Blogs from our Scientific Researchers

Carnegie Museum of Natural History is home to active research and vast scientific collections. Our scientific researchers regularly contribute to the blog at the museum.

August 24, 2021 by wpengine

Bringing Light to Dark Places

by Suzanne Mills

“May it be a light to you in dark places, when all other lights go out.” ― J.R.R. Tolkien, The Fellowship of the Ring

“Elrathia kingi,” the small square of paper declares. Regal yet a bit mysterious, the Latin name on the museum-issue label conjures Tolkien. From an unlidded box small enough to hold a wedding ring, I remove a chalky gray pebble. Its minute weight slides easily through my fingers; it seems as inconsequential as a penny. But it is not hard to see what gives this iota of stone its value. As if sculpted in bas-relief, a pair of tiny eyes peek out of a crescent-shaped head. Thin ridges of a segmented body, symmetrically paired about two fine center lines, taper to a tail. Each detail is delicately edged in violet. It is a fossil trilobite, an extinct relative of the horseshoe crab.

Penny next to a trilobite fossil, both are approximately the same size. — The trilobite *Elrathia kingi.*

But she is a humble beauty who lives a secret life. She is found behind the scenes in the Section of Invertebrate Paleontology (IP). In the fluorescent-lit museum basement, Elrathia kingi idles quietly in a long drawer with dozens of equally elegant companions. It is just one of thousands of drawers shelved in rows upon rows of gray metal cabinets. The cabinets stand silently at attention, protecting their specimens from dust, light, and heat while awaiting further orders.

More than 800,000 fossil marine organisms call the IP lab home. Collected from all over the world, they range in age from several thousand to almost a billion years old. Four thousand of these specimens have been featured in over 400 peer-reviewed publications. But others have never been studied in detail and hold valuable “dark data,”¹ ² undocumented information useful for studies about extinction³ and climate change.⁴ These data are central to the future advance of the science of paleontology and geology.⁵

Woman looking through a drawer in a large cabinet. — *Suzanne Mills working with the collections.*

As a part-time Collection Assistant, I help bring this “dark data” to light. My main tools are a laptop and a microscope. When I examine a trilobite, or fossil “bug,” under the microscope, I look for characteristics that verify the biological classification, based on what is written on the fossil’s label. Further information recorded on the label about the geologic layer and location where it was found helps to validate the scientific value. I verify all this information in professional peer-reviewed publications. Finally, I enter the data I glean into a new digital database and develop charts and graphs to summarize it. This is the beginning of highlighting the IP collection’s “dark data.”

The task of bringing more than three-quarters of a million IP specimens to light is daunting. My colleagues and I bow our heads to that number and acknowledge that it is far more than a life’s work. But we persist, hoping to help the world see the value of Elrathia kingi and her ancient ocean companions, one fossil at a time.

Suzanne Mills is a Collection Assistant in the Section of Invertebrate Paleontology at Carnegie Museum of Natural History. Museum employees are encouraged to blog about their unique experiences and knowledge gained from working at the museum.

Citations:

1. California Academy of Sciences. 2018. Scientists quantify the vast and valuable finds stored on museum shelves: Quantifying “dark data” in fossil collections is a call to arms; heralds a digital revolution. ScienceDaily. https: /www.sciencedaily.com/releases/2018/09/180920102122.htm (accessed July 21, 2021)

2. Thiers, Barbara, John Bates, Andrew C, Bentley, Linda S, Ford, David Jennings, Anna K, Monfils, Jennifer M, Zaspel, James P, Collins, Manzour Hernando Hazbón, and Jyotsna L, Pandey. 2021. Implementing a Community Vision for the Future of Biodiversity Collections. BioScience, Volume 71, Issue 6, June. Pages 561–563. https://doi.org/10.1093/biosci/biab036 (accessed July 23, 2021)

3. Casey, M. M., E. E. Saupe, and B. S. Lieberman. 2021. The effects of geographic range size and abundance on extinction during a time of “sluggish” evolution. Paleobiology, 47:54-67.

