Category: Europe

Fir Trees & Building the World of the Distant Past

Understanding when and where a group of species evolved tells a story of the world they emerged into.

This past week, I had an interesting new scientific paper come across my desk, on the systematics of fir trees – genus Abies in the Pine family. I realize fir tree systematics is not what the average person might consider compelling reading, but if you look past the statistical tests and lines of code, systematics can be great reading for the imagination. In this paper, the researchers reconstructed the speciation pulse (a period of time when a bunch of species came into existence fairly quickly) of fir trees native to the Mediterranean Basin, then dated it using fossils. The main finding of the paper was that this burst had actually happened millions of years earlier than had been supposed.

The really neat part is how they then used this finding to paint a picture of the world when fir trees were colonizing the Mediterranean. At the time these fir trees diversified, what we now think of as the Mediterranean climate, temperate and favourable to biodiversity, didn’t exist, and wouldn’t for tens of millions of years yet. At this time, the Oligocene-Miocene boundary, around 23 million years ago, the global climate had been cooling for some time, which favoured the expansion of gymnosperms like firs. A single ancestor came to the Mediterranean from Asia and quickly (for trees) spread through the whole of the Mediterranean Basin, leaving a dozen or so new species in its wake. This was going on at a time when the first apes were evolving and glasslands were just forming for the first time. The Andes didn’t exist yet and Australia was moving northward and drying out. What we now know about Mediterranean fir trees adds a new detail to this picture of a world very different from, but turning into, our own.

In my own work on the systematics of the Dialiinae, I’ve always been captivated by a genus called Labichea. It’s a group of about 14 shrubs native to Queensland, Australia. The earlier evolving species of the genus have pinnate leaves with broad leaflets, sort of like walnut trees (but smaller and more oval). From this, there is an evolutionary progression to species with fewer leaflets, becoming long and thin, covered with hairs to keep the wind from pulling water away form the surface. They become tougher and more leathery to the touch. In one species, the leaflets have narrowed and curled up on themselves so much that they are, for all intents and purposes, needles now. Lining these species up next to one another is like watching a plant evolve and adapt to an increasingly hot, dry Australian outback in real time.

1cd40a9b21a55ec11d40b22d8183a7ea
Labichea stellata, one of the intermediate forms, with tough, leathery, narrow leaves adapted to a hot, dry climate.

Studying the morphology – the physical form – of a plant will tell you a lot about the challenges of the place it evolved and what it had to survive to make it to today, but reconstructing the evolutionary tree of a group creates a sort of speculative saga of a group of species changing as the world changed and it pushed out to new territories and new niches. 

I think that’s the difference between finding science a collection of dry facts and finding it utterly compelling to learn about… knowing that you need to see the forest rather than just the trees, and to find the story of life that all those facts come together to tell you.

 

[Note to sharp readers: yes, I know those are not fir trees in the image. But those are definitely the mists of time you’re seeing between them.]

Cuckoos: Outsourcing Childcare, Hogging the Bed

(Via:)
(Via: Batsby)

Common Name: Parasitic Cuckoos

A.K.A.: Subfamily Cuculinae (Family Cuculidae)

Vital Stats:

  • Range in length from 15-63cm (6-25”) and weigh between 17g (0.6oz.) and 630g (1.4lbs.)
  • The majority of cuckoos are not parasites, but around 60sp. are (about 56 in the Old World, and 3 in the New World)
  • Babies of brood parasites are initially coloured so as to resemble the young of the host species

Found: The cuckoo family is present throughout the temperate and tropical world, with the exceptions of southwest South America and regions of North Africa and the Middle East. Parasitic cuckoos occupy a subset of this range, principally in the Old World.

Cuckoo Map

It Does What?!

Parenting is tough… less sleep, less free time, all those all those hungry mouths to feed. What’s a busy mother to do? You know you need to perpetuate the species, but who has the time? Impressively, cuckoos have come up with the same answer that many humans have: outsourcing! Involuntary outsourcing, in this case.

One of these things is not like the others.(Via: Timothy H. Parker)
One of these things is not like the others.
(Via: Timothy H. Parker)

Once a female cuckoo has mated and is ready to lay the eggs, rather than build a nest and slog her way through childcare, she waits for another female with freshly laid eggs to take off for some food and just lays her egg there, spreading her clutch across several nests. In theory, when the duped female returns, she’ll just settle in and care for the new egg along with her own. Cuckoo eggs have a shorter incubation period than that of their host, so the foreign egg usually hatches first, at which point the baby cuckoo just gives the other eggs (or chicks, if the timing didn’t quite work out) a good shove, and enjoys having both a nest and a doting mother to itself. The cuckoo chick will tend to grow faster than its host species, so it keeps its adoptive parent busy with constant begging for food, having eliminated the competition.

