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Posts tagged ‘invertebrates’

Paleo Video: Snail shell mystery

If you study snails, you’ve got to be patient. But two UCMP graduate students, Jann Vendetti and Scott Fay, used time-lapse photography to kick slow snails into high gear. They discovered some surprising behavior in snails living today—and in snails that lived millions of years in the past.

The video features snails of two species: Kelletia kelletii, and Busycotypus canaliculatus (also known as Busycon canaliculatum). This group of animals is so numerous and diverse—in lifestyle, natural history, and morphology—that research questions are virtually infinite.

Shortly after we made this film, Jann and Scott graduated from UC Berkeley with Ph.D.s in Integrative Biology. Jann is now a post-doc at Cal State Los Angeles, studying photosynthetic sea slugs called sacoglossans.  And Scott is a post-doc at Temple University, in Philadelphia; he studies the trophic ecology of Antarctic protists. While they work on disparate groups, their potential for collaboration continues: Jann’s sea slugs and Scott’s dinoflagellates have a similar strategy for energy acquisition: they both steal chloroplasts.

Even a mantis shrimp is what it eats

Neogonodactlyus wounds

Neogonodactlyus bredini with damage on its predatory appendage from another mantis shrimp's strikes! Photo by Roy Caldwell.

Ask most anyone what butterflies use their wings for or what fish do with their fins and you will undoubtedly hear an answer like, "Wings are used for flying and fins are used for swimming!" Some body parts just seem so well-adapted to perform certain functions; this is why there is a paradigm in biology that "specialized" body parts correspond to specific ways in which animals go about their daily business. In other words, specialization in morphology corresponds to specialization in ecology. A classic example of this concept is variation in the beaks of the Galapagos finches. Some finches have beaks adapted to crush hard seeds, while others have beaks specialized for eating insects.

However, not all animals seem to exhibit this pattern. The marine crustacean known as the mantis shrimp has legs, called predatory or raptorial appendages, which can produce one of the fastest movements in the animal kingdom. These raptorial appendages come in many shapes ranging from sharp spear-like appendages to hammer-like appendages. Mantis shrimp use their fast-moving appendages to crush open snails and other hard-shelled marine organisms, so they can eat the soft bodies inside. However, mantis shrimp also appear to eat other foods, like fish, which probably do not need to be smashed to bits before they are consumed. Even though they have specialized legs well adapted to smashing or spearing prey, some species may not use their raptorial appendages for this purpose. The goal of my research is to determine if mantis shrimp have diverse diets. Then if so, I will see how diet diversity correlates with raptorial appendage morphology across the mantis shrimp family.

First, a little background about mantis shrimp. Mantis shrimp are closely related to decapods, such as lobsters, crabs, and true shrimp. Even though mantis shrimp look like decapods, they actually branched off and became their own group 400 million years ago. Mantis shrimp have the most complex visual system ever reported in the animal kingdom. They are also one of the fastest swimmers in the sea, swimming at speeds of up to 30 body lengths per second — comparable to speeds measured in squid, which previously held the record.

But my favorite characteristic of mantis shrimp is of course their lightning fast raptorial appendages. Researchers in the Patek Lab at the University of Massachusetts and Caldwell Lab at Berkeley have found that a mantis shrimp’s predatory strike can move 23 meters per second (50 miles per hour) and produces accelerations that are comparable to a flying bullet! So it would be surprising if some mantis shrimp species were capable of this rapid movement, but didn't use it to catch prey. Hence, my study of mantis shrimp diets! I am using two techniques, stable isotopes and behavioral studies, to figure out which food items mantis shrimp eat.

Before I could study their diets, I first had to collect several different species of mantis shrimp and their possible prey. Most mantis shrimp live in the tropics, so I have traveled to Lizard Island, Australia and Mo’orea, French Polynesia to collect the animals. However, my main field site is in Colon, Panama where I collect at the Smithsonian Tropical Research Institute’s Galeta Marine Laboratory. After collecting, I transport all of the specimens back to the UC Berkeley Center for Stable Isotope Biogeochemistry, where I analyze the carbon and nitrogen stable isotopes of mantis shrimp and their prey.

