wildlife

Shining in the Dark

/ Robinne Weiss / 1 Comment

Not much to look at in the light, but spectacular in the dark.

I’m a morning person. I’m rarely in bed past six o’clock, and am often up long before that. But I will admit that even I get tired of getting up in the cold and dark at this time of year.

Of course, sometimes the most amazing things happen before the sun is up.

Yesterday morning, I stepped into the chicken paddock feed ‘the girls’. It was still dark, with just enough starlight to see my way. I bent to tip a scoop of feed into their dish and froze.

Something glowed on the ground—the eerie glow of bioluminescence.

I’ve seen bioluminescence while feeding the chickens before—a tiny sea creature whipped up and blown in with a violent snowstorm—but this was different.

I flicked my light on and saw something pink glistening on the ground. When I tried to pick it up, I discovered it was the head of an earthworm.

A brightly glowing earthworm.

I couldn’t get it out of the ground in order to bring it in and identify it yesterday, but I took the spading fork with me this morning when I went to feed the chickens, and I collected a little glowing earthworm from where I’d seen one yesterday.

I already knew that at least one of our native earthworms is bioluminescent—Octochaetus multiporus, which I’ve blogged about before. But O. multiporus grows to enormous size, and I’ve never found any worms in the garden that match its description. Doing a little research, I found that bioluminescence is quite widely employed by earthworms, presumably as a deterrent to predators.

Most earthworms produce light in much the same way that fireflies do, with a chemical known as luciferin that reacts with oxygen-containing compounds in the presence of luciferase to create light.

So, what species is my little glowing worm? There are about thirty New Zealand species within the genera where bioluminescence has been recorded. I’ve found record of only two of those species being bioluminescent: O. mulitporus and Microscolex phosphoreus, a small worm considered native here, but widely distributed around the globe. My best guess is that it’s M. phosphoreus, but data on that worm’s distribution in New Zealand is almost nonexistent (it’s been recorded from only one location), and data about any earthworm in New Zealand is scanty. Perhaps my worm is M. phosphoreus, but it might also be a worm in which bioluminescence hasn’t been recorded. After all, most people aren’t out in the garden at night to notice glowing worms.

Hopefully, I’ll be able to have the worm identified by an expert. If not, well, I still think it’s the coolest thing I’ve seen in a long while! And I won’t be grumbling about getting up in the dark and cold tomorrow.

Nifty Nematodes

/ Robinne Weiss / 2 Comments

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.

Fabulous Flatworms

/ Robinne Weiss / 7 Comments

Australian flatworm

One of the common animals in my yard and garden is the flatworm. Strictly speaking, “the” flatworm here in New Zealand is actually multiple species—possibly up to a hundred—but they have been poorly studied, so it’s unclear just how many species there are.

Flatworms are some of the most impressive predators in the garden, able to consume prey up to 55 times their own size. That’s the equivalent of your house cat taking down a female elk. They eat snails, slugs, and earthworms, digesting them externally before sucking them up with one or more mouths located midway along their bodies.

I love to find flatworms around the yard. They come in striking colours, and some have lovely brown stripes—the orange Australian flatworm (Australoplana sanguinea) is most common in my garden, followed by the relatively nondescript brown New Zealand flatworm (Arthurdendyus triangulatus). Like the slugs they eat, they prefer damp places, and they protect themselves with a layer of mucous. Flatworm mucus is stickier than slug mucous, and they use it to attach themselves to their prey during feeding.

New Zealand is full of non-native invasive organisms, but New Zealand flatworms are one of the few organisms that have turned the tables and become pests overseas. They are easily transported in potted plants, and have successfully invaded Ireland and Scotland. Though there was widespread panic at first about their potential to threaten the local ecology, they appear to have caused little damage to earthworm populations in the UK. Like most cold-blooded animals, their appetites are small. Far from being a devouring hoard, each flatworm can manage, on average, just one earthworm per week. And if they don’t manage to find an earthworm every week, it’s not a problem—they can go a year without eating.

To the Beach

/ Robinne Weiss / 1 Comment

While all you folks in the Northern Hemisphere are flocking to be beach for a swim and some sun and sand, we are shivering down here in the dark days of winter. But that doesn’t mean we don’t go to the beach.

Research from England has found that people living by the coast have better physical and mental health than those living inland. I can certainly understand that.

Growing up three hours’ drive from the beach, I visited the ocean about once a year. My husband, raised in the midwestern US, doesn’t remember seeing the ocean until age twelve or thirteen.

Today, we live a mere four kilometres from the beach. When the wind is calm, we can hear the surf. When the wind is high, we can smell the sea. Even without research to back us up, we’ve learned to head to the beach when we’re stressed.

Our beach isn’t a white-sand swimming beach—it’s made of cobbles, and the waves pound viciously on the shore. It’s not a place to swim, nor really a place to sit for very long (those rocks get uncomfortable fast). It’s a place to walk. A place to search for wave-polished rocks in glittering colours. A place to watch sea birds, dolphins, and the occasional seal. A place to leave all the stress of daily life behind (I challenge anyone to remain stressed while watching dolphins cavorting in the waves).

Researchers point to the calming blue colour, the hypnotic sound of waves, and the cultural context of the beach to explain its calming effect. But for me its influence is more profound. Our beach is usually free of other people—on a busy day you might see four others. From the beach, it is difficult to see any sign of humans at all—the odd bit of flotsam, but not even much of that. On our beach, the world is reduced to sky, water, and rock, shared only with wildlife. It’s easy to imagine the world is in better shape than it is. It’s easy to believe the vast ocean will endure, in spite of human stupidity. It’s easy to think those rare Hector’s dolphins, which we see nearly every time we visit the beach, are actually common. For the space of time we inhabit the beach, all is right in the world.

