By Hannah Knighton
“A good amount of the job is observational,” Taylor Sakmar said as he crouched in front of a tank, peering in at the unusual, multicolored creature staring back at him. It was early September and my first day as a cephalopod operations intern at the Marine Biological Laboratory (MBL) in Woods Hole, Massachusetts. Sakmar stood to step aside so I could begin to make some observations of my own.
Looking back at me through a W-shaped pupil was a Metasepia pfefferi, commonly known as the flamboyant cuttlefish, a name inspired by its vibrant color palette, with eight arms ranging from shades of pink and yellow to orange and brown waving gently with the flow of the water. Its mantle, the main body cavity, flashed bands of brown and white. Like a cool breeze pricks goosebumps across human skin, soft tissue known as papillae mocked horns all over the creature’s body as it bobbed close to the water surface.
“With these guys, it’s actually not a good sign to see them swimming around. It usually means they’re stressed,” Sakmar said. Metasepia pfefferi, often referred to in the lab simply as metas, are the smallest species of cuttlefish, at their largest growing to about the size of a credit card. They spend much of their time on the ground, trudging slowly across the sand and nestling under rocks or shells. Sakmar, the senior cephalopod culture specialist at MBL, relayed a list of other behaviors to look out for and left me to begin distributing snacks of live grass shrimp to the colorful creatures.
From then on, I would be the point woman for this species (Queen of the Metas, as one co-worker jokes). Everything from feedings to cleaning the intake tubes that supplied water to their tanks would fall under the umbrella of my responsibility. But my ultimate goal was to “close the life cycle”—in other words, get them to reproduce. Successful reproduction and subsequent maintenance of ideal growth conditions are referred to as culturing. The cephalopod lab aims to culture a variety of species as we work to define and maintain the standard of care for cephalopods in lab and aquarium settings.
Being crowned Queen of the Metas was not a title to take lightly. Nicknamed the divas of the sea, these cuttlefish are easily stressed and difficult to care for in captivity. In fact, my supervisor, Bret Grasse, was the first to successfully have this species lay eggs and raise those hatchlings to adulthood in captivity at the Monterey Bay Aquarium in California in 2010.
Cephalopods, the class that includes squid, octopus, and the chambered nautilus alongside cuttlefish, are sensitive creatures, generally easily stressed. That means even obtaining the species and acclimating them to human care was difficult. From there, the challenges only continued.
Prior to Grasse’s work in culturing the flamboyant cuttlefish, very little was known about the species. The only notes that existed were from divers or researchers observing the cuttlefish in their natural habitat in the Indo-Pacific—there was no knowledge of keeping them in lab or aquarium settings. He figured out what prey items they preferred, what kind of substrate and rock formations they liked, and where they preferred to lay eggs. But once they lay eggs, that’s where the real challenge starts.
They have to hatch away from any adults or aggressive flow so they can begin the early, most sensitive stages of their lives in the most optimal conditions possible. The first time these optimal conditions were obtained and baby Metasepia began to hatch, Grasse felt a large sense of relief. He believes this pioneer work paved the way for a deeper scientific understanding of cephalopods. Since then, they’ve become integral in aquariums worldwide and are now being investigated as model organisms for human disease research.
Today, the cephalopod operations team works to produce multiple generations of various cephalopod species with the goal of raising organisms for aquariums or for human disease modeling, such as anesthetic testing, limb regeneration studies, and genetic testing. Captive culturing programs like ours help to reduce the strain on wild populations and maintain nature’s biodiverse habitats, making this practice sustainable.
Sakmar wasn’t kidding when he said most of the job was observational. I would spend the next month trying to determine each cuttlefish’s gender from simply watching their behavior. Flamboyant cuttlefish show little sexual dimorphism, meaning there are no physical external characteristics to determine their gender. The only physical characteristic to look for is size, as females tend to get slightly bigger. But that can be a tricky and not always reliable way to distinguish them. Instead, the way they act unveils their sex.
One day I hopped up on a step stool to drop a few shrimps into a tank at feeding time. I came eye level with two metas having a face-off. Both metas had their arms outstretched; they were light in color except the tips of their arms, which had turned to black. They wiggled back and forth, dusting each other with their outstretched arms. I watched for a moment before turning and calling out to Sakmar. He walked over to where I was standing with my eyes glued to the tank. “That’s what we call paint brushing.”
As I had observed it, paint brushing is a form of male-versus-male aggression. The more dominant male, which in this case was the larger male, wins. Males will also exhibit this behavior when mating to determine if a fellow flamboyant is male or female. As I had learned, males will return aggression, while females will be submissive, usually a sign they’re willing to mate. But other times, as I often observed, the females simply try to get away.
