science

Beach Hangout

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We nipped out to the beach after dinner on Saturday. We had a nice walk on our lovely, lonely bit of coastline.

But the beach was busy with youth hanging out (up to no good, probably). Some were alone, and some were in groups, strutting their stuff.

But these youth weren’t your usual crowd of city kids, they were juvenile spotted shags, Strictocarbo punctatus punctatus, also known as spotted cormorants, parekareka, and kawau tikitiki.

Shags were once heavily persecuted as pests. Fisherman believed they destroyed the fisheries, snapping up all the commercial fish and decimating their numbers. Research has shown, however, that their impact on fisheries is minimal. On the other hand, there is some evidence that, in our area at least, shag populations are hurt by commercial fishing. Spotted shag populations on the Banks Peninsula rose from 9,787 pairs in 1960 to 22,123 pairs in 1996 following a reduction in commercial fishing around the peninsula. Illegal shooting can also cause local population declines.

The spotted shag is a marine species, never venturing far from the sea and feeding in deep water up to 16 km from shore. They’re gregarious, breeding and roosting in colonies with up to 2000 birds. The groups of juveniles on our beach were small—a few dozen birds at most. These birds were probably born on cliffs around the Banks Paninsula, and when mature, they’ll head back to those cliffs to lay eggs and rear their young.

So they really were just hanging out on the beach, just like teenagers from Christchurch hang out on the beach on weekends, away from the adults, goofing off and getting takeaways.

Alpine Delights

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The family spent a delightful hour on the Dobson Nature Walk in Arthur’s Pass National Park on Wednesday. The track is an easy one, and hiking it quickly takes about 20 minutes. But it’s not a walk you want to do quickly, especially in summer. It winds through alpine and sub-alpine vegetation, including some beautiful tarns, and in summer, so many plants are blooming, it’s hard to take five steps without finding another lovely orchid, daisy, or hebe in bloom.

For me, the best part of the walk is the abundance of sundews in the tarns. As an entomologist, I’m naturally drawn to carnivorous plants like sundews. Sundews catch insects on the sticky hairs you can see glistening in this photo. The hairs are sensitive to both touch and taste, and when they sense a struggling insect, they fold inward to further entangle their prey. Enzymes exuded by the hairs then digest the insect, and the leaf takes up the nutrients in order to grow in the nutrient-poor alpine wetlands. 

These sundews were just beginning to flower—many plants had flower buds, but none had yet opened. The flowers sit above the leaves—an important adaptation, since the plant needs to be pollinated by the very insects it eats.

The alpine summer is short, so when these plants are done flowering, the leaves will slowly shrink into a structure called a hibernaculum that sits near the soil surface and protects the plant through the winter.

A Weakness for Weevils

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I was excited to find a new weevil on our property the other day. At least until I identified it.

Meet Otiorhynchus sulcatus—the black vine beetle—pest on a wide range of garden plants, including grapes, black currants and strawberries (all common in my garden).

I admit, I have a weakness for weevils—no matter how much of a pest they are, I think they’re cute. And this one is no exception. She’s lovely, in spite of her diet. And I’m certain she’s a ‘she’, because no males of this species have ever been found. The black vine beetle reproduces parthenogenetically, producing viable eggs without the need for fertilisation by males. 

This ability is the result of a bacterial symbiont in the genus Wolbachia. When researchers in California eliminated Wolbachia in black vine beetles (by giving the beetles antibiotics), the beetles’ unfertilised eggs were no longer viable. It’s a clever little ploy by the bacterium to ensure its own reproduction—only infected insects can reproduce, and they can do so without the trouble of finding a mate (I wrote more about this fascinating relationship in Putting the Science in Fiction and on Dan Koboldt’s Science in Fiction blog).

Another cool feature of the black vine beetle is that it is flightless. It’s not uncommon to find flightless insects and birds here in New Zealand, but it’s a little unusual to see it in invasive pests like the black vine beetle. Native to Europe, the black vine beetle is now distributed all around the world. Pretty impressive travelling for a 6 mm-long flightless insect.

