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Thank a Horseshoe Crab

(Via: reefguide.org)

Common Name: Horseshoe Crab

A.K.A.: Family Limulidae

Vital Stats:

  • Four extant species of horseshoe crab in three genera (Limulus, Carcinoscorpius, and Tachypleus)
  • Females are larger than males, and can reach up to 60cm (24”) long in some species
  • Believed to live between 20 and 40 years

Found: Coastal waters of southeast Asia, Oceania, and eastern North America

It Does What?!

Like the platypus and the lungfish, horseshoe crabs are what biologists refer to as “living fossils,” meaning their basic form has gone essentially unchanged for many millions of years. In the case of horseshoe crabs, fossils as old as 445 million years have been found that are quite similar to the extant species of today.

Despite their common name, the Limulidae aren’t true crabs. They’re arthropods, like crabs, but are actually more closely related to spiders and scorpions. In fact, beneath that tough shell, they do look quite spider-like. If spiders had tails, that is.

Basically a tarantula in combat gear.
(Via: Wikimedia Commons)

Horseshoe crabs live in shallow coastal waters, feeding off worms and molluscs from the ocean floor. They are able to feed in near complete darkness at night due to a remarkable visual system. The creatures have three different types of eyes – compound, median, and rudimentary – located to both sides and to the front of their shell. What’s more, their compound eyes become a million times more sensitive to light at night than they are during the day. Since that’s roughly how much less light they have to work with at night, the crabs are able to see equally well at night and during the day.

Most people who have observed horseshoe crabs know them from their unusual breeding habits. Each spring and early summer, male crabs will search out a mate and attach themselves to the female’s shell using a special modified leg. Then, during the highest tides of the year, usually at night, the females crawl up onto shore by the hundreds, carrying their male cargo. Having picked a spot that’s moist, but not so low as to be washed away with the tide, they dig a nest into the sand and lay their eggs. The attached males get first dibs at fertilising the pre-laid eggs, but must share the task with numerous mate-less onlookers who rush in to get their shot at fatherhood as well (crabs are so uncouth). Since eggs number in the tens of thousands per female, many will probably be successful. Most of these thousands of eggs, however, will become food for migratory birds, who appreciate the extra protein snack on their long journeys. After a month or so, the uneaten eggs will hatch into larvae, which remain on the beach in groups for a couple of weeks before moulting into juvenile horseshoe crabs and finally moving into the water.

Horseshoe crabs, making more horseshoe crabs.
(Via: Wikimedia Commons)

Now you might be thinking, “That’s all well and good, but what can horseshoe crabs do for me?” Well, as it turns out, these creatures are some of the most prolific blood donors on Earth (whether they like it or not). Like our friend Mr. Spock, horseshoe crabs have copper-based blood, rather than the iron-based concoction favoured by humans. They are literally blue-blooded. And instead of white blood cells to fight off infection, they have amebocytes. These amebocytes are so valuable in detecting certain types of bacterial infections in humans that a quart of horseshoe crab blood is worth approximately $15,000 US. Crabs are caught, transported to a lab, and drained of about 30% of their blood before being released. The company behind this 50 million dollar per year industry states that only about 3% of the quarter million crabs die from the procedure annually, while other studies have found the number to be nearer to 15% (read more about it here). Knowing who’s right may become very important, as horseshoe crab populations are declining worldwide, additionally affecting the migratory birds that feed on their eggs. Either way, next time you survive an E. coli infection, thank a horseshoe crab.

No, no… we don’t mind. Really.
(Via: TYWKIWDBI)

[Fun Fact: Horseshoe crabs are thought to be the closest living relative of the extinct trilobite.]

[Also, here’s a cool video of (who else?) Sir David Attenborough explaining the mating habits of horseshoe crabs.]

Says Who?

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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?

