Caterpillars Can “Blink” A Fake Eye

22373_origMany animals have a fake eye — or eyespot — or two that they can use for protection from predators, often by frightening or distracting the hungry creature. Eyespots are especially common among tropical caterpillars. And researchers conducting a caterpillar inventory in Costa Rica have documented two species (Eumorpha phorbas, above, and E. labruscae) in which the eyespots can sort of blink. They report their findings in the Journal of Natural History.

How can an eye that’s not real blink? To find out, Thomas J. Hossie of Carleton University in Ottawa, Canada, and colleagues collected and reared caterpillars of the two species. When each species reaches the last instar before turning into a moth, it takes a form that has an eyespot on a tentacle that pops up from its butt; this is known as the anal horn. For the study, the researchers would remove a caterpillar from its rearing bag, let it acclimate for a minute, and then prod its rear three times. The result was a “blink,” such as the E. labruscae captured in the video below:

“Both caterpillars can ‘blink’ their posterior eyespot upon perceiving a threat,” Hossie writes on his blog Caterpillar Eyespots. “That is, they can move the skin around the eyespot such it either conceals/reveals the eyespot or flashes (i.e. reflects light) conspicuously towards an onlooker.”

Being able to blink the eye would make it look more like a mammal or bird eye, which is a little odd because scientists had thought that the eyespots on caterpillars were supposed to look more like snake eyes. Snakes can’t blink because they don’t have eyelids. Unfortunately Hossie and the other researchers haven’t been able to test how predators respond to these distinctive eyespots — including whether they might interpret them as mammal, bird, or snake — because these are really rare species.

But Hossie notes on his blog that these caterpillars have another defensive trick that is truly snakelike: “Interestingly,” he writes, “both Eumorpha caterpillars also inflate their thoracic body segments, while pulling their head into their body, to form a diamond shape which appears similar to the head shape of dangerous co-occurring snakes (at least to human observers).”

Image copyright CAPEA, used with permission under Creative Commons license

Human Presence Takes A Toll On Galapagos Sea Lions

sea_lionWhen you think about the Galapagos Islands, there are a few things that come to mind. There’s Charles Darwin, of course, and the studies he made there that contributed to his development of the idea of evolution. And the amazing wildlife, including tortoises and iguanas and a whole host of birds. What you don’t think of are things like pollution and invasive species, but these are growing problems, especially in the areas inhabited by humans.

Some islands are still pristine, though, and that gave a group of biologists, led by the Zoological Society of London, a chance to see how one species, the Galapagos sea lion, is affected by the presence of humans. The researchers compared immune activity and body condition of two populations, one in Bahia Paraiso on the undeveloped island of Santa Fe and another that lives in the center of the rapidly growing town of Puerto Bazquierizo Moreno on San Cristobal. The study was published last week in PLOS One.

None of the animals appeared to have signs that they were sick, but those that lived in town had more active immune systems. And among the pups in that colony, those that had higher levels of antibodies had thinner skinfolds and were skinnier.

“A tell-tale sign of an unhealthy sea lion is a thinner than normal layer of blubber, which is what we saw in the sea lions on San Cristobal,” study coauthor Paddy Brock of the ZSL said in a statement. The more active immune systems could indicate “a threat of infectious disease, which could mean human activity is increasing the chance of potentially dangerous diseases emerging in the Galapagos sea lion,” Brock said.

Puerto Bazquierizo Moreno does not seem like it would be a great place to be a sea lion. The bay is home to more than 200 boats and filled with fecal contamination from the vessels and sewage from the town. And the land has a bunch of animal threats, including people’s pets, feral cats and rats. If these factors are impairing the immune systems of the sea lions that live in the area, the impaired immunity could reduce the marine mammals’ ability to hunt, the researchers say.

And the Galapagos sea lions don’t need anything else to hamper their survival. The species was listed as endangered by the IUCN after its already-small population declined by more than 50 percent in the last three decades. The sea lions, which are a bit smaller than the more familiar California species, are not afraid of humans and like to hang out on rocky shorelines and sandy beaches (above). That can put them in direct contact with the human population and make them vulnerable to threats like uncontrolled dogs that will kill sea lion pups.

These sea lions have figured out ways to deal with some threats — they’ve been known to mob Galapagos sharks that approach their rookeries — but they haven’t yet evolved to deal with the ones humans have brought to them. Their immune systems didn’t evolve to exist in a sewage-filled, pet-dominated environment. And it appears that’s put them at even more risk of disappearing from the planet.

