Tadpole Tails, Cancer and Science Education
Tadpoles, sometimes referred to as polliwogs, are the aquatic larval form of amphibians, such as frogs. As children, I spent countless warm summer hours watching them with my friends in shallow Michigan ponds in the woods near my house. I recall first seeing the massive, sticky egg clusters near the pond's edge. One day, nearly all at once, the small, fish-like tadpoles emerged. They swam (more like wiggled) and swarmed by the thousands in the water. They were fun to play with and extremely easy to catch! A single sweep of an open Mason jar would yield a dozen captives.
As time passed, the free-swimming, fish-like tadpoles did something very strange. They sprouted legs! Hind legs first, if I recall, then front legs. After gaining appendages, the tadpoles lost their tails and became frogs, and then could hop out of the water. Thousands of tiny frogs appeared in the mud and grass around the pond.
Perhaps it can be ascribed to the brevity of the childhood attention span, or perhaps it was the beginning of sandlot baseball and other summer activities, but appearance of the frogs always marked the end of my amphibian-watching season. Nonetheless, one question remained on my mind—what happened to the tadpole tails? We searched for, but never found, a single tadpole tail. Where did they go when the tadpoles lost them?
Formal Science Education
A decade passed. As an eighteen-year-old college freshman, I sat one evening in the library and read an assigned section about cellular organelles in a Biology textbook. The section was about lysosomes. With my yellow highlighter in hand, I learned that these small sub-cellular structures contained dozens of strong digestive enzymes, called hydrolases. The hydrolases could breakdown almost anything they came in contact with. Materials brought into the cell, such as small food particles, would come in contact with the lysosomes and the hydrolases digested the food.
I had a lot of homework to do, and I might have just turned the page and continued my highlighting. However, there was one additional point about lysosomes that the textbook mentioned... lysosomes were thought to be involved in morphogenesis, the process of, among other things, the degradation of tadpole tails. I dropped my highlighter.
Tadpole tails and lysosomal hydrolases, of course! The tails didn't drop off; they were absorbed. The materials that made up the tadpole tails were broken down and reused to make legs... perfect! Somehow, the tadpole tail cells simply knew when it was time for their lysosomes to spill their powerful hydrolases into their own cytoplasm and destroy themselves. Everything seemed to make sense. Biology was wonderful. There was an answer for everything. A great feeling of confidence came over me.
Unfortunately, that wonderful feeling of understanding lasted only a few peaceful moments. How did the lysosomes know they were in tadpole tail cells? How did the lysosomes know it was time and that the tail was no longer needed? What if tadpole brain cell lysosomes mistakenly thought they were in tadpole tail cells instead and dumped their nasty hydrolases into the tadpole's growing brain? What if... What about...
Nothing else I was studying seemed as interesting to me as lysosomes. I read way more about the subject than my courses warranted. I chatted with a fellow biology student I often studied with. What if there was some way to make lysosomes in cancer cells think they were in a tadpole tail cell that was ready to be destroyed? Wouldn't that kill the cancer cells?
We read all we could find. One idea sprang from another. Then we came to a point I had never experienced before. Call it a wall. A wall that no scientist can ever avoid. That wall represented not just the limit of what I personally knew about the subject of lysosomes, but the limit of what ANYONE knew about the subject at the time! Somehow, my friend and I were confident, controlling lysosomes could cure cancer. But we weren't sure of how. And the details we needed to proceed in our thinking simply did not exist. It seemed so important, but it was out of our hands. The questions we asked could only be answered by new research. We were eighteen-year-old freshmen. We had many other classes to take and pass before we would be in a position to have a lab and write research grants and make new discoveries about lysosomes and cancer on our own. We moved on, disappointed that we hadn't cracked the code to treating cancer but energized by our belief that the answers were out there to be found.
To this day, the potential of controlling lysosome activity in cancer cells is still the subject of research. Though I have "left the bench" of active research, I continue reading about the topic and rooting for the researchers' success in finding successful cancer treatments.
Tadpole Tails: A Lesson for Science Education
As this story shows, scientific concepts can develop over a long period of time. They can lead anywhere, perhaps into areas of study only remotely related to the original concept. Further, at any point in the development of a scientific concept, one need not know the ultimate destination of the conceptual journey. Likely, there is no end to the journey!
There is great value in introducing children to scientific concepts and phenomena that they might not be able to fully understand at the time. The introduction serves to pique their imagination and keep their eyes open for answers. At its best, a so-called ‘spiraling’ science curriculum organizes a series of observations and information that matures with educational and life experiences. This way, when an answer finally becomes clear to the student, perhaps months or even years later, it contains depth and meaning that would be impossible to acquire through a brief encounter or a canned explanation.