But this wouldn’t be a fun evolutionary arms race if the host species just took it on the chin. Birds plagued by cuckoo eggs have worked out several ways to try to cope with the problem. First off, and not surprisingly, they’ve developed a burning hatred of cuckoos. Adult cuckoos seen in the area of the hosts’ nests will immediately be mobbed and run off by a group of angry mothers. The cuckoos, however, have learned to use this to their advantage by having the male of a pair tease and lure the angry mob away while the female lays her eggs in peace. Advantage: cuckoos.

And this, kids, is how you deal with those annoying younger siblings.(Via: M. Bán, PLoS ONE)
And this, kids, is how you deal with those annoying younger siblings.
(By: M. Bán, PLoS ONE)

A second strategy used by the parasitised birds is to learn to recognise foreign eggs and pre-emptively toss them out of the nest. Cuckoos responded to this in two ways. First, they slowly evolved eggs to match those of their host bird in colour and size (or, in the case of covered nests, very dark eggs which aren’t easily seen at all). Bird species with higher levels of egg rejection just end up with cuckoo eggs which look more and more similar to their own. Second, if a host does reject the foreign egg, the cuckoo who laid it will sometimes come and just destroy the entire nest, killing anything left inside it in an act of motherly vengeance. Advantage: cuckoos.

A third strategy, developed by the Superb Fairy Wren (not to be confused with the equally floridly named Splendid Fairy Wren) is a bit more clever. As soon as the host mother lays her eggs, she begins to sing to them in a very specific pattern. Now, in this case, the cuckoo egg will hatch around the same time as her own eggs, but was deposited there several days later than her own. This means that her own chicks have been sitting there, unborn, learning her song for a longer period of time than the cuckoo has. Once the eggs are hatched, only her own chicks will be able to properly replicate her calls. Can’t sing the song? No food for you. And if, prior to starving to death, the parasite chick does manage to push her chicks out of the nest, the mother will fail to hear the proper response at all and know to simply abandon the nest entirely. Advantage: Fairy Wren. Superb indeed.

Shrikes: don't try to outsmart a bird that kills mammals for sport.(Via: Arkive.org)
Shrikes… don’t try to outsmart a bird that kills mammals for sport.
(Via: Arkive.org)

There is at least one known case of a former host species throwing off the yoke of cuckoo parasitism entirely. The red-backed shrike, aside from being particularly murderously aggressive toward adult cuckoos (and many other things), became very good at identifying cuckoo eggs, very quickly. So quickly, in fact, that researchers believe the cuckoos simply didn’t have time to adapt. In laboratory experiments, the shrikes correctly identified and rejected 93.3% of all cuckoo eggs placed in their nests. Pretty good pattern recognition for a brain the size of a pea. While cuckoo-red shrike parasitism has been known historically for some time, it hasn’t been seen in nature for the last 30-40 years.

Shrikes for the win.

Fun Facts:

  • Even typically non-parasitic cuckoos will sometimes lay their eggs in the nests of their own or other species, but will still help to feed the chicks (parental guilt, perhaps?).
  • The eggshells of parasitic cuckoos are unusually thick, helping prevent them from cracking as their mother drops them from above into the host nest.
  • Striped cuckoos, not content to just shove their adoptive siblings out of the nest, actually peck them to death with their beaks.
  • A few birds deal with homicidal cuckoo chicks by building steep-sided nests, making it difficult for any chick to be pushed out (and raising them as one big, happy family, I guess).

Says Who?

  • Colombelli-Négrel et al. (2012) Current Biology 22: 2155-2160
  • Feeney et al. (2012) Animal Behaviour 84: 3-12
  • Lovaszi & Moskat (2004) Behaviour 141(2): 245-262
  • Spottiswoode & Stevens (2012) American Naturalist 179(5): 633-648
  • Wang & Kimball (2012) Journal of Ornithology 153: 825-831

Living in Filth and Looking Up at the Stars

(Via:)
(Via: Wikimedia Commons)

Common Name: Dung Beetles

A.K.A.: Subfamily Scarabaeinae

Vital Stats:

  • Many subsist entirely on faeces, while others also consume fungi and decaying plant matter
  • Found in extremely diverse habitats, on all inhabited continents
  • Grow up to 6cm (2.4”) long, and can live for up to three years

Found: Across the temperate and tropical regions of the world

Dung Beetle Map

It Does What?!

Dung beetles… if you believe in reincarnation, these are why you try to stay on the straight and narrow. Otherwise, you might end up coming back as a creature whose life quite literally revolves around excrement. Dung beetles owe their entire existence to the fact that larger animals have inefficient digestive systems, consuming manure for its remaining nutrients and even laying their eggs inside it as food for their future young. Gross, yes, but once you get past the “ick” factor, it’s a pretty practical system.

