Smithsonian Science » collections

For a dentist, the narwhal’s smile is a mystery of evolution

John Barrat — Wed, 18 Apr 2012 16:33:32 +0000

When a dentist says “open wide,” he or she knows pretty much what they’ll find inside a patient’s mouth. But when a dentist peers into the mouth of an Arctic narwhal, all bets are off.

“Nothing makes sense,” explains Martin Nweeia, a practicing New England dentist and member of the Smithsonian’s Department of Vertebrate Zoology and the Harvard School of Dental Medicine. For one, narwhals have no teeth. “They eat large fish, yet swallow them whole. If you look in its mouth there’s nothing. There are absolutely no teeth.”

Image right: The mouth of a narwhal has no teeth. (Photo by Martin Nweeia)

Incredibly, the narwhal’s only visible tooth is outside of its mouth. Its tusk, in fact, is a giant canine tooth—that can grow as long as 9 feet—with a distinct left-hand spiral, covered in a tissue called cementum, normally only found around the base of a tooth lodged in bone.

Nweeia and a team of dentists and zoologists from the Smithsonian’s National Museum of Natural History, Harvard and other research organizations recently took a very close look at the dentition of the narwhal’s mouth. They studied more than 130 skulls in museum collections and 21 skulls of narwhals killed by native hunters in Canada. In a new paper published in The Anatomical Record, the team determined:

The long spiral tusk of the male narwhal is one of a pair of canine teeth positioned horizontally in the animal’s skull. They determined it was a canine and not an incisor because the tusk originates in the narwhal’s maxillary bone, where canine teeth in mammals originate. This is the first study to confirm the tusk as a canine tooth. In most mammals, canines are vertical in the mouth and are used for holding food or as weapons.

It is the left tooth of the pair that grows into a long tusk that erupts through the narwhal’s upper lip. The right canine tooth is also a tusk but it remains embedded in the narwhal’s skull unerrupted. Only occasionally do both tusks erupt. Female narwhals have two embedded tusks that erupt only very rarely.

Image left: A rare double-tusked narwhal in the collection of the National Museum of Natural History is examined by Martin Nweeia, left, and Charles Potter, collections manager, Smithsonian Marine Mammal Program. (Photo by Joseph Meehan)

A second pair of tiny teeth is located in open tooth sockets in the narwhal’s snout alongside the tusks. These teeth are vestigial, meaning they have no function. Close inspection across many specimens reveal extreme variation in location, morphology and histology (tissue structure) of these teeth, all indications they “are following a pattern consistent with evolutionary obsolescence,” the scientists write.

“It is striking when you think that this animal decided to take all of its tooth-producing energy and put it into one thing [a tusk] that sticks out nine feet into the ocean. With the amount of energy that it takes to produce that one tusk it could easily have 30 to 40 teeth in its mouth doing other things,” Nweeia explains. “Evolutionary-wise something is saying don’t do this, instead it is better to grow this extraordinary tusk.” A pretty compelling reason must be behind such a decision.”

Image right: An array of vestigial teeth collected from narwhals. (Photo by Joseph Meehan)

Did the narwhal once have teeth oriented vertically in its mouth as do other mammals? “One might assume this animal once had more teeth positioned vertically in the mouth, but there is no evolutionary evidence to say that would be true,” Nweeia explains. “With whales the evolutionary pieces of the puzzle are scant and I prefer to leave speculation out of the equation.”

There are many kinds of curious expressions of teeth in whales, narwhals being the most extraordinary, Nweeia says. “The strap-toothed whale, for example, has two teeth that wrap over its upper jaw preventing the animal from opening its mouth.”

Image left: The dissection team at the Osteo-Prep Lab of the Smithsonian’s National Museum of Natural History begins dissection on a male narwhal specimen. From left, James Mead, curator emeritus, Museum of Natural History; Ted Cranford, San Diego State University; and Martin Nweeia. (Photo by Chip Clark, Smithsonian Institution)

“The whole thing that is great about the teeth of the narwhal is that nothing makes sense,” Nweeia adds. “The tusks are an extreme example of dental asymmetry. They exhibit uncharacteristic dimorphic or sexual expressions since females do not exhibit erupted tusks as commonly as males. Also, the tusk has a straight axis and a spiraled morphology. Conventional mechanisms of evolution do not help explain these expressions of teeth.”–John Barrat

Article link: “Vestigial Tooth Anatomy and Tusk Nomenclature for Monodon monoceros,” The Anatomical Record, April 2012. Authored by Martin T. Nweeia, Frederick C. Eichmiller, Peter V. Hauschka, Ethan Tyler, James G. Mead, Charles W. Potter, David P. Angnatsiak, Pierre R. Richard, Jack R. Orr, and Sandie R. Black.