What is a stable isotope? Let's go back to high school chemistry for a moment! A normal atom has the same number of neutrons and protons in the nucleus, but a stable isotope has more neutrons than protons in the nucleus. For example, a normal carbon atom has 12 neutrons in the nucleus, but its stable isotope has 13 neutrons. These isotopes are stable, because they do not exhibit radioactive decay over time — they won't lose that extra neutron — which means that the isotope will always have 13 neutrons in the nucleus. Researchers look at the ratio of normal atoms to stable isotopes to track diet, because the ratio of normal atoms to stable isotopes in the body of a predator can reflect the type of prey it has eaten. For example, if the mantis shrimp has a ratio of 10 carbon-13 atoms to carbon-12 atoms and the crab that you think the mantis shrimp eats has a ratio of 8, then there is a good chance that the mantis shrimp eats this species of crab. The reason why the mantis shrimp’s ratio is not exactly 8 is that there is an expected change in the predator’s ratio that occurs when the predator metabolizes the prey. You are what you eat (plus a little bit!), and stable isotopes allow us to track this pretty accurately.

Back In the laboratory, my assistants and I identify all of the prey items and stomatopods that we collected. We then take muscle tissue samples from the mantis shrimp and from the prey. We use a mass spectrometer to analyze the carbon and nitrogen stable isotopes in both the mantis shrimp and prey tissue. Finally, we compare the isotope ratios of the mantis shrimp and prey to determine who ate what. Since the mantis shrimp is what it eats, all prey items that have isotope ratios similar to the mantis shrimp’s ratios are likely a part of the mantis shrimp diet.

To confirm the accuracy of the stable isotope analyses, I also conduct behavior experiments that help me to determine which animals mantis shrimp are physically capable of eating. To do this, I stock aquaria with mantis shrimp and potential prey, and I wait to see which prey the mantis shrimp eat. So far, I have performed this experiment on only one species, but eventually I will look at many species of mantis shrimp, with different appendage morphologies, to see if mantis shrimp with different appendage shapes have different diets. Together with the isotope analyses, these experiments will give me a good picture of mantis shrimp diet and ultimately lead to an in-depth understanding of the relationship between raptorial appendage morphology and diet across the mantis shrimp family. This fall, I’ll return to Panama to complete my field experiments, so stay tuned for updates in future blog posts!

To learn more about Maya's research, watch the Paleo Video Field notes: Collecting stomatopods on the Great  Barrier Reef.

Neogonodactlyus wounds Mo'orea collecting Panama collecting stomatopod 2 stomatopod 1 tanks for behavior experiment Dissecting specimens

The game of prehistoric life

EOP-cover

Evolve or Perish is a new board game – not from the makers of Monopoly, but from ETE, the Evolution of the Terrestrial Ecosystems Program, at the Smithsonian National Museum of Natural History. UCMP Faculty Curators Cindy Looy and Ivo Duijnstee designed the game in collaboration with illustrator Hannah Bonner. Hannah is well-known for her cartoon paleobooks When Bugs Were Big and When Fish Got Feet. The three enjoy collaborating -- Hannah created the logo for Cindy's lab's web site, and she is currently consulting with her on a regular basis for her next book.

Evolve or Perish is similar to Chutes and Ladders. It begins 635 million years ago, with the first multi-celled organisms. Each square on the board represents 10 million years. On the path to the present, numerous fates await you: slip on an early animal and go back one square; land on the Cambrian Explosion and jump ahead; land on the largest extinction event the world has ever known and go back nine spaces. The game is populated by cute animals (the first four-legged animal wears a party hat!) and strange-looking plants (like Lycopods from the coal swamps of the Carboniferous). All of the beautifully drawn creatures represent real plants and animals, known from the fossil record; a taxa list helps you learn your Oxynoticeras from your Omeisaurus. As you move your game piece from the past to the present, Earth's major milestones appear along the way – you'll pass meteors, millipedes, and the rise of giant mammals. The first player to make it to the present day wins the game – but experiences a gross revelation about how some of Earth's first inhabitants inhabit us humans, too.