Dung beetles come in three main varieties: rollers, tunnellers, and dwellers. Rollers, which are the type most people are familiar with, roll faeces into small balls which they roll away with them to consume and bury elsewhere. Tunnellers dig under the dung, burying it on site as an underground food source. Dwellers, the slackers of the dung beetle world, don’t bother with burying their treasure, preferring to simply live in it where it falls. I’ll focus on the rollers from here on in, as they’re the most bizarrely specialised of the bunch.

Dung beetles find their warm, fresh meals either through their excellent sense of smell or, in the case of some species, by simply riding around on their chosen food provider until the right time comes. Studies have shown that the beetles prefer omnivore or herbivore droppings to those of carnivores, perhaps for the more easily-digestible plant matter. One particularly intrepid group of researchers even determined that human faeces are favoured above those of most other large mammals. Good job, guys. Your funding agency must be proud.

It's a hot commodity... so to speak.(Via: Wikimedia Commons)
It’s a hot commodity… so to speak.
(Via: Wikimedia Commons)

Rollers immediately set to work on a new pile of droppings by shaping a dense little ball of up to ten times their weight (about TimBit sized, for you Canadians out there. Mmm!). Before rolling the ball away to be eaten/buried for later, the beetle will climb up on it and do a sort of dance, rotating around its top. Researchers also observed the beetles doing this dance if their rolling path was disturbed, or if another beetle stopped them to try to steal their ball.

So why the dance? As you might guess, it’s a means of getting their bearings, but what’s really fascinating is how they’re doing it. Dung beetles always roll their balls in a straight line directly away from its origin, probably as a means of reducing competition from other nearby beetles as quickly as possible. And they do this despite facing the ground as they roll the ball with their hind legs. During the day, this was fairly obviously accomplished by positioning themselves according to the direction of the sun, using their dorsal vision. However, they can also do it on a clear, moonless night. How?

Using a planetarium and a series of experiments which, hilariously, involved fitting the dung beetles with little cardboard hats to block their overhead vision, a South African researcher has determined that the beetles are actually using the light from the Milky Way to navigate. This is the only known instance of animals using an entire galaxy to orient themselves. Birds and seals have been known to use stars for positioning, but never the Milky Way itself. This from a tiny creature that cleans up piles of poop for a living… there’s probably an inspiring metaphor here somewhere.

Goes great with coffee!(Via: Wikimedia Commons)
Goes great with coffee!
(Via: Wikimedia Commons)

In the “But what does it do for me?” department, dung beetles are actually immensely useful to humans. Beyond restoring important soil nutrients, in areas of intense cattle-grazing, the beetles cart off and bury literally tonnes of manure that would otherwise host dangerous parasites and disease-carrying flies. Australia has intentionally introduced African dung beetles for this express purpose. Results have been much better than certain other introductions there.

The value of dung beetles has apparently been recognised for a very long time. Ever heard of the sacred scarab beetles of ancient Egypt? Yep… they’re dung beetles. One and the same. The beetles represented transformation and were linked with the god of the rising sun, who was believed to remake the sun and roll it across the sky each day, like the beetle with its ball. Something to think about next time you’re watching a beautiful sunrise.

[Fun Fact: Dung beetles in the African savanna use their dung balls as thermal refuges, periodically climbing up on them to moisten and cool their feet, which can increase in temperature by as much as ten degrees as they travel over the hot ground.]

Says Who?

  • Baird et al. (2012) PLoS ONE 7(1): e30211
  • Chamorro-Florescano (2011) Evolutionary Ecology 25: 277-289
  • Dacke et al. (2013) Current Biology 23: in press
  • Smolka et al. (2012) Current Biology 22(20): R863-R864
  • Whipple & Hoback (2012) Environmental Entomology 41(2): 238-244

Necessity is the Mother of Invention, or, How to Eat Like a Shrike

(By: Arthur Morris, Via: Livebooks Blog)

Common Name: The Shrike

A.K.A.: Family Laniidae

Vital Stats:

  • Family consists of three genera and around 30 species
  • Shrikes range in size from 17cm (6.5”) up to 50cm (20”) long
  • Feathers may be black and white, cream, grey, or brown

Found: Various species found in North America, Southern Africa, and Eurasia

It Does What?!

Sometimes a creature aspires to a spot a little higher on the food chain, but doesn’t quite have all the equipment to get there. Behold the shrike, the bird that wishes it were a raptor. Like birds of prey, shrikes have strong, hooked beaks, sharp eyes, and an appetite for meat, but they’re missing a couple of important features. First, and most important… no talons. Shrikes can’t grab a victim and tear it into pieces like a hawk or falcon could. And second, no crop (a sort of internal storage pouch), so they can’t eat a large quantity of meat in a single sitting.

