Tag: gastropods

Miniature Snail in a Rock Sandwich

First fossil record of thorn snails in the southern United States

Researchers from the USA and Switzerland, including Senckenberg scientist and first author Dr. Adrienne Jochum, have described the first fossil Carychium land snails from Florida. The rock layer containing the snail fossils, which are only a few millimeters in size, was accidentally uncovered during construction work and dates from the Pleistocene period between 2.58 million and 11,700 years ago. In their study, published in the open-access journal ZooKeys, the scientists also describe a previously unknown carychiid fossil species.

Light microscopic images of Carychium nashuaense.

The tiny snails of the genus Carychium with a maximum height of 2.5 millimeters and a width of 1.5 millimeters are known mostly east of the Mississippi River in the USA and from eastern Canada, Mexico and Jamaica as well as in sheltered humid habitats in Central America to Panama. “However, unlike the extant species, fossilized thorn snails are rarely found east of the Mississippi River. In our recent field work we have now provided the first fossil record of the genus in the southeastern United States, as well as the first fossil record ever for the species Carychium floridanum,” explains Dr. Adrienne Jochum of the Senckenberg Research Institute and Natural History Museum in Frankfurt and the Natural History Museum in Bern.

During the construction of a track bed for the Brightline railroad, which will connect Port Canaveral with Orlando International Airport, civil engineers accidentally came across a one-meter-thick layer of fossilized non-marine gastropods between two marine shell beds. “This ‘rock sandwich’ was formed during the Pleistocene, a geologic era characterized by repeated glaciations, climate changes, and fluctuations in water level that greatly influenced and shaped the region around present-day Florida. The shell layer is sandwiched between rock layers from the Lower Pleistocene, 2.58 to 0.77 million years ago, and the Upper Pleistocene, 140,000 to 120,000 years ago, and contains 14 freshwater and 28 terrestrial snail species.”

Later stage of excavation showing middle stratum of freshwater marl (c. 1 m thick) wedged between two layers of marine shell layers (each c. 3 m thick).

Among them is the snail Carychium floridanum, whose current representatives still live in humid, forested, and undisturbed habitats in central and northern Florida. The researchers also described a new species, Carychium nashuaense, which is less than 1.6 millimeters long and was previously unknown to science.

“To dislodge the fossil miniature snails from the rock layers, we first washed them through a graduated series of sieves. Next, 32 Carychium shells were culled under a microscope from a mixture of other mollusks and rock debris. A high-resolution X-ray tomograph helped us examine the spindle structure inside the fragile fossil shells and compare them with 3D reconstructions of the inner shell of still-living thorn snail species from the southeastern U.S., Mexico, Central America, and Jamaica,” explains Jochum.

While the design of the inner shell structure of Carychium floridanum has changed little from the Pleistocene to the present, the shell structure of Carychium nashuaense suggests a relationship with Central American Carychium relatives. “We suspect that the spread of the snails occurred via birds, mammals, and reptiles, who transported the small snails in their guts, fur, or feathers to the wetlands from which the alluvial sediments in the rock layer we studied originated. The subsequent mixing with other members of the genus led to the emergence of new species,” adds Jochum in conclusion.

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Publication:

Jochum A, Bochud E, Haberthür D, Lee HG, Hlushchuk R, Portell RW (2023) Fossil Carychiidae (Eupulmonata, Ellobioidea) from the Lower Pleistocene Nashua Formation of Florida, with the description of a new species. ZooKeys 1167: 89-107.
https://doi.org/10.3897/zookeys.1167.102840

Press release originally published by Senckenberg. Republished with permission.

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Tiny thorn snail discovered in Panama’s backyard

*Close-up view of live individuals of the new species crawling on a leaf.*

Discoveries of biodiversity at the Lilliputian scale are more tedious than it is for larger animals like elephants, for example. Furthermore, an analysis producing a DNA barcode – a taxonomic method using a short snippet of an organism’s DNA – is not enough to adequately identify it to the species level.

In the case of tiny thorn snails – appearing as minute white flecks grazing in moist, decomposing leaf litter – it is the shell that provides additional and reliable information needed to verify or question molecular assessment of these otherwise, nondescript critters.

*Broadleaf forest litter with white arrows indicating the newly described species on the leaves.*

However, at 2 mm, thorn snails are too small and fragile to handle and the few, if any, tangible details on the outside of the shells can only be seen using a high-powered microscope and computed tomographic (CT) images.

This is exactly how the interdisciplinary team of Dr Adrienne Jochum, Naturhistorisches Museum der Burgergemeinde Bern (NMBE) and University of Bern, Dr. Bernhard Ruthensteiner, Zoologische Staatssammlung Muenchen, Germany, Dr. Marian Kampschulte, University Hospital of Giessen and Marburg, Gunhild Martels, Justus-Liebig University Giessen, Jeannette Kneubühler, NMBE and University of Bern, and Dr. Adrien Favre, Senckenberg Research Institute and Natural History Museum Frankfurt, managed to clarify the identity of a new Panamanian species. Their study is published in the open-access journal ZooKeys.

