A Dispatch from the Center for Documentary Studies at Duke University
In late April, we had the great pleasure of hosting one of our prizewinning artists here at the Center for Documentary Studies (CDS). Her presentation on science writing and storytelling—which included selected readings from her new book on freshwater mussels—truly entranced the crowd.
Our Documentary Essay Prize honors the best in documentary photography and writing in alternating years. Those of us who reviewed the written essays submitted for the 2015 prize were immediately struck by one titled Immersion—lovely, graceful writing punctuated by the lyrical and surprising names of hidden creatures almost impossible for the untrained eye to see, with names like fatmucket and pigtoe. We’d found our winner: Abbie Gascho Landis, a veterinarian/naturalist/writer from upstate New York.
Abbie’s essay eventually grew into a book. Immersion: The Science and Mystery of Freshwater Mussels was published in April 2017 by Island Press. “This is nature writing at its best,” said no less an authority than E.O. Wilson.
This latest dispatch for The By and By includes the following excerpt from the essay for which Abbie won our prize and audio of her reading from the new book.
—Alexa Dilworth, CDS Publishing and Awards Director
On a March day I stand in roadside weeds near the County Road 10 bridge over Chewacla Creek, Alabama, wiggling first my legs, then my arms into a borrowed wetsuit. The wetsuit’s zipper gapes like an open shell, displaying my pregnant belly, almost four-months round. With considerable effort, I zip up the two halves, encasing myself entirely.
I have joined this Auburn University field crew on a whim—one of these biologists is my husband, Andrew. He watches his whole family squeeze into my wetsuit, then points us toward the creek. I sink to my knees, letting cool water flow over my thighs. Biting the snorkel mouthpiece, I submerge my head through a layer of crisp-edged floating leaves and into another world.
A fish darts close, and I see its eyes and finely-lined fins. Its gills clap against its head like it is slowly applauding my green-rimmed face. I revel in the bright underwater world. The creek fills my ears, dimming other sounds. Sediment stays on the creek bed, leaving the water clear until my fingers sweep the rocks, raising a cloud. I graze my belly upstream into better visibility, moving to the rhythm of my breath whooshing up and down my snorkel.
The biologists have told me that the creek’s edges often hold many hidden native freshwater mussels, of the family Unionidae. Finding mussels is our purpose for snorkeling Chewacla Creek in March.
Look for two small openings, they tell me. Mussels filter feed through these apertures. They’re like two short tubes often sticking up just a bit from the mud. “Once you get your search image, it’s easy,” Professor Jim Stoeckel, a compact man who rarely stands still, assures me, “You’ll really start seeing mussels.” After about an hour, the extent of Stoeckel’s optimism becomes apparent. I have plucked, flipped, and groped at least fifty rocks, leaves, twigs, and bulges in the mud. I’ve never seen a mussel in the wild.
These are not the coal black mollusks clinging like butterflies to rocks in the ocean. The family Unionidae includes almost three hundred species in North America. Nearly 70 percent of them are imperiled.
My search image, which resembles two short drinking straws poking up from the mud, wavers like a mirage. “It’s really hard to describe what to look for,” Andrew tells me later. “I look for what is not mud and rocks. Something that has a particular shape. Something that’s more perfect than everything surrounding it.” Freshwater mussels live mostly buried. Their shell edges are parted like a surprised gasp, exposing two apertures. One intakes and the other releases water, which is how mussels eat, breathe, and even gather sperm to meet their eggs. Those apertures actually look like Georgia O’Keefe paintings—flower, female anatomy—elegant ovals decorated with variously shaped and colored papillae. Apertures, papillae, curve of a shell.
These mussels ingest particles suspended in water. Sucking water across their gills, they sort particles as edible or inedible. The water flowing in Alabama’s creeks and rivers, the water sitting in catfish ponds and reservoirs, the water gushing from my own faucet, has passed through the interiors of freshwater mussels.
Although I do not see her, a mussel is there, near my feet. We stand in our wetsuits, leaning toward the creek bank. Andrew points; I still cannot see this mussel. Between my gravid abdomen and taut wetsuit, I can’t bend my waist. I bend my knees and tip forward.
“She’s displaying,” he tells me. He waits while I stare.