New exhibition looks at fishes from the “Inside Out”

John Barrat — Thu, 02 Feb 2012 12:01:33 +0000

“X-Ray Vision: Fish Inside Out,” is a new exhibition of striking x-rays that reveal the complex bone structure of fishes in the collections of the Smithsonian’s National Museum of Natural History. These x-rays allow scientists to study “the skeleton of a fish without dissecting or in any other way altering the specimen,” says curator Lynne Parenti. Ichthyologists at the museum study fish skeletons, fin spines, teeth and other morphological features to differentiate one species from another and exmaine evolutionary development. “X-Ray Vision: Fish Inside Out,” from the Smithsonian Traveling Exhibition Service, opens at the Natural History Museum in Washington, D.C. on Saturday, Feb. 4. More information about each of the fish species featured is available at: eol.org/info/xrayvision.”(All images by Sandra J. Raredon, Division of Fishes, National Museum of Natural History.)

Moray eel. Moray eels are legendary predators on coral reefs. Note the second set of jaws in the “throat”; these are the gill arches, which are present in all fish. Gill arches support the gills, the major respiratory organ of fish.

Lookdown. Because of its sloped head and the enlarged crest on its skull, the Lookdown appears to “look down” as it swims. These fish often swim in small schools.

Alligator Pipefish. Pipefish may be thought of as seahorses unfurled. The numerous bony body rings are used to differentiate one species of pipefish from another.

Ox-eyed Oreo. The name Oreosoma (“mountain body”) refers to the cone-shaped bony structures on the underside of this larval specimen. Adults are more elongate, less oval, and covered with scales.

Dhiho’s Seahorse. Just over one inch long, this elegant fish is readily identified as a seahorse by its characteristic head. The body ends in a tail that can curl around and hold on to algae or coral. This species is found only in the waters around Japan.

Bryan’s shearwater, new Hawaiian seabird species, discovered

John Barrat — Fri, 26 Aug 2011 19:48:28 +0000

For the first time in decades, researchers have found a new bird species in the United States. Based on a specimen collected in 1963 on Midway Atoll, Northwestern Hawaiian Islands, biologists have described a new species of seabird, Bryan’s shearwater (Puffinus bryani), according to differences in measurements and physical appearance compared to other species of shearwaters. Scientists at the Smithsonian Conservation Biology Institute analyzed the specimen’s DNA to confirm that it is an entirely new species.

“Usually we see a species split into two because we find that one of them has a very different DNA than the other, without other indicators,” said Rob Fleischer, head of SCBI’s Center for Conservation and Evolutionary Genetics. “It’s very unusual to discover a new species of bird these days and especially gratifying when DNA can confirm our original hypothesis that the animal is unique. This bird is unique, both genetically and in appearance, and represents a novel, albeit very rare, species.”

Image left: Bryan’s shearwater (Photo by Reginald David)

Researchers have rarely discovered new species of birds since most of the world’s 9,000-plus species (including about 21 other species of shearwaters) were described before 1900. The majority of new species described since the mid-1900s have been discovered in remote tropical rain and cloud forests, primarily in South America and southeastern Asia. The Bryan’s shearwater is the first new species reported from the United States and Hawaiian Islands since the Po’ouli was described from the forests of Maui in 1974.

The Bryan’s shearwater is the smallest shearwater known to exist. It is black and white with a black or blue-gray bill and blue legs. Biologists found the species in a burrow among a colony of petrels during the Pacific Ocean Biological Survey Program in 1963. Peter Pyle, an ornithologist at the Institute for Bird Populations, recently examined the specimen and found that it was too small to be a little shearwater (P. assimilis) and that it had a distinct appearance.

According to Fleischer and Andreanna Welch, a former graduate student and Smithsonian predoctoral fellow at SCBI who worked on the genetic analysis, the Bryan’s shearwater differs genetically to a greater degree than found between most other species of its genus, and is distantly related to another similar-looking species, the Boyd’s shearwater (P. boydi). Based on this DNA evidence, researchers estimate that the Bryan’s shearwater separated from other species of shearwaters perhaps more than 2 million years ago. These findings have been published in a paper, A new species of Shearwater (Puffinus) recorded from Midway Atoll, Northwestern Hawaiian Islands, in the current issue of The Condor.