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Randomly Assembled and Surprisingly Dangerous: The Platypus

(Via: National Geographic)

Common Name: The Duck-Billed Platypus

A.K.A.: Ornithorhynchus anatinus

Vital Stats:

  • Only species of Family Ornithorhynchidae
  • Males average 50cm (20”) long, females 43cm (17”)
  • Weigh between 0.7 and 2.4kg (1.5 – 5.3lbs.)
  • Body temperature of 32 degrees Celcius; five degrees lower than placental mammals
  • Live up to 17 years in captivity
  • Eat freshwater crustaceans, worms, and insect larvae

Found: Eastern Australia and Tasmania

It Does What?!

Besides looking like it was assembled from spare parts? We’ve all seen pictures of platypuses (yes, “platypuses”, not “platypi”) before, and everyone knows what total oddities they are: the duck-like bill, the beaver-esque tail, the fact that they lay eggs, despite being mammals; but behind these weird traits lie… even more weird traits! So let’s take a moment to appreciate the lesser-known eccentricities of the platypus, shall we?

First off, these cuddly looking freaks are actually dangerous. Male platypuses have a spur on each hind foot which is filled with a venom powerful enough to kill a large dog. While it isn’t enough to take out a human, it does cause severe, incapacitating pain whose after-effects can last for months. One of only a very few venomous mammals, the male’s venom production increases during the breeding season, suggesting its purpose may lie in competition with other males.

Why your dog and your platypus shouldn’t play together.
(By Jason Edwards, via: How Stuff Works)

And speaking of breeding, reproduction in platypuses isn’t exactly ‘mammal standard’, either. Unlike all other mammals, which have two sex chromosomes (X and Y; XX for females, XY for males, with rare exceptions), the platypus has ten. Talk about evolutionary overkill. A male platypus has the pattern XYXYXYXYXY, while a female has ten Xs. Researchers have found that the actual genetic structure of these sex chromosomes is actually more similar to birds than mammals, although 80% of platypus genes are common to other mammals.

After this alphabet soup of chromosomes arranges itself, up to three fertilised eggs mature in utero for about four weeks; much longer than in most other egg-laying species (in birds, this may be only a day or two). Once laid, the eggs are only about the size of a thumbnail, and hatch in around ten days. While platypuses produce milk, they don’t actually have proper teats to suckle their babies- the fluid is released from pores in the skin. A small channel on the mother’s abdomen collects the milk, which is then lapped up by the young. Strangely, the babies are actually born with teeth, but lose them before adulthood. Such is the impracticality of platypus design…

Adorably impractical.
(Via: noahbrier.com)

Finally, let’s explore platypus hunting methods. Platypuses are the only mammals with the sixth sense of electroreception. Those leathery duck bills of theirs are actually precision receptors that can detect the electric fields created in the water by the contractions of muscles in their prey. Considering the prey in question is largely worms and insect larvae, we’re talking big-time sensitivity here. The bill is also very receptive to changes in pressure, so a movement in still water can be picked up in this way as well. Researchers have suggested that by interpreting the difference in arrival time of the pressure and electrical signals, the hunter may even be able to determine the distance of the prey. This would be especially useful, given that platypuses close both their eyes and ears when hunting. In fact, they won’t even eat underwater; captured food is stored in cheek pouches and brought to land to be consumed.

So there you have it. The platypus: even weirder than you thought.

[Fun Fact:The female platypus has two ovaries, but only the left one works.]

Intelligent Design’s Worst Nightmare
(Via: Animal Planet)

Says Who?

  • Brown (2008) Nature 453: 138-139
  • Grant & Fanning (2007) Platypus. CSIRO Publishing.
  • Graves (2008) Annual Review of Genetics 42: 565-586
  • Moyal (2002) Platypus: The Extraordinary Story of How a Curious Creature Baffled the World. Smithsonian Press.
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Vacation Time!

Time for a break, dear readers. For the next two weeks, I’m off to the farm to do as little as possible!

I’ll be thinking about new and exciting freaks and oddities to write about, so if you have a request or suggestion for a future post, be sure to write a comment, and I’ll see what I can do.

I’ll be back September 5th with a new article. Until then, for your viewing pleasure, here are some photos of my favourite place to pass the last days of summer…

(Click on a photo for a larger view.)