4. Lawing, A. M. 2021. The geography of phylogenetic paleoecology: integrating data and methods to better understand biotic response to climate change. Paleobiology, 47:178-197.

5. The Unique role of the Curator in Palaeontology. Special Papers in Palaeontology, 22, 7-15.

Special thanks to Albert Kollar and Joann Wilson for their insightful comments.

Diet-wise, Snails are Like Cows, Not Bugs

by Timothy A. Pearce

When classifying organisms into broad categories, many people would group snails with insects rather than mammals. When it comes to diet, however, snails are much more like mammals than insects. That’s because, when choosing what to eat, insects tend to be specialists, while most mammals, and most snails, tend to be generalists. This pattern is especially striking when considering just herbivorous species.

Snail eating a leaf — *Webbhelix multilineata* snail eating leaf.

Two cows in a grassy field. — Cows eating grass. Image by Shubham Khatri, from Wikimedia Commons.

Many herbivorous insects specialize on eating one or a few species of plants, and most often within a single plant family. For example, when we think of tent caterpillars, we expect to see them on cherry trees. In the caterpillar life stage of butterflies and moths, 69% of species feed upon just a single family of plants. If you look at just tropical butterflies and moths found within 25 degrees of the equator, the figure rises to 83% (Forister et al. 2015). Herbivorous mammals, on the other hand, tend to be generalists, eating a wide variety of plants from numerous plant families. Snails, it turns out, have broad diets including a variety of plants from numerous plant families, making snails more like mammals than insects, at least in their diets.

Of course, there are exceptions. While most herbivorous mammals are generalists, two mammals are famous diet specialists. Can you think of them? Hint: one eats bamboo, the other eats Eucalyptus leaves. Did you come up with panda and koala? Good for you! Similarly, while most insects are diet specialists, sometimes we do hear about plagues of locusts that have broad diets, so they eat practically every green thing in sight.

Most plants make chemicals that are not directly involved in growth or other metabolic functions. Scientists call these chemicals secondary compounds. In fact, secondary compounds are responsible for many of the distinct aromas and tastes in the spices we rely upon to flavor our cooking. But why would plants bother making secondary compounds that don’t directly benefit the plant? The most common hypothesis for why plants make secondary compounds is to protect the plants from diseases or herbivores.

Herbivores have ways (e.g., enzymes) to detoxify or reduce the effects of plant chemical defenses. Herbivorous insects that specialize on a few related species of plants can, over evolutionary time, develop strategies that effectively detoxify the defenses of those plants. Sometimes co-evolution results, an ongoing process in which the plant will modify its secondary compound to be more toxic, then the insect will develop the ability to detoxify that, and so on. The plant’s arsenal of chemical defenses protects it from the vast majority of herbivorous insects, but not the insects that specialize on that particular plant group. For example, milkweed is fed on by only a very few insects, including monarch butterfly caterpillars, that have countered its defenses.

Caterpillar hanging upside down eating a leaf. — Caterpillar eating leaf. Image by Krishna A. Gopala, from Wikimedia Commons.

In contrast to specialist insect herbivores, mammals tend to eat a wide variety of plant species. Consequently, mammals need general detoxification strategies that will protect them from a variety of plant secondary compounds. Thanks to detoxification enzymes located mostly in our livers and kidneys (Freeland & Janzen 1974), we can enjoy eating a wide variety of tasty plants without being poisoned.

Like herbivorous mammals, herbivorous snails also have general detoxification strategies, which might account for their large livers, where most of the detoxification occurs.

Now you know one way that snails are more like cows than insects: their diet!

Here is a joke about snails eating:

Two snails were munching a tasty salad made with a large number of different plants. One of the snails accidently dropped one of the exotic leaves from the salad. The other snail said, “You can still eat it, use the five-hour rule.”

Timothy A. Pearce is the head of the Section of Mollusks at Carnegie Museum of Natural History. Museum employees are encouraged to blog about their unique experiences and knowledge gained from working at the museum.

