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 16, 2024 by Erin Southerland

Natural History Collection Managers: The Stewards of Time Travel

by Serina Brady and Mariana Marques

For centuries, naturalists have collected the living world with the primary goal of understanding the diversity and complexity of our planet. In vast shelves and cabinets located in natural history museums, we find a diversity of specimens used daily by researchers, students, naturalists, and conservationists from around the world. These collections are not just archives of the past, but they also play a crucial role in addressing present-day challenges. By documenting the diversity of life, natural history collections provide a wealth of information that can be used to tackle issues such as climate change, pandemics, pathogen dispersals, deforestation, habitat fragmentation, and biodiversity loss. They can be considered the world’s most comprehensive and complex library, serving as a valuable resource for understanding and addressing the health of our planet.

Each specimen can be seen as a unique document or book recording an aspect of life on Earth at a particular time and place. They testify to the existence of a given species in a given locality and at a particular time, and they have a fundamental role as a guarantee of the scientific method: they allow objective observation that can be replicable. Natural history collections are an unparalleled source of information. For instance, a single bird or reptile specimen can provide data on its species, its habitat, its diet, and even its health. This wealth of information continues to allow researchers to understand better the past, the present, and the future of biodiversity, as well as the health of our planet – from local communities to the entire Earth.

*Carnegie Museum of Natural History Alcohol House, Collection of Amphibians and Reptiles. ©Photo by: Luis Ceríaco.*

*Carnegie Museum of Natural History, Collection of Birds. ©Photo by: Luis Ceríaco.*

These collections are usually housed in natural history museums. These museums are research, conservation, education, and public outreach hubs. Their collections are not limited to public exhibitions; in fact, the majority are housed in storage locations, generally out of sight and knowledge of the public. The process of collecting and storing these specimens is methodical. Each specimen is carefully collected, identified, and cataloged, then stored in a controlled environment to ensure long-term preservation. This process ensures that these specimens, often fragile and irreplaceable, are protected and can continue to be used for research and education for future generations.

Natural History Collections: a Tool to Face Global Changes

How can a specimen collected more than 100 years ago still be relevant today? Historical collections, like the one housed at Carnegie Museum of Natural History, provide baseline data points. These initial measurements or observations serve as a starting point for future comparisons. By providing a snapshot of life on Earth at a particular time and place, these specimens allow us to study change over time. The first and most crucial step is to gather those baseline data points!

From their early days, natural history collections’ primary goal was to inventory all life on Earth. However, with new cutting-edge technology, researchers can recover different data from historical specimens, data that the original collector didn’t even imagine. For example, when birds were collected from the U.S. Rust Belt, collectors didn’t realize that the specimens would be used to infer information about the history of pollution. Similarly, in the early twentieth century, the collectors of salamanders in the Appalachian woods didn’t even realize that some of those specimens were already infected with a pathogen that is devastating some of the world amphibian populations today.

However, because specimens were collected, we can now map the expansion of this pathogen through time or trace the amount of black carbon in the air over time through birds’ feathers to help fight and understand climate change. Part of the job of Collection Managers like us is not just to preserve and maintain the existing collections, but also to anticipate and predict the questions future researchers will be asking. This proactive approach ensures we gather today’s data to answer tomorrow’s questions. Specimens collected over a century ago are actively used today to answer questions about current and future environmental changes.

Specimens at the Carnegie Museum of Natural History collected during the early 1900s continued to have a significant role in research questions. These specimens give researchers insight into environmental changes through time, such as soot deposited on bird feathers or the presence of pathogens such as the chytrid fungus on amphibian populations across a specific time and place. Top: Two Eastern Towhee (Pipilo erythrophthalmus) specimens, one from 1895 (bottom) and the other from 1993 (top), showing the change in air quality over time (DuBay and Fuldner 2017). © Photo by Luis Ceríaco. Below: Amphibian specimen of Common Mudpuppy (Necturus maculosus) being swabbed by a student from the University of Pittsburgh (Richards-Zawacki Lab) to detect the presence of the amphibian chytrid fungus – Batrachochytrium dendrobatidis. ©Photo by: Rachel Verdi.

New applications of technologies, such as computed tomography (CT) scans, provide novel insights and usages for specimens. CT scans allow a complete 3D model of a specimen, including access to its internal morphology without damaging it. Using next-generation sequencing, scientists can use fragmented and degraded DNA for advanced analyses such as phylogenetic and phylogeographic analysis. These specialized methods allow us to study species’ evolutionary relationships and geographic distribution. These advanced techniques are just some of the ways natural history collections are being used to push the boundaries of scientific knowledge.

