One of the many delights of using a microscope is that second before you peer into it, when
you are only a breath away from seeing into another world and uncovering organisms familiar
and unfamiliar.
That moment is full of mystery. What will
you find this time…an amoeba under attack? A tardigrade orgy? Or perhaps an understated,
calming minute of oscillatoria sliding across the scene? In that moment, anything is possible.
But sometimes, there are clues even before the organisms come into focus, like a whiff
of something a little smelly that alerts you to synura blooms.
Or in the case of Lacrymaria olor, a ciliate whose name translates to “tears of a swan,”
what you’re looking for is a wanton path of destruction.
In a 1911 paper in the Journal of Animal Behavior, the scientist S. O. Mast described Lacrymaria
as “among the most interesting of living beings.”
Now, I’m sure we all have our biases about what the most interesting living beings actually
are. And on the surface, Lacrymaria don’t necessarily seem inherently more interesting
than any other organism. Sure, they’re ciliates, but so are plenty
of other organisms. Also, they get to be around 100 micrometers long,
they have both macronuclei
and micronuclei, and some contractile vacuoles. Which again, is all very good, but none of
those details make Lacrymaria particularly interesting.
No, I mean, what we really want to know is what’s going on with that neck!
The lacrymaria’s teardrop-shaped body extends off that neck-like thing that has a sort
of “head” at the end of it. Obviously, this “head” and “neck” are not actual
heads and necks in our bodily sense of the words. But the structures are distinct, and
so the terms are convenient ones for us to use here.
And what makes the Lacrymaria’s neck so remarkable is just how long it can get. Sure,
the microbe may be named for a swan. But in his paper, Mast notes the more obvious animal
comparison, punching the numbers to see how a Lacrymaria’s neck compares to that of
a giraffe. He writes (as dismissively as one can in an
academic paper) that a giraffe has a neck that is “scarcely as long as its body.”
By contrast, the Lacrymaria’s neck can reach anywhere from 7 to 8 times its body length.
As Mast goes on to say, if a giraffe could pull off such a feat, then we would “find
the giraffe browsing leaves from the tops of trees well towards one hundred feet in
height.” Plus, the Lacrymaria’s neck is just so flexible, able to wind itself around
debris in a way a giraffe definitely could not.
But where giraffes use their relatively shorter and stiffer necks to forage through treetops,
Lacrymaria are much less vegan, using their neck to ambush prey.
The Lacrymaria’s hunting style is incredibly successful, but it’s built in part on chaos.
Instead of lying in wait for food to come by, the Lacrymaria plays the odds. It zaps
its neck out incredibly fast, sub-second movements to whip around and randomly sample the area
around it for food. This strategy helps the Lacrymaria capture all sorts of prey. And
that’s why when you’re looking down at your slides, you might see the damaged remains
of the Lacrymaria’s unfortunate victims before you see the hunter itself.
If we saw this kind of carnage on the savannahs of east africa, pieces of animals strewn across
the landscape, none of us would ever get within a mile of a giraffe ever again.
When the Lacrymaria finds its target, it fires off a set of organelles called extrusomes
to release toxins into their prey. And you can see that the flexibility of the Lacrymaria’s
neck comes in handy not just for hunting, but also for eating, expanding as it does
here to contain the entire meal.
And even if the prey is larger or faster than
the Lacrymaria and it can’t get the whole microbe, it can still tear off quite a sizable
chunk and make a nice meal out of that piece. Of course, all that movement is…a lot. And
it’s not something the organism can be doing all the time. Our master of microscopes was
excited to find some of these Lacrymaria and observe them in action, only to find that
they’d become much less active. Their necks would pull further and further inward until
it was retracted entirely, and the ciliate itself was completely still.
Lacrymaria are a rare enough find as it is, and when James saw this strange stillness,
he was worried that he might be doing something that was hurting his precious friends.
Months later, he found some more Lacrymaria olor. But after 10 minutes of watching them,
they did the same weird dormant pose thing again. Concerned again that he might be killing
them, James left the slide in a humidity chamber overnight.
So imagine his relief when the next morning, he found that the slide was full of reproducing
Lacrymaria! That’s when James noticed that this activity
and dormancy seemed to be a repeated cycle. The Lacrymaria would awake and be active for
about 10 minutes, and then retreat back to their inactive state for another 10 minutes,
and then become active again. Scientists studying this phenomenon have used
high-speed cameras to find that Lacrymaria cycle between 4 total states. There’s an
active state where the microbe’s neck is out and about to find some food. Then there’s
a resting state where it all retracts. And then there is an activation and inactivation
state that transitions the microbe between active and resting, possibly allowing for
the structures underlying the neck to rearrange as the Lacrymaria moves from one way of life
to the next. And so while it’s resting, the Lacrymaria
is much less of a threat. It’s neck, which, again, is not actually a neck, retracts, leaving
its neighbors in a moment of peace. But when it awakens, it will return to twisting
and turning and elongating, menacing the microcosmos until it has made a meal of it.
Thank you for coming on this journey with us as we explore the unseen world that surrounds us.
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