Apparently black vine beetles can cause significant damage to plants. The larvae eat roots in the soil and do the most damage, particularly in potted plants, where root growth is limited. I’ve decided not to worry about them at the moment. I’ve got more damaging pests to worry about, and to be honest, I wouldn’t mind seeing them again. They are awfully cute.

Awesome Alpine Plants

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Whipcord hebe flowering in the snow

My daughter and I went for a hike on Saturday after being cooped up in the house all day Friday by a rip-roaring southerly storm. The storm lashed us with rain and hail, but in the mountains, it brought snow. Saturday morning, the beech forest at Cragieburn Forest Park was a winter wonderland.

Climbing up out of the forest into the alpine areas, the intensity of the storm was clear—thigh-deep drifts filled the path in some places, while other areas had been blown clear down to the scree. Every tussock had a long train of sculpted snow on its leeward side, so you could almost feel the howling wind and the sting of blowing snow, in spite of it being a clear calm day.

Nestled among the rocks, we found this lovely whipcord hebe, flowering in spite of its slowly melting blanket of snow. And there were other plants peeking out of the snow, clinging to the scree.

Alpine plants are some of the toughest organisms around. They have to cope with intense sun, wide temperature fluctuations, drought, wind, and ice and snow. They have evolved a variety of adaptations in order to combat these dangers.

Short, cushion-shaped growth: A tight ball of branches and leaves resists damage and drying from fierce wind. The pinnacle of this growth form has to be plants in the genus Raoulia. Known as ‘vegetable sheep’, they form hard, tight masses of tightly packed leaves (akin to the texture of a head of cauliflower). Inside the mound, dead plant material builds up around the branches and acts like a sponge, soaking up rain when it’s available. Adventitious roots on the plant’s branches tap into this reservoir of water when the weather is dry.

Long roots: Unstable rocks and shifting scree make it difficult for alpine plants to stay put, and water is often far below the surface. To cope, they have long roots that anchor them deep into the rock. Some are also able to regrow from their roots if the top of the plant is snapped of by rockfall.

Drought-resistant leaves: Many alpine plants have leaves that are fuzzy on the underside, where the stomates (the breathing holes) are located. The hairs trap a layer of calm air against the leaf surface, slowing down water loss from the stomata. Other plants have narrow, vertically-oriented leaves that minimise exposure to the intense alpine sunshine, reducing evaporation.

Sunscreen: A waxy coating on many alpine plant leaves protects against intense sunlight and high temperatures.

Antifreeze: Ice crystals forming inside a living cell break the cell walls and kill it, so organisms living in cold environments have to somehow avoid freezing. Alpine plants protect themselves from freezing by manufacturing antifreeze from proteins in their tissues. The antifreeze prevents ice crystals from forming in the plant’s cells.

Energy conservation: The growing season in alpine areas is short, and nutrients are scarce. Many alpine plants respond by not reproducing every year. Instead of producing low-quality seeds that may not survive, they hoard resources until they have accumulated enough to reproduce successfully.

All these adaptations give most alpine plants a similar look—low, mounded, small-leaved and tough. But one plant in particular stands out as oddly showy and out of place.

Mount Cook buttercup (Ranunculus lyallii)

The Mount Cook buttercup (aka Mount Cook lily), is an unusual alpine plant, in that it has big leaves and large, showy flowers. But even so, it is well-adapted to the alpine environment. Most plants have stomates on the underside of their leaves, because the underside is generally shaded and cooler, leading to less water loss. But in the alpine environment, sun-warmed rocks radiate heat, making the underside of the leaves warmer than the upper side on sunny days. The Mount Cook buttercup and its relatives have evolved stomates on the upper side of the leaves, in addition to the ones on the underside. The stomates on the top open when the underside of the leaf grows too warm.

Putting the Science in Arthropod Borne Disease

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Aedes aegypti (US Department of Health and Human Services)

The slam of a screen door—a quintessential part of summertime in the United States.

But not here in New Zealand. Most houses have no screens in windows or doors.

Why? Because we don’t have arthropod-borne diseases (of humans) here.