Literature Cited

Forister, M.L., Novotny, V., Panorska, A.K., Baje, L., Basset, Y., Butterill, P.T., Cizek, L., Coley. P.D., Dem, F., Diniz, I.R., Drozd, P., Fox, M., Glassmire, A.E., Hazen, R., Hrcek, J., Jahner, J.P., Kaman, O, Kozubowski, T.J., Kursar, T.A., Lewis, O.T., Lill, J., Marquis, R.J., Miller, S.E., Morais, H.C., Murakami, M., Nickel, H., Pardikes, N.A., Ricklefs, R.E., Singer, M.S., Smilanich, A.M., Stireman, J.O., Villamarín-Cortez, S., Vodka, S., Volf, M., Wagner, D.L., Walla, T., Weiblen, G.D. & Dyer, L.A. 2015. Global insect herbivore diet breadth. Proceedings of the National Academy of Sciences, 112(2):442-447; DOI: 10.1073/pnas.1423042112

Freeland, W.J. & Janzen, D.H. 1974. Strategies in herbivory by mammals: the role of plant secondary compounds. American Naturalist, 108(961): 269-289.

Eating Shipworms to Save the World

by Timothy A. Pearce

Shipworms, which bore into the wood of ships and the pilings of docks have been a menace to mariners for centuries. Recently, however, some sustainable food advocates are pointing to the disreputable creatures as a key to feeding the growing human population.

Black and white illustration of a shipworm. — Figure 1. Body of a shipworm showing the tiny shell at the lower right. Image from Wikimedia Commons taken from Goode (1884).

Surprisingly, shipworms are not worms at all, but are a type of clam in the family Teredinidae whose bivalved shells have been reduced to small rasp-like structures at one end of a worm-like body (Fig. 1). Some shipworms grow exceptionally fast, reaching 30 cm (12 inches) in six months. The small shells, which are roughly 5% of the creature’s body length, function as excavators. The shipworm uses the tiny pair to dig into wood, forming a burrow to protect its soft body, and digesting the excavated bits of wood as food. Symbiotic bacteria in the clam’s gills provide the necessary enzymes to digest the wood.

wood damaged by shipworms — Figure 2. Wood bored by the shipworm *Lyrodus pedicellatus*. Image by T.A. Pearce.

Sailors and stevedores (dock workers) have battled shipworms over the centuries because the holes created by the tiny mollusks weaken the wood, eventually causing ships to sink and docks to collapse (Fig. 2). Consequently, instead of causing yawns, these boring mollusks caused people to take notice. And while the shipworms’ wood-eating regime continues to plague sea-faring people who rely upon wooden vessels, other people are now taking note for a culinary reason.

From baddy to buddy, from scourge to supper, shipworms are undergoing a reputation transformation. As we look to the future, we see staring back at us both the hungry, growing human population and the threat of climate change. We understand the need to produce more food sustainably, including more protein, while reducing our greenhouse gas emissions. As an alternative to methane-belching cattle, some experts have advised eating sustainable protein sources such as insects and shipworms.

Among the advantages of shipworms as food are their exceptionally fast growth, their ability to thrive on a diet of waste wood or sustainable microalgae, and their high protein and omega-3 fatty acids content. (Willer & Aldridge 2020).

Today, shipworms are eaten primarily in parts of southeast Asia. But because they show great promise as a sustainable protein source, they are being considered for aquaculture to help feed the growing human population. In the not-so-distant future, you might be spicing up your meals by including (not so) boring clams!

Keep clam and carry on.

Literature Cited

Goode, G.B. 1884. Fisheries and Fishery Industries of the United States: Section I, Natural History of Useful Aquatic Animals, Plates. Washington, DC: Government Printing Office.

Willer, D.F. & Aldridge, D.C. 2020. From pest to profit—the potential of shipworms for sustainable aquaculture. Frontiers in Sustainable Food Systems, 4: 575416. doi: 10.3389/fsufs.2020.575416

Bird Architecture on Human Infrastructure

by Patrick McShea

cliff swallow nests — Image credit: Amy Henrici

Cliff Swallows are potters. The gourd-shaped earthen vessels the birds construct, one tiny mouthful of mud at a time, provide shelter for their eggs and young. In Pennsylvania, and across much of the species’ current continent-wide breeding range, bridges provide favored nest sites for birds whose ancestors, until the early decades of the 1800’s, seem to have been restricted to nesting against low elevation cliffs in western mountain ranges.