Not to be deterred by their anatomical shortcomings, these inventive go-getters have come up with a single solution to both problems. Two birds with one stone, if you will. After dispatching their prey with a quick beak to the back of the neck, shrikes will carry the carcass to a nearby shrub and actually impale it on a short branch or thorn. Aside from looking incredibly badass, this serves to anchor the body in one place, allowing the shrike to use its beak to rip the meat into pieces. What’s more, the bird can just leave its leftovers hanging there for later, like the meat locker at a butcher shop. [Wondering what that looks like? Here’s a video, set to appropriately ominous music.]

And now they’re learning to use human technology…
(Via: Nature Saskatchewan)

What kind of prey are we talking about here? Anything from small insects right up to mice, frogs, lizards, and other birds. There’s even a record of one killing and impaling a good-sized bat. Impressively, shrikes have also hit on the value of ageing their food – one species hunts the toxic lubber grasshopper of the southern United States. The dead grasshoppers are then left hanging for several days to let the poison degrade before being eaten. Clever birds.

Shrikes are monogamous and share in parenting duties; when the female is sitting on eggs, it’s the male’s job to go out and kill something nutritious for two. Of course, this makes selecting a good hunter an important task for females during mate selection. When a single male wants to advertise his skills, he makes a conspicuous display of his biggest, most impressive kills for any prospective ladies. Once he’s gotten one’s attention, he performs a mating dance that mimics the action of impaling prey on branches and then feeds her from his assortment of carcasses. (Be sure to include this point next time you’re explaining ‘the birds and the bees’ to someone.)

The owner of this lizard is probably off getting lucky.
(Via: Wikimedia Commons)

I guess when you have only one major skill, you want to make the most of it, because aside from eating and attracting mates, shrikes also use their impaling trick for communication. Bonded pairs are territorial and will defend their terrain from others of their species. In a sort of macabre message to would-be trespassers, the couple will mount their kills around the borders of their land, perhaps in an effort to show others what could become of them if push came to shove. (Did I mention these things actually have a comic book monster named for them? Eat your heart out, Batman.) Unfortunately for them, researchers note that this action often resulted in the prey being snatched by opportunistic passers-by and having to be replaced. It’s so hard to look murderous when everybody keeps stealing your victims…

[Fun Fact: Shrikes with young chicks will often eat only the head of their prey, saving the bodies for the kids. ‘Cause that’s just good parenting.]

Says Who?

  • Keynan & Yosef (2010) Behavioural Processes 85: 47-51
  • Sarkozi & Brooks (2003) Southwestern Naturalist 48(2): 301-303
  • Smith (1973) Behaviour 44(1/2): 113-141
  • Yosef & Pinshow (2005) Behavioural Processes 69: 363-367
You’re next.
(Via: Tough Little Birds)

Ergot: Bringing the Crazy Since 800 A.D.

(Via: The University of Illinois Extension Collection)

Common Name: Ergot, Ergot of Rye

A.K.A.: Claviceps purpurea (and other Claviceps species)

Vital Stats:

  • Around 30-40 species in genus Claviceps, all parasites of various types of grasses
  • Parasitizes rye, barley, and wheat crops in temperate regions
  • Problematic in Africa due to its parasitism of sorghum and millet

Found: Throughout temperate and tropical regions, though historically most problematic in Europe, Africa, and North America

It Does What?!

Disrupts human history and generally scares the hell out of people, to put it mildly. But before we get into that, let’s start with what this stuff is. An ergot infection begins when a microscopic fungal spore lands on the open floret of a grass plant. In northern agricultural areas, rye and, to a lesser extent, barley are particularly susceptible to these spores. Once on the receptive flower, the spore behaves as though it were a pollen grain, growing down the style until it reaches the ovary. At this point, it destroys the ovary and links into the adjoining vascular tissue, where it can parasitize the plant for nutrients.

With plenty of food on tap, the fungus grows into the space that the grain would have otherwise filled. Early on, it forms into a soft, white mass that causes a sugary liquid to drip from the flower. This liquid is filled with spores and is spread to other plants by hungry insects as they fly from flower to flower. Later in the growing season, around the time neighbouring non-parasitized grains are ripening, the fungal mass dries and hardens into a sclerotium (a sort of fungal seed body) that looks a bit like wild rice, and drops to the ground. This sclerotium will sit dormant on the ground until spring, when moisture will cause it to sprout small mushrooms, which produce spores for the new season.

Hint: Wild rice doesn’t do this when you get it wet.
(Via: mycotopia.net)

Still reading? Good. Here’s the interesting part. Let’s say you’re a farmer in the Middles Ages, and the infected plants in question are in your field. Before the ergot sclerotia drop to the ground, they get harvested with the rest of the crop, and end up getting made into bread for you and your family. Well, it turns out those sclerotia are full of a toxic alkaloid called ergotamine, and after eating enough loaves of bread to build the compound up in your systems, you and your nearest and dearest have contracted ergotism. Fed some of that rye to your cows? Now they’ve got it, too!

