeast Asia. They have needle-sharp claws, useful for holding onto bark and branches, and are herbivorous. These nocturnal creatures pass the day sleeping in hollow trees or suspended from branches. They get their name from their faces, which resemble those of lemurs.

Through enhancing their understanding of gliding animals, researchers may also be able to help improve the design of flexible winged aircraft like hang-gliders and micro air vehicles, they say.

Image courtesy Wikipedia

Wildlife news from around the world

Life in the chilly Southern Ocean Feb 25 2008

Australia’s census of life in the Southern Ocean, CEAMARC, has drawn to a close.

“Specimens collected will be sent to universities and museums around the world for identification, tissue sampling and bar-coding of their DNA,” said project leader Dr Graham Hosie. “Not all of the creatures that we found could be identified and it is very likely that some new species will be recorded as a result of these voyages.”

The Australian research vessel Aurora Australis sampled the ocean floor as part of the census. “In some places every inch of the sea floor is covered in life,” said voyage leader Dr Martin Riddle. “In other places we can see deep scars and gouges where icebergs scour the sea floor as they pass by. Gigantism is very common in Antarctic waters – we have collected huge worms, giant crustaceans and sea spiders the size of dinner plates.”

CEAMARC is part of the international Census of Antarctic Marine Life, co-ordinated by the Australian Antarctic Division.

Image of giant-scale worm (250mm or 10in long, 300g or 11oz) on the Antarctic seabed at a depth of 645m (2116ft) © Martin Riddle, Australian Antarctic Division

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New mammal species found in Tanzania Feb 14 2008

A new species of mammal, a shrew-like creature called a grey-faced sengi, has been discovered in the mountains of south-central Tanzania, reports Scientificblogging.com.

The newcomer (Rhynchocyon udzungwensis) stands head and shoulders above his cousins. It’s about 25% larger than any of the 15 known species of sengi.

“It is the first new species of giant elephant shrew to be discovered in more than 126 years,” says California Academy of Sciences scientist Galen Rathbun, a sengi-watching veteran.

The new species was discovered in Tanzania’s remote Udzungwa Mountains rainforests. The age, isolation and fragmented nature of the Udzungwa range makes it an important centre of biodiversity. It’s home to many species that cannot be found anywhere else on earth.

Sengis – small, furry, insect-eating mammals that live on forest floors – are also called elephant shrews. They are monogamous and live only in Africa. Several species of sengi are able to alter their physiology to meet environmental extremes, slipping into deep hibernation when they encounter low temperatures. Snakes, raptors, and other carnivores are known sengi predators.

Sengis have a well-developed sense of sight, hearing, and smell. Although they’re relatively silent creatures, many species drum their feet or tail-slap the ground in stressful situations.

They owe their name to scientists who initially thought they were true shrews. The mammals were termed elephant shrews because of their long, flexible snouts. Ironically, sengis are more closely related to elephants than to shrews. They belong to a group of mammals called Afrotheria, which evolved in Africa more than 100-million years ago. Other sengi relatives include the aardvark and the now-extinct sea cow.

Subsistence hunting and the clearing of forests for agricultural and urban development is a serious threat to giant sengis. 

Image courtesy Francesco Rovero

Wildlife news from around the world

Secrets of Antarctic superglue Feb 14 2008

Plunging into the icy waters of McMurdo Sound in Antarctica is paying off for New York scientist Sam Bowser, whose research could lead to stronger biological adhesives.

Operating about 1 300km (800mi) from the South Pole, Bowser is studying single-celled creatures known as foraminifera (or forams for short), which are among the most abundant organisms in the oceans.

The intriguing characteristics of these organisms, which grow no bigger than a fingernail, far outweigh their physical size.

What fascinates scientists like Bowser is how forams build minuscule but sophisticated shells out of grains of sand using a super-effective underwater adhesive.

If the foram research reveals the chemistry underlying the naturally produced glue, stronger biological adhesives could be developed and possibly benefit dentistry, neurological surgery and the development of prosthetics.

It has also been discovered that forams absorb carbon from the water when they make their shells. Scientists are investigating how this activity contributes to balancing greenhouse gases such as carbon dioxide.

Forams are found on the seabed and floating in the waters above. They feed on dissolved free amino acids, bacteria, unicellular algae and tiny crustaceans.

Researchers believe that forams are a key link in the marine food chain, as they feed on small prey mostly inaccessible to bigger creatures and are food for the latter.

Remains of forams have been found in rocks of marine origin thought to have been around 550-million years ago. These organisms are highly sensitive to changes in food availability and the salinity and temperature of water, making them useful indicators of environmental change.

Image of foraminifera, microscopic floating organisms that live in shells in the ocean, courtesy Scripps Institution of Oceanography

Wildlife news from around the world

World Wetlands Day: Okavango Delta Feb 1 2008

As World Wetlands Day (2 February) approaches, Earth-Touch continues to publish video footage from an unlikely place for a wetland: the edge of a desert. (See video links below.)

The Okavango Delta is situated at the edge of the Kalahari Desert in Botswana, Southern Africa. It is a remarkable ecosystem where land and water mingle closely.

From north to south, the 12 000 square kilometre (4 633 square mile) Okavango Delta slopes very slightly along its 250km (155mi) length. The water from rain that falls in summer in the catchment area takes five or six months to reach the far end of the swamps. This water is low in nutrients because the soils in the catchment are sandy.

Even though annual evaporation is more than three times the rainfall, the water does not get saline. That’s because of the way the delta’s vegetation regulates the dispersal of water and sediment and influences the accumulation of salts.

When old channel systems dry out and peat catches fire, nutrients and clays are released and form fertile soils which produce grass that large herbivores can graze. For a fuller explanation of the role plants play in this system, see the work of the Okavango Research Group at the University of the Witwatersrand in Johannesburg, South Africa.

For a sample of the videos documenting the changing seasons in the Okavango, and the way water, plants and animals interact, see the Earth-Touch clips:

Barbel run in the Okavango
Flood plain teems with life
Dramatic change in the delta
Dramatic sunset in the Okavango Delta
Elephant bulls follow new growth
Wattled cranes forage on floodplain
New grass sways and ripples in the wind

Image © Earth-Touch 2008