Researchers do not know where Bryan’s shearwaters breed. According to Pyle, shearwaters and other seabirds often visit nesting burrows on remote islands only at night, and researchers have not discovered the breeding locations of many populations. Individual seabirds from colonies also often “prospect” for new breeding locations, usually far from existing colonies. Bryan’s shearwater could conceivably breed anywhere in the Pacific Ocean basin or even farther afield.

Given that Bryan’s shearwaters have remained undiscovered until now, they could be very rare and possibly even extinct.

“If we can find where this species breeds, we may have a chance to protect it and keep it from going extinct,” Welch said. “Genetic analysis allows us to investigate whether an animal represents an entirely different species, and that knowledge is important for setting conservation priorities and preventing extinction.”

Bryan’s shearwater is named after Edwin Horace Bryan Jr., who was curator of collections at the B.P. Bishop Museum in Honolulu from 1919 until 1968.

Marquesas Islands in French Polynesia yield 18 new species of rare ferns and flowering plants

John Barrat — Tue, 19 Jul 2011 14:44:10 +0000

Recent botanical exploration efforts in the rugged Marquesas Islands (French Polynesia) have increased the known flora of the archipelago by an impressive 20 percent. Field research and collecting in conjunction with the Vascular Flora of the Marquesas Islands and Flore de la Polynesie française projects have yielded 62 new species of ferns and flowering plants bringing the total native species to 360, of which 18 are newly described and illustrated in a special issue of PhytoKeys.

Image right: Oxalis simplicifolia growing on a cliff at Ua Huka, Marquesas Islands, shows distinctive simple leaves, flowers and fruits. (Photo by Steve Perlman)

New findings by researchers from the National Tropical Botanical Garden the (David H. Lorence) and Smithsonian’s National Museum of Natural History (Warren L. Wagner), in collaboration with French IRD and French Polynesian researchers, have brought to light 18 new species and one new variety of ferns and flowering plants from the rugged Marquesas Islands. Since 1988, 62 new species have been described in conjunction with the Vascular Flora of the Marquesas Islands and the Flore de la Polynésie française projects, representing a 20% increase in the known native flora. Ten precursor papers by the authors and collaborators describing the new species were published in issue the open access journal PhytoKeys.

Image left: Botanist Steve Perlman collects Oxalis simplicifolia on a cliff, Ua Huka, Marquesas Islands. (Photo by Jean-Yves Meyer)

According to senior project leader David Lorence, “Intensive field work has revealed that most of these new species are extremely rare and localized endemics, often confined to a single island. Many are known only from one or two localities harboring intact native vegetation that have so far escaped pressures from invasive plant species and feral animals. Consequently we assigned preliminary IUCN Red List ratings of Critically Endangered (13), Endangered (5), or Vulnerable (1) to these new species.” Over 6,000 herbarium specimens collected by field botanists were pressed, dried, and distributed to collaborating institutions in Tahiti, Hawaii, Washington DC, Paris, and elsewhere for study by botanical specialists. Ferns comprise an important element of the Marquesas flora, and 11 of the 18 new species are ferns. In addition, the botanists collected numerous new island records for native species and documented non-native, potentially weedy species that comprise about half of the islands’ flora.

As this project clearly shows, the biodiversity of many tropical islands is still poorly documented and explored. Field work and biological inventories of this type are essential to enhance our knowledge of insular biodiversity and provide critical information for conservation of these organisms and their habitats. However, staffing and funding for this type of work are scarce. Results of this project are available on an Internet-based resource hosted on the Smithsonian’s Department of Botany website, which provides access to a database with species descriptions, photos, distribution, literature, specimens lists, and other information: http://botany.si.edu/pacificislandbiodiversity/marquesasflora/index.htm.

The final goal of this project is publication of a comprehensive two-volume book covering the Vascular Flora of the Marquesas Islands, a goal which is nearing completion with the publication of these new species.–Source: National Tropical Botanical Garden

New study reveals desert tortoise is actually two distinct species

John Barrat — Thu, 30 Jun 2011 12:00:27 +0000

A new study shows that the desert tortoise, thought to be a single species for the last 150 years, is in fact two separate and distinct species, based on DNA evidence and biological and geographical distinctions.

This genetic evidence confirms previous suspicions, based on life history analysis, that tortoises west and east of the Colorado River are two separate species.

Image right: An Agassiz’s desert tortoise hides in a burrow; a radio transmitter is attached to its shell as part of a USGS study. (Photo by Steven Schwarzbach, USGS)

The newly recognized species has been named Morafka’s desert tortoise (Gopherus morafkai) and represents populations naturally found east and south of the Colorado River, from Arizona extending into Mexico.