Ergotism delivers a one-two punch of physical and psychological symptoms. Physically, the alkaloid constricts blood vessels, leading to an intense burning sensation in the arms and legs which can eventually cause gangrene and loss of the entire limb. Some sufferers also develop a persistent ringing in the ears. That’s before the seizures and untimely death set in. Psychologically… well, it makes you crazy. As in, hallucinations and irrational behaviour, which lead many victims to be ostracised by their communities. Ergotism is speculated to have been the cause of the Dancing Mania (not as fun as it sounds) that hit Europe in the Middle Ages. Huge numbers of people were struck by an uncontrollable urge to dance – violently and while screaming – until they collapsed from exhaustion. Did I mention that this stuff is where LSD came from? The drug was originally synthesised from ergotamine, handily delivering all the craziness with none of the gangrenous limb loss.

Nope, nothing suspicious-looking here.
(Via: Wikimedia Commons)

The cure for all this horror? Well, if you got to it early enough, simply not eating any more contaminated grain would cause symptoms to slowly abate. Unfortunately for medieval peasants, who ate a lot of rye and suffered most of history’s outbreaks, the cause of the disease was completely unknown. Weird-looking sclerotia were so common that they were thought to be a natural feature of rye. That old standby, “It’s the wrath of God” actually seemed supported, since sufferers who left the affected area on pilgrimages immediately began to show improvement (hence another term for the disease, ‘Holy Fire’). Sadly, it took the better part of a millennium before someone worked out what was really going on, and major outbreaks occurred right up to the 19th century. Even in the 21st century, minor outbreaks have occurred in developing countries, such as the case in Ethiopia in 2001, caused by infected barley.

Speaking of disrupting human history, some researchers have speculated that an ergotism outbreak caused the strange behaviour that resulted in the Salem witch trials of the late 17th century. Others have disputed this claim, noting, among other points, that ergotism was known and recognisable by this point in history. We may never know for sure.

[For other historical events in which ergotism may have played a role, check out the first reference below.]

[Fun Fact: Due to its action as a vasoconstrictor, ergotamine is now used, in purified form, to treat migraines and post-natal bleeding.]

Says Who?

Death from Below! (The Purse-Web Spider)

(Via: Wikimedia Commons)

Common Name: Purse-Web Spiders

A.K.A.: Family Atypidae

Vital Stats:

  • The family contains three genera; Atypus, Calommata, and Sphodros
  • Females reach up to 30mm (1.2”) in length
  • Fangs can measure up to half the spider’s body length
  • Prey includes crickets, beetles, millipedes, ants, wasps, and other spiders
  • Web tubes measure up to half a metre (20”) from top to bottom

Found: Africa, temperate regions of North America, Europe, and Asia

It Does What?!

Imagine you’re a beetle, peacefully strolling along the forest floor, minding your own business, when suddenly, two enormous black spikes drive up out of the earth and impale you through the abdomen. As everything fades to black, your last beetle-ly thought is, “What the hell was that?!”

You have just become a tasty lunch for the purse-web spider.

So how does this work? Well, unlike most of the spiders we’re familiar with – those with small, pincer-like mouths that sit in webs all day – purse-webs are a type of primitive spider called a mygalomorph. In this group, the fangs are like a pair of large (relative to the spider) tusks that only move up and down; they don’t pinch, and this feature lends itself to some rather creative hunting methods.

Rather than constructing a flat, aerial web designed to have something fall into it, the purse-web spider spins what is essentially a silken tube-sock. The ‘foot’ of this sock lies along a slight depression in the ground, while the upper part lies vertically against a tree or rock (or, in some species, angles downward into the earth). The spider will then place bits of bark and lichen onto both parts of the web as camouflage. Over time, moss will actually begin to grow on the web, completing the disguise. All the spider needs to do now is wait, suspended from the ceiling of her underground lair, for some unwitting creature to walk over it. When this happens, she rushes to the source of the disturbance and spears her prey from below with her fangs before they realise what hit them (like this).

Invisible by spider standards, anyway.
(Via: Wikimedia Commons)

The spider will be vulnerable to larger predators if she ventures out into the open, so she simply cuts a slit in the web, drags her impaled prey inside, and seals up the hole again. Having sucked out their delicious insides, she then drops the dead husks out of the top of her sock like so much household garbage. In fact, researchers determined the diet of the purse-web spider by noting the various exoskeletons hanging from the outside of the web, having gotten caught on their way down. Apparently, all the dead bodies seemingly stuck to the side of a nearby tree aren’t much of a deterrent to other passersby.