The ubiquitous window screens and screen doors in the US are a direct result of the efforts to eliminate malaria in the early 1900s. In some areas, screens were mandated by local government. They caught on, even in areas where they weren’t required, and remain popular today, in spite of the fact malaria is no longer endemic to the United States.

Lone Star Tick–transmits ehrlichiosis and a carbohydrate that can trigger meat allergies. (Centers for Disease Control and Prevention, Dr. Amanda Loftis,  Dr. William Nicholson, Dr. Will Reeves, Dr. Chris Paddock)

Arthropod-borne diseases have shaped human cultures, changed the course of wars, and stymied economic development throughout the world for millennia. Malaria alone kills 400,000 people annually, and hundreds of millions of people worldwide suffer from other arthropod-borne diseases like Chagas disease, yellow fever, dengue and leshmaniasis.

Arthropod-borne diseases are transmitted from one person to another by, you guessed it, an arthropod—often a mosquito, fly, or tick. These arthropods (just the females, in the case of mosquitoes) feed on human blood. They draw up the disease from a sick person with one meal, and transmit it to another person with the next. The disease—a virus, protozoan, plasmodium, flatworm, or other organism—often has a complex life cycle, requiring specific hosts and specific vectors in order to complete each stage of its life. Combating these diseases requires an understanding of every part of the life cycle of both the disease and the vector.

Though humans have been battling malaria for the entirety of recorded history, new arthropod-borne diseases emerge regularly, challenging public-health systems worldwide. With increased air travel, infected people and vectors can quickly spread diseases to new places. And diseases don’t necessarily act the same when transplanted into a different population.

Zika is a great example of the complex interactions between host, vector and disease that make arthropod-borne diseases so scary and difficult to combat. Zika was first identified in humans in 1952, after first being found in monkeys. It was confined to Africa and Asia until 2007. Only 14 cases were documented, though testing indicated people had wide exposure to the virus. Symptoms were usually mild, and it wasn’t considered a major problem.

The first large Zika outbreak occurred on the island of Yap in Micronesia in 2007. Further outbreaks in the Pacific Islands in 2013 and 2014 brought the first information connecting Zika with congenital malformations like microcephaly and severe neurological complications.

Then, in March 2015, Zika appeared in Brazil. Because Zika was unknown in Brazil, the outbreak wasn’t identified as Zika until May. In October, Brazilian health officials reported a dramatic increase in microcephaly, which was linked to the Zika outbreak.

By the end of 2015, Zika outbreaks had been reported all over Central and South America.

In February 2016, the World Health Organization declared Zika a Public Health Emergency of International Concern. Emergency plans were enacted to control the spread of the virus by eliminating the suspected vector mosquitoes, Aedes aegypti, and to study how to manage the complications of the disease.

The disease and our understanding of it moved rapidly throughout 2016. The virus was found in another species of mosquito. It was proven to also be transmitted through sex and through blood transfusions. It was discovered to cause a much wider range of neurological problems than first thought. Vaccine development began. Travel advisories were put in place. Innovative new mosquito control strategies were launched.

Still, Zika spread and infected over 180,000 people. By November 2016, it was clear Zika was here to stay, and needed to be managed on an ongoing basis, not as an emergency. In the space of 18 months, Zika had invaded the world.

The full timeline of Zika can be found on the WHO’s website: http://www.who.int/emergencies/zika-virus/history/en/

The WHO also has great information about other arthropod-borne diseases: http://www.who.int/campaigns/world-health-day/2014/vector-borne-diseases/en/

All the real-life science of arthropod-borne disease can make for exciting fiction. Fancy writing a story? Here are a couple of ideas to get you going:

1. A cluster of people in a small town in Iowa fall ill with an unusual rash that progresses to a deadly autoimmune disease. Doctors are stymied until one of the women mentions she’s just returned from a trip to Africa. Blood tests confirm she is carrying antibodies to a rare arthropod-borne disease not seen outside of Sub-Saharan Africa before.

