Ducky orchids and insects

February 21, 2013 • 9:41 am

When I first saw these pictures I was startled, for the resemblance of this Australian orchid (Caleana major) to a flying duck is amazing.

Picture 1

In fact its common names are the “flying duck orchid” and the “big duck orchid”.

From Friends of the Cove National Park, Inc: http://www.friendsoflanecovenationalpark.org.au/Flowering/Flowers/Caleana_major.htm
From Friends of the Cove National Park, Inc: http://www.friendsoflanecovenationalpark.org.au/Flowering/Flowers/Caleana_major.htm

Kuriositas has the botanical details:

The duck orchid is a perennial but blooms in late spring or early summer.  At up to 45 centimeters in height you might think it would stand out in its natural habitat.  However, because of the reddy-brown colors of both the stem and flowers it moulds in to its Australian environs so expertly that it becomes almost invisible – unless you are deliberately seeking out its company.

Image Credit Flickr User Davidfntau: http://www.flickr.com/photos/96936558@N00/4208765488/
Image Credit Flickr User Davidfntau: http://www.flickr.com/photos/96936558@N00/4208765488/

I was tempted to write that this orchid is pollinated by male ducks, who try to copulate with the flowers and thereby affix pollen to their heads (this is in fact true for insects pollinating the wasp and bee orchids), but I knew at least one reader would be taken in. But the facts are just as striking:

The ‘upside-down’ flower is reddish-brown, 15-20 mm long. The labellum or tongue, at the top, is a deep red and attached to the rest of the flower by a sensitive strap. Pollination is via male sawflies. When the insect touches the sensitive labellum it snaps shut, trapping the insect in the sticky body of the column. It deposits pollen it may be carrying and picks up more. It is then released to fly to the next orchid.

I’d love to grow one of these (I have several wild orchids in my lab), but, alas, that won’t be. As Kuriositas notes:

 If you have suddenly been gripped by the desire to own your very own duck orchid then you will be disappointed.  Despite numerous attempts, this orchid stubbornly refuses to be propagated, and is only found in the wild. This is because the roots of caleana have a symbiotic relationship with the vegetative part of a fungus which only thrives in the part of Australia in which it originates. The fungus helps the plant to stave off infections and without its help the duck orchid never lasts long.

And the Aussies, God bless them, have put the orchid on a stamp:

Caleana-Orchid-04-210x300

Finally, in a bizarre coincidence, I found this—a duck-faced lacewing fly! (It’s actually a “spoon-winged lacewing” in the genus Nemia, family Nemopteridae.) Spoon-winged lacewings are also called “thread-winged antlions”, for their larvae are predators on ants and other insects.

It’s described on Piotr Naskrecki’s website, The Smaller Majority. Here’s the bill:

The head and mouthparts of spoon-winged lacewings is elongated and well-adapted for fitting into long corollas of flowers [Canon 1Ds MkII, Canon 100mm macro, 2 x Canon 580EX]; photo by Piotr Naskrecki
The head and mouthparts of spoon-winged lacewings is elongated and well-adapted for fitting into long corollas of flowers [Canon 1Ds MkII, Canon 100mm macro, 2 x Canon 580EX]; photo by Piotr Naskrecki
But it’s not just the face that’s weird—check out its hindwings!:

Spoon-winged lacewings (?Nemia sp.) from Richtersveld National Park, South Africa [Canon 1Ds MkII, Canon 100mm macro, 2 x Canon 580EX]; photo by Piotr Naskrecki
Spoon-winged lacewings (?Nemia sp.) from Richtersveld National Park, South Africa [Canon 1Ds MkII, Canon 100mm macro, 2 x Canon 580EX]; photo by Piotr Naskrecki
As Naskrecki explains, the “duckface” is adapted to dip into flowers to eat nectar and pollen, but we don’t know why those hindwings are so large:

These lacewings are easily recognizable thanks to their unique, extremely elongated or enlarged hind wings, reminiscent of the long plumes seen in some birds-of-paradise. The function of this unusual morphology is still not entirely known. In species with particularly enlarged hind wings their function appears to be to deter some predators by giving a false impression of the insect as much larger—and thus potentially stronger—than it really is. In species with long, thread-like wings their function may be related to the aerodynamics of the flight, and in members of the subfamily Crocinae the hind wings play a sensory function in cavernicolous habitats that these insects occupy.

I would have thought sexual selection is involved, making these beasts the insect equivalent of long-tailed widowbirds, but that would lead to sexual dimorphism, with males having much longer wings than females. And that’s apparently not the case.

To see other species in this bizarre group, go here.

h/t: GN

The assassin bug: aggressive mimicry of prey

February 15, 2013 • 1:35 pm

I’m shamelessly stealing this story from Alex Wild’s great Scientific American website, Compound Eye. His latest post describes a paper from the Proceedings of the Royal Society B (link below) by Wignali and Taylor, who show that assassin bugs from Australia (Stenolemus bituberus; these are true bugs in the order Hemiptera) kill spiders by entering their webs and producing vibrations that lure the spider by mimicking either the vibrations made by normal prey trapped in the web.  This shows that the evolution of mimicry need not involve any change in appearance but simply a change in behavior: in this case natural selection has favored those assassin bugs who are able to vibrate spider webs with the proper frequency.

