Katrina Lohan packs rubber gloves, Ziploc bags and other field essentials for a science expedition. (Kristy Hill)
Katrina and I leave for Panama City in next week, so we’re gathering supplies and mapping out our game plan. We’re stoked to get this project rolling—beautiful surroundings and mandatory snorkeling in the tropics won’t be such bad work!
The critters we’re looking for grow on coral reefs, mangrove roots, sponges, pilings, sea walls and rocks. Our goal is to collect at least 50 to 60 oysters of three or four different species from three sites along the Caribbean coast. At each site, we’ll take water quality measurements such as salinity, temperature and oxygen content. We’ll take additional notes about the oysters’ habitats, such as their distance from the shore, the depth of the water, their proximity to ports or marinas, etc. We want to obtain as much data (or information) as possible so we can better understand the environment where the oysters and their potential parasites live.
by Katrina Lohan, Smithsonian Environmental Research Center and National Zoo postdoc
Many people cringe when they hear the word “parasite”—not Katrina Lohan and Kristy Hill. Combined, the two of us have spent 12 years conducting research on parasites that infect bivalves (oysters, clams, mussels, etc.), crustaceans (crabs, shrimps, lobsters, etc.), and songbirds. We are both passionate about studying marine parasites and want to better understand how parasitism impacts marine animals. For the next few months, we’ll be searching for these parasites in waters all along the east coast of North America, from Maryland to Panama.
Katrina Lohan (right) and Kristy Hill are preparing to scour the coasts of North America for marine parasites infecting oysters and other shellfish. (Kim Holzer/SERC)
Artist's depiction of the prehistoric synapsid Varanodon agilis (left) under attack from an ancient amphibian. (Wikimedia Commons/Smokeybjb)
Milk—the white, calcium-rich liquid common to mammals and refrigerators across the globe—may have evolved long before the mammals that secrete it. It may have evolved even before dinosaurs. It’s an idea SERC lactation expert Olav Oftedal proposed a decade ago and is now gaining momentum among biologists who study the evolution of what we drink.
Tom Mozdzer explores a patch of invasive Phragmites in SERC's global change wetland.
Is it better to be a jack of all trades or a master of some? In the plant world, it’s possible to do both–and that could make a huge difference in deciding which plants dominate under climate change. This holds especially true for one: the invasive reed Phragmites australis. Its ability to alter its anatomy enables it to grow well in just about any environment, including one spiked with CO2 and nitrogen, SERC ecologists discovered in a study published Oct. 31.
Plants like this are called “jack-and-master” plants. Typically, the most competitive plants surpass their neighbors through one of two strategies. “Jack-of-all-trades” plants do moderately well under most scenarios. Their competitors will surpass them when conditions are good, but if the environment becomes stressful, the jack of all trades will grow better. “Master-of-some” plants do very well under only a few conditions, so if the environment shifts in their favor, they are certain to emerge victorious. But a few types—the jack-and-master plants—can use both tactics. And the invasive Phragmites is one of them.
Homestead House, called Woodlawn by its first residents in the early 1700s. (SERC)
On the western shore of Chesapeake Bay, less than a mile from the Rhode River, there is an old red house on an abandoned farm. Once, in the 18th century, it belonged to a thriving plantation. The hilled rows of tobacco have vanished, along with the slaves and field hands who planted them. But the scars on the landscape remain. The surrounding earth carries traces of how each of its inhabitants have used it, or abused it.
The house’s first inhabitants in the early 1700s called it Woodlawn. Today it is known simply as the Homestead House. The building and its surrounding farmland now sit within the Smithsonian Environmental Research Center. Instead of slaves and field hands, teams of volunteers are overturning the soil in search of clues about its past.
Archaeologist Jim Gibb began the excavation at SERC earlier in August. His volunteers come for a single afternoon, or several weeks. He isn’t terribly picky about long-term commitments. Gibb welcomes anyone who can handle a shovel and is at least ten years old (and even that rule is flexible). Under his guidance, they are piecing together the story of one household’s legacy on the land.
The team made one of their biggest discoveries just a few weeks into the project, when they uncovered a brick foundation sprinkled with household artifacts. One possibility is that it was a storage shed. Another, that it was someone’s home.
“If someone was living in that in the early 19th century, and we know where the owners were living, then we do the math,” Gibb said. “They have to be labor. And at that point, probably slave labor.”
Propellor of a transient boat, veiled beneath a thick layer of biofouling. (Ian Davidson)
If several pounds of plant and animal material were attached to the underside of your car, slowing you down and increasing your fuel costs, you’d probably be concerned enough to remove it. The same applies to boats. But since boaters don’t have easy access to the undersides of their vessels, it can often be a surprise to discover large communities of organisms residing and hitchhiking on their hulls and running gear.
Slide of an oyster completely infected with Dermo.
Oysters in Chesapeake Bay face more dangers than overfishing and habitat loss. Over the last few decades they’ve also had to contend with crippling disease outbreaks. And according to marine ecologist Denise Breitburg, the wild day-night fluctuations in Bay waters aren’t helping.
Some of the most horrific images in high school biology textbooks depict parasitic tapeworms blocking the intestines of humans, or inside an unfortunate dog or cat. But not all flatworms are parasites, and their free-living cousins are capable of equally gruesome feats of nature. The slender flatworm Euplana gracilis consumes its victims by sucking out their insides, as displayed in the video above from benthic ecologist Dean Janiak.
It starts by wrapping its body around the dorsal (back) side of its prey–in this case, a shrimp-like amphipod. A massive struggle ensues until the amphipod is completely immobilized. Then the flatworm begins to feed. Sticking its tube-like pharynx through a segment of the amphipod, the flatworm consumes and digests its internals–a process that takes about half an hour. Once finished, it abandons the empty carcass and goes into a resting period until its next meal. On the outside, an amphipod that’s been eaten doesn’t look that different from a normal amphipod…except for the fact that it’s, well, dead.
Infected crab. The sacs on its abdomen contain thousands of parasite larvae the crab will later release into the water.
The world is full of parasites that can force their hosts to do strange things. One such parasite lurks in Chesapeake Bay: an invasive barnacle that hijacks a mud crab’s reproductive system and impregnates it with parasite larvae—even if the crab is male.
The invasive parasite Loxothylacus panopaei (Loxo for short) is a type of barnacle, but looks and acts nothing like the typical barnacles growing on rocks along the shoreline. Loxo has a highly evolved life cycle, essentially custom-made for acting as a crab parasite. As a free-swimming larva, Loxo resembles a typical barnacle larva. A female larva infects a recently molted crab by burying into its shell. Once inside, she undergoes a series of changes and assumes control over the host crab, dictating major functions such as molting and reproduction.
A large adult male Aratus eating a juvenile of its species. (Megan Riley)
As adults, mangrove tree crabs (Aratus pisonii) tend to forage on fresh mangrove leaves in the canopy. As omnivores, they will also prey on nitrogen-rich insects, larvae, and even juveniles of their own species. However, it’s unclear how these organisms balance their nitrogen requirements and other nutritional demands. This summer I have focused my research on addressing this question. Specifically, I am investigating how their diet choices affect their overall health and ability to reproduce.
In order to perform this research, I first have to catch the Aratus! Despite the abundance of these animals in mangrove stands on the Indian River Lagoon, tree crab hunting is a tricky business. Over the course of the summer, I’ve learned a number of tips for trapping the elusive crustacean…