The game can be downloaded for free here.

Middle schoolers and marine biodiversity in Moorea

GK-12 students in MooreaScientists from institutions like the UCMP travel all around the world and interact with many local communities. Last year the Berkeley Natural History Museums launched a project called the GK-12 Moorea fellowship to foster collaboration between graduate students and local communities in Moorea, French Polynesia. The program sends one graduate student to Moorea, a small island about 10km from Tahiti, to teach interactive science lessons in public schools and do ecological research. As the current GK-12 Moorea fellow, I am living in French Polynesia, teaching in a local middle school, and continuing my research on the evolution of monogamy in mantis shrimps.
For the past five weeks, I have been teaching lessons about marine biodiversity in two special education classrooms at the middle school in Pao Pao, Moorea. We kicked off the biodiversity unit with a field trip to a local public beach, where the students collected many animals from the shallow, sandy lagoon. The kids had a great time wading in the water, looking under rocks, and using a huge “Slurp Pump” to suck up critters that live in burrows. For many of these students, the lagoon is their backyard and they have been swimming, boating, and fishing in it since they were old enough to walk. Yet, I soon realized that for most of them every crab that they saw was just a crab and every snail was just a snail. They didn’t notice the differences between different species at all!

The students now have spent several lessons learning how to identify species and measure biodiversity using the collection that we made at the public beach. To measure the biodiversity of the public beach, the students are counting the number of species of mollusks (snails, clams, and octopuses) and decapods crustaceans (crabs, shrimps, lobsters). Although the students had an intuitive knowledge about how to classify organisms into mollusks and crustaceans, they were very skeptical when I showed them the thirteen different crab species we caught — they repeatedly told me “Toutes sont les crabbes” (They are all crabs)! I finally decided to try an impromptu activity — the students drew pictures of several different species of crustaceans and listed ways in which they differed. In doing this, they convinced themselves that each species was a morphologically unique group of organisms. The funny thing is that scientists at UC Berkeley argue all the time about the definition of “species” and whether “species” really exist. Species are notoriously hard to define — as Darwin said in On the Origin of Species, “No one definition has satisfied all naturalists; yet every naturalist knows vaguely what he means when he? speaks of a species.”

I love doing research on a small tropical island. In addition to the staff at Gump Station, I also have made friends with several Mooreans who live near sites where I collect mantis shrimps. One of my favorite research sites, Motu Tiahura, is frequented by picnicking families. The children often ask to see my animals. It is great fun to see their eyes widen as they look at my mantis shrimps swimming around in a falcon tube. I often explain my research to their parents — I study the evolution of monogamy in mantis shrimps. Monogamy is rare in crustaceans, but is common in the clade of mantis shrimps that I study. One of these monogamous species, Lysiosquillina maculata, or “varo” in Tahitian, is an expensive and overfished culinary delicacy here in French Polynesia. People here are fascinated to learn that the “varo” can live together in monogamous pairs for decades! They also love to check out my SCUBA diving setup and hear about my research methods.

During the height of my fieldwork, I dive for 3 or more hours a day surveying and collecting smaller mantis shrimp species. The backreef of the Moorean lagoon is a great place to dive. It’s clear, shallow waters abound with colorful fish and large coral heads. Since arriving in Moorea, I have learned all of the common fish and coral species so that I can do environmental surveys in areas where I collect mantis shrimps. As a naturalist, I love being able to name all of the species in the waters around me. Here in French Polynesia, many locals who fish for a living feel the same way. However, as in most developed countries, the younger generations are often less connected with nature. As I work and teach here in Moorea, I hope to open the eyes of my young students to the amazing marine ecosystem that surrounds them.

Gump Station, Moorea Moorea Moorea GK-12 5 Moorea GK-12 6 Moorea GK-12 2 Moorea GK-12 3 Moorea GK-12 4 Moorea GK-12 1 Moorea GK-12 7 Moorea GK-12 8

Creatures from the black lagoon

Lake Merritt

Lake Merritt, Oakland, California.