Our Nearest Neighbours
Remains of an Old Wagon
Dawn on the Farm
Early Morning Soybeans
The End of the Day
The Dirt Road to the End of the World
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Killing Me Softly, or, The Fatal Embrace of the Strangler Fig

(Via: Wikimedia Commons)

Common Name: Strangler Figs

A.K.A.: Ficus species

Vital Stats:

  • There are around 800 sp. of figs, over half of which are hemi-epiphytes, like stranglers
  • Around 10% of all vascular plants are epiphytes (about 25,000 species)
  • The trees which produce the figs we eat are terrestrial, and do not grow in other trees

Found: Tropical forests of Latin America, Southeast Asia, and Australia

It Does What?!

What does it take to squeeze the life out of a full-grown tree? A lot of time and some very long roots, apparently. Many parasites eventually bring about the untimely death of their hosts, but few do it as slowly and as insidiously as the strangler fig.

Stranglers begin life as a tiny seed that leaves the back end of a bird and happens to land on a tree branch high in the rainforest canopy. The seed germinates, and the young fig begins to grow as an aerial plant, or epiphyte, taking its moisture from the air and its nutrients from the leaf litter on its branch. Thousands of plant species, including most orchids, grow in this manner. But then an odd thing begins to happen. The seedling produces a single long root. Very long. From tens of metres up in the canopy, this root grows all the way down to the ground. Many young stranglers will die before their questing root reaches the earth, but for those that make it, a connection is formed with the soil through which water and nutrients can be extracted. From this point on the great, towering giant which holds this tiny little interloper is in mortal danger.

The strangler fig, playing “harmless epiphyte.”
(Screenshot from The Private Life of Plants, BBC)

A secure connection to the soil allows the fig to speed up its growth and to begin sending more and more roots earthward. Rather than dropping straight down, like the initial root, these later organs will twine around the bark of the host tree. At first, the roots are tiny, like mere vines crawling over the host trunk. Over time, however, they thicken, covering more and more of the trunk’s surface. Where they touch or overlap, the roots actually fuse together, forming a mesh over the surface of the bark. Up above, the stem of the strangler is growing as well. It rises through and above the host branches, soaking up the light and leaving the other tree shaded and starved for energy.

In fact, this is a war fought on two fronts. As the starving host tree struggles to gather light energy to send downward from the leaves, it is also increasingly unable to bring water up from its roots. This is because the tree’s trunk continues to expand even as the strangler’s grip grows tighter around it. These opposing forces effectively girdle the tree, crushing the vascular tissues that carry moisture from the soil. Eventually, the battle is lost and the tree dies. Fortunately for the fig, its major investments in root growth have paid off – the dead host tree does not fall, taking the strangler with it. Instead, it simply rots where it stands. Finally, many years after its arrival on the scene, the strangler fig has achieved independence. It is now a free-standing tree, completely hollow and supported by its interwoven lattice of aerial roots.

The first root finds the ground.
(Screenshot from The Private Life of Plants, BBC)

So what happens when more than one strangler fig seed lands on a particular tree? Something quite unique… the roots of the different individuals fuse and form an organism which is indistinguishable from a single tree, except by molecular testing. These are what biologists refer to as ‘genetic mosaics.’ What’s more, the individuals actually begin to act like a single tree. You see, figs typically have staggered flowering times, such that it is unlikely for numerous trees in a small area to be in bloom at the same time. This helps in keeping their wasp symbionts well nourished. Once trees fuse, however, they seem to become physiologically linked as well, with researchers reporting that they bloom as a single individual.

The most hurricane-proof tree ever.
(Screenshot from The Private Life of Plants, BBC)

[Fun Fact: Some strangler fig species have very high growth rates, and huge individuals have actually been found engulfing abandoned buildings in the tropics.]

Says Who?

