Nifty Nematodes

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

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

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.

Noddy’s Back!

Okay, call me a complete geek, but I’m inordinately pleased about today’s find in the vegetable garden—Noddy’s flycap. This striking and mysterious mushroom showed up last year, causing great excitement and a blog post. The word from the scientific community was we weren’t likely to see it again for a long time, as it doesn’t seem to fruit every year.

Ha! Another thing we can tick off as an unknown for this fungus. Second year in a row Noddy’s has popped up in the garden.

As far as I know, the fungus still has no official scientific name, and its origin remains as mysterious as it was when I wrote about it last year. So for now I’ll simply enjoy the whimsy of this most delightful of fungi.

Summer Rock Concert

It’s a cicada; it must be summer.

The main cicada season doesn’t really start until the chorus cicadas (Amphisalta zealandica) come out after Christmas, but two weeks ago, we found a few chirping cicadas (Amphisalta strepitans) on the rocks around Okains Bay.

Cicadas are largish, as insects go, but they’re well camouflaged. Usually, you find them by sound. As with most insects, it’s the males that do the singing. The main part of a cicada’s song is made by flexing plates (tymbals) on top of the body. Built-in amplifiers (opercula) pump up the volume to an astonishing level. Cicadas are noisy. I don’t know if any of the New Zealand species have been tested, but the calls of some North American cicadas are over 105 decibels at a distance of 50 cm. That’s nearly as loud as a rock concert (115 decibels). When the chorus cicadas here in New Zealand come out in large numbers, they can be so loud in some places that it’s impossible to carry on a conversation.

Some New Zealand cicadas add an extra feature to their song—a bit of drumming called clapping. The cicada snaps the leading edge of its wings against a branch to make a sharp click. Females also clap, and I’ve read (though I’ve never tried it) that you can call the males to you by snapping your fingers.

There are about 2500 species of cicada worldwide. Because of their size and volume, they seem to be culturally important wherever they live. They are eaten as food in many areas, and sometimes used as fish bait. Growing up, my siblings and I used to collect the shed exoskeletons of cicadas and attach them to our clothing like jewellery. When I lived in Panama, the children would catch cicadas and tie strings to their feet, then carry them like helium balloons, flying on the end of the string.

Wherever they live, they mark the seasons. Here in New Zealand, and in America where I grew up, summer hasn’t really started until the cicadas sing.

Loud singing? Drumming? Must be a summer rock concert!

Wasp 1: Cleaning 0

I try to keep a clean and tidy house, but sometimes it’s just not possible.

I was going to dust this weekend, but the first spot I ‘dusted’ was the dining room windowsill. It’s a big window and, for some reason, most of the insects that get into the house seem to end up there when they die.

Next thing I knew, I had a handful of dead insects in a petri dish and was looking at them through the microscope. Most were insects I was familiar with—old friends I was catching up with—but this lovely lady was new. A tiny parasitic wasp, but I couldn’t quite place her family. Several hours, a couple of taxonomic keys, and a stack of entomology books later, I still wasn’t certain, but I tentatively put her in the family Pteromalidae.

Oh, and the cleaning was entirely forgotten.

Spittlebugs

Spring is spittlebug season. Just about the time I want to start picking and dehydrating the perennial herbs, the spittlebugs descend upon them. In bad years, it makes harvesting herbs a slimy task.

Spittlebugs are also known as frog hoppers. As adults, they are cute, squat, dun coloured insects with spectacular leaping abilities. They really do resemble frogs (with a little imagination).

It’s the nymphs that have the disgusting habit of spitting. Well, it’s actually not spit at all. The foamy slimy ‘spittle’ is a combination of fluid from the insect’s anus, and slimy gunk from glands on the insect’s abdomen. The insect sits head downward on the stem of a plant and exudes the ‘spittle’, letting it pour over its body and cover it completely. The resulting mass keeps the young insect protected from enemies and from drying wind and sun. Gross, but effective.

Like humans, who usually stop blowing bubbles in their milk as adults, spittlebugs leave off spittle production when they grow up. As adults, they use their hopping ability to avoid predators.

Some species of spittlebug can become significant agricultural pests, stunting the growth of herbaceous plants and some forestry trees, but in the home garden, they’re usually not much more than a minor nuisance.