Image credit: ZSL_Paddy Brock, via EurekAlert

 

Andean Condors Eat Their Veggies

Figure 1

Everyone knows that vultures eat carrion, and Andean condors (Vultur gryphus) are no different from their scavenging brethren. The world’s heaviest soaring bird survives on a steady diet of rotting sheep, goat, rabbit and red deer, with the occasional horse or cow thrown in the mix. A group of researchers studying carotenoids — red and yellow pigments found in plants — in these birds, however, have come to the conclusion that condors are likely also eating a lot of vegetation. (The study was published last week by PLOS One.) That might mean they’re munching on some kind of plants, or it could be that they’re finding, as the scientists put it, “vegetal content” in the herbivores they eat, that is, whatever the birds come across in the stomach and intestines. Yum.

Andean condors may have need for carotenoids in their diet: Males of the species (above, a) have a brown iris in the eye, and neck wattles and skin on the head that can vary in color from gray to yellow. Females (b) have a red iris and less yellow skin (and no comb). During arguments over carcasses, the bare skin of grown and nearly grown condors can change in a moment from pale to deep yellow or orange or red (c and d). All that color requires pigment.

But how do they get that pigment, the researchers — a team from Spain and Argentina — wondered. They took blood samples from 22 wild Andean condors and 17 American black vultures in Patagonia in 2010, along with 27 captive condors from the Buenos Aires Zoo. The American black vultures are a much plainer species, and they wouldn’t seem to have as great a need for carotenoids. And the captive condors were fed a diet of meat only; if they had fewer of the pigments in their blood, then it would mean the wild birds were getting their colors from something other than herbivore flesh.

The wild condors and the black vultures, living in the same area, ate pretty much the same meals, but the condors had three times the concentration of carotenoids in their blood. The wild condors also had higher concentrations than their captive counterparts. The captive birds did have some carotenoids in their blood, but it was at lower levels.

The researchers concluded that the captive condors are getting some carotenoids solely from the herbivore meat they eat. But the wild birds are probably getting a lot more by eating “viscera and vegetation.” The Andean condors may also be biologically more competent at taking up or accumulating the chemicals than the black vultures, a necessity since they have a greater use for them.

But an analysis of 135 pellets (i.e., regurgitated food) taken from communal roosts gives added evidence that the wild birds are getting their carotenoids from vegetal matter of some sort: About 35 percent of the pellets consisted of 80 percent or more vegetal remains.

If Andean condors do indeed have a taste for veggies, they wouldn’t be the first vultures to snack on the green stuff. Egyptian vultures, which have their own need for carotenoids to color their bright yellow faces, get their fix by eating herbivore poo.

Image used under Creative Commons license, from Blanco G, Hornero-Méndez D, Lambertucci SA, Bautista LM, Wiemeyer G, et al. (2013) Need and Seek for Dietary Micronutrients: Endogenous Regulation, External Signalling and Food Sources of Carotenoids in New World Vultures. PLoS ONE 8(6): e65562. doi:10.1371/journal.pone.0065562

The Gene That Gives One Breed Of Cat A Curly Coat

cats

Depending on how cat mad you are, you’ve probably never seen a Selkirk rex kitty, let alone seen or held one. They’re not a popular breed — far less than the Persian (b, in the picture above) or the Scottish fold (c) — but their main feature is a curly coat (a, left). The curly trait is dominant, so about a quarter of any Selkirk rex litter will be the less-wanted straight-hair variety (a, right).

The Selkirk rex is a very new breed, having been developed after a curly-coated (aka rex) mutation arose in a cat in 1987. There have been about 8.4 generations of these kitties, which have been outbred to British shorthairs, exotic shorthairs and Persians to establish the breed (without too much inbreeding).

Though scientists (and breeders) have known that the curly trait is dominant, they hadn’t been able to find the responsible gene. The latest — and successful — attempt comes from a team led by Barbara Gandolfi at the University of California Davis. They published their results in Scientific Reports.

The team looked at the genes of nine curly coated Selkirk rex cats and 29 control kitties, a group that included Persians, British shorthairs and straight-haired Selkirk rex cats. The cats may look different, but they all belong to a big group of related kitties known as the “Persian family.” Gandolfi’s team eventually traced the curly trait to a gene KRT71 — they’re not sure exactly what the gene does, but they know it has something to do with the development of the hair follicle (not exactly surprising).