Then the mussel seems to materialize, differentiating from the leaves and rocks. Before my eyes, the creek bottom gains a dimension. A little spectaclecase, Villosa lienosa. She is doing the work of a freshwater mussel—filtering. She is also doing the work of many females this time of year. Her gills bulge with offspring—larval mussels—that she has brooded for months. Now the time has come. Above those offspring waves her mantle lure, decorated with multiple tentacles that look like a clump of small black worms. The bait.
Ripe with offspring, a female mussel must attract a piscine obstetrician to deliver her babies into the world. Striking the bait, a fish will release thousands of larval mussels, which will hitch a ride on its gills, transforming into independent juveniles, then let go and sink into their new creekbed lives.
Watching this wild mussel display her lure opens a door in my mind. I recognize this turning inside out for the next generation. This mussel and I are similarly vulnerable, preparing to empty our bodies into the future.
Male and female mussels reproduce without touching. In fact, they reproduce without necessarily being near each other. Mussel biologists don’t actually know how far apart two mussels can be and still “mate” with each other.
Step into the right creek at the right time of year, and you could be standing in a swill of mussel sperm. Female mussels, constantly filtering, draw in sperm along with bits of algae, phytoplankton, and tiny suspended particles of dirt. Inside the female, sperm fertilize eggs to form the mussels’ larval form, called glochidia.
Mussels begin as these very miniature larval versions of themselves: Their shell at this stage is made of a pliable, yet tough material, chitin, that also forms the shells on shrimp.
While they wait, open-jawed, for a fish, glochidia stay with mom. Sort of like an opossum, females brood their babies in a marsupial structure, gills, holding mature glochidia for a span of weeks to months. Inside the gills, a mussel keeps her glochidia in sealed tubes. Until they are released these larval mussels have no contact with the river.
How long will a mussel brood her babies? Some species release their offspring after only a few weeks. They are short-term brooders, referred to as tachytictic. The word reminds me of tachycardia, which describes a rapidly beating heart, a fast pulse. Others, the long-term brooders—bradytictic mussels—tend their glochidia for up to seven months, typically over winter. A pulse so slow that each beat lasts half a year.
“Aristotle thought bivalves arose spontaneously from mud or sand,” biologist Wendell Haag writes in North American Freshwater Mussels. “This would be remarkable indeed, but as always, the truth is even more interesting.” Even the phrase “mussel reproduction” is too general, Haag tells me over the phone. Asking, “How do mussels reproduce?” is like asking, “What do birds eat?” You have to be more specific. Are you asking about a hummingbird, which eats mostly flower nectar; or a goose, which eats mostly grasses; or a buzzard, which eats mostly carrion?
Wendell Haag becomes animated in this point of our conversation about mussel sex. For years, I had carried in my head a formidable image of Haag. A Mississippi-based U.S. Fish and Wildlife Service biologist, Haag has literally written the book on freshwater mussels and proliferates published scientific articles.
A few decades ago, we didn’t really know how female mussels got their glochidia onto fish. The 1984 Missouri Naiades: A Guide to the Mussels of Missouri, for example, describes a pregnant female mussel waving her “mantle flaps with an undulating motion that mimics the swimming of a small fish.” Many experts at the time were uncertain about this mantle-flapping behavior, speculating that it might aerate the glochidia within the mussel’s gills.
In 1988, however, biologist Bob Butler observed a lure caught on a snag in a tributary of the Choctawhatchee River in Alabama. The lure, uncannily resembling a small fish, was connected by a thin mucus strand to a southern sandshell, Hamiota australis. The mussel had apparently deployed this lure to dance in the current, angling for host fish. The lure turned out to be a package of glochidia. This showstopping behavior, previously unknown to science, helped to define our understanding of mussels’ reproductive tactics.
Wendell Haag suggests that butterflies are a close analogue to mussels’ host use and larval transformation. Butterfly larvae—caterpillars—require a host plant, on which they feed, then transform into beautiful adult creatures. Some butterfly species, like monarchs, can only use a specific plant, like milkweed, to raise their caterpillars. Other butterflies are generalists; their larvae can eat almost any kind of plant and will manage metamorphosis into adulthood. So it is with mussels and the host fish their larvae require.
