The mystery of Sonneborn’s weird paramecia

[This is a repost, with added imagery and links, from a post in 2000, which was itself a reprint from the magazine. Thus do things propagate….]

Sonneborn and the Persistently Shapely Paramecia

A new look at forgotten or overlooked science

by Marc Abrahams

EDITOR’S NOTE: This is the beginning of a new, not necessarily humorous, AIR column. The column will look at genuine scientific discoveries that have fallen by the wayside, but that raise intriguing — and perhaps important — questions.

In the early 1960s, a fellow named Sonneborn discovered a big peculiarity in a tiny animal, the paramecium. Sonneborn would take a paramecium, and disfigure it. Later, after the paramecium reproduced itself, its children (and their descendants, too!) inherited that same disfiguration. That inheritance raises a question that should disturb and intrigue every living biologist: How was the information — the location and shape of the disfiguration — passed from one generation to the next?

About Paramecia, and About Inheritance

First, a little background about paramecia.

A paramecium is a one-celled creature. It has a distinctive shape, rather like that of a slipper; it’s the shape you see repeated on a paisley tie. The paramecium is a ciliate, which is to say that its surface has lots of little, whip-like projections called cilia. The cilia are generally arranged in parallel rows, and within the rows, each cilium has pretty much the same orientation. (This is analogous to the hairs on a patch of your skin — on a small patch the hairs all point in the same direction). The cilia wag back and forth rather like floppy oars. This concerted wagging is how the animal moves itself about.

Second, a little background about how shape and other information is passed on from generation to generation. Every living thing has received from its parent (or parents) the set of instructions necessary to physically live and grow. Those instructions are carried, in tickertape fashion, in the genes. The genes are made entirely of deoxyribonucleic acid (the famous DNA), arranged as long, long, astoundingly thin, twisty, scrunched-up tickertape-like molecules. All of modern biology is based on this idea — that virtually all the physical information that’s passed from parent to child is contained in the DNA. In a paramecium, the most famous chunks of DNA are contained in the nucleus. Some other parts of the cell also contain their own little chunks of DNA.

What Sonneborn Found

With that background in mind, consider what Sonneborn found, and how puzzling his discovery is.

Tracy M. Sonneborn was an Indiana University biologist, known and much respected for doing careful research. His paramecia experiments, in particular, are carefully documented. In these experiments, Sonneborn would slice off a little chunk of a paramecium’s surface, then rotate the slice and plop it back on. It was easy to see where the grafted slice now lay. Its rows didn’t line up with the neighboring rows, and the individual cilia were oriented in the “wrong direction” compared to cilia in the neighboring, undisturbed rows. And because its cilia in the altered patch were wagging in a different direction from that of their neighbors, the altered paramecium would, typically, move in some mildly eccentric way.

The startling thing is what happened after the paramecium reproduced. For a paramecium, reproduction is usually a lonely, mitotic affair. The thing just splits itself in two.

Each offspring of a maimed paramecium turned out to have the same graft pattern as its parent, with the rotated patch of cilia in the same, odd orientation. This flipping of the paramecium’s wig makes biologists flip their own wigs, those few who have heard about it.

It’s hard, very hard, to see how this could possibly be inherited via the genes. Yet somehow the information is passed on from the paramecium that got the disfiguration to its children, and on to subsequent generations. How? How?

Where Might This Lead?

Sonneborn died in 1981. Nary a soul has picked up on his work and tried to see where the big question might lead. Maybe it leads nowhere, maybe it leads somewhere very, very interesting. Perhaps you, or someone you know, will be the person who discovers the answer to this question.

Where to Start

If you want to dig into Sonneborn’s work, a good place to start is one of his reports: “Cytoplasmic Inheritance of the Organization of the Cell Cortex in Paramecium Aurelia,” Janine Beisson and T.M. Sonneborn, Proceedings of the National Academy of Sciences, vol. 53, no. 2, February 1965, pp. 275-82. Good luck. If you do some experiments and find an answer, please let us know.

Here’s some visual detail from Beisson and Sonneborn’s paper:

BONUS: One of Sonneborn’s students was a fellow named James Watson, who later co-discovered the structure of the DNA molecule.

BONUS: There are other such mysteries, probably lots of them. Here’s a new one.