The nests pictured above adhere to the concrete supports of a bridge crossing an arm of Lake Arthur in Butler County’s Moraine State Park. During field survey work leading up to the publication of the Second Atlas of Breeding Birds in Pennsylvania in 2012, bridges accounted for 44% of Cliff Swallow nest sites, barns for 33%, and churches, houses, other buildings, and dams for the balance. The species nests in colonies, and the number of nests in bridge-based colonies also far outnumbered those at other sites.

In Birds of Western Pennsylvania, a 1940 publication by W.E. Clyde Todd, then the museum’s Curator of Birds, nest descriptions are a highlight of the Cliff Swallow account.

“The type is retort-shaped, globular, with a neck springing from above and turned to open downward: a beautiful, symmetrical structure. The shape however is modified to suit the space – truncated or extended, as need requires; and where the nests are close-set, the chamber within, though pouch-like, is not truly symmetrical.”

“The nests are built of pellets of mud laid wet and retaining in the finished structure, each its smooth-rounded individuality. The walls speak of cunning and labor and of security, as does a wall of human masonry.”

cliff swallow feeding young in the nest — Image credit: Amy Henrici

On a recent early summer morning the Cliff Swallows’ incorporation of our culture’s indispensable highway architecture into their reproductive cycle made for easy and entertaining bird watching. There were hungry young in every chamber of an easily viewed eight-nest cluster. As parent birds returned regularly from insect-catching forays over the nearby lake, the entryways to the dark clay pouches were brightened by the bright yellow gaping beaks of the young.

cliff swallow hanging out of nest — Image credit: Amy Henrici

Appreciation of the beneficial match between people and birds was leavened by a sight at another nest cluster on an adjacent bridge support. When a swallow perched against a nest remained still through several feeding cycles of its neighbors, an inspection with binoculars revealed a tragic circumstance. The bird appeared to have become entangled in, and eventually strangled by discarded fishing line, eight inches of which dangled from the lifeless feathered body.

Patrick McShea works in the Education and Visitor Experience department of Carnegie Museum of Natural History. Museum employees are encouraged to blog about their unique experiences and knowledge gained from working at the museum.

Reference

Second Breeding Bird Atlas of Pennsylvania – http://www.pabirdatlas.psu.edu/

Fish and the Fourth of July?

by Patrick McShea

During the cold early months of 1778, did the outcome of the American colonies’ armed struggle for independence hinge upon a spawning run of fish up a Pennsylvania river? A 22-inch-long American shad displayed on a wall in Discovery Basecamp can serve as a focal point for consideration of this question, but many viewers will be aided by some framing background information.

In the chronology of the American Revolution, the harsh winter of 1777-1778 was notable for the British Army’s control of Philadelphia, and the encampment, some 23 miles northwest, of the opposing Continental Army, led by George Washington, at a site along the Schuylkill River known as Valley Forge.

In the more than two centuries since the United States achieved independence from Great Britain, an often repeated anecdote about the desperate conditions endured by the poorly clothed, poorly fed, and poorly sheltered soldiers at Valley Forge contends that starvation conditions were ended late in the winter by an unusually early spawning run of thousands of American shad up the Schuylkill.

American shad are an anadromous species, a term for fish that hatch in freshwater, migrate to the ocean where they spend most of their lives, and then migrate back to their natal waters to reproduce. The historic range for the species, whose Latin name, Alosa sapidissima, references its delectable flavor, encompasses western Atlantic Ocean waters bordering the east coast of Canada and the United States.