CT scans provide details of internal anatomy, presence of parasites, reproduction, etc., without damaging the specimen. CT scans are a significant technological advance for fields such as taxonomy, developmental and evolutionary biology, and studying functional morphology for natural history specimens. © Edward Stanley, Florida Museum of Natural History, University of Florida (oVert – OpenVertebrate project).

A Biodiversity Backup

Continuing to grow our collections is not only scientifically essential but undeniably needed. Currently, 1.8 million species have been formally described to science, although worldwide experts predict that around 8.75 million species still await to be discovered, described, and named. Given current extinction rates, we are racing against time to describe the remaining 86% of the world’s species, many of which may become extinct before we know they even existed!

New species of birds, amphibians, reptiles, mammals, and insects continue to be discovered worldwide, sometimes based on specimens tucked away in a museum for decades! These collections are not just archives of the past but also living libraries that continue to grow and evolve as new species are discovered. Each new discovery adds to our understanding of the natural world and underscores the importance of these collections in documenting and preserving Earth’s biodiversity. These new specimens contribute to our most significant and longest dataset of the natural world. But just as a library that stops acquiring new books, a natural history collection that doesn’t add new specimens will eventually lose its scientific value and relevancy. If we don’t continue to add physical proof of today’s biodiversity, we create unfillable gaps in one of our most powerful natural history data sets. Today is tomorrow’s past, and natural history collections act as a biodiversity backup of our planet!

Serina Brady is Collection Manager of Birds and Mariana Marques is Collection Manager of Amphibians and Reptiles at Carnegie Museum of Natural History.

What’s in a Name? The History of the Naming of the Eastern Mole

by John Wible

In the tenth edition of the “Systema Naturae” (1758), the Swedish botanist and natural historian Carl Linnaeus recognized eight orders of mammals, all of which include species that today are not particularly closely related. His order Bestiae included pigs, armadillos, hedgehogs, moles, shrews, and opossums. Of these, the hedgehogs, moles, and shrews are considered today to form a natural group, with the others coming from very far-flung branches of the mammal tree of life.

For the shrews, Linnaeus named three species of Sorex, Sorex araneus, Sorex cristatus, and Sorex aquaticus, with their habitats Europe, Pennsylvania, and America, respectively. Sorex araneus is recognized today as the common shrew (see image), distributed in Great Britain, much of the European continent, and far into Russia. However, the other two are not shrews, but are moles! Today, we recognize these as the star-nosed mole, Condylura cristata, and the Eastern mole, Scalopus aquaticus (see image). The former has a broad distribution in Pennsylvania with the latter only in the eastern part of the state.

common shrew and a worm — *Common shrew,* Sorex araneus. Photo credit: Soricida, CC BY-SA 3.0, via Wikimedia Commons

close-up of an eastern mole — *Eastern mole,* Scalopus aquaticus. Photo credit: Kenneth Catania, Vanderbilt University, CC BY-SA 3.0, via Wikimedia Commons

Just before the shrews in the tenth edition, Linnaeus named two species of moles, Talpa europaea and Talpa asiatica, with their habitats Europe and Siberia, respectively. Given the remarkable similarity in body form between the Old World and New World moles, it is surprising that Linnaeus did not recognize these four species (Sorex cristatus, Sorex aquaticus, Talpa europaea, and Talpa asiatica) as closely related.

Regarding the Eastern mole, subsequent nineteenth century authors realized Sorex aquaticus did not belong in the shrew genus Sorex. However, it was bounced around between several mole genera, including Talpa, and it was not until 1905 that the Latin binomial we use today, Scalopus aquaticus, was first used, 147 years after Linnaeus! The formal naming of species is not static, but evolves over time as we discover more about our natural world that causes us to reconsider and reevaluate past practices. Changing the shrew aspect of the common name lagged behind the formal one, as it was not for quite some time that the shrew moniker imparted by Linnaeus disappeared. A halfway point is in the famous 1846 “The Viviparous Quadrupeds of North America” by John J. Audubon and Reverend John Bachman, where they called it the common American shrew mole.