  • Harrison (2006) Journal of Tropical Ecology 22(4): 477-480
  • Perry & Merschel (1987) Smithsonian 17: 72-79
  • Schmidt & Tracey (2006) Functional Plant Biology 33: 465-475
  • Thomson et al. (1991) Science 254: 1214-1216
Don’t meditate under strangler figs.
(Via: Flickr, by vincenzooli)
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The Zombie Apocalypse: Already Underway

(Via: this site)

Common Name: The Zombie-Ant Fungus

A.K.A.: Ophiocordyceps unilateralis

Vital Stats:

  • Whole “graveyards” of 20-30 ants may be found within a single square metre
  • Telltale bitemarks on fossil plants suggest this fungus, or a related species, may have been in operation for the last 48 million years
  • Host species is the carpenter ant Camponotus leonardi

Found: Tropical forests throughout the world

It Does What?!

Despite all the advances of modern neuroscience, the fact is, human understanding of brain chemistry and its manipulation still has a long way to go. Much to the chagrin of those plotting world domination, we won’t be chemically controlling each other’s minds any time soon. How embarrassing then, that a mere fungus seems to have perfected this technique. Almost fifty million years ago. Scooped again, humanity.

It begins with an ant walking along the ground, deep in a tropical forest somewhere. This ant, Camponotus leonardi, lives high in the trees, but must occasionally come down to cross from one tree to another when there is a break in the canopy. As it walks, a minute fungal spore drifts down from above and lands in its back, unnoticed. The unseen spore springs into action, producing an enzyme which breaks down the ant’s exoskeleton just enough to allow a fungal hypha, like a tiny root, to enter. The host’s fate is now sealed.

This is your brain on ‘shrooms.
(Via: Flickr, by Alextkt)

While the ant climbs back up into the canopy and goes about its business, the fungus grows through its insides, breaking down and consuming the non-vital soft tissues as it goes, keeping the animal alive even as it is being eaten. Soon, the fungal tendrils reach the brain and begin to produce chemicals which affect the host’s behaviour in very specific ways. First, it will experience convulsions that cause it to fall out of its tree. These will continue periodically, preventing it from returning to its colony. Over a period of hours, the ant will then wander, erratically and aimlessly, over the ground and low-growing plants.

This is where the precision of the fungus’ mind control becomes truly impressive. At solar noon, when the sun is highest in the sky, the infected ant will abruptly climb the stem of a small plant and find a leaf pointing north by northwest at a height of 20-30cm above the ground. Yes, really. No one knows how this jaw-dropping specificity is accomplished, but it’s what the fungus wants, providing a temperature of 20-30 degrees Celcius (68-86F) and a relative humidity of around 95%. In cases where ants were experimentally moved to different heights or orientations, the fungus was unable to reproduce properly.

What the fungus wants, the fungus gets.
(Via: Wikimedia Commons)

Having found the perfect leaf, the zombified ant will go to its underside, find a major leaf vein, and just bite down on it as hard as it can. The fungus has already destroyed the muscles required to release this grip, and so there the ant stays, slowly dying over the course of the afternoon. Once its victim has been dispatched, the fungus grows toward the leaf, further anchoring itself to the plant. Around a week later, the parasite completes its horrifying circle of life by growing a fruiting body, similar to a mushroom, from the back of the dead ant’s head. This will open to release thousands of tiny spores, raining down over any potential hosts which may be walking below.

While the fungus is able to infect other, closely related, species of carpenter ant, it has less precise control over these hosts and isn’t always successful in getting the ant to do its bidding, suggesting that even minor variations in brain structure can stump it. So we’re probably safe from the fungal zombie apocalypse. At least for the time being…

Says Who?

  • Andersen et al. (2009) American Naturalist 174(3): 424-433
  • Hughes et al. (2011) Biology Letters 7: 67-70
  • Hughes et al. (2011) BMC Ecology 11: 13
  • Pontoppidan et al. (2009) PloS ONE 4(3): e4835
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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
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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)
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Anglerfish: Absorbing Ladies and their Freeloading Mates

(Via: Inglestic)

Common Name: Anglerfish

A.K.A.: Order Lophiiformes

Vital Stats:

  • Comprised of 322 species in 18 different families
  • Most range in size from that of a ping pong ball to that of a football
  • Some can reach over a metre in length and weigh 27kg (59lbs.)

Found: Throughout the world’s oceans, mostly in deeper regions

It Does What?!