  • How do researchers try to contain the disease? The first step is usually to quarantine sick people and those who have come into contact with them, but if this fails, control has to turn to other ways of breaking the disease cycle. Strategies may include vaccines, preventive medicine, killing the disease vectors, eliminating the vectors’ habitat, and separating people from the vector (with screens, curfews, etc).
  • Is there a competent vector for the disease in Iowa? In its native range, the disease may be vectored by an arthropod not found in North America, but some widespread arthropods are capable of vectoring many diseases. Arthropods within the same genus of the original vector are most likely to be able to transmit the new virus.
  • How does the progression of the disease in Iowa differ from in Africa, where people have been exposed to the disease for longer, and have developed a measure of immunity. Mild diseases can become deadly in populations never exposed to them before.
  • How does society as a whole react to disease survivors? The social impact of emerging diseases can be as devastating as the disease itself—survivors may still be sources of infection, and some arthropod-borne diseases can also be spread through other means (sexually, in feces or saliva, etc). How does this affect those who survive?

2. A government wants to unleash a new arthropod-borne virus to wipe out a rival nation (Don’t laugh, Japan tried to do this during WWII, breeding up disease in prisoners of war and releasing cholera-infected flies and plague-infested fleas in China, killing more people than the atomic bombs on Hiroshima and Nagasaki).

  • How will they choose a vector and disease to minimise the danger to their own people? Will they vaccinate their own people first? Or chose a disease already present in their country, but not in the target country?
  • How will they deliver live, infected vectors to the intended target?
  • How will they produce enough of the disease organism to infect the vectors?

And don’t forget to get yourself a copy of Putting the Science in Fiction, to be released on October 16! This is a great resource you don’t want to miss!

Science and technology have starring roles in a wide range of genres–science fiction, fantasy, thriller, mystery, and more. Unfortunately, many depictions of technical subjects in literature, film, and television are pure fiction. A basic understanding of biology, physics, engineering, and medicine will help you create more realistic stories that satisfy discerning readers.

This book brings together scientists, physicians, engineers, and other experts to help you:

  • Understand the basic principles of science, technology, and medicine that are frequently featured in fiction.
  • Avoid common pitfalls and misconceptions to ensure technical accuracy.
  • Write realistic and compelling scientific elements that will captivate readers.
  • Brainstorm and develop new science- and technology-based story ideas.
  • Whether writing about mutant monsters, rogue viruses, giant spaceships, or even murders and espionage, Putting the Science in Fiction will have something to help every writer craft better fiction.

Putting the Science in Fiction collects articles from “Science in Sci-fi, Fact in Fantasy,” Dan Koboldt’s popular blog series for authors and fans of speculative fiction (dankoboldt.com/science-in-scifi). Each article discusses an element of sci-fi or fantasy with an expert in that field. Scientists, engineers, medical professionals, and others share their insights in order to debunk the myths, correct the misconceptions, and offer advice on getting the details right.

Go in the draw to win a FREE copy of Putting the Science in Fiction

Sticky Feet! The Eucalyptus Tortoise Beetle

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Hanging up the laundry this morning, I found this lovely beetle making its way along the washing line. It’s a eucalyptus tortoise beetle (Paropsis charybdis). I see them occasionally, but with only one eucalyptus tree in the yard, they’re not common.

I’m quite fond of tortoise beetles. This one isn’t much to look at, but many species are sparkling gold, and my first glimpse of them, as a kid, was a truly magical experience that I’ve never forgotten. What tortoise beetles have in common is their domed tortoise-like shape.

Their shape, combined with some pretty awesome feet is what keeps them safe.

Tortoise beetles have wide pads on their feet (this one obligingly sat on a clear surface and showed its feet under the microscope). The pads are covered densely in short hairs, like the bristles of a toothbrush. Each hair is moistened by oil, which helps it stick to the waxy surfaces of leaves in the same way two wet drinking glasses stick together if they’re nested. The oil bonds to both surfaces and acts as glue. When disturbed, the tortoise beetle presses its feet against the surface, employing as many as 60,000 sticky bristles (about 10 times more than other beetles have) to keep it attached. These sticky feet, combined with the dome-like shape make it difficult for predators to dislodge the beetle.

Entomologist Tom Eisner performed a series of elegant experiments with the palmetto tortoise beetle, attaching weights to the beetles to see how much force they could withstand before being pulled off a leaf. He found they could hold up to 240 times their body mass. Those are some seriously sticky feet!