So, since these spiders never leave their burrows, and kill anything that approaches, mating must be tricky, right? Right. The male is attracted to the female’s web by means of pheromones, and ventures out to find it. Once he locates the web, he must be very careful, tapping at the outside of the tube in a way that indicates he isn’t prey. Ultimately, though, whether he’s prey or not will be up to her. If the female inside isn’t yet mature or is already pregnant, she won’t hesitate to eat him when he attempts to enter the burrow. Researchers experimenting with placing male spiders in or near the webs of unreceptive females noted, essentially, that they run like hell as soon as they figure out what’s what. Research is amusing sometimes.

A male purse-web spider on what will be either the best or worst day of his life.
(Via: Florida Backyard Spiders)

But in the happy instances where the female is willing to mate, the male enters safely, and in fact continues to live with her for several months of domestic bliss before he dies naturally. And then she eats him anyway. Spiders are not sentimental creatures. Her eggs will take almost a year to hatch, and the young will stay with her for nearly another year after that, before striking out in the world to spin their own tube-sock of death.

Says Who?

  • Beatty (1986) Journal of Arachnology 14(1): 130-132
  • Coyle & Shear (1981) Journal of Arachnology 9: 317-326
  • Piper (2007) Extraordinary Animals: an encyclopedia of curious and unusual animals. Greenwood Press, Westport CT.
  • Schwendinger (1990) Zoologica Scripta 19(3): 353-366

The Bloodhounds of the Plant World (Cuscuta sp.)

(Via: Marine Science)

Common Names: Dodder, Goldthread, Witch’s Shoelaces

A.K.A.: Genus Cuscuta

Vital Stats:

  • Approximately 200 species
  • Part of the Convolvulaceae family, which includes morning glory and sweet potato
  • Only 15-20 species are considered to be problematic crop parasites

Found: Throughout temperate and tropical parts of the world

It Does What?!

We’ve discussed a few parasites on this blog already, and they’ve all been pretty typical of what comes to mind when we think of parasitic organisms- tiny, malignant little creatures that invade the host’s body, steal its resources, and, in some cases, eat its tongue. But when we think ‘parasite,’ we don’t usually think ‘plant.’ As it turns out, there are an estimated 4500 parasitic species just among the angiosperms, or flowering plants. Among them, dodders have to be one of the strangest.

Found nearly throughout the world, these vine-like plants begin as tiny seeds that germinate late in the spring or summer, after their potential host plants have established themselves. The young seedling has no functional roots and little or no ability to photosynthesize, so initially, it must make do with what little nutrition was stored in its seed. This isn’t much, so the plant has only a few days to a week to reach a host before it dies. To better its chances, the dodder stem swings around in a helicopter-like fashion as it grows, trying to hit something useful.

Much more impressive is the plant’s other method of finding suitable hosts- a sense of smell. Recent research has found that, uniquely among plants, the dodder can actually detect odours given off by surrounding plants and grow towards them. In experiments, the seedlings were found to grow toward the scent of a tomato, even if no actual plant was present. What’s more, they are capable of showing a preference among hosts. Presented with both tomato plants, which make excellent hosts, and wheat plants, which make poor hosts, seedlings were found to grow toward the aroma of tomatoes much more often. Like herbivores, they can use scent to forage amongst a variety of species for their preferred prey.

Smells like lunch… even to other plants.
(Via: Wikimedia Commons)

Once a host plant is found, the dodder begins to twine itself around the stem and to form haustoria (singular: haustorium). These are like tiny tap roots that pierce the host’s stem and actually push between the living cells inside until they reach the vascular system. Once there, the haustoria enter both the xylem (where water and minerals move upward from the roots) and the phloem (where sugars from photosynthesis move around the plant). From these two sources, the dodder receives all its nutrients and water, freeing it from any need for a root system, or even a connection to the soil. And since it doesn’t need to capture solar energy, all green pigment fades from the parasite, and it turns a distinctive yellow or red colour. Leaves aren’t necessary either, which is why the plant is essentially nothing but stem, explaining its common name of “witch’s shoelaces.”

Not what you want to see when you head out to weed the garden.
(Via: County of Los Angeles)

Once it gets comfortable on its new host, the dodder can grow at a rate of several centimetres a day (impressive for a plant) and produce stems of a kilometre or more in length, quickly overrunning an area. It can also attach itself to additional hosts – hundreds, in fact – which is problematic, because at this point it becomes the plant equivalent of a dirty shared needle. Since the vasculature of the hosts is connected, any virus present in one host can be freely transferred to any other. This ability, coupled with its affinity for potatoes, tomatoes, tobacco, and several other important crops, makes dodder a major nuisance for many farmers. And since it’s able to regenerate from just a single, tiny haustorium left in a host plant, it’s really hard to get rid of. There’s always a flip side, though; in some ecosystems, dodder can actually maintain biodiversity by preferentially parasitising the more competitive plants, allowing the weaker ones to survive. It seems dodder may also be the Robin Hood of the plant world.