The more dissimilar a creature’s habitat is to our own, the more dissimilar we have to expect its lifestyle to be, so when we plumb the pitch black, cold, high pressure depths of the ocean, we’re counting on some serious weirdness. The anglerfish goes above and beyond in this department.

First off, have you seen these things? They’re essentially a set of mobile fangs. And what’s with that thing hanging down off their heads? It’s all part of an efficient setup that allows the anglerfish to survive in an environment with minimal light and sparse prey. These fish are what biologists call “sit and wait” predators. In order to avoid expending precious energy, they hang motionless in the water, waiting for something edible and foolish to approach. The dangly piece is actually a lure, filled with bioluminescent (glowing) bacteria. Seeing the glow and thinking it might be food, curious creatures draw near and are quickly gobbled up by the anglerfish. That enormous mouth, combined with a flexible bone structure, allows the fish to swallow very large prey, relative to its own size.

Really… how unobservant must their prey be?
(Via: National Geographic)

Amazingly, the anglerfish’s horrifying appearance isn’t its most notably odd trait. Not even close. You see, all these characteristics we’ve discussed so far are only present in the female of the species. The male is a different creature entirely. Many times smaller than the female, you’d be hard pressed to immediately recognise a male anglerfish as even being part of the same species. In fact, researchers initially thought they were babies. Their adult form is only 6-10mm (0.24-0.39”) long in some species, placing male anglerfish among the smallest vertebrates on earth.

What’s more, they don’t have a functional digestive system… they literally don’t ever eat. Sustained only by the energy in his own tissues, the young male must find a female and mate before he starves to death. To aid in his quest, he has very well-developed eyes and huge nostrils, which allow him to follow the pheromone trail of a potential mate.

The somewhat less intimidating male anglerfish.
(Via: Anglerfish Info)

Now it gets weird. Upon locating a female, the male swims up and latches on to her with his teeth, usually on the lower side of her body. He then starts to release an enzyme which dissolves both his mouth and her skin, right down to their respective blood supplies. Soon, their bodies actually fuse together, and blood from the female begins to nourish the now-parasitic male. In some species, this fusion goes all the way to the base of the male’s skull, giving him the appearance of having his entire head absorbed into his mate’s body. Once fused, the male undergoes a growth spurt, thanks to his new food source, but his internal organs, as well as his eyes and nostrils, degenerate and atrophy. The exception, of course, being his testicles, which grow along with the rest of his outer body.

A female anglerfish and her clingy boyfriend.
(Via: Wikimedia Commons)

Her mate degenerated down to a mere sperm-producing external organ, the female anglerfish is now essentially a self-fertilizing hermaphrodite. With anywhere between one and eight males attached to her, she has an abundant supply of sperm available whenever she has ripe eggs to be fertilized. As for the males, they will “live” for as long as the female lives, and continue to reproduce indefinitely.

[Fun Fact: the species Ceratias holboelli has the most extreme size difference between the sexes. Females are more than 60 times the length and about half a million times heavier than the males.]

[And if you like your science lessons in cartoon form, be sure to check out this out.]

Says Who?

Come to Mama!
(Via: fugly.com)
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Missing Carpels & the Building Blocks of Science

(Photo by: Domingos Cardoso)

Common Name: Amarelão (Brazil), Grapia (Argentina), Khare Khara (Bolivia)

A.K.A.: Apuleia leiocarpa

Vital Stats:

  • Once considered a genus of three different species, now collapsed down to one by taxonomists
  • The only trimerous (three-parted) flower in the whole legume family
  • Male flowers grow an extra stamen in place of the missing carpel

Found: In the rainforests of central South America

It Does What?!

Nothing quite as bizarre as our usual subjects, actually, but stick with me here. This week, I’m attending the annual conference of the American Society of Plant Taxonomists in Columbus, Ohio. I’ll be giving a talk on some of my research dealing with Apuleia and the development of its flowers. I thought I’d take this week to share some of that research here, and to try to make it interesting for people who aren’t into obsessing over obscure plants. If you still find this entry painfully tedious, though, rest assured, we’ll be back to freaks and oddities next week.