Very little was known about wetland ecology back in 1869, when Samuel Merritt dammed a former tidal slough and began developing its surrounding wetland as his "Jewel of Oakland." By restricting the flow of waters in and out of the newly created tidal lagoon, a.k.a. Lake Merritt, silt and algae were allowed to accumulate and within a few years the lake had become a bit of an environmental disaster. Nevertheless, part of it was designated by Teddy Roosevelt as our nation's first wildlife refuge, protecting more than 90 species of migrating waterfowl. Lake Merritt serves as a drainage basin for the regional flood control system, receiving urban runoff from a 4,650-acre watershed through 60 storm drain outfalls. Four creeks drain into this 145-acre lagoon from the east, while tidegates regulate flow to the south through a narrow channel that connects it with Oakland Inner Harbor and San Francisco Bay. The lagoon is also polluted by illegal dumping of substances such as paints, solvents, and oil, which are highly toxic to marine life. In addition to mechanical harvesting of its widgeon grass, 1,000 to 7,000 pounds of trash are removed from the lagoon every month. Merritt’s short-lived dream as a spectacular swimming hole in downtown Oakland is, in reality, more accurately described as a very large recreational sewer.

Despite all of its tarnish, the Jewel of Oakland has been a haven for some organisms that thrive on an abundant supply of bacteria and algae and tolerate the tidal, seasonal, and anthropogenic changes of this stressed environment. Among them are a few species of microscopic foraminifera (think of sand-sized shelled amoebas) that are being monitored by Ken Finger, Jere Lipps, and Dawn Peterson. Recent studies have shown that foraminifera might be useful environmental indicators of pollution. Lake Merritt presents an opportunity to study how they will respond to the remediation measures planned by the City of Oakland. Currently, only the shoreline of the lake supports living populations of foraminifera, while the deeper lake bottom is a dead zone of black mud stinking of methane. Why is that, you ask? Well, all of the algae, widgeon grass, bird droppings, and other organic waste that escapes harvest sinks to the bottom, and the process of their bacterial decomposition depletes the dissolved oxygen in the stagnant water just above. In contrast, wind-driven circulation keeps the surface waters and shallow margins circulating and aerated, enabling fish, invertebrates, plants, and foraminifera to survive.

But the foraminifera have a higher coincidence of malformed shells in Lake Merritt than in San Francisco Bay, which could be related to their stressed environment, where temperature, salinity, and oxygen levels change regularly. Studies elsewhere suggest that these micro-mutants result from high levels of contaminants, heavy metals, industrial pollution, and domestic sewage. In 2002, Oakland passed a bond measure that will clean up and improve the health of the lake by increasing tidal flow and installing aeration units. With these changes, will the shell deformities become less severe or more infrequent? Will living foraminifera begin to colonize the deeper parts of the lake? We hope to answer these and other intriguing questions as we continue to collect and analyze these minute “creatures from the black lagoon.”

Lake Merritt Dawn Peterson Ammonia tepida - normal Ammonia tepida - deformed Ammonia tepida

No backbones allowed

Erin in collections The UCMP Invertebrates Collection includes over 31,000 catalogued specimens! Corals, crabs, bivalves, snails, ammonites… both fossil and recent — if it doesn't have a backbone, it's in this collection. I am a UCMP and Integrative Biology graduate student and have been assisting with curation of the Invertebrate Collection. I catalogue and label specimens, process loan requests, manage the Invertebrates Collection database, curate private collections that are donated to the UCMP, and do numerous other small tasks. This might sound tedious, but I really enjoy the process of curation and am constantly exposed to exciting and unique inverts. Why am I interested in animals without backbones? Well, I was hooked after my first introduction to them during an Invertebrate Zoology course, while I was an undergraduate at Rutgers University. Since taking that class, I have traveled all around the world working on projects that focus on invertebrates, including crustaceans and mollusks in the kelp forests off of Alaska; gastropods, cephalopods, and corals in Bermuda; and bivalves in Thailand. My current research takes me to the islands in the Caribbean Sea and Western Atlantic. (Read more about my research on Caribbean inverts in my previous UCMP blog post!)