[Extra Credit: Here’s a video showing how dodder can completely take over a group of nettle plants, complete with ominous soundtrack. Narrated by the fantastic Sir David Attenborough.]

Says Who?

  • Costea (2007-2012) Digital Atlas of Cuscuta (Convolvulaceae). Wilfred Laurier University Herbarium, Ontario, Canada
  • Furuhashi et al. (2011) Journal of Plant Interactions 6(4): 207-219
  • Hosford (1967) Botanical Review 33(4): 387-406
  • Pennisi (2006) Science 313: 1867
  • Runyon et al. (2006) Science 313:1964-1967

    Cuscuta: 1, Acacia: 0
    (Via: Wikimedia Commons)

Advertising in the Wild… Not So Very Different (Ophrys sp.)

(Via: lastdragon.org)

Common Name: Bee Orchids

A.K.A.: Genus Ophrys

Vital Stats:

  • 30-40 recognised species in the genus
  • Grows to a height of 15-50 cm (6-20”)
  • The name Ophrys comes from a word meaning “eyebrow” in Greek, for the fuzzy edges of the petals
  • First mentioned in ancient Roman literature by Pliny the Elder (23-79 A.D.)

Found: Throughout most of Europe and the British Isles

It Does What?!

We tend to think of animals (including humans) as using plants to serve our ends exclusively- we eat them, clothe ourselves with them, build homes with them, and so on. But for all the obvious ways in which the animal kingdom takes advantage of the plants, there are numerous, more subtle, ways that they use us to do their bidding. One of those ways is as pollinators; plants enlist animals to help them reproduce. And while that enlistment often takes a rather mundane form – a bit of pollen brushed onto a bird’s head as it sips nectar, say – sometimes a group of plants will get a bit more creative about it. Such is the case with the bee orchids.

These highly specialised flowers depend on very specific relationships with their pollinators; often only a single species of bee (or wasp, in some cases) will pollinate a given species of orchid. Without those pollinators, the orchids can’t produce seed and would die out. So how do you control a free-roving creature that has other places to be? Why, sex, obviously. (Isn’t that the basis of most advertising?) The bee orchid has evolved a flower that not only looks, but smells like a virgin female of the bee species which pollinates it.

May not be appropriate for younger readers.
(Via: This Site)

At a distance, the bee detects the pheromones of a receptive female. Once he moves in closer, there she is, sitting on a flower, minding her own business. So he flies in and attempts to do his man-bee thing, only to find that he’s just tried to mate with a plant. Mortified (I imagine), he takes off, but with a small packet of pollen stuck to his head. He’s memorised the scent of this flower now and won’t return to it, but amazingly, the orchids vary their scent just slightly from one flower to the next, even on the same plant, so that the duped bee can never learn to distinguish an orchid from a female. What’s more, because the scent is more different between plants than between flowers on the same plant, he is more likely to proceed to a different plant, decreasing the chances that an orchid will self-fertilise.

Hilariously, researchers have shown that, due to their higher levels of scent variation compared to true female bees (variety being the spice of life, right guys?), male bees actually prefer the artificial pheromones of the orchids over real, live females. In experiments where males were given a choice between mating with an orchid and mating with a bee, they usually chose the flower, even if they had already experienced the real thing.

So there you have it. Plants: master manipulators of us poor, stupid animals.

Who could resist?
(Via: Wikia)

Says Who?

  • Ayasse et al. (2000) Evolution 54(6): 1995-2006
  • Ayasse et al. (2003) Proceedings of the Royal Society, London B. 270: 517-522
  • Streinzer et al. (2009) Journal of Experimental Biology 212: 1365-1370
  • Vereecken & Schiestl (2008) Proceedings of the National Academy of Science 105(21): 7484-7488
  • Vereecken et al. (2010) Botanical Review 76: 220-240

A Shellfish Goes to the Dark Side (Sacculina carcini)

The crab barnacle, hitchin’ a ride.
(Image by Hans Hillewaert)

Common Name: Crab Barnacle, or the charmingly descriptive Dutch term “krabbenzakje,” meaning “crab bag”

A.K.A.: Sacculina carcini (and other Sacculina species)

Found: In the coastal waters of Europe and North Africa

It Does What?!

Most barnacles, those almost quaint crusts seen decorating old piers and ships, live their lives by cementing themselves to a hard underwater surface and using their arm-like limbs to pull passing bits of food into their mouths all day. Not so for the crab barnacle, who decided that all that arm-waving was for chumps and set about evolving into the ultimate free-loader.