Apuleia leiocarpa is part of the legume family, which, if you’re from a temperate part of the world, brings to mind little annuals like beans and peas and clover. In the tropics, though, legumes are just as often towering trees of the rainforest canopy (like Apuleia) or scraggy shrubs of arid grasslands (such as Acacia). Most of the nearly 20,000 species of legumes have flowers with the same basic groundplan: 5 sepals, 5 petals, 10 stamens (the male organs), and a single carpel (where the fruit and seeds form). There are closely related chunks of the family, though, in which some of these floral organs have been lost over the course of evolution. (Now, ‘lost’ can mean two things; either the organ starts to grow and is suppressed before it finishes developing, or it just never forms at all. To the naked eye, these two kinds of loss look exactly the same. I’ll come back to this later.) Apuleia is one such legume- it has entirely lost two of its sepals, two of its petals, and most of its stamens, making for a very simplified flower.

The Hermaphodite (‘Normal’) Flower
S=sepal, P=petal, A=anther/stamen, C=carpel, St=stigma

What’s more, it now forms two different types of flower (called ‘morphs’). If you were to look closely at a flowering branch on one of these trees, you would see that the vast majority of the flowers were male-only, having no carpel with which to form fruit. Only every fourth or fifth flower would be the hermaphrodite type that we think of as a ‘normal’ flower. Botanists refer to this type of plant as being andromonoecious (pronounced “an-dro-mon-ee-shus”). So why would a tree evolve to become andromonoecious? There are a couple of different theories, based on two different ways that the male-only flowers can be produced.

In the first and most common type of andromonoecy, all the flowers on the plant begin as normal hermaphrodites. There are flowers of all different ages, so while some are beginning to open, others haven’t finished forming yet. Pollination starts on the earlier flowers, and the plant detects that it has far more ovaries (future seeds) than it’s going to need. Maybe the soil isn’t providing enough nutrition to produce all those potential fruits, or maybe there’s a drought in progress. So, according to its needs, the tree simply suppresses the development of the carpels in the younger flowers before they have time to mature, leaving parts of each branch with hermaphrodite flowers and parts with male flowers.

The Male-Only Flower
S=sepal, P=petal (both removed)
Arrow= where the carpel would have been

In scenario two, some flowers never develop carpels; they are male-only from the time they are first formed. This type of andromonoecy is thought to occur because the tree requires large amounts of pollen to reproduce successfully (perhaps the species is wind pollinated and individuals tend to be far apart, for example), and it’s “cheaper” to produce male flowers than hermaphrodites. In this situation, we don’t see the pattern of younger versus older flowers with respect to which ones are male.

That white asterisk in the very middle shows the hole through which the carpel would have emerged. It’s just a small, empty cavity in the male flower.

So which type of andromonoecy does Apuleia have? In order to find out, a colleague and I studied pressed herbarium specimens as well as flowers preserved in alcohol. The flowers, we dissected and viewed under an incredibly powerful microscope called a scanning electron microscope, which allowed us to see minute details, such as where a suppressed carpel might have been. In the end, we found that male Apuleia flowers show no sight of having ever developed a carpel. We also noticed that the hermaphrodite flowers always occurred symmetrically, right in the centre of a group of male flowers, a pattern that we wouldn’t see if the andromonoecy was environmentally influenced.

So in the end, we’re able to say that in this species, the different floral morphs probably arose in evolution due to an increased need for pollen, rather than as a control on fruit production. Groundbreaking… right? Well, maybe not, but obscure little discoveries like this are the building blocks for the big important breakthroughs we read about in the news. If you want to make something huge, you need a good foundation to start from.

Now imagine spending three hours of your life staring at this.
Science is so glamourous.

Says Who?

  • Beavon & Chapman (2011) Plant Systematics and Evolution 296: 217-224
  • de Sousa et al. (2010) Kew Bulletin 65: 225-232
  • Gibbs et al. (1999) Plant Biology 1: 665-669
  • Spalik (1991) Biological Journal of the Linnean Society 42: 325-336
  • Zimmerman et al. (In Press) International Journal of Plant Sciences