It doesn’t last, of course, but it’s good to have that escape so close at hand.

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.

The Sound of a Story

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I sit down at my desk and breathe a sigh of relief. It’s quiet here, in my office. Not like the noisy library where I worked yesterday.

But, no, that’s not true. I hear the roar of the surf in the distance. The trickle of the artificial stream in the garden overlays the sound of the ocean. When I step to the office door, a goat greets me with a maa. Starlings mutter in the treetops, magpies warble on the fenceposts, and a fantail chitters in the shed. A plover’s percussive call is underlain by the chirping of a thousand crickets.

The neighbour rumbles past in his tractor, carrying a bale of silage. I can hear his son in the paddock shouting and whistling at his five barking sheep dogs.

It is far from quiet.

And yet …

Somehow, the sounds here caress my thoughts, rather than intruding upon them like the horrible Muzak from the library cafe, or the screams of tired children, or the drone of the automatic returns machine—please place the item on the trolly.

The fantail flits in and out of the story I’m writing without knocking over my coffee. The goats and sheep graze beside me without barging across the keyboard. The crickets keep to the grass. The tractor rumbles along without leaving tire tracks on my manuscript. The ocean doesn’t even wet my toes.

But somehow, I’m certain these sounds end up in my stories, caught up in the weave of plot and characters. The fantail is there, in the flick of a character’s fingers. The ocean is the relentless sound of the plot line. The tractor is the rumble of disaster bearing down on my protagonist. The goats’ deep maa is the voice of wisdom, and the crickets’ chirping lightens the mood.

Pigeon Bay Walkway

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View from the head toward Christchurch.

Yesterday was a beautiful autumnal day. We headed out to the Banks Peninsula and did the Pigeon Bay Walkway.

It has been over a decade since we’ve been to Pigeon Bay. Last time we went, the kids were preschoolers. Then, we’d hoped for some sort of beach where the kids could play in the water, but Pigeon Bay is rocky. The shoreline is covered in cobble-sized rocks teeming with life. Lift any rock and a dozen crabs scuttle away. A decade ago, the pursuit of crabs delighted the kids. Still does. Yesterday, we also noted starfish, chitons, limpets and snails under the rocks.

But the main activity for yesterday was the walkway. It’s rated as a five hour return walk, but is mostly on a well-graded farm track. It’s easy going, and we did it in four hours, including a lunch break.

The track runs all the way to the head of the bay. It’s not exactly a wilderness experience—the land is a beef and sheep farm—but the views are spectacular. It’s one of the few places on the Banks Peninsula where you can get right out to the tip of the headland.

Out on the head, the cliffs are quite spectacular, and you can see the layers of volcanic deposits, well-spattered with poo from the shag colonies there. In the clear air yesterday, we could see all the way to the Kaikoura ranges.

The best part of the walk for me was looking down on a small pod of Hector’s dolphins feeding in the bay below. The dolphins were clearly circling and corralling fish, and there was a trio of gulls shadowing them in the air, picking off the fish the dolphins missed.

A lovely walk. Hard to believe it took us this long to get around to doing it.

Nursery web spiders

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The nursery web spider (Dolomedes minor) is one of New Zealand’s larger spiders, in spite of it’s species name. At this time of the year, it’s also one of the more visible spiders, or at least its webs are.

Nursery web spiders don’t use webs to catch food. Instead, they use their silk to create shelters for their eggs and newly-hatched young. These shelters are visible in late summer and autumn on the tips of shrubby plants, especially gorse.

The female spider can sometimes be seen hanging around the web during the day. In fact, if she’s nearby, its hard to miss her, with a body nearly two centimetres long, and a leg span reaching six centimetres.

The nursery web isn’t the only care the nursery web spider gives her young. Until the spiderlings are near to hatching, she carries the egg sac with her to protect it. The young hatch out inside the nursery web, staying within the web’s protection for about a week.

The spiderlings disperse by ballooning—they let out a strand of silk until the force of the wind blowing on it is greater than their own weight, and then they float away on the end of the thread to a new home.

Like other members of the genus Dolomedes, the nursery web spider is an ambush hunter, chasing down its prey on foot. But most other Dolomedes do this exclusively on or in water, whereas the nursery web spider hunts on land as well as water, eating a wide range of invertebrates.

Belated Poetry Day

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I missed World Poetry Day last week, so here’s a belated poem in honour of the day, inspired by the little spider who has built its web over the kitchen window.

David and Goliath

Honeybee caught
In a spider web
Buzzes murder to
All eight-leggers,
Stinger stabbing at
Offending silk.

Alerted,
Out rushes
The tiny spider,
Dwarfed
By its angry prey.

Dart in,
Avoid the sting,
Dart out.
Throw silk with
Frantic hind legs.
Tangle wings, tangle legs.
Dart in.
Avoid the sting.
Bite.
Dart out.
More silk.
More silk.

Bee’s wings are stilled
Though she still buzzes
A warning,
As though through
Gritted teeth.

More silk.
More silk.
Dart in.
Bite again.
Dart out.

The bee’s movements slow.
Abdomen goes slack.
Legs twitch once.
Twice.

More silk.
More silk.

David slays Goliath.