Normal, hardworking barnacles, for the sake of comparison…
(Image by Michael Maggs)

In its immature larval form, Sacculina has a similar body plan to other barnacles and is able to swim about freely; however, rather than finding a surface to settle down on, it finds itself a crab. Typically, this will be a green crab, species Carcinus maenas. The female barnacle (more on the males later) crawls along the surface of the crab’s shell until she comes to a joint – a chink in the armour – where she turns into a sort of hypodermic needle, injecting herself into the crab and leaving her limbs and shell behind. Now nothing more than a tiny slug-like mass, she makes her way to the crab’s abdomen and proceeds to grow rootlike tendrils throughout her host’s body, drawing nutrients directly from the bloodstream.

If that wasn’t disturbing enough, consider Sacculina’s mode of reproduction. In addition to its internal root system, the parasite forms an external sac (hence the nickname ‘crab bag’) where the female crab normally keeps her fertilized eggs. This is where the male barnacle comes into play. Upon finding a crab already infected by a female, the male will do the same needle trick, injecting himself into the external sac and living for the rest of his life as a parasite inside the female’s body. Fertilization takes place and the sac is soon full of microscopic Sacculina larvae.

In case you needed a closer look.

Since the barnacle infection has rendered the host sterile, and because crabs aren’t very bright, the crab will now care for this sac of larvae as if they were her own young. But what if the infected crab was male, you ask? No problem. The parasite is able to interfere with his hormones to such an extent that, in addition to changing his body shape to that of a female, he now actually behaves like, and even carries out the mating gestures of, a female crab.

Now, this may not seem so bad from the point of view of the crab; I mean, it doesn’t know it’s carrying around evil changeling spawn, right? But it’s a bit worse than that. Wanting to keep all the available energy for its own use, the parasite prevents the crab from moulting its shell or re-growing lost claws, as crabs normally do. This leads to a variety of secondary infections which, coupled with malnutrition, leads to the premature death of the crab. But nature isn’t without a sense of fair play… research has now found that Sacculina sometimes succumbs to viruses and yeast naturally present in the crab’s body, via infection of its rootlets. Take that, bloodsucking barnacle!

Says Who?

  • Powell & Rowley (2008) Diseases of Aquatic Organisms 80: 75-79.
  • Zimmer (2000) “Do parasites rule the world?” Discover Magazine (August issue).
  • Russell et al. (2000) Journal of the Marine Biological Association of the U.K. 80: 373-374.
  • Mouritsen & Jensen (2006) Marine Biology Research 2: 270-275.
  • Goddard et al. (2005) Biological Invasions 7: 895-912.

The Plight of the Spheroid Seaweed (Aegagropila linnaei)

Everyone’s Favourite Freshwater Pet
(via: http://commons.wikimedia.org/wiki)

Common Name: Lake Balls, Marimo

A.K.A.: Aegagropila linnaei

Found: Japan, Iceland, Scotland, Estonia, Germany

It Does What?!

Sure, you’ve had dogs and cats as pets, maybe even fish or lizards… but what about a big ball of algae? Probably not, but if you live in Japan, this idea won’t seem so odd.

Lake balls, or marimo, as the Japanese refer to them, are a rare and unique growth form of the filamentous green algae species Aegagropila linnaei. They occur in only a few isolated habitats worldwide because, unlike most algae, the species lacks a desiccation (dryness) resistant life stage which would allow it to be carried to distant bodies of water. The balls are formed from a densely-packed clump of algal strands which grow outward in all directions, and can reach up to 25cm (10 inches) in diameter. New balls can form from the free-floating form of the same species, or from the breakup and re-growth of an old ball. Found in shallow lakes with sandy bottoms, gentle wave action rolls the clump around, forming a near-perfect sphere and allowing all sides of the ball to receive light for photosynthesis. Seen rolling lazily around the lake bottom, and even rising and falling on columns of warm water, the marimo can almost seem sentient.

It is this bizarre movement and their strangely beautiful appearance which have made marimo so popular in Japan, where they are protected as a “natural monument” and even appear on postage stamps. Unfortunately, it has also been their downfall. Because the algae reside in fresh water and are adapted to low light conditions, they are easily cared for, leading many people to collect them and keep them in their homes. The Japanese believed that a healthy, well looked-after marimo would make the owner’s wishes come true. Lake balls eventually became so rare, due to both human collecting and pollution, that in the early 1950s, a campaign was launched asking Japanese citizens to return their beloved marimo to the lakes from which they had been taken. Impressively, people did so, and in large numbers. In honour of their selflessness, the first annual marimo festival was held, and has continued ever since. Today, the lake ball has become an important environmental symbol in Japan, and children even have their own stuffed marimo toy character, Marimokkori, to play with.

Japanese kids have the best toys, no?

Says Who?

  • Boedeker et al. (2010) BioScience 60(3): 187-198
  • Soejima et al. (2009) Aquatic Ecology 43: 359-370
  • www.marimoballs.com