KRT71 had been ruled out as the curly coat gene in the Selkirk rex in an earlier study that looked at curly-coated cats of several breeds, but it seems that the Selkirk rex in that study was a straight-haired cat, so the researchers would have never been able to find a curly coat gene in it. That study did find, though, that various mutations in KRT71 produced curly hair in the Devon rex breed and the naked look of the sphinx cat.

What else might mutations in this gene produce? Scientists still have a couple more curly-haired breeds to check out — the LaPerm and the American wirehair. Perhaps they’re KRT71 mutants as well.

Photos by Barbara Gandolfi, via Creative Commons license: Gandolfi, B. et al. A splice variant in KRT71 is associated with curly coat phenotype of Selkirk Rex cats. Sci. Rep. 3, 2000; DOI:10.1038/srep02000 (2013).

Aww…Kissing Fish Win Fan Favorite In Underwater Photo Contest

kissingfish

Several years ago, when I went snorkeling on the Great Barrier Reef, I didn’t bother buying or renting an underwater camera. While my photo skills on dry land are pretty decent, I knew that beneath the ocean’s surface I was pretty clueless and my time would be better spent just admiring all the amazing creatures in my sight rather than fiddling with a box. And now, having viewed the winners of the 2013 Annual Underwater Photography Contest hosted by the University of Miami Rosenstiel School of Marine & Atmospheric Science, I’m glad that I didn’t even try my hand at this. The winners are masters at this art. Just take the fan favorite (above). The pair, a species called Mandarinfish or Mandarin dragonets (Synchiropus splendidus), were caught on camera by Italian amateur photographer Pietro Cremone in Puerto Galera, Philippines. These vividly colored fish can be found throughout the western Pacific, from Hong Kong to Australia. And while this pair may look like they’re kissing, mating is actually a bit different. Small groups of males and females gather at night on the reef. A pair will get in alignment, rise about a meter from the reef itself, then release their eggs and sperm. And that’s where parenthood (and romance) ends for these fish.

Fire Versus Crazy: Battle Of The Invasive Ants

Fire_ants02There’s a good chance you’ve heard of the red imported fire ant (above), a pest that’s found across the southern half of the U.S. and is now one of the world’s 100 worst invasive species. These aggressive ants, natives of South America, not only have a painful sting but also a penchant for attacking in swarms.

Less known is the Caribbean crazy ant, a more recent invader that’s been found in Florida and Texas (where it was once called the raspberry crazy ant). Unlike fire ants, Caribbean crazy ants — named for their erratic behavior — don’t have stingers and hardly bite. But infestations can be huge and incredibly hard to control. In one story from 2008, a woman describes how she kept killing and killing the ants that swarmed her house and within a week had filled a five-gallon bucket with dead ants.

News reports sometimes say that Caribbean crazy ants will attack and drive out fire ants, but there hasn’t been any scientific data that backs up the claims. So a trio of biologists from Rice and Texas A&M universities staged battles between nests of the two species. Their study appears in PLOS One.

The bad news is that, while there was no outright winner in the ant-on-ant combat, the crazy ants came off the worse of the two species; crazy ants were twice as likely to die as fire ants. It seems that the fire ants may be better equipped for a war, the scientists say. The fire ants are armed with stingers, which may be a more effective weapon than the crazy ants’ ability to spray formic acid. “It is possible that the ability to sting makes fire ants a more potent combatant than crazy ants,” the researchers write.

One odd thing that the scientists discovered is that crazy ants get more aggressive when they’re fed a low-carb diet. They even do better in battle and die less often when fighting fire ants. That’s different from most other ant species, which get more aggressive when given high-carbohydrate food. But what that means for which species wins out and spreads its misery farther, well, we’ll just have to wait and see.

Image courtesy of USDA/ARS via wikimedia

A Scientist Tried To Determine Whether Mice Like Art

picasso

Scientists study a lot of crazy things, but it’s rarely that I look at a study and think it must have been a joke (not unless it’s April 1st). But this weekend I found “Preference for and discrimination of paintings by mice” by Shigeru Watanabe of Keio University in Tokyo, which was published last week in PLOS One.

It’s real.

The experiment begins with a box with three rooms. Two of the rooms each had a transparent wall behind which was an iPod that cycled through 10 images, changing the image every 10 seconds. The first test had paintings from two abstract artists, Kandinsky in one room and Mondrian in the other. Over a six-day period in which mice lived in the three-roomed box, only one mouse out of 20 spent more time in one of the artist’s rooms over the other; he preferred Kandinsky. The experiment was repeated with paintings from Renoir, an impressionist, and the cubist Picasso. Again, one mouse preferred one artist (Renoir), but the rest did not.