From the short text in the “Systema Naturae” where Linnaeus named Sorex aquaticus, his motivation for identifying the Eastern mole as a shrew is unclear. Equally or perhaps more enigmatic is his motivation for using the specific name aquaticus. A direct translation of Sorex aquaticus is “water shrew,” with the strong implication that this mammal lived in the water or at least spent considerable time in the water. However, Linnaeus did not travel to America and so never saw Sorex aquaticus in the wild. The Eastern mole is a fossorial (burrowing) animal that spends most of its life underground with enormous forepaws for digging. Skin covers its tiny eyes, although it does perceive light and dark, and it lacks an external ear. Maybe its enlarged forepaws were viewed as flipper-like by Linnaeus. Yet, these paws resemble those of the Old World Talpa named by Linnaeus as true moles. In 1936, mammalogist A.V. Arlton stated, “The term “aquaticus,” as applied to our common species refers to the webbed hind feet, which indicated to some early writers a possible use in swimming” (Journal of Mammalogy, 17, p. 355). Unfortunately, Arlton did not name names for these early writers! Consequently, his statement cannot be fact checked. The bottom line is that in his description of Sorex aquaticus, Linnaeus did not mention webbing for either the fore- or hind feet. And ultimately, as the namer of the species, it is Linnaeus’ motivation that we need to know.

There are some general rules for naming new species. For example, you can’t name a new species after yourself. In the Linnean era, the general trend was to apply Latin or Greek descriptors that would capture some aspect of the organism in question, a tradition continued today by most authors. For instance, our species, Homo sapiens, was named by Linnaeus and it translates to “wise man.” While we might debate the appropriateness of that as the binomial for our species, there is no debate that Sorex aquaticus is inappropriate for our ground dwelling Eastern mole.

John Wible is Curator of Mammals at Carnegie Museum of Natural History.

The Moon Snails Neverita duplicata and Euspira heros: Cannibal Predators of the Sea! … who also enjoy a nice algae salad

by Sabrina Spiher Robinson and Tim Pearce

Imagine you’re a clam, hanging out in your cozy little hole under shallow ocean water, with your siphon out, just filtering lunch out of the water current, happy as a…you. Then, all of a sudden, something flips you gently out of that hole.

You pull in your siphon and your foot, clamp shut your valves. You’re pretty tough to get open, strong adductor muscles keep your two shells held tightly together, and you’ve survived danger by closing up shop and waiting before. And nothing seems to be trying to pry you open, even though something has wrapped itself around you, and is now pulling you down into the sand with it. Then:

scrape scrape scrape

Or imagine you’re a young moon snail, Neverita duplicata – one of the most common species of moon snails that live on the eastern seaboard of North America. You’re a gastropod with a lovely round grayish shell, such that people call it a “shark eye,” and you’ve got a huge foot that can come out of that shell and cover almost all of your body – or all of your prey’s body! But at the moment you’re just cruising along the sand, slurping at a bit of detritus. Suddenly, you’re enveloped by something. You instinctively pull your body into your shell and tightly close your door-like operculum for safety. Then your aperture is covered by…something familiar? Then:

scrape scrape scrape

It doesn’t matter how tightly the clam clamps, or how mighty the young snail’s foot, both are going to come to the same fate, slowly.

scrape scrape scrape

Eventually, your shell is penetrated. A rasping radula – a mollusk’s organ containing its teeth – has bored a hole through your shell with the help of a gentle acid secreted by a gland by the mouth, and then you feel a burning: gastric juices are being pumped through the hole to begin to digest your flesh. Your killer begins to slurp you up, right where you lie, wrapped up in their hug, as you’re slowly eaten alive.

The young moon snail might have figured out who its killer was before the end: that’s how it eats too. The thing is, moon snails are cannibals, the larger preying on the smaller.

There are hundreds of kinds of moon snails all over the world, but the ones that are probably most familiar to beach goers on the eastern coast of the USA are two species also commonly called “shark eyes” – Neverita duplicata and Euspira heros. From the top, they’re hard to tell apart (the spire on E. heros is a little pointier than on N. duplicata) but once you flip them over, it becomes easy to distinguish them: N. duplicata, the Atlantic moon snail, has a big callus over its umbilicus, and E. heros, the Northern moon snail, doesn’t. Technically, only the Atlantic moon snail has a shark eye shell, but since they’re often mixed up with Northern moon snails, the term shark eye is sometimes applied to them too.

N. duplicata, left; E. heros, right. *Photo credit: Sabrina Spiher Robinson*

These two moon snails aren’t the only marine gastropods that drill their prey and digest them alive to suck them up for dinner – lots of marine gastropods are predatory drills. But moon snails have distinct boreholes that allow people to identify when a shell has been bored specifically by a moon snail – scientists can even tell the difference between the Atlantic and Northern species’ holes. These “countersunk” holes look like little funnels, wider on the outside of the shell than on the inside. Other kinds of drilling snails leave behind straight-sided holes.