So if their feet are so sticky, how do they walk? Eisner showed, by looking at palmetto beetle footprints on glass, that when they walk, they don’t let all the bristles on their feet touch the surface. Their full adhesive power is only deployed for defence.

I don’t think anyone has tested eucalyptus tortoise beetle grip strength, but it’s definitely impressive. I popped this one into a narrow jar, and it never hit the bottom—it reached out with one leg, like some movie superhero, and grabbed the smooth wall of the jar, arresting its fall. Then, when I tried to get it out of the jar, it stuck like glue to the side. I had to slide a stiff piece of paper under its feet, prying them up one by one. It was obliging for the photo shoot, but when I tried to let it go, it stuck itself to the paper. It took a few determined nudges, but eventually I got it to the edge of the paper and it dropped off.

The eucalyptus tortoise beetle is not native to New Zealand, and is considered a pest in the forest industry here. Still, I have to admire the beetles’ sheer tenacity, and am willing to share my eucalyptus tree with them for the opportunity to see those sticky feet in action.

Ice and Fire

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One of the things I like best about springtime here is the juxtaposition of hot and cold, especially in the high country. The sunshine is warm, but winter lingers in the shade. I’ve gone hiking in shorts and t-shirt through 15 cm of snow in past years.

This weekend, we didn’t make it up to snow, but there was spectacular frost on our little Saturday jaunt. Hiking up the shaded side of a hill, we were treated to glistening plants as the first rays of the sun hit thick frost.

In addition to the frost, we crunched over a lot of needle ice. Needle ice can occur when the soil temperature is above freezing, but the air temperature is below freezing. Liquid water rises through the soil via capillary action and freezes on contact with the air. As more water is drawn upward, the ice needles grow in length. They’re common in the high country in springtime, when warm sun heats the ground during the day, but the temperature drops quickly after dark.

Ice needles are more than just a curiosity. They’re a significant factor in soil erosion, because they often push soil upward along with the ice. This loosens the top layer of soil, making it prone to erosion by wind and water.

The air was cold on Saturday morning, and as we started up the hill, we were well-bundled. But like all good tracks in New Zealand, this one started off by going straight up. Between the climb and the sun, we were soon stripped to our t-shirts, enjoying the crunch of ice underfoot and the warmth of the sun overhead.

Nifty Nematodes

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Nematodes under the microscope. Image: CSIRO

A week or so ago, during a writing break, I spent some time peering through the microscope in my ongoing quest to find tardigrades in our yard. I had no luck on the tardigrades, but as usual I came across lots of fabulous little invertebrates.

Perhaps the most common creatures under the microscope were nematodes. No surprise, really. Nematodes are the most common multicellular organisms on earth; there are several million in every square metre of soil here in New Zealand. Most are tiny (less than 3 mm). But not all are so minuscule; the largest, a parasite of sperm whales, can grow to 8 to 9 metres in length.

Nematodes can be free-living or parasitic on animals and plants. In fact, most animals (vertebrate and invertebrate) and plants are host to at least one specialist nematode parasite. Free-living nematodes eat bacteria, fungi, or small invertebrates (including other nematodes).

As you can imagine, nematodes are of huge importance ecologically, economically, and from a human health perspective.

Humans are host to about 60 species of nematode. Diseases caused by nematode parasites in humans include: ascariasis (an intestinal infection that can cause growth retardation and a variety of intestinal and other problems), hookworm (causing anaemia and developmental problems),filariasis (a lymph infection, causing swelling in many body parts, including elephantiasis of the legs), trichinosis (an intestinal infection causing diarrhoea, fever, and other symptoms). Many nematode infections are asymptomatic, and it’s likely most of us play host to nematodes for most of our lives.

The control of nematodes is important in agricultural systems. Worldwide crop loss to nematodes is estimated to be 12.3 percent of production (US$157 billion). Livestock and domestic pets are also susceptible to nematode infection, and millions of dollars annually are spent to control nematode infections including lungworm, hookworm, trichinella, heartworm, and many others.