Watanabe was able to show that the mice could distinguish between two artists by conditioning them to associate a shot of morphine with works by one artist. When placed in the three-roomed box, they spent more time in the room with the paintings that they had once received morphine upon viewing. When they aren’t conditioned, though, mice appear not to care about art.

What you might find even more surprising is that this is not the first time that Watanabe has done a study like this. In his introduction, he summarizes similar studies he has made of birds, including a study of Java sparrows in which “six of seven birds preferred cubist paintings to impressionist paintings,” and several findings in pigeons. “Pigeons can discriminate paintings by Monet from those by Picasso, paintings by Chagall from those by Van Gogh, and Japanese paintings from impressionist paintings,” he writes. He has “also shown discrimination of ‘good’ and ‘bad’ children’s paintings by pigeons.”

Huh. Though this does leave me wondering how in the world Watanabe distinguished between “good” and “bad” art done by kids — even parents have a hard time doing that.

Image (Picasso’s Nude Standing by the Sea at the Metropolitan Museum of Art) courtesy of flickr user Wally Gobetz

Like Humans Waltz And Polka, Lyrebirds Match Dance To Tune

lyrebird1Not every song has its own specific dance, but there are certain tunes — from the tango to the Twist — that demand distinct moves. Now scientists have caught birds doing something similar: Male superb lyrebirds (Menura novaehollandiae) coordinate movement to the type of song they’re singing. The study appears in Current Biology.

Male superb lyrebirds sing and dance to attract the ladies, and their repertoire can contain more than 90 tunes. They don’t have such a big variety when it comes to dance moves, but with their elaborate tail feathers, these visual displays can be pretty spectacular. To study the song-and-dance combo, a group of Australian scientists filmed a dozen of these birds in Sherbrooke Forest in Dandenong Ranges National Park in Australia, east of the city of Melbourne.

Despite having such a large number of songs to choose from, only four tunes were accompanied by dance (you can see a video of one here); the researchers named those songs A, B, C, and D (not the most inventive names, but this is a scientific paper we’re dealing with). Each of these four dances had it’s own set of moves, the researchers write:

Our analysis revealed that each of the four song types within the display was associated with one particular gesture. The gesture accompanying song A consisted of steps, often to the side, with wings motionless and a wide tail. In contrast, the male’s tail was narrowed while he sang song types B and C, and during the latter he nearly always jumped or bobbed, and flapped his wings. When males sang song type D, the tail was usually wide and the legs and wings still.

“Just as we ‘waltz’ to waltz music but ‘salsa’ to salsa music, so lyrebirds step sideways with their tail spread out like a veil to one song—which sounds like a 1980s video-arcade game—while they jump and flap their wings with their tail in a mohawk position while singing a quiet ‘plinkety-plinkety-plinkety,’” study coauthor Anastasia Dalziell of Australian National University said in a statement.

lyrebird2While the lyrebirds sometimes sang each of these songs without dancing, they never danced without an accompanying tune. And occasionally, just like we do when dancing, the birds would mess up. The researchers say that this shows that the song-and-dance routine is difficult for the birds

How these birds develop their musical theater skills isn’t known, but the males spend years practicing before they reach the age of maturity. These skills are incredibly important, because females choose their mates after watching several males put on these displays. What the females are looking for, though, is still a mystery. Dalziell said, “Sometimes after what seems to me to be a perfectly wonderful display by a male, I watch a female leave and check out his neighbor.”

Images credit: Alex Maisey/Current Biology

Predatory Life On The Savanna Is Complicated (Unless You’re A Lion)

lions

In a simple system, there’s a predator and its prey; the predator roams wherever the prey is found. Add in more predator and prey species, and where the predators live should be decided by what they eat. Real life, though, is not that simple. Just look at this new study published online by Ecology of four predator species in South Africa.

An international group of researchers studied an 85-square-kilometer, fenced-in region of South African savanna — the Karongwe Game Reserve. In this area there are four main predator species: lions, cheetahs, leopards, and wild dogs. These predators hunt 12 different ungulate species, mostly impala, blue wildebeest, waterbuck, Burchell’s zebra, warthog, and giraffe.

To figure out where the predators were going and what they were doing, many of the adults of each of the four species were outfitted with VHF transmitters during the study period of 2001 to 2005. The distributions of the prey species were determined by aerial surveys and sampling in the wet and dry seasons (respectively, November to March and April to October).