These unique boreholes allow scientists to track the evolution of moon snails from the Miocene to recent times. One group of researchers found that moon snail cannibalism might have driven a kind of coevolution between and among moon snail species. Because one moon snail can make dangerous prey for a fellow moon snail predator, over time moon snails seem to have learned to drill other moon snails at a spot on their shells that allowed the predator to cover the prey’s entire aperture, preventing the strong foot of their prey from fighting back. This means boring through a thicker part of the shell, however, so it takes longer to hold down and bore through the prey snail’s shell. But the record of natural selection in fossils throughout time suggests the added cost must be worth the benefit of moving target drilling zones. Meanwhile, small moon snails almost always lose out to larger ones when attacked, so both N. duplicata and E. heros have evolved to get bigger and bigger over time – although a bigger snail is also a more enticing snack target. Same-sized moon snails don’t even bother to attack one another, suggesting that a fellow moon snail is just too dangerous a prey when the winner of the battle between snails is a toss-up. As evidence that these are often battles between predator and prey snails, there are many incomplete boreholes found – a moon snail started attacking another moon snail, but only managed to get the job halfway done before the prey moon snail escaped. [1]

To be fair, moon snails aren’t just vicious cannibals – they also enjoy the snail equivalent of a nice salad. Another study that analyzed the tissues of moon snails revealed that their bodies have the chemical signatures of omnivores. The technique is called stable isotope analysis, wherein scientists use the ratio of carbon and nitrogen isotopes in an animal’s body to determine its diet, in broad terms. Carbon exists in three isotope forms, meaning the number of protons is the same in all three atoms, but the number of neutrons is different in each (carbon-12, carbon-13, and carbon-14); Nitrogen also has three isotope forms, nitrogen-14, nitrogen-15, and nitrogen-16. The vast majority of carbon on Earth is carbon-12, which is a stable isotope, as is carbon-13, meaning they do not decay over time; nitrogen-14 and -15 are stable, and make up the vast majority of nitrogen atoms. Different plants and animals have different ratios of carbon and nitrogen isotopes. The ratios of isotopes in plants and animals differ and these differences transfer to the body of the consumer, and so the isotope ratios of a meat-eating animal will differ from those of a vegetarian animal, and an omnivorous animal will be different again. Scientists were surprised to find that wild moon snail isotopes suggested they also ate non-animals, so to check their findings they fed captive moon snails nothing but clams, and then tested their isotopes – which looked exactly as one would expect in an all-meat diet. Apparently the wild moon snails were actually eating things other than meat, probably algae. This was a big deal, since so much of the literature on moon snails is about their predatory drilling! [2]

Moon snail shells are a relatively common find on east-coast beaches (and another moon snail, Euspira lewisii, is a common find on the west coast), but if you’re at the beach this summer, there’s more to look for than just shells – moon snails also leave behind very distinctive egg nests, often called “sand collars.” The fertilized female snail nestles into a little hole in the sand (as all moon snails do during the day when they’re not feeding) and produces a sheet of mucus, which she mixes with sand and pushes up to the surface, as she does so, the sheet curls around her shell and eventually right around to form a ring. This fusion of mucus and sand grains solidifies, she attaches her thousands of eggs to it, and then covers those with another layer of mucus and sand. Once the eggs are ready to hatch after a few weeks, when the next high tide comes along the eggs let go thousands of little larvae called veligers, which will drift off to finish developing into baby snails who will eventually settle into the intertidal zone and start lives for themselves. Once the eggs hatch, the collar becomes brittle and disintegrates, but if you find one that’s still plastic-y on the beach, leave it! There are thousands of tiny baby vicious predators in there waiting to hatch! Awww.

*A sand collar full of shark eye eggs. Image credit: Blenni, Public domain, via Wikimedia Commons.*

Sabrina Spiher Robinson is Collection Assistant for the Section of Mollusks and Tim Pearce is Head of the Section of Mollusks at Carnegie Museum of Natural History.