Even though the molecular analysis flagged what it was later to be named as the new to science species, Carychium panamaense, the examination left no shell for the description of the new snail to be completed, let alone to serve as tangible, voucher material in a museum collection available to future researchers. The mini forest compost-grazer had to wait for another five years and Dr. A. Favre, who collected fresh material while traveling in Panama.

The new snail is currently the second member of the family Carychiidae to be discovered in Panama. The first Panamanian, and southern-most member of its kind in the Western Hemisphere, is C. zarzaae, which was also described by Dr. A. Jochum and her team along with two sister species from North and Central America. The study was published in ZooKeys last year.

Much like X-rays showing the degree of damage in a broken bone, CT images visualise the degree of sinuosity of the potato chip-like wedge (lamella) along the spindle-like mast (columella) inside the thorn snail’s shell. These structures provide stability and surface area on which the snail exerts muscular traction while manoeuvring the unwieldy and pointed, signature thorn-like shell into tight nooks and crannies. The alignment and degree of waviness of the lamella on the columella is also used by malacologists (mollusc specialists) to differentiate the species.

*These are computed tomographic (CT) images of the new thorn snail species.*

Normally, a study of a thorn snail’s shell would require drilling out minute ‘windows’ in the shell by using a fine needle under a high microscope magnification.

“This miserable method requires much patience and dexterity and all too often, the shell springs open into oblivion or disintegrates into dust under pressure,” explains Dr. A. Jochum. “By exposing the delicate lamella using non-manipulative CT imaging, valuable shell material is conserved and unknown diversity in thorn snails becomes widely accessible for further study and subsequent conservation measures.”

The authors are hopeful that C. panamaense and C. zarzaae, which both inhabit the La Amistad International Park, Chiriquí, will remain a conservation priority along with other animalian treasures including the Resplendent Quetzal, Three-Wattled Bellbird and the Crested Eagles.

The park is considered the 1st bi-national biosphere reserve, as it occupies land in both Costa Rica and Panama, and constitutes a UNESCO World Heritage Site since 1990.

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Original Source:

Jochum A, Ruthensteiner B, Kampschulte M, Martels G, Kneubühler J, Favre A (2018) Fulfilling the taxonomic consequence after DNA Barcoding: Carychium panamaense sp. n. (Eupulmonata, Ellobioidea, Carychiidae) from Panama is described using computed tomographic (CT) imaging. ZooKeys 795: 1-12. https://doi.org/10.3897/zookeys.795.29339

New ‘scaly’ snails species group following striking discoveries from Malaysian Borneo

Six new species of unique land snails whose shells are covered with what look like scales have been described from the biodiversity hotspot of Malaysian Borneo by scientists Mohd Zacaery Khalik, Universiti Malaysia Sarawak, Kasper Hendriks, University of Groningen, Jaap Vermeulen, JK Art & Science, and Prof Menno Schilthuizen, Naturalis Biodiversity Center. Their paper is published in the open access journal ZooKeys.

Thanks to their conspicuous structures, the mollusks have been added to a brand new species group of land snails to be commonly known as the ‘scaly’ snails, so that they can be set apart from the rest in the genus Georissa. Why it is that only some of the species in the genus sport the unique ‘scales’, remains unknown.

Fascinated with the minute ‘scaly’ snail fauna of Borneo, the researchers carried out fieldwork between 2015 and 2017 to find out how these curious shells evolved. In addition, they also examined material deposited in museum and private snail collections.

Apart from DNA data, which is nowadays commonly used in species identification, the team turned to yet-to-become-popular modern tools such as 3D modelling, conducted through X-ray scanning. By doing so, the researchers managed to look at both the inner and outer surfaces of the shells of the tiny specimens from every angle and position, and examine them in great detail.

The researchers note that to identify the ‘scaly’ snails to species level, one needs a combination of both DNA and morphological data:

“Objective species delimitation based solely on molecular data will not be successful for the ‘scaly’ snails in Georissa, at least if one wishes for the taxonomy to reflect morphology as well.”

The six new species are all named after the localities they have been originally collected from, in order to create awareness for species and habitat conservation.

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Watch rotation and cross-section of the 3D models of the studied species here.

Original source:

Khalik MZ, Hendriks K, Vermeulen JJ, Schilthuizen M (2018) A molecular and conchological dissection of the “scaly” Georissa of Malaysian Borneo (Gastropoda, Neritimorpha, Hydrocenidae). ZooKeys 773: 1-55. https://doi.org/10.3897/zookeys.773.24878

Threatened Alabama snail renamed after a case of mistaken identity

Contrary to what scientists have known for over 100 years, the Painted Rocksnail turns out to have never existed outside the Coosa River system

Alabama has some of the highest diversity of freshwater snails in the world, but many snails are at high risk of extinction.

An essential part of determining extinction risk is knowing the range of a given species and determining how much its range has contracted owing to anthropogenic impacts, but mistaken identity or misidentification can complicate conservation efforts.