Cephalopods, sometimes referred to as the shape-shifters of the sea, are able to create dazzling color displays and achieve a range of body patterning by manipulating a combination of factors. Behind their ability to create such displays is an important group of cells known as chromatophores. Chromatophores are pigment-containing cells that have muscles attached to them. Imagine how spokes look on a bicycle—that’s how the muscles surround these sacs of pigment. The muscles expand and contract the cells, allowing for the variety of colors a cephalopod can put on display. Body postures, like the one termed paint brushing, can also be made up of textural components, when papillae extend outward to form small, soft peaks on the animal.
There are other behaviors aside from paint brushing that help aquarists determine the gender of metas. Males, for example, typically seek higher ground, while females will spend more time under rocks and shells. But metas rarely make things easy, and their tricky tactics can only add to the confusion. Some males will be more submissive, making them appear to be females to caretakers. In other populations there may be dominant females that display male behaviors.
As they get older and closer to sexual maturity, the act is eventually dropped, and distinguishing sex differences comes easily. While males still react slowly and feed meticulously, female Metasepia begin to take out shrimp with gusto. Females quickly lock their W-shaped pupils with their prey and aim their feeding tentacles with great accuracy. Previously eating one shrimp per meal, they’ll now take down three to five times more food as they put vast amounts of energy into ova production. Metas are often slow-moving creatures, so when they begin to eagerly attack prey, it’s a good sign for reproductive health. As the days passed, I noticed the metas were getting hungrier, the females were getting larger, and the males were paint brushing more and more. We had to be close to getting eggs, I was sure of it.
While cleaning a tank on an afternoon at the end of October, I noticed a small, white blob bouncing along the sand. Eyes widened and heart racing, I began to look under rocks and shells. Sure enough, on the underside of one large scallop shell clung seven small sacs of tissue. Eggs. EGGS. We had eggs! I clambered around the lab excitedly looking for Sakmar. “We have eggs!” Sakmar did a spin, punched the air excitedly, and shouted, “Yes!”
***
From the end of October through December, I practiced techniques in harvesting and incubating Metasepia eggs. Carefully lifting low-hanging rocks and checking under the smooth, vaulted surfaces of shells, I’d find clutches of around a dozen eggs delicately waving with the undulations of the water in the tank. When females are ready to lay their eggs, they seek out low, vaulted surfaces. Lifting their arms up into shells or low-hanging rocks, they carefully deposit eggs one by one, tacking them to the chosen surface with a biological glue.
Taking sharp-tipped forceps, I gently scraped away the biological adhesive connecting the eggs to the shells, delicately plucking them off and carefully depositing them into a bucket of seawater, one by one. The importance of the task was not lost on me. Every dime-sized egg felt valuable, a small promise of life within. Every step I took during harvesting could affect the possibility of that small promise reaching reality. Although just an intern, I felt I had been given a great task, and with it, the inherent pressure of succeeding in nurturing each little life.
At the MBL, our mission is to work toward creating and providing the standard of care for cephalopod species. This includes optimizing the animals’ hatching success, which is why we practice techniques in artificial incubation. Artificial incubation, as opposed to keeping the eggs in the tank with their mothers and other co-habituating adults, allows for close observation and proper oxygenation of embryos. Cuttlefish mothers provide little to no maternal care, and removing eggs from their habitat allows the females to lay additional viable eggs. This method is also safer for hatchlings who may find their parent’s environment harsh with high water flow that could push them around and the possibility of being mistaken for prey by adults. In the end, artificial incubation allows aquarists and researchers to create the most optimal conditions for hatching.
As the days passed and the embryos bounced and bubbled around inside their incubators, the transparency of the egg casing welcomed me into their tiny worlds. I watched as their beady, red eyespots developed, their heads and arms began to form and wrap around the yolk. Their mantles began protruding, followed by the formation of chromatophores, the pigment cells that allow for their color-changing abilities. Right before my own eyes, I watched tiny replicates of adult Metasepia form. I began to feel attached to the growing embryos, as if I had laid the eggs myself.
By January, hatchlings had taken over the lab. Still leading the care of the adults and now their 220 offspring, I would dote on the tiny cuttlefish, carefully conducting counts each morning, then feeding them. Feeding would take an hour and a half of my morning or longer, as I meticulously assessed the number of miniature mysid shrimp to place into the tank. Mindful not to startle them, I would bend down and peer into the tank with an angled flashlight to watch them feed. Their tiny movements were minuscule. They’d turn slowly, bounding around on mantle papillae projections known as glutapods, a term that quite literally means “butt feet.”
Over countless hours of feeding and caring for these delicate animals, I created my own narrative with the critters. I’d chide the chunky ones for taking more food than their fair share, although regardless, I was happy to see them eating and growing, as any caretaker would be. Just like a litter of puppies, there tended to be a runt in each group. I’d keep a close eye on the little guys during feeding to make sure they got at least one shrimp each. Time consuming as it was, it was time that never felt wasted. The early stages of life are the most critical.