References

[1] Gregory P. Dietl and Richard R. Alexander, Post-Miocene Shift in Stereotypic Naticid Predation on Confamilial Prey from the Mid-Atlantic Shelf: Coevolution with Dangerous Prey PALAIOS Vol. 15, No. 5 (Oct., 2000), pp. 414-429

[2] Casey MM, Fall LM and Dietl GP, You Are What You Eat: Stable Isotopic Evidence Indicates That the Naticid Gastropod Neverita duplicata Is an Omnivore. Front. Ecol. Evol. 4:125. (2016) doi: 10.3389/fevo.2016.00125

Mineral Gazing

by Debra Wilson

Have you ever gazed up at the sky and noticed a cloud that looks like a face, or an animal, or an object? You can apply the same concept when you visit Hillman Hall of Minerals and Gems! Many minerals on display have nicknames because of how they resemble certain animals, objects, or even characters from movies or TV shows. As you walk through the exhibits, let your imagination wander and search for minerals that look like things. Here are some to get you started.

Silver mineral that looks like an American flag — *“The Flag” – Silver in the Native Elements case of the Systematic Mineral Collection*

Image of the American flag that says "we here highly resolve that these dead shall not have died in vain...rememeber Dec. 7th!" — *Photo credit: Allen Saalburg, Public domain, via Wikimedia Commons.*

Nessie silver mineral — *“Nessie” – Silver in Minerals from the Former Soviet Union exhibit*

Loch Ness monster sculpture in the water — *Photo credit: Immanuel Giel, Public domain, via Wikimedia Commons*

snowball calcite on quartz — *“Snowball” – Calcite on quartz in the Maramures District of Romania exhibit*

snowball held in mitten-covered hands — *Photo from Shutterstock.*

Inch Worm berthierite on quartz — *“Inch Worm” – Berthierite on quartz in The Maramures District of Romania exhibit*

photo of an inch worm — *Photo credit: gbohne from Berlin, Germany, CC BY-SA 2.0, via Wikimedia Commons*

The Scream septarian concretion — *“The Scream” – Septarian concretion in the Weathering Processes exhibit*

"The Scream" painting — *Image credit: Edvard Munch, Public domain, via Wikimedia Commons*

the oyster natrolite on quartz — *“The Oyster” – Natrolite on quartz in the Deccan Plateau of India exhibit*

oyster shell with a pearl — *Photo from Shutterstock.*

French fries laumontite — *“French Fries” – Laumontite in Masterpiece Gallery*

cup of French fries — *Image by ha11ok from Pixabay*.

As you enter Hillman Hall, check out the minerals in the Entrance Cube, their nicknames are on the labels. There are many more minerals on display throughout the hall that have acquired nicknames. Here’s just a handful of other nicknames for minerals in the exhibits, see if you can find them. Good luck and enjoy your mineral gazing!

Nickname	Exhibit
The Bat	Igneous Rocks
Polar Bear	Weathering Processes
Sea Slug	The Maramures District of Romania
The Chariots	The Maramures District of Romania
Smog Monster	The Maramures District of Romania
Sea Serpent	Pennsylvania Minerals and Gems
Pine Trees On a Cliff	Oxides
BBQ Chips	Masterpiece Gallery
Cookies and Cream	Masterpiece Gallery

Debra Wilson is Collection Manager for the Section of Minerals at Carnegie Museum of Natural History.

Slipper Snails Slide Between Sexes in Stacks

Or, Crepidula fornicata say, “Trans Rights!”

…if they don’t get eaten by their siblings first.

by Sabrina Spiher Robinson

*A pair of slipper snails seen from below. Image credit: Ecomare/Sytske Dijksen, CC BY-SA 4.0 https://creativecommons.org/licenses/by-sa/4.0, via Wikimedia Commons*

A stack of Crepidula fornicata, grown together (with a little chiton, another type of mollusk, hanging out on the top of the family). — *A stack of* Crepidula fornicata, grown together (with a little chiton, another type of mollusk, hanging out on the top of the family). *Image credit: User Lamiot on fr.wikipedia, CC BY-SA 1.0 https://creativecommons.org/licenses/by-sa/1.0, via Wikimedia Commons*

Slipper snails, Crepidula fornicata, are a common find for shell collectors along the American east coast, and in some places on the west coast as well, where they have been accidentally introduced as an invasive species. But just because they’re common, doesn’t mean they’re not interesting – in fact, they’re one of the most well-studied marine snails, and all of that study has revealed a creature with a fascinating life cycle.

Crepidula are protandrous hermaphrodites – this means that all slipper snails begin their lives as male, and end their lives as female. As juveniles, they wander over the substrate, preferring hard surfaces like rocks, dock pilings, other shells, and even horseshoe crabs. But most C. fornicata will choose to settle on top of another C. fornicata, who might be settled atop another, and another, and so on. They live in stacks, sometimes of up to a dozen animals, one balancing on top of the next until their shells grow around each other, and they can no longer move, becoming sessile (stationary) by default.