The UCMP Invertebrates Collection's 31,000 cataloged specimens may sound like a lot, but the collection contains far more than 31,000 individual invertebrates. The actual holdings are nearly impossible to accurately estimate because a single specimen number could be associated with 100 individuals.  Why do we keep so many individuals of the same species from a single locality? Well, having more than one individual is extremely useful to researchers, especially when they are investigating the morphological variation of a species, because the quality of the preservation can vary from specimen to specimen.

The collection consists of specimens that were collected by museum scientists, faculty curators, and graduate students in the course of their research, as well as specimens that were donated to the museum. Some of the major holdings within the UCMP Invertebrates collection include the USGS fossil invertebrate collection, the Crawfordsville crinoid collection, the Geological Survey of California fossil invertebrate collection, the Lambert modern coral collection. For more information about the special collections within the UCMP, please check out this article written by Jere Lipps, one of our Faculty Curators.

Working as Graduate Student Researcher in the UCMP has allowed me to experience what it is like to be a museum scientist, which is something that I may want to do after I finish my PhD. Also, working in the collections has exposed me to all sorts of amazing fossils that I never would have seen otherwise, including Tessarolax sp. (marine gastropods of the Cretaceous), the strange organisms of the Vendian, and rugose corals of the Permian, to name a few.

Check back to the UCMP blog later this fall and spring for more posts about my work with the Invertebrates Collection!

Tessarolax sp. Erin in collections

Stomatopods and DVDs

Odontodactylus scyllarus

Photo: Roy Caldwell

Sometimes, the study of basic biology can lead to technological advances, and a recent discovery about the vision of mantis shrimp is a perfect example, providing insight that could help us improve the technology inside DVD players. What is the connection? Circularly polarized light!

You're probably familiar with linearly polarized light. Fishermen often wear polarized sunglasses to reduce the glare from the water and make it easier to see the fish. Typically a ray of light vibrates randomly in all planes, referred to as e-vectors. When light reflects off water at a certain angle, only waves with certain e-vectors are reflected. A linear polarizing filter can be oriented to block those waves, allowing us to see the rest of the light that has passed through the water and is reflected by the fish below. But light can also be circularly polarized, travelling like a corkscrew, twisting either clockwise or counter-clockwise. We can’t see this property of light, but there is one animal that can!

Odontodactylus scyllarus is a stomatopod, or mantis shrimp, living in the Great Barrier Reef. Stomatopods have the most complex eyes in the animal kingdom. About a year ago, UCMP Director and Faculty Curator Roy Caldwell was part of a team of scientists who discovered that when light bounces off the hard exoskeleton of some stomatopods, that light is circularly polarized. What was particularly surprising was that the stomatopods responded to that light — they were capable of seeing circularly polarized light!  What eluded Roy and others was how.

Now colleagues have discovered that the stomatopods don't see the circularly polarized light directly. Special photoreceptor cells in their eyes, called R8 cells, filter/convert the circularly polarized light into linearly polarized light, which can then be sensed by other photoreceptor cells below it. The R8 cell is quite remarkable and might serve as a model for tiny manmade dual-function microsensors.

Manmade filters that convert polarized light are called quarter-wave retarders and are effective only across a very narrow band of wavelengths. The R8 cell (acting like a quarter-wave retarder) can filter light across a wide band of wavelengths, spanning the entire visual spectrum, into the UV spectrum.

There are lots of applications for a highly effective quarter-wave retarder, including DVD players. As DVD technology advances, people are already using circularly polarized light to create 3D movies — one eye sees the clockwise corkscrews of light, and the other eye sees the counter-clockwise corkscrews (Roy received some prototype 3D glasses using this technology and used them to verify that the stomatopods were producing circularly polarized signals!). Digital cameras along with many other optical devices also include quarter-wave retarders in their sensors.