Assassin bugs are usually called “thread-legged bugs” for obvious reasons:

Reduviidae: Emesinae (Belize); not the species used in the study but a related one. Photo used with permission.
Reduviidae: Emesinae (Belize); not the species used in the study but a related one. Photo used with permission.

They’re cryptic, too; as Alex notes: “In the field the insect looked like so little I thought it merely debris in a disorganized spider’s web. I didn’t see the faint outline of a young assassin bug until the debris shuddered, ever so slightly.” (Remember that some spiders, and of course bug-hunting birds, have keen vision.)

I hope my readers are now biology-savvy enough to understand the paper’s abstract:

Assassin bugs (Stenolemus bituberus) hunt web-building spiders by invading the web and plucking the silk to generate vibrations that lure the resident spider into striking range. To test whether vibrations generated by bugs aggressively mimic the vibrations generated by insect prey, we compared the responses of spiders to bugs with how they responded to prey, courting male spiders and leaves falling into the web. We also analysed the associated vibrations. Similar spider orientation and approach behaviours were observed in response to vibrations from bugs and prey, whereas different behaviours were observed in response to vibrations from male spiders and leaves. Peak frequency and duration of vibrations generated by bugs were similar to those generated by prey and courting males. Further, vibrations from bugs had a temporal structure and amplitude that were similar to vibrations generated by leg and body movements of prey and distinctly different to vibrations from courting males or leaves, or prey beating their wings. To be an effective predator, bugs do not need to mimic the full range of prey vibrations. Instead bugs are general mimics of a subset of prey vibrations that fall within the range of vibrations classified by spiders as ‘prey’.

Here’s another photo showing the bug entering a spider’s web for nefarious purposes:

Picture 2

Finally, a video (taken from the original paper via Alex) showing an assassin bug luring a spider to its death:

Some assassin bugs also kill spiders not by mimicking prey vibrations, but by sneaking up on them and stabbing them with their mouthparts (ergo their name). An earlier BBC report notes that, when using this latter tactic, assassin bugs are most likely to move toward their spider prey when the wind is blowing, masking any vibrations produced by their movement. They’re like ninja cats! This was demonstrated in clever experiments using fans to mimic the vibrations of spider webs produced by wind.

_________________

Wignali, A. E. and P. W. Taylor. 2013. Assassin bug uses aggressive mimicry to lure spider prey. Proc. R. Soc. B 7 May 2011 vol. 278 no. 1710 1427-143, Published online October 27, 2010 doi: 10.1098/rspb.2010.2060

See also: Wignall, A.E. . & Taylor, P.W. (2008). Biology and life history of the araneophagic assassin bug Stenolemus bituberus including a morphometric analysis of the instars (Heteroptera, Reduviidae).. Journal of Natural History 42: 59-76. (pdf here)

How the pebble toad rolls

January 12, 2013 • 12:40 pm

The best part of being an evolutionary biologist is learning about the endless ways that animals adapt to their existence and environment.  (The classic aphorism is “Natural selection is cleverer than you are.”)

And here’s a behavior completely new to me: the escape behavior of the pebble toad, Oreophrynella nigra, from Bolivia and Guyana. The inimitable Attenborough tells the tale:

An article at BBC EarthNews notes:

The toad is so small and light that the forces of impact are too tiny to cause it any harm.

However, as well as being less than impressive jumpers, the toads do not swim well.

So while most that land in puddles survive, there are reports of toads drowning after tumbling into deeper pools of water.

h/t: Christopher

The amazing mimicry of frogfish

November 29, 2012 • 4:54 am

I have a penchant for cases of mimicry, not only because they served as some of the earliest evidence for natural selection in Darwin’s time, but also because they show how far natural selection can achieve “perfection”—that is, how far do developmental and physical constraints prevent the evolution of an “optimum phenotype.” The answer is that constraints don’t matter much.

There are few cases in nature where one can judge how “optimum” an adaptation is, and mimicry is one of them. (Sex ratio is another.) What it shows, as this post demonstrates, is that it can be remarkably precise; that is, natural selection is pretty good at molding animals (and some plants) to hide their true nature by evolving to resemble either another organism or their environment. The resemblance can be astonishingly precise.

Finally, many examples of mimicry are simply unexpected, cool, and stunning. The first one below was sent to me by Matthew Cobb who got it from a tweet by M.J. Walker from the Blue Planet Society The photo is by Andrew Taylor.

One of these animals is a frogfish; the other is a sponge (yes, sponges are animals).  If you look closely you can see which is which, but it may not be so easy for a predator or a prey item. (Frogfish are almost all predators.)

Frogfish, sometimes known as “anglerfish” are in the order Lophiformes and the family Antennariidae; 47 species are recognized. 

