This is a photo I snapped of some microorganisms, awkwardly using a cell phone camera aimed through the eyepiece of a light microscope. The large black needle shape is a pointer visible through the eyepiece; the tiny black specks are bacteria, caught swimming and wriggling in a quick moment in time. The main objects of my interest at that moment, however, were the teardrop-shaped cells. These single-celled microbes belong to a large category of organisms called protists. You can see that each of these protist cells is much bigger than the bacteria, and they were swimming around very fast under my coverslip. I felt lucky to click the shutter in time to catch them in action. These creatures came from a sample of hay, soaked in water under the light of a desk lamp for about a week.
I never tire of gazing at the various protists that lurk in well-brewed hay. However, it’s difficult to know exactly what they are. (Someone knows, but it’s not me!) In general, protists are famous for being extremely diverse and difficult to classify. They’re eukaryotes, which means that their cells, like our own, are generally large and contain internal compartments, such as the nucleus, which stores the cell’s DNA. Other categories of eukaryotes include animals, plants, and fungi, which differ based on their cellular composition, other features of their anatomy, and how they obtain energy from their environment. But if an organism is a eukaryote and isn’t one of these three groups, it is classified as a protist, which contributes to the huge amount of diversity in this group. Many protists are single-celled, but some, such as certain algaes, can be multicellular and quite large (kelp in the ocean is a great example).
It occurred to me to try to identify the cells in my photo by comparing them to images in books or on the internet. One online image search decided my photo was likely a picture of water. Good guess, but not quite. Ultimately, I decided just for fun to see if my academic library had any books about protists that might have pictures for comparison. A shelf search turned up a real gem that I wanted to share here.
I obtained a copy of “Biology of the Protozoa,” by Gary N. Calkins, Ph.D., Professor of Protozoology at Columbia University, ©1926 by Lea & Febiger. I love old books, and I joined a cast of dozens who had checked out this book before me–though the last user was in 1974! I knew I likely wouldn’t find anything in this book to help me identify my mystery protists, but I was struck by the fabulous illustrations (238!) embedded throughout the 12 chapters and over 500 pages of all things cutting-edge-protozoa from this era. Various categories of protists were one of the earliest kinds of organisms painstakingly rendered by early laboratory biologists armed with microscopes and incredible patience. They were also helped in their chronicling of the life history of such creatures by talented and painstaking scientific illustrators. Calkins acknowledges the efforts of some of his assistants and illustrators, including “Miss Mabel L. Hedge, Mr. B. Manson Valentine, Mrs. Martha Clark Bennett, and Miss R. Bowling.” It is thanks to the efforts of this (notably predominantly female) staff that the book ever made it off the shelf and into my hands nearly 100 years after it was published.
This book is no longer under copyright protection, so I would like to share some of my favorite images to give a sense of the diversity and beauty of these “animalcules” (as they were often referred to in the early days of their description).
Of course, a digital photo capturing these intricate drawings doesn’t really do them justice, just as my phone camera failed to capture the real essence of the creatures on my own microscope slide. It is amazing to me to consider the efforts needed to observe so many details of these tiny organisms and render them accurately in pen and ink. Their diversity and beauty is astounding.
Nearly 100 years later, I wouldn’t necessarily trust Calkins’ descriptions of some of the categorization or descriptions of the life histories of these organisms, as we’ve come a long way in exploring the cellular workings and genetic ancestry of many protists in more detail. Nonetheless, the protists remain somewhat mysterious, still diverse, and still mesmerizing under the microscope. Kudos to the pioneers of microscopy and biology illustration for wowing us with the beauty of life forms we cannot easily observe.
And…maybe someday I’ll learn what my mystery protist is. Let me know if you have any ideas on its identity!