But Haag’s analogy ends there. Butterflies can deposit their eggs on host plants. To get their larvae onto host fish, female mussels must bring the fish to them. For this, they have evolved complex strategies—mimicry, disguise, lures, and in certain species, entrapment. When this type of mussel attracts a fish, she clamps down on its head, forcing it to wait in a cloud of freshly released glochidia.
I have become a freshwater mussel groupie. I fawn over their photographs, mussels ranging in size from thumbnail to dinnerplate, building glassy or ridged or pimpled shells that are brown or black or yellow, with or without dark stripes fanning across them, and always paved inside with pearl—white, pink, deep violet. I stalk them from a distance, writing their names in my notebooks: fatmucket, pistolgrip, heelsplitter, shinyrayed pocketbook, spectaclecase, pigtoe, snuffbox. I pore over their bios. Posters of mussels hang in our bedroom.
In the wild, mussels are in peril because they’re sensitive. Burrowing and filter feeding at the intersection of water and earth, they suffer with disruptions to both creek bed and water. They’re also vulnerable because they’re specific. They have been called naiads, after Greek mythology’s freshwater nymphs, each linked inextricably to a particular stream or river. Some mussels are widespread, while some exist only in a single river system and some live in only a few creek sites. Mussels evolve with their river’s flow and geology, requiring particular river-bottom habitats. Their need for host fish links them to vulnerable fish diversity.
Human-driven changes to creeks and rivers often disrupt water flow and quality, destroy the creek bed, and alter fish populations. When a waterway changes, mussels are the first to know. They may die outright, or be unable to reproduce. Like the check engine light on a dashboard, mussels indicate when there’s a problem with how their river is running. Of the 300 freshwater mussel species native to North America, 29 are extinct. Only 89 species are considered stable, while 182 species are classified as vulnerable, threatened, or endangered.
One morning I sit in our family room and stare into our aquarium, which holds several fat bullfrog tadpoles beginning to transform. I call eighteen-month-old Sam over, pointing to things so small that he can’t see them. Legs. No longer than an eyelash, they end in three distinct toes flattened against a thick tail.
Metamorphosis is ordinary, repeated many times on this planet, like gestation. I am well along in my second pregnancy; I’ve done this before. But I can’t keep my hands off my kicking belly, and I can’t pull my eyes from that tadpole’s two new legs. The sperm-shaped tadpole will unfold into a frog, as legs and feet stretch from a sleek round body. Reverse amputation. Transformation. Those who can only swim will soon leap and breathe air.
We begin wet, swimming, tethered to a woman’s body. We breathe through her lungs, while our lungs lie folded like a butterfly’s wings in the chrysalis. Our hearts shortcut the flow of blood, skipping the lungs, in nearly the two-chambered way of fish. We will abandon this way of pumping with the umbilical cord—at birth—when we seal the windows in our hearts to make four chambers and arrive on dry land. “Breaking waters,” writer Terry Tempest Williams notes. “We are born from what is fluid, not fixed. Water is essential. A mother is essential.” After birth, we hold all of our water inside our skin.
In Chewacla Creek, the water holds me while my body holds my child suspended in fluid. A few thin, complex tissue layers separate the creek water soaking my abdomen from the water bathing my child. We swim. I feel continuous with the life inside me and life surrounding us. In some way, I have arrived where I began.
Abbie Gascho Landis reads from the last chapter of her new book, Immersion, at an event on April 27, 2017, at the Center for Documentary Studies.
This installment of The By and By is curated by the Center for Documentary Studies at Duke University (CDS). CDS is dedicated to documentary expression and its role in creating a more just society. A nonprofit affiliate of Duke University, CDS teaches, produces, and presents the documentary arts across a full range of media—photography, audio, film, writing, experimental and new media—for students and audiences of all ages. CDS is renowned for innovative undergraduate, graduate, and continuing education classes; the Full Frame Documentary Film Festival; curated exhibitions; international prizes; award-winning books; radio programs and a podcast; and groundbreaking projects. For more information, visit the CDS website.
* Mussels graphic by Emily E. Wallace, a freelance writer and illustrator and deputy editor of Southern Cultures at the University of North Carolina–Chapel Hill. To see more of Wallace’s work, visit eewallace.com.