The Painted Rocksnail, a small snail from the Coosa River system, has been mistakenly identified as other species for over 100 years.

In a study published in the open access journal ZooKeys, scientists Dr. Nathan Whelan, U.S. Fish and Wildlife Service, Dr. Paul Johnson and Jeff Garner, Alabama Department of Conservation and Natural Resources, and Dr. Ellen Strong, Smithsonian Institution National Museum of Natural History, tackled the identity of the Painted Rocksnail, a small federally threatened species native to the Mobile River basin in Alabama.

Freshwater snails are notoriously difficult to identify, as the shells of many species can look very similar. Keeping this in mind, the researchers began to notice that many shells identified as the Painted Rocksnail in museums around the world were misidentified specimens of the Spotted Rocksnail, another snail species found in Alabama.

After examining shells at the Academy of Natural Sciences of Philadelphia, Museum of Comparative Zoology at Harvard, National Museum of Natural History, North Carolina Museum of Natural Sciences, Florida Museum of Natural History, and Natural History Museum in London, in addition to hundreds of hours of their own sampling throughout the Mobile River basin, the authors determined that all previous reports of the Painted Rocksnail from outside the Coosa River system were mistakes.

Despite the Painted Rocksnail dwelling in well-studied rivers near large population centers, mistaken identity of the species has persisted almost since the species was described back in 1861 by Isaac Lea.

Only after careful examination of shells collected in the last 150 years and analyses of live animals were the researchers able to confidently determine that the Painted Rocksnail never occurred outside the Coosa River system.

The study has implications for the conservation of the Painted Rocksnail, as the species was historically more restricted than previously thought. Recent surveys by the authors only found the species in small stretches of the Coosa River, Choccolocco Creek, Buxahatchee Creek, and Ohatchee Creek.

In conclusion, the authors note the importance of natural history museums and the importance of studying snails in the southeastern United States.

“Without the shells stored in natural history museums we would have never been able to determine that the supposed historical range of the Painted Rocksnail was incorrect, which could have resulted in less effective conservation efforts for an animal that is very important to the health of rivers in Alabama,” they say.

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Original Source:

Whelan NV, Johnson PD, Garner JT, Strong EE (2017) On the identity of Leptoxis taeniata – a misapplied name for the threatened Painted Rocksnail (Cerithioidea, Pleuroceridae). ZooKeys697: 21-36. https://doi.org/10.3897/zookeys.697.14060

Species new to science named after a ‘Dungeons & Dragons’ character

Focused on terrestrial gastropods, more commonly known as land snails, a joint team of biologists from the Natural History Museum of Stuttgart, Germany and the Zoology Museum of São Paulo, Brazil, have been researching Brazilian caves.

In their latest paper, published in the journal Zoosystematics and Evolution, the scientists describe the fauna from several caves in central Brazil, including a new tiny species named after a character from the popular fantasy tabletop role-playing game Dungeons & Dragons.

The team of Dr. Rodrigo Salvador, Daniel Cavallari and Dr. Luiz Simone encountered a rich assembly of species, several of which measured only a few millimetres.

Beyond filling important knowledge gaps, they went even further, discovering a land snail new to science. While it is not uncommon for studies dealing with the invertebrate fauna to end up describing new species, this minute mollusc (nearly 2 mm in length) attracted extra attention. The team named it Gastrocopta sharae, after Shar, the goddess of darkness, caverns and secrets in Dungeons & Dragons.

“It’s a fitting name for a tiny snail that lives hidden in the dark recesses of a cavern,” explain the authors. “If your knowledge of mythological beings seems to have failed you, do not fret. Usually biologists tend to honour Greek and Roman deities when naming species, but the goddess Shar has a more colourful background. She is from Dungeons & Dragons, the most famous role-playing game in the world, currently in its 5th edition and a staple of geek culture.”

This is not the first time that Dungeons & Dragons has been immortalised in a species’ scientific name. In 2014, the very same team described another tiny snail, this time, one with a taste for deep waters, specifically those of the Atlantic Ocean. The scientists named it Halystina umberlee, after another Dungeons & Dragons goddess, Umberlee, who commands the harshness and perils of the sea.

Tropical snails are still poorly understood, and they are one of the most threatened animal groups – both from human activities and environmental changes. Moreover, since cave-dwelling invertebrates, in general, receive scarce attention from researchers, it should come as no surprise that cave-dwelling snails are even less known.

“Getting to know the fauna inhabiting each cavern is a demanding task, but a much-needed one,” note the researchers. “Caverns are known to have very fragile ecosystems and several lack proper protection, so works like ours are an important step for conservation efforts.”

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Original source:

Salvador RB, Cavallari DC, Simone LRL (2017) Taxonomical study on a sample of land and freshwater snails from caves in central Brazil, with description of a new species. Zoosystematics and Evolution 93(1): 135-141. https://doi.org/10.3897/zse.93.10995