But nematodes aren’t just doom and gloom. They’re integral parts of natural ecosystems, and critical components in nutrient cycling (especially nitrogen) and food webs. They regulate the bacterial population in the soil, and provide food for many organisms (including some fungi, which catch nematodes with lassos, like tiny cowhands). They can be useful, too. Some insect parasitic species are bred to help control insect pests—a highly species-specific, organic control method.

And like the tardigrade, nematodes are tough. A culture of live nematodes aboard the Space Shuttle Columbia were the only organisms to survive the re-entry breakup of the shuttle, making them the only organism known to survive unprotected atmospheric descent.

Beautiful Brawny Barnacles

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My daughter and I went for a walk on the beach after school yesterday. It was chilly, but calm, with a clear mid-winter sky and dolphins in the surf.

Washed up on the beach was a large tree stump crusted with barnacles whose colours mirrored the evening sky. The size and profusion of barnacles indicate the tree was lodged in the water for a long time before it was hurled onto our beach.

Barnacles are strange creatures. They’re crustaceans—kin to crabs, shrimp, and lobsters—but they don’t look anything like their relatives. Barnacles have given up the ability to move on their own (after a brief mobile larval stage), and instead settle down in places where the water moves around them—intertidal zones, the backs of whales and the bottoms of ships are popular barnacle real estate. Instead of having to wander in search of food, moving water carries lunch to the barnacles, and they filter it out of the water with feathery appendages called cirri.

Staying put in places where waves pound day in and day out isn’t easy. Barnacles produce a ‘glue’ that’s one of the strongest natural adhesives around. With a tensile strength of 35 N/mm2 (5000 psi), it rivals the best commercial epoxies. In a strange quirk of biology, the glue is produced by a gland at the base of the barnacle’s antennae, and so the animal is glued head-first to the substrate. Once glued to its home, the barnacle forms a ring of plates around its body to protect it (this is all that is left of the barnacles pictured here—the animals themselves have died).

There are costs to gluing oneself in place. Unlike other sessile animals like corals who release their eggs and sperm into the water for fertilisation, most barnacles rely on internal fertilisation. To reach their neighbours and manage this feat, the hermaphroditic (both male and female) animals have penises that can be 8 times the length of their bodies. Until recently, researchers thought this was the only way barnacles could reproduce, but in 2013, a study found that at least one species of barnacle (with a particularly short penis) can capture sperm from the water if it’s too far from its neighbours.

Barnacles are of human importance. They encrust ships, leading to increased drag and fuel costs. But their habit of attaching themselves to all sorts of debris can also be used forensically to track marine wildlife like whales and turtles, items from shipwrecks and airplane crashes, and marine debris. Additionally, barnacles are considered culinary delicacies in Spain, Portugal and Chile.

Beautiful and brawny, weird and wonderful, barnacles always make me smile.

Backyard Biodiversity

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Craterium minutum

I know it’s been a good weekend when I arrive in my office Monday morning to find my microscope in the middle of the desk, and dirt and bits of plant material strewn about.

It means I’ve been outdoors, seeing cool stuff, identifying plants, insects, or other organisms.

Once you start looking at and identifying what lives around you, the variety is astounding. A glance at the citizen science website iNaturalist shows a pile-up of dozens of observations at our address—and those are only the species we’ve bothered to upload.  I’ve identified 58 species of weeds in the vegetable garden alone. We have half a dozen slime moulds, dozens of fungi and lichens, who knows how many insects and other invertebrates. Then, of course, there are the birds, rats, mice, stoats and other vertebrates. I’ve never bothered to make lists of anything beyond the weeds.

So here in the dark depths of winter, I’ve decided to start a comprehensive list of the biodiversity on our little acre and a half. It will take time. It will require my microscope and many Monday mornings brushing dirt off my desk. But wouldn’t it be cool to know exactly how many other species we share this patch with?

And though many of the species I’ll put on my list are ones I’ve noted many times before, I’m sure some will be new and surprising, like the beautiful slime mould, Craterium minutum my daughter found last week.

Because, the truth is, we needn’t travel far to find natural wonders. We merely need to look closely and have a sense of wonder.