The originally recognized species, the Agassiz’s desert tortoise (Gopherus agassizii) is listed as threatened under the federal Endangered Species Act. It represents populations naturally found west and north of the Colorado River in Utah, Nevada, northern Arizona and California.

The U.S. Fish and Wildlife Service (FWS), which manages the recovery of threatened and endangered species, had already been treating tortoises on each side of the Colorado River as distinct populations The genetic evidence simply backs up previous observations, such as differences in life history and reproductive strategies.

Image left: A Morafka’s desert tortoise in Saguaro National Park, with radio transmitter attached to its shell as part of a USGS study. (Photo by Jeff Lovich, USGS)

“The two species have different habitat preferences,” says Kristin Berry, a United States Geological Survey biologist who has studied desert tortoise biology for more than 40 years and is a coauthor on the study. “Morafka’s tortoise prefers to hide and burrow under rock crevices on steep, rocky hillsides, while the Agassiz’s tortoise prefers to dig burrows in valleys.”

Roy Averill-Murray, the desert tortoise recovery coordinator for the Fish and Wildlife Service said, “The study’s finding that the Morafka’s desert tortoise is a new species confirms the Service’s decision to evaluate this population independently from the Agassiz’s desert tortoise, and will not change the status of either species under the Endangered Species Act or change existing recovery plans.”

Image left: This map shows the range of both the Morafka’s desert tortoise (Gopherus morafkai), gray area lower right, and the Agassiz’s desert tortoise (Gopherus agassizii), black area upper left. (Map courtesy USGS)

Distinguishing the two species required some historical detective work. Desert tortoises were first described in 1861 by Army physician, J.G. Cooper. But two of the original specimens were lost, possibly as a result of the San Francisco earthquake and fire of 1906. Fortunately, Cooper sent a third specimen to the Smithsonian. Carefully held in the collection of the Division of Reptiles at the Smithsonian’s National Museum of Natural History in Washington, D.C., DNA from this tortoise helped researchers in their analysis 150 years later.

The study is published in the journal ZooKeys. A detailed FAQ about the study on the Webpage of the USGS Western Ecological Center.–Source: United States Geological Survey

Fossil skull of an extinct toothed whale excavated from Panamanian sediments

John Barrat — Fri, 24 Jun 2011 12:47:13 +0000

A scientist from the Smithsonian Tropical Research Institute uses a pick to dislodge the fossil skull of an extinct toothed whale from sediments on the Panamanian Coast near the town of Piña. Researchers from STRI and the Smithsonian’s Museum of Natural History encased the skull in a plaster cast to protect it before removal. The fossil likely represents one of the youngest occurrences of a squalodontid, (a prehistoric shark-toothed dolphin) and certainly the first one from the Caribbean, says Nick Pyenson, curator at the Natural History Museum. Click this Ocean Portal link to read Pyenson’s blog on the find and see a short video of the excavation. (Photo by Aaron O’Dea)

Learn about the National Zoo’s flamingo flock with keeper Sara Hallager

John Barrat — Tue, 04 Jan 2011 13:06:29 +0000

National Zoo scientists successfully grow two species of anemones in aquarium tanks

John Barrat — Tue, 24 Aug 2010 11:45:18 +0000

The Smithsonian’s National Zoo has become the first in the zoo and aquarium community to use coral larvae settling techniques to successfully grow two species of anemones—an accomplishment that will provide the Zoo a unique opportunity to learn how anemones grow.

Image right: After this adult anemone broadcast spawned, Smithsonian’s National Zoo animal keeper Mike Henley collected the eggs off the surface. Using coral settling techniques learned in the field, Henley is successfully growing anemones. (Photo by Mike Henley)

“We have many questions about how to care for these animals as they grow from larvae to adults,” said Mike Henley, an animal keeper at the Zoo’s Invertebrate Exhibit who applied the technique to the anemones after they had spawned. “The oceans are not an infinite resource and so anything that we can learn about the captive management of coral and anemones will go far in our ability to conserve them.”

The anemones—both of which are commonly called Tealia red anemones under the species of Urticina—spawned in late April and early May, just days apart. Hours after they spawned, Henley collected the eggs and sperm from the more than 2,000-gallon tank and put them together in smaller tanks to increase the chances of fertilization. After fertilization, the larvae settled and metamorphosed into a polyp. Henley put some of the developing larvae in a circular tank—called a kreisel—that automatically stirs the water to prevent the larvae from binding to one another, which would kill the animals. The kreisel is the same tank Henley and others use in the field in Puerto Rico to hold coral larvae. Other free-swimming larvae went into a regular tank with aeration and rocks to settle on. Now the Zoo has hundreds of thriving anemones behind the scenes, all smaller than the tip of a pencil.