Of course, a stack of all males won’t get very far reproductively. So, it’s time for at least a few C. fornicata to begin the next stage in their lives, and transition to females. Several things influence when the change takes place, primarily the animal’s size, because producing gametes is energetically costly: more sperm takes more energy than less sperm, and eggs take more energy than sperm altogether. But it’s not so straightforward as just growing to a certain size and changing sex. If there are no females around, for instance, some males will transition to females at smaller sizes than they usually would.¹ Alan Carillo-Boltodano and Rachel Collin write:

“In our experiment, pairs of snails (one small and one large) were kept in cups, either together or partitioned off with fine or coarse mesh, or partitioned, but switched from side to side to allow contact with the cup mate’s pedal mucus. The larger snails that were allowed contact with the smaller companions grew faster, and generally changed sex sooner, than did the larger snails in the barrier treatments, which allowed no physical contact. The smaller snails that were allowed contact with the larger cup mate delayed sex change compared to those separated from their cup mates … Our results suggest that the cue that affects size and time to sex change requires some kind of physical interaction that is lost when the snails are separated. Furthermore, contact with another snail’s pedal mucus does not compensate for the loss of physical contact.”²

In other words, when the slipper snails are in actual contact with each other, they seem to send signals to one another that help to coordinate growth and sex change.

In general, though, males will wait until they’re a certain size to transition, because larger males are more reproductively successful than smaller males, as determined by experiments that genetically test offspring to see whose genes were most successful in the stack. There’s one exception to this though – sneaky little guys! Male Crepidula inseminate females directly, so in general the male right on top of the female at the bottom of the stack will be the most successful fertilizer, and then the male on top of him, and then the others on top of them can’t reach and are out of luck for the moment. But! The smallest juvenile Crepidula, who have not yet chosen a stack of their own, have been found to sneak up on the substrate next to the female, inseminate her, and sneak away, using a strategy that gets around “bigger = more sperm.”³

Larger males might have more reproductive success than smaller males, but no one has more reproductive success than slipper snails who have transitioned to females. Eggs are a much bigger energy investment for an animal than sperm are, and so becoming a female requires a certain size to make the transition worthwhile. But once a slipper snail is female, she has a couple reproductive advantages: in the first place, she can hoard sperm for a long time, including her own from when she was a male, so she always has plenty of material to fertilize her eggs. This also means that while only a third or a quarter of the embryos will have a given male’s DNA, they’ll all have hers. Secondly, Crepidula females brood their young. Unlike many marine mollusks, who release their eggs and sperm into the water column where they meet and the embryo has to grow up among the plankton, at risk of becoming a meal for many things before they ever even get to grow into larvae, Crepidula keep their eggs in brooding pouches. Females keep between 15 and 20 pouches inside their shells, each containing between 50 and 450 embryos. She’ll brood them until they turn into larvae that can swim about on their own, keeping them safe to grow at least for a little while.

And thus, every Crepidula fornicata begins their life as a tiny, and sometimes sneaky, roaming male, sowing his wild oats; eventually he finds a nice stack to settle down on to become a dad; and then they transition sexes and live out her days as mother and base of the stack, brooding little babies in safety until they’re ready to hatch into larvae. Slipper snails make small stacks, but big happy families.

However, perhaps nowhere is safe. Once the eggs are brooding in their capsules, the mother slipper snail has no way to transfer additional nutrients or oxygen to the embryos. This environment of scarcity leads some species of Crepidula embryos to start cannibalizing each other! The embryos of Crepidula coquimbensis, a species of Crepidula first described in Chile, have at least been found to be choosy about eating their brothers and sisters. Brood capsules are fertilized by multiple males, meaning all the embryos have the same mother, but not every embryo has the same father. It was discovered that cannibalistic embryos were much more likely to eat their half-siblings than their full siblings, thus protecting embryos they shared a complete set of DNA with. It’s still not known how these embryos recognize kinship, though.⁴ In another species of Crepidula, Crepidula navicella, a gene in some of the embryos in each capsule switches on and arrests their development, basically turning them into meals for their siblings, a genetic predisposition to being either a cannibalizer or a cannibalizee.⁵

Of course, once the larvae are released into open water, all bets are off, and a lot of filter-feeding animals, including other mollusks, including other Crepidula, might eat them. However, Jan Pechenik reports:

“… in our study the same adults usually ingested their own larvae at much slower rates than predicted from the rates at which they cleared water of phytoplankton. These slower rates may in part reflect an inability or reluctance of adults to ingest particles of such large size … However, most of the larvae that we observed being entrained into adult feeding currents were ingested, and later appeared in feces, and adults were capable of ingesting larvae that were larger … Thus, lower than predicted rates of [larvae eating] by C. fornicata more likely reflect larval behavior – deliberate or not – reducing the likelihood of [getting drawn] into the adult feeding current, as suggested previously from studies with [other marine filter feeders].”⁶

At least baby Crepidula, once free, seem to have developed a way to avoid being eaten by their parents, if not their siblings!

Sabrina Spiher Robinson is Collection Assistant for the Section of Mollusks at Carnegie Museum of Natural History.

References:

[1] Proestou, Dina A., Goldsmith, Marian, Twombly, Sarah (2008) “Patterns of Male Reproductive Success in Crepidula fornicata Provide New Insight for Sex Allocation and Optimal Sex Change.” The Biological Bulletin (Lancaster), vol. 214, no. 2, 2008, pp. 194–202, https://doi.org/10.2307/25066676.

[2] Carrillo-Baltodano, Allan, and Collin, Rachel (2015). “Crepidula Slipper Limpets Alter Sex Change in Response to Physical Contact with Conspecifics.” The Biological Bulletin (Lancaster), vol. 229, no. 3, 2015, pp. 232–42, https://doi.org/10.1086/BBLv229n3p232.

[3] Broquet, Thomas, et al. “The Size Advantage Model of Sex Allocation in the Protandrous Sex-Changer Crepidula fornicata: Role of the Mating System, Sperm Storage, and Male Mobility.” The American Naturalist, vol. 186, no. 3, 2015, pp. 404–20, https://doi.org/10.1086/682361.

[4] Brante A, Fernández M, Viard F (2013) Non-Random Sibling Cannibalism in the Marine Gastropod Crepidula coquimbensis. PLoS ONE 8(6): e67050, doi:10.1371/journal.pone.0067050

[5] Lesoway, MP, Collin, R, Abouheif, E. (2017) “Early activation of MAPK and apoptosis in nutritive embryos of calyptraeid gastropods.” J. Exp. Zool. (Mol. Dev. Evol.) 328B: 449–461. doi:10.1002/jez.b.22745.

[6] Pechenik, Jan, Blanchard, Michel, Rotjan, Randi (2004) “Susceptibility of Larval Crepidula fornicata to Predation by Suspension-Feeding Adults.” Journal of Experimental Marine Biology and Ecology., vol. 306, no. 1, 2004, pp. 75–94, https://doi.org/10.1016/j.jembe.2004.01.004.

Type Specimens: What are they and why are they important?

by Timothy A. Pearce and Rachel Thomas Beckel

What do we mean when we say we have type specimens in the Carnegie Museum of Natural History (CMNH) collections?

Type specimens are (usually) the specimen(s) a person describing a new species looks at as they write the description (it’s this tall, this wide, this color, sculptured with bumps like this, etc.) and type specimens are the official name bearers for the whole species.

There are many kinds of type specimens, but the most important kind is the holotype. Paratypes (other specimens the original describer believes are the same new taxon) are also important, but holotypes are the most important. Two other kinds of type specimen are lectotypes (selected from the paratypes if the holotype is lost) and neotypes (selected from any specimen if all type material is lost). Every time we add another holotype it bolsters the significance of CMNH’s already significant collections. It raises our visibility on the “radar” of researchers and puts us on the map for that taxon.

Carnegie Museum collaborator Dr. Aydin Örstan recently named a new subspecies of snail Albinaria coa tek (Örstan & Yildirim 2023). He deposited the holotype and 12 paratypes of the new subspecies in the Mollusks collection at CMNH.

*Holotype of* Albinaria coa tek *Örstan, 2023. Image from Örstan & Yildirim (2023).*

If a researcher wants to know if they have found another specimen of Dr. Örstan’s new subspecies, they could read his description. However, to be absolutely sure, a researcher might need to compare their finding to the type specimen.

Think of types as the gold standard. Because of their importance to nomenclature and taxonomy (the science of naming species), most museums (including CMNH) keep their type specimens securely locked in a special cabinet.