We can learn a lot about optics from the stomatopod eye, and apply this knowledge to new technologies.

Want to learn more about stomatopods? Watch the UCMP video Field notes: Collecting collecting stomatopods on the Great Barrier Reef. And check out Secrets of the Stomatopod: An Underwater Research Adventure.

A summer studying snails in the Caribbean

Cpica_webI am a graduate student with the UCMP and the Department of Integrative Biology at Berkeley, and I study the biogeography, conservation biology, and microevolution of molluscs. From July through August of 2009, I traveled to nine islands in the Eastern Caribbean looking for Cittarium pica, a large, marine gastropod, or snail. This species has many common names, including West Indian Topshell, burgao, burgos, cingua, magpie shell, wilke, and “whelk”, which is why knowing the scientific name is so important!

Cittarium pica is the largest snail that lives along rocky coasts, reaching a maximum width of 13.6 cm! Since at least the Pliocene, about 5.2 million years ago, the species has lived in the West Indies and along the Caribbean coasts of South and Central Americas. Humans have fished this snail since they first arrived in the region, eating the meat and using the shell for both jewelry and as tools.

Conducting research on the islands of the Caribbean and Northwestern Atlantic is a breathtaking experience, both because of the spectacular views and because it’s hard work! When I found locations on the islands with C. pica populations, I recorded the size and location of individuals within the intertidal zone. I will use this information to assess the fishing pressure on island populations, determine the habitat preferences of the species, and map the distribution of habitat during the Pleistocene. This map can then be used to predict the future distribution of C. pica habitat as the sea level rises due to global warming. During the Pleistocene, sea level fluctuated from ~130m below to ~6m above present day sea level!

At each site, I also collected tissue samples from 25-30 snails (taking them does not fatally harm the animals) to determine the genetic variation of the species on both local and regional scales. These data will provide information on the patterns of larval dispersal within the region and help to identify populations that are at high-risk of local extinction (due to low genetic diversity).

During six weeks of fieldwork, I collected 385 tissue samples from 13 different field sites, conducted ten population surveys, recorded habitat and size information for 2,542 individuals, and collected shells from each site. Whew! I had a busy six weeks! While exploring the rocky coastlines, I also found C. pica fossils in Barbados and several locations with fossil corals. I didn't have a permit to collect fossils, so I'll have to return to those sites in the future.

This trip was the third of four field seasons for my dissertation research. To read more about my summer adventures, please check my research blog.

My 2009 fieldwork was funded by the American Museum of Natural History, Unitas Malacologica, and the Reshetko Family Scholarship Fund.

Cittarium pica Anguilla Barbados C. pica fossil Map of the Caribbean C. pica shell tools

Rudists

RudistNot to be rude, but what in the world is a rudist? Well, rudists are invertebrates, and they lived in the world’s oceans during the late Jurassic and the Cretaceous, about 150-65 million years ago; they are now extinct. They are bivalves — the name means “two shells.” Today’s familiar bivalves, clams and mussels, have two shells that are more or less symmetrical. But rudists were a bit unusual: their two shells were very different from each other. One shell was either conical or coiled, and it was attached to the ocean floor (or neighboring rudists). The other shell sat on top, like a little hat. The organism lived inside. They were probably filter feeders, feeding on plankton in the water, like many other bivalves today.

Rudists would grow on top of one another and form rudist reefs. They were the major reef-building organisms of their time — corals weren’t so abundant back then. Reefs are really important habitats for other marine organisms, like fish and crustaceans. So rudists played an important role in the ancient ocean.

So if rudists were so ecologically important, how did they get stuck with such an odd name? Lamarck dubbed them rudists in 1819, but it’s a little unclear what he meant. The Latin word rudis means rude, raw, or uncultivated. The Latin word rudus means rubble, or broken stone — specifically, the stones that made up Roman roads. Rudists do seem sort of coarse and unrefined, and they do look an awful lot like stones. But who knows what Lamarck was thinking.

This fossil rudist was found in Chiapas, Mexico. Learn more about rudists on the UCMP’s rudist page.