As I astutely cared for the delicate divas, a new idea was forming. I had now spent every day for around five months observing and caring for these creatures. The pressure to succeed in raising the cuttlefish kept me working at my highest caliber. I felt my understanding of their care was not quite perfected, but reached a professional level. My notes had begun to pile up, my observations numerous. I wanted to dig deeper; there was much to still be discovered about these animals beyond their care and keeping.
***
It was summertime, and Woods Hole had evolved into a different town. Once quaint and quiet, it had transformed into a bustling beachside hot spot. I often describe the change from the winter to the summer as a human migration. Thousands of people flock to the Cape; everyone from vacationers to summer researchers fill up the campus and bring a whole new life to the area.
There was a new breath of life for my work at MBL, too. As I harvested and incubated the transparent orbs of life, I was welcomed into their tiny world, watching them hit developmental milestones safe inside their eggs, yet right before my eyes. Despite all the ongoing and already published research about cephalopod embryonic development, I found the literature lacking for Metasepia. So, I made a plan and typed up an experiment proposal. Grasse and Sakmar approved, agreeing the existing information felt incomplete. Just as I had fostered the growth of the cuttlefish themselves, I would now be nurturing my own research project.
My experiment aimed to look at and mark the growth of Metasepia. As days passed, I would note at what point in gestation key anatomical features began to form. With a delicate hand, I’d manipulate the position of the growing Metasepia under the microscope, trying to get the best angle for an image. I photographed them in this manner three times a week, and I did it for three weeks, watching as they developed key morphological features such as eyes, arms, cuttlebones, and chromatophores.
Through the clear outer egg casing at the yolk, I saw the first sign of organ development, which are two dark, half-moon-shaped spots forming on the yolk’s surface. These half-moons will quickly form into eyestalks, and a central protrusion from the yolk becomes the cuttlefish’s main body cavity, the mantle. Below are eight dots that will soon develop into arms. As the arms develop, they wrap around the yolk such that the animal appears to be grasping its source of sustenance. The animal grows and the yolk shrinks, and a distinct head forms. The arms and the mantle elongate, and after twenty days, the cuttlebone—the internal hard structure that aids in buoyancy control—and the color-shifting chromatophores have formed. The animal inside the egg is a tiny replica of an adult flamboyant cuttlefish, fully equipped with all its body parts, even able to camouflage and dispense ink inside its egg sac.
The Metasepia took about twenty-nine days to hatch. The imaging process went by quickly, and before we knew it, tanks throughout the lab were once again populated with the tiny creatures bounding around on their glutapods and flashing their vibrant bands of color. My focus could now turn to data analysis.
After running through the records and looking for significant milestones, I found the embryos developed consistently, with only one individual lagging behind. I was able to mark at what day, over weeks of development, key anatomical features could be expected to develop. These initial insights are a prerequisite to further understanding of the development and evolution of Metasepia, which in turn allows aquarists and researchers to track normal growth in captive-held metas. A world of scientists and aquarists could potentially benefit from this. It could even have the potential for publication. For me, this was the ultimate validation of the trials and triumphs I had experienced over my time with the cephalopod program.
I realized that despite the fact I had been mentored almost exclusively by male faculty members, it was my own attention to detail and nurturing qualities, which one might label “feminine,” that had led to my success. I often found myself doubting my own intrinsic abilities, but those inherent qualities were ultimately the key to my success. On the last day of my internship at MBL, I sat down with another great mind, Dr. Carrie Albertin, an embryologist known for her work sequencing the genome of the California two-spot octopus. Grasse believed Albertin would provide expert guidance as I contemplated going through with the publication process. As I sat in her office, I found myself apologizing for my research, stating it wasn’t quite on the level of what she does, but it could still have value to researchers. Albertin stopped me in my tracks. “What you’ve done here is real research. And there’s no doubt you can publish this. I would be happy to look at it for you and point you in the best direction I can.”
As two women sitting across from each other, I felt she must have a depth of understanding to my doubts one could only sympathize with through their own similar experiences. My gratitude for her confidence in me was an overwhelming feeling, possibly as overwhelming as the amount of thank-yous that poured out of me as we talked. “Go be excellent,” Albertin said as I left her office. Washed over with emotion, I turned and smiled back; I finally saw I have what it takes to be a scientist. I don’t need to fulfill a male-dominated “scientist” archetype; I just need to follow my sense of curiosity and practice skills of discipline and observation, qualities that were always within me.
Hannah Knighton is a freelance writer and editor with focuses on wildlife, environment, sustainability, and travel topics. Her work has been published with Smithsonian Magazine online, the Ocean Portal, and Motif Magazine and her editorial contributions extend to Science Magazine, Science News online, and the Science Writer. She holds dual bachelor's degrees in marine science and English from Jacksonville University and a master's degree in science writing from Johns Hopkins University. More recently, she began exploring themes of grief, race, identity, and motherhood through her essays. Her writing reflects a profound connection between the intricacies of the natural world and the human experience.
Photo credit: Monterey Bay Aquarium