With regard to this land snail holotype, for Carnegie Museum to have the holotype of Albinaria coa tek means that people studying that subspecies or closely related taxa might need to travel to the museum to examine the type specimen or ask for additional information about it. For their research paper to be complete, they would need to refer to that holotype specimen. In addition to the holotype, Dr. Örstan gave CMNH paratypes of Albinaria coa tek, which can be important for understanding the range of variation in the subspecies.

Albinaria are land snails that occur in SE Europe and the Middle East and are typically found on limestone. In some cases, they appear to have been able to form new colonies when ancient humans moved limestone around for buildings (the snails likely hitchhiked on the limestone blocks). That means we can trace trade routes over which ancient humans were moving limestone.

The family Clausiliidae (which contains the genus Albinaria) are of interest because they bear a clausilium, a kind of door for closing the shell (hence the common name “door snails”), which is unique to the family and is very different from the operculum, which is a different kind of door in many sea snails and some land snails. Furthermore, most snails in the family Clausiliidae coil counterclockwise, which is the opposite direction of more than 99% of all other snails. Additionally, Clausiliidae have a peculiar global distribution, being found in western Europe, Eastern Asia, and northern South America. People who study biogeography (how species came to be living where they are now) scratch their heads wondering how Clausiliidae came to be living in those three separate places without any individuals being found in between – for example, if they migrated from Europe to northern South America, why don’t any Clausiliidae occur in North America?

In addition to this new holotype (and paratypes) in the Section of Mollusks, holotype specimens of new species of vertebrates and paratypes of a new species of insect were named in 2023 and deposited in the relevant sections of the CMNH collection:

Pietro Calzoni, from the Universitá di Padova, Italy, and colleagues designated a CMNH Vertebrate Paleontology fossil as the holotype of a new bony fish species, Rhamphosus tubulirostris (Calzoni et al. 2023).

Three new species of the insectivore mammal genus Plagioctenoides (P. cryptos, P. dawsonae, and P.goliath), and one new species of Cuetholestes (C. acerbus), were recently named from CMNH Vertebrate Paleontology fossils (Jones and Beard 2023).

A CMNH Vertebrate Paleontology gekko fossil was designated as the holotype of Limnoscansor digitatellus (Meyer et al. 2023). CMNH visitors can view this specimen on display in the Solnhofen case in the Dinosaurs in Their Time exhibition.

A male and six female moths from the CMNH Invertebrate Zoology collection were named the new moth species Meganaclia johannae (Ignatev et al. 2023). The moths were collected between 1918 and 1925 in Cameroon and were housed in the Invertebrate Zoology collection awaiting discovery as new species.

While CMNH welcomes hundreds of thousands of visitors per year to the public galleries, scores of researchers work behind the scenes to expand our understanding of the different kinds of organisms, as evidenced by their type specimens, that are present in our incredible world. As the moth example demonstrates, Carnegie Museum of Natural History (and other museums around the world) hold specimens that have yet to be recognized as new species!

Timothy A. Pearce is Curator of Mollusks and Rachel Thomas Beckel is Administrative Coordinator for Science & Research at Carnegie Museum of Natural History.

References

Calzoni, P., J. Amalfitano, L. Giusberti, M. Carnevale, and G. Carnevale. 2023. Eocene Rhamphosisdae (Teleostei: Syngnathiformes) from the Bolca Lagerstätte, Italy. Rivista Italiana di Paleontologia e Strigrafia, 129(3): 573-607.

Ignatev, N., G.M. László, A. Paśnik, Z.F. Fric, H. Sulak, and G.C. Müller. 2023. Five new species of the genus Meganaclia Aurivillius, 1892 (Lepidoptera: Erebidae: Arctiinae: Syntomini). Zootaxa, 5296: 457–474.

Jones, M., and K.C. Beard. 2023. Nyctitheriidae (Mammalia, ?Eulipotyphla) from the Late Paleocene of Big Multi Quarry, southern Wyoming, and a revision of the subfamily Placentidentinae. Annals of Carnegie Museum, 88(2): 115-159.

Meyer, D., C.D. Brownstein, K.M. Jenkins, and J. Gauthier. 2023. A Morrison stem gekkotan reveals gecko evolution and Jurassic biogeography. Proceedings of the Royal Society B., 290: 20232284.

Örstan, A., and M.Z. Yildirim. 2023. A new insular land snail, Albinaria coa tek Örstan, from Marmaris, Türkiye (Clausiliidae: Alopiinae). Archiv für Molluskenkunde, 152(2): 175-182.

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