All that data was then combined. The patterns and interactions of the various species are complex, but there were definite patterns:

Lions: The big cats (above), as might be expected, are the dominant predators in this environment. That power gives them unrestricted access to pretty much anything they want. They go where the best and most vulnerable prey can be found and where they’ve got the best cover for hunting. They don’t worry about where other predator species are. Even the season doesn’t affect them much.

Leopards: These cats overlap in range with lions — the best prey is found where the lions live — but they avoid the much-bigger cats. They also avoid each other. In this area at least, the biggest killer of leopards is other leopards. And during the dry season, when it’s easier to see through parched vegetation and the risk of detection by other cats is higher, leopards find it safest to move towards the smaller wild dogs.

cheetah

Cheetahs: Like leopards, these spotted cats (above) are also smaller than lions, and it would be expected that they would also avoid the big cats. But, like the leopards, their range overlaps with the lions. And in the wet season, these cats tended to actually move towards locations where lions were recently roaming. The researchers theorize that cheetahs may be using other tactics to avoid lions, such as by choosing habitats, like woodlands, that the bigger cats don’t use, or being active when lions aren’t. Staying near the lions, and their high-quality prey, proved beneficial; some cheetahs were able to take down large prey like wildebeest instead of having to stick with smaller meals. But just because the cheetahs were comfortable venturing into lion territory doesn’t mean that they were entirely fearless; these cats generally stayed away from leopards.

Wild dogs: The African wild dogs — the smallest of the predators — tended to avoid all three of the cat species, but they behaved differently depending on the season. In dry times, when they could be more easily seen, the wild dogs stayed away from the other carnivores’ activity centers. In the wet season, though, when there was more cover available, they took a little more risk and only avoided areas where the other species had been recently. Constrained as they were by the movements of the other predators as well as the boundary fence they could not cross, the wild dogs had to settle for prey species they did not prefer.

The researchers’ take-away message from all these interactions is that for subordinate carnivores like the cheetahs, leopards, and wild dogs, competition with other predators can matter more than what they eat. Because if you have to eat an impala instead of a wildebeest, or even wait another day for a hearty meal, being hungry is better than getting mauled to death by another predator.

Images courtesy of flickr user Jean-Louis A

How A Sea Star Handles The Heat

seastar

If you’re a human, the rocky intertidal zone can be a great place to explore. There are plenty of interesting critters to find. But if you’re one of those creatures, life can be rather rough — in addition to putting up with humans that may pull you out of your home, there’s dangers ranging from predatory birds to punishing waves to dramatic temperature fluctuations that come from being submerged in water and exposed to air over and over. And many of the animals that live in this zone either don’t move or don’t move fast.

This is life for the purple sea star, Pisaster ochraceus, which is a common find on Pacific shores. The sea star (or starfish, if you must) is an ectotherm, meaning that it’s body temperature is determined by its environment, not the organism. But a study published last week in the Journal of Experimental Biology finds that this sea star does appear to have a little control about where that heat goes in its body. The key is hot arms.

A trio of researchers from the University of South Carolina in Columbia and the University of California, Davis started with 70 purple sea stars collected from the California coast. When they viewed the invertebrates with an infrared camera they discovered that the sea stars’ arms were warmer than the core. This was surprising — they had expected the arms to be cooler.

The scientists then subjected groups of sea stars to increasingly warm temperatures by placing them under heat lamps. The temperatures ranged from 26 degrees Celsius (comfortable) to 42 degrees (deadly). At lower temperatures, a sea star’s arms were a couple degrees warmer than its core. At middle temperatures, the arms were also warmer, but after a couple days in this heat, many sea stars would shed one or more arms. And at even higher temperatures, when sea stars’ core temperature got above 35 degrees, they died within 24 hours; their arms, though, were cooler than the core.

The arms are likely acting as heat sinks for the sea stars, the scientists say. That would imply that the invertebrates have the ability to transfer heat from the core to the arms. Though the animals don’t have a circulatory system like we do (that’s what allows humans to transfer heat through our bodies and do things such as conserving heat in our core when it’s cold), sea stars can move fluid within themselves.

“Under this scenario,” the scientists write, “directional movement of fluid within the body might facilitate the transfer of heat from right below the dorsal integument, where solar energy is collected, to the arms where heat can be released to the environment.”

That heat movement alone only works so much, though. If there’s too much heat for the arms to contain, the sea star sheds an arm in an attempt to keep its core below 35 degrees. That’s not a great choice — regrowing an arm is costly — but it’s better than death. But even that won’t work when it’s just too darn hot.

Image courtesy of flickr user Jerry McFarland