Wikipedia has a good section on frogfish mimicry. I’ve reproduced it in the indented parts below, and inserted some pictures of different species of frogfish:

The unusual appearance of the frogfish is designed to conceal it from predators and sometimes to mimic a potential meal to its prey. In ethology, the study of animal behavior, this is known as aggressive mimicry. Their unusual shape, color, and skin textures disguise frogfish. Some resemble stones or coral while others imitate sponges, or sea squirts with dark splotches instead of holes. In 2005, a species was discovered, the striated frogfish, that mimics a sea urchin while the sargassumfish is colored to blend in with the surrounding sargassum.

Here’s the one, Antennarius striatus, that’s supposed to mimic a sea urchin:

Some frogfish are covered withalgae or hydrozoa. Their camouflage can be so perfect, that sea slugs have been known to crawl over the fish without recognizing them.

Here’s one that looks like an algae-covered rock:

Here’s another that looks like a sponge, hiding in a sponge:

For the scaleless and unprotected frogfish, the camouflage is an important defense against predators. Some frogfish can also inflate themselves, like pufferfish, by sucking in water in a threat display. In aquariums and in nature, frogfish have been observed, when flushed from their hiding spots and clearly visible, to be attacked by clownfish,damselfish, and wrasse, and in aquariums, to be killed.

Many frogfish can change their color. The light colors are generally yellows or yellow-browns while the darker are green, black, or dark red. They usually appear with the lighter color, but the change can last anywhere from a few days to several weeks. It is unknown what triggers the change.

If your appetite for mimetic frogfish isn’t sated, there’s a whole site devoted to them, http://www.frogfish.ch, which has a great page showing many mimetic animals.

To show how the mimicry works, here’s a sponge-mimicking frogfish nomming a cardinal fish. It’s fast!

Finally, a short clip of a frogfish feeding. It was filmed at 1000 frames per second and played at 10 frames per second, so this whole 17-second video represents 0.17 seconds in real time. Note how opening the mouth creates a suction that draws the prey in:

A free journal issue on experimental evolution

October 31, 2012 • 10:41 am

Biology Letters is offering free access to its latest issue on “experimental evolution,” an issue edited by Thomas Batailon, Paul Joyce, and my friend Paul Sniegowski. You can see the table of contents at the link above, and here are the free articles:

Feature Articles

Introduction – As it happens: current directions in experimental evolution
by Thomas Bataillon, Paul Joyce and Paul Sniegowski

Temperature, stress and spontaneous mutation in Caenorhabditis briggsae and Caenorhabditis elegans
by Chikako Matsuba, Dejerianne G. Ostrow, Matthew P. Salomon, Amit Tolani and Charles F. Baer

Mutational effects depend on ploidy level: all else is not equal
by Aleeza Gerstein

Genetic background affects epistatic interactions between two beneficial mutations
by Yinhua Wang, Carolina Díaz Arenas, Daniel M. Stoebel and Tim F. Cooper

Epistasis between mutations is host-dependent for an RNA virus
by Jasna Lalic and Santiago F. Elena

The role of ‘soaking’ in spiteful toxin production in Pseudomonas aeruginosa
by R. Fredrik Inglis, Alex R. Hall and Angus Buckling

Experimental evolution of multicellularity using microbial pseudo-organisms
by David C. Queller and Joan E. Strassmann

Model and test in a fungus of the probability that beneficial mutations survive drift
by Danna R. Gifford, J. Arjan G. M. de Visser and Lindi M. Wahl

Evolution of clonal populations approaching a fitness peak
by Isabel Gordo and Paulo R. A. Campos

Evolutionary rescue of a green alga kept in the dark
by Graham Bell

Competition and the origins of novelty: experimental evolution of niche-width expansion in a virus
by Lisa M. Bono, Catharine L. Gensel, David W. Pfennig and Christina L. Burch

Related Content

Discussion Meeting issue ‘Genetics and the causes of evolution: 150 years of progress since Darwin’ organized and edited by Michael Bonsall and Brian Charlesworth

‘Genomics of Adaptation’ Guest Edited by Professor Jacek Radwan and Dr Wiesław Babik

Evolution articles
Special Feature articles

Free articles on the genomics of adaptation

October 30, 2012 • 11:00 am

The Proceedings of the Royal Society (B) has a special issue on the genomics of adaptation that it’s making available for free to everyone. You can see the contents here; they include these articles, which can be accessed directly from my links.

Introduction: The genomics of adaptation
by Jacek Radwan and Wieslaw Babik

Research article: Genomic consequences of multiple speciation processes in a stick insect
by Patrik Nosil, Zach Gompert, Timothy E. Farkas, Aaron A. Comeault, Jeffrey L. Feder, C. Alex Buerkle and Thomas L. Parchman

Review: How does adaptation sweep through the genome? Insights from long-term selection experiments
by Molly K. Burke

Review: Gene duplication as a mechanism of genomic adaptation to a changing environment
by Fyodor A. Kondrashov

Review: The probability of genetic parallelism and convergence in natural populations
by Gina L. Conte, Matthew E. Arnegard, Catherine L. Peichel and Dolph Schluter