Fantastic water bears and how to photograph them

At Te Papa we’re constantly photographing our collection items – whether that be art works, historical objects, or scientific specimens. 

Recently, our imaging specialist Jean-Claude Stahl has taken pictures of some bizarre creatures – water bears, also known as tardigrades.

Here, Jean-Claude explains why photographing a water bear is such a ‘bugbear’ and bug expert Phil Sirvid fills us in on exactly what a water bear is, and why they are one of the most indestructible creatures on the planet.

Tardigrade bug seen by a microscope

Tardigrade water bear (Macrobiotus snaresensis). Photograph by Jean-Claude Stahl. Te Papa (AT.000010)

What is a water bear?

Phil: ‘Little water bears’ were so named by Johann Goeze, a German pastor-naturalist who was the first to describe them in the 1770s.

Also known as moss piglets, water bear is a common name for a phylum of animals formally called Tardigrada (phylum is the highest classification rank below kingdom). Tardigrade means ‘slow stepper’, a description of their lumbering gait on stumpy legs with claws.

All species are very small, with the largest of them coming in at just over a millimetre long. They have eight legs and like insects, have to moult to grow.

Water bears have lumbered around for at least 500 million years (mid Cambrian).

Their closest relatives are velvet worms, arthropods (e.g. spiders, centipedes, crustaceans, insects) and round worms. There are about 1,200 species described worldwide, of which nearly 90 are found in New Zealand.

We almost certainly have more species waiting to be discovered.

Tardigrade water bear Echiniscus zetotrymus. Photograph by Jean-Claude Stahl. Te Papa (AT.000014)

Tardigrade water bear (Echiniscus zetotrymus). Photograph by Jean-Claude Stahl. Te Papa (AT.000014)

Where to find a water bear

Phil: Water bears are found just about everywhere.

They live in terrestrial, freshwater, and marine environments from the highest mountains (over 6,000m in the Himalayas) to the bottom of the ocean (-4700m and counting), and from the tropics to Arctic and Antarctic polar regions.

Notwithstanding their ability to withstand desiccation, they are essentially aquatic creatures. They are very common in moss and lichen, where they live in the film of water around leaves, stems, and other substrates.

Most feed on plants, but a few are carnivorous. While they might be called water bears, they are considerably smaller and less dangerous to people than actual bears!

Tardigrade water bear Echiniscus palmai. Photograph by Jean-Claude Stahl. Te Papa (AI.012595)

Tardigrade water bear (Echiniscus palmai). Photograph by Jean-Claude Stahl. Te Papa (AI.012595)

The toughest animals on Earth?

Phil: Water bears are unbelievably tough – and even that is an understatement.

While they don’t prosper in such conditions, they can survive periods of exposure to extremes of radiation, heat up to 150ºC for a few minutes, cold (-270 ºC), pressure (6,000 atmospheres), and more that would kill a human very quickly.

They are also the only animal known to survive exposure to the vacuum of space – as proved by a European Space Agency experiment.

If they are deprived of water they can almost totally shut down their metabolism and survive several decades of being nearly completely dried out – add water, and off they go again.

No surprise then that they are predicted to be among the last survivors once a dying and expanding sun starts incinerating our planet.

Tardigrade water bear Hypsibius allisoni. Photograph by Jean-Claude Stahl. Te Papa (AT.000001)

Tardigrade water bear (Hypsibius allisoni). Photograph by Jean-Claude Stahl. Te Papa (AT.000001)

Te Papa’s water bear collection

Phil: As a national museum, one of the missions of Te Papa is to assemble and care for comprehensive collections of plants and animals found in New Zealand.

Just as New Zealand has many unique species of plants and other animals, many tardigrade species are only found here.

These specimens help us understand New Zealand’s biological heritage, and serve as reference material for current and future generations.

An added bonus is that they occupy somewhat less storage space than a whale collection…

Te Papa has around 2,500 specimen lots of tardigrades with 27 of these being primary types.

As tardigrades are extremely small, specimens are permanently mounted on glass slides so they can be looked at under a microscope. The slides are stored in covered trays and in sturdy boxes. This protects the specimen slides from dust, damage, and fading from exposure to light.

Phil Sirvid holds slides containing the tiny water bears

Phil Sirvid holds slides containing the tiny water bears, 2017. Photograph by Rachael Hockridge. Te Papa

Where water bears are stored. In slides protected by a cardboard casing

Water bears in their slides, 2017. Photograph by Rachael Hockridge. Te Papa

How to photograph a water bear

Jean-Claude: Water bears are more like bugbears when it comes to photographing them.

First, they are tiny, and filling a 20mm sensor with a 1mm or smaller critter, requires a compound microscope, or bellows, fitted with a 10x, 20x, or 40x lens.

Next comes the hard part: when preserved on microscope slides as in the museum’s collection, water bears are essentially as transparent as the glass slides that entomb them.

Olympus BH2 compound microscope. Photograph by Jean-Claude Stahl. Te Papa

Olympus BH2 compound microscope. Photograph by Jean-Claude Stahl. Te Papa

There are fortunately various contrast enhancing methods to get around this, one of which is Differential Interference Contrast, which is the one we used at Te Papa. This is an optical microscopy technique used to enhance the contrast in transparent samples.

The effect obtained appears like a 3D image with (false) oblique lighting. The ‘limestone slab’ type background on the water bear images shown results from the false lighting on the dried out preservation medium between the slide and the cover slip.

If you find these little creatures fascinating you can browse through photographs of more water bears or tardigrades on Collections Online.

Tardigrade water bear Pseudechiniscus perplexus. Photograph by Jean-Claude Stahl. Te Papa (AT.000006)

Tardigrade water bear (Pseudechiniscus perplexus). Photograph by Jean-Claude Stahl. Te Papa (AT.000006)

2 Responses

  1. Phil

    Hi Paige,
    They will be quite dead by the time they are mounted. They are rather translucent so look a bit flatter than they are when viewed this way. The mounting medium they are in is thicker than they are and slide preparations are typically left to dry and harden in an oven for about a month at 50 degrees Celsius. The edges of the cover slip and mounting medium are also ringed with epoxy paint to seal everything in.

    Reply
  2. Paige Hammond

    Just a few silly questions that I’m very curious about.
    Are the water bears alive in the glass slides? How did you seal the sides of the slides, wouldn’t they be able to slip through if they’re so small? Are they actually that flat looking, or are they being squished?

    Reply

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