In 2002, renowned author and Princeton University professor John McPhee brought American shad to the attention of the book-reading public with the publication of The Founding Fish, a 358-page encyclopedic compilation of personal experience, firsthand reporting, historical accounts, and scientific research. (Farrar, Straus, and Giroux) The book’s title is a nod to the Valley Forge account, and in a central chapter of the same name McPhee addresses the story’s veracity by citing the research of a now retired professor of American History from Indiana University of Pennsylvania, Wayne Bodle. “When I first got in touch with Bodle, in 1998, he said that fresh shad in all likelihood were consumed by soldiers at Valley Forge in the weeks before they broke camp in June, but that the large and providently early run is a legend not supported by a single document.”

Bodle’s analysis of his research into all aspects of the Continental Army’s storied winter encampment in eastern Pennsylvania is presented in his book, The Valley Forge Winter: Civilians and Soldiers in War (The Pennsylvania University Press, 2002). Like The Founding Fish, it’s available for borrowing from Carnegie Library of Pittsburgh. If your summer reading schedule isn’t yet set, you might consider checking out either book.

Cuttlefish Pass Marshmallow Test

by Tim Pearce

The club for species that can pass the marshmallow test has recently gotten a new member: the cuttlefish. Cuttlefish are the first invertebrate known to show self-control.

The marshmallow test examines whether an individual has sufficient self-control to use delayed gratification. In the original marshmallow test, a child could have one marshmallow immediately, or if they were able to wait 15 minutes, they received two marshmallows. Some of the 3- to 5-year-old children waited and got the double treat, indicating that they could delay gratification for a larger reward. Other species such as chimpanzees, crows, parrots, and dogs have passed modified versions of the marshmallow test

We humans think we are special. We form clubs in which we initially believe we are the only member, but then other species creep into those clubs. In times past, humans thought they were the only members of the language club and the tool use club, but now we know many other species are in those clubs.

cuttlefish on dark background — Cuttlefish. Image by David Sim, from Wikimedia Commons under the Creative Commons Attribution 2.0 Generic license.

To examine whether cuttlefish could delay gratification for a better reward, researchers (Schnell et al. 2021) offered them an Asian shore crab (a less preferred food) immediately, or a grass shrimp (a more preferred food) if they were able to wait. The food was offered in two chambers with sliding doors. Before the test, cuttlefish were trained to recognize symbols on the doors that indicated if it would open immediately (a circle) or with a delay (a triangle). Most of the cuttlefish waited 50 to 130 seconds to get the more desirable grass shrimp, comparable to time delays shown by chimpanzees and crows.

Some cuttlefish appeared to move their bodies away from the immediate, less preferred reward. Similar behaviors are seen in humans and other animals (e.g., parrots close their eyes, dogs turn away) as they try to resist temptation while waiting for the better reward.

Furthermore, those cuttlefish that waited longest for their favorite foods also performed best during learning tests. Cuttlefish have good memories and can learn from past experiences.

The standard explanation for ability to use delayed gratification, is that it helps animals with long, social lives. This reasoning doesn’t apply to cuttlefish. They live just two years and are not social, so the benefits of delayed gratification to cuttlefish are less obvious. One possibility is that the evolution of self-control in cuttlefish is related to predator avoidance and camouflage; those that can stay camouflaged longer might avoid detection by predators.

Relevant joke:

What is the most affectionate fish in the ocean?

The cuttlefish!

Tim Pearce is the head of the Section of Mollusks at Carnegie Museum of Natural History. Museum employees are encouraged to blog about their unique experiences and knowledge gained from working at the museum.

Reference

Schnell, A.K., Boeckle, M., Rivera, M., Clayton, N.S. & Hanlon, R.T. 2021. Cuttlefish exert self-control in a delay of gratification task. Proceedings of the Royal Society B, Biological Sciences, 288 (1946): 20203161 doi.org/10.1098/rspb.2020.3161.

Bringing Light to Dark Places

by Suzanne Mills

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Diet-wise, Snails are Like Cows, Not Bugs

by Timothy A. Pearce

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Eating Shipworms to Save the World

by Timothy A. Pearce

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Bird Architecture on Human Infrastructure

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Fish and the Fourth of July?

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