Image left: The result of National Zoo keeper Mike Henley’s work is hundreds of thriving anemones, all smaller than the tip of a pencil. The one shown here is no bigger than 1-2 mm. (Photo Mehgan Murphy)

“Sometimes we take the lessons we learn with animals in captivity and apply that to conserving them in the wild,” said Alan Peters, curator of the Zoo’s Invertebrate Exhibit. “But here we were able to apply what we’ve learned both in the field and from ex situ work and it is yielding some exciting results.”

While anemones and coral are both in the Anthozoa class of animals, they differ in a few notable ways. Anemones metamorphose into a single polyp, while coral will divide into a second polyp and a third and so on, to form a colony. In addition, anemones have a muscular foot they use to attach to rock, while stony corals make their own calcium carbonate rock that they live on. But both can sting and are carnivorous, feeding on crabs, shrimp, fish and zooplankton. More than 1,000 sea anemone species inhabit the world’s oceans at various depths, from the sandy seashore up to the surface. Visitors to the Zoo can see six different species of anemones, including cold and warm water anemones. Although anemones are not endangered, ocean habitats around the world are in decline as the result of pollution, runoff and sedimentation, climate change, acidification and poor fishing practices.

Henley will continue to observe the anemones to learn about their growth rate and the conditions that are necessary to rear these species in captivity, including the food, light and water temperature they require.

“In the past if the anemones spawned in the tank, it’d be a big headache,” said Henley. “You’d have to do frequent water changes because when the gametes—or reproductive cells—get too concentrated and deteriorate, it causes the water quality to crash. That’s the common experience among many of our zoo and aquarium colleagues. But this was different—so far it’s amounted to young anemones that we will continue to learn from for months, even years, to come.”

Modern African basketry joins anthropology collections of National Museum of Natural History

John Barrat — Thu, 29 Jul 2010 19:35:50 +0000

The Smithsonian’s National Museum of Natural History recently acquired the donation of a stunning handcrafted storage basket from Botswana made by Mashe Mbombo, a member of the Etsha women’s craft cooperative. The basket was a gift from the Art and Crafts Programme of Anglo American, PLC.

Basket making by Botswana women has a long history and it continues to be a robust craft tradition. During the last three decades it has become increasingly well known in the international craft market.

Etsha Weavers Group, a Botswana craft group made up of 24 skilled basketmakers, has played a pivotal role in bringing attention to Botswana basketry as a unique art form.

“This contemporary Botswana basket is an important addition to the Smithsonian’s collection,” says Mary Jo Arnoldi, curator, African ethnology, at the Natural History Museum. “This piece provides an updated visual timeline in the collection showcasing both the continuity and the evolution of basket making in Botswana.” As an integral part of the Botswana culture, baskets have been used for a variety of purposes. Closed baskets with lids, like the recently acquired piece, are used for storing grain and seed. Large, open bowl shaped baskets are used by the women for the transportation of goods and smaller, plate shaped baskets are used for winnowing grain after it has been processed.

Photo right: Mashe Mbombo of the Estha Weavers Group

Basket makers in Botswana use a method called coiling to create their modern baskets. The process of making a coil basket can take up to six weeks to complete. Basket makers use a thick bundle of palm fiber, grass or vine to begin the inner coil. The next step is to pierce a small hole into the coil and begin wrapping strips of palm around the core of the basket. This process is repeated until the basket reaches the desired size – designs are created by weaving strips of dyed palm into the basket pattern. Arnoldi notes that, “The National Museum of Natural History Anthropology collection had only five smaller plate shaped basketry trays from Botswana, all collected in rural villages prior to the 1960s. We certainly welcome the addition of this large and beautifully made storage basket to the collections.” –Jessica Porter

Slide Show: Smithsonian’s National Museum of Natural History is 100!

John Barrat — Tue, 22 Jun 2010 17:24:14 +0000

Since its doors first opened in 1910, the National Museum of Natural History has inspired curiosity and learning about the natural world and our place in it. Building upon the strong foundation of our extensive collections, the staff of the museum have been at the forefront of essential scientific exploration and research, and groundbreaking public exhibition and education. This slideshow and the website (www.mnh.si.edu/onehundredyears/) is a living documentary of the Museum’s 100-year history.