12.20.07

Planting the Seeds of Change

Posted in Eastern Shore, GPS, Hog Island Bay, Jacob Canon, The Oscar Show, UVa College of Arts & Sciences, University of Virginia, VIMS, Virginia Institute of Marine Science, coastal bays, crustaceans, environmental science, environmental scientist, marine life, restoration at 11:55 am by Jacob Canon

Today, from an article found on the Oscar web site written by Faris Samarrai, we discuss the efforts being made by environmental scientist Karen McGlathery to reestablish the natural environment needed to insure those crustaceans and other marine life can thrive and return to their previous population levels on Virginia’s Eastern Shore.

As environmental scientist Karen McGlathery slips from the side of the boat into the shallow, murky waters of Hog Island Bay, one of three major lagoons on the oceanside of Virginia’s Eastern Shore, the chill of the morning water hits her, she exclaims “Oh, that’s cold.”

McGlathery is the University of Virginia’s lead investigator on a project to restore sea grasses to the region. Last fall she worked with a team of scientists from VIMS, the Virginia Institute of Marine Science, to seed a 500-acre area of Hog Island Bay with eelgrass, a submerged sea grass that is common in temperate waters worldwide. It was hoped it would establish a meadow that may eventually spread outward, potentially propagating new areas.

McGlathery and her team of graduate students, a few undergrads and even a couple of local high school students, are now back to see if the grass is growing. The team finds the site using GPS — the Global Positioning System — to pinpoint their plots, which are not visible from the surface of the turbid water. They wade and snorkel along the beds, taking measurements of the length of the grass and the extent to which it has spread. They also take core samples from the muddy bottom, and water samples for later analysis. McGlathery said, “what we learn from these studies will help us determine the baseline conditions for future restoration efforts.”

Sea grass once flourished in the seaside bays of the Eastern Shore. But in the late 1920s and early 1930s a pathogen began killing the grasses. A hurricane in 1933 essentially finished them off. In the years since, the bay bottoms have been mostly muddy and barren. A once thriving scalloping and fishing industry collapsed. “I’ve read accounts by old watermen of how the water here was once crystal clear and that the sea grass meadows were so extensive and visible from the surface that it looked like a lawn of long grass,” McGlathery said.

Not anymore. The water is murky green most days and even muddy on windy days. Without extensive sea grass beds to stabilize the bottom, the sediment is continually stirred up, blocking out the sunlight needed by eelgrass to photosynthesize and flourish. But when grasses grow well, they stabilize the bottom, clear up the water and serve as habitat for an assortment of creatures: scallops, crabs, shrimp, mollusks, and the fish that feed on these animals.

McGlathery is encouraged by what she is finding. Most of the half and one acre plots in the 500-acre area are doing well. Apparently, about 10 percent of the 1.5 million seeds that were scattered last fall took root and the plants are growing. Many are 12 to 18 inches long. McGlathery is not surprised. Prior to the seeding, she and her team surveyed the area, tested the sediment and the water quality, and determined that the area might be receptive to a crop of eelgrass.

VIMS has conducted similar work during the past 10 years in South Bay, a lagoon to the south of Hog Island Bay, that extends between the barrier islands of the Virginia. “In areas of South Bay there are now lush sea grass beds… as far as you can swim, continuous meadows,” McGlathery said. “It shows that we can not only get these grasses to grow, but we can also get them to thrive.” And recently, scientists discovered a few sparse natural areas of eelgrass in Hog Island Bay, likely seeded by tide and current from the manmade beds in South Bay.

It is hoped that these restoration efforts will allow the coastal bays to regain their health and vitality, leading to the return of the indigenous marine populations in the waters of the Eastern Shore.

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12.13.07

Inside the brain of crayfish

Posted in Biology at the University of Virginia, DeForest Mellon, The Oscar Show, University of Virginia, biology, brain, crustaceans, evolution, nervous system, neurophysiology, sensory inputs, visual processing at 11:37 am by Jacob Canon

Today’s show, from an article published on the Oscar web site written by Fariss Samarrai, we examine lobsters and other crustaceans. What most people think of as food, is being utilized by UVa biology professor DeForest Mellon in his research of how the brain detects, integrates and uses co-joined yet dissimilar sensory inputs.

Imagine you are on a voyage to the bottom of the sea, or simply looking along the bottom of a clear stream observing lobsters or crayfish waving their antennae. Looking closer, you see them feeling around with their legs and flicking their antennules — the small, paired sets of miniature feelers at the top of their heads between the long antennae. While the long antennae are used for getting a physical feel of an area, such as the contours of a crevice, the smaller antennules are there to both help the creature smell and also to sense motion in the water that could indicate the presence of food, a mate or danger. The legs also have receptors that detect chemical signatures, preferably those emanating from a nice hunk of dead fish.

“They constantly flick their antennules,” says DeForest Mellon, a University of Virginia biology professor, “it is doing two things that are processed simultaneously in the brain as he flicks: smelling the water, and also sensing motion in the water, which can indicate the presence of food or other things of interest.” Mellon said, “I’m interested in understanding how these senses are combined and interpreted in the brain of these animals. My question is how does the brain detect, integrate and use these co-joined but dissimilar sensory inputs?”

“We taste food by a combination of senses, taste, aroma, texture and how good that dish looks. This complex process of brain processing is not much different with crustaceans, though their brains are much simpler, which makes them a great study model,” Mellon says. Mellon and other neurophysiology researchers commonly use crustaceans to try to gain basic understanding of the nervous systems of creatures in general. Extrapolating what they find to gain a basic understanding of the much more complex human brain.

Mellon says, “due to the large-sized nerve cells of invertebrates, we can conveniently and practically examine these systems that are largely the same among all creatures, and antennule flicking can serve as a practical model that helps us understand how two or more senses work together in the brain.”

Mellon has been investigating sensory systems for half a century, since his grad school days at Johns Hopkins University. And he’s still learning. Recently Mellon perused the research in the field — his own and that of many other scientists — of the past 45 years or so and published a review of the literature in the August 2007 issue of The Biological Bulletin.

What he’s found is that there is still much to be understood. “It’s fertile ground for ongoing research,” he said. “The size of an area of the brain devoted to a particular sense gives us a good idea of how an animal perceives the world. About 40 percent of a crustacean’s brain is devoted to the sense of smell. This shows how important detecting odors are to the animal.” “Crayfish and lobsters are generally solitary creatures, inhabiting an aquatic environment that is often dark, and they need that highly acute sense of smell.”Humans, by contrast, have less than 1 percent by volume of the brain devoted to interpreting smells, but about 30 percent of the human brain is concerned with visual processing.

Mellon said, “I have always been fascinated by the diversity of animal types and their equally diverse behaviors. Both are genetically based. And through often very subtle adoption of genetic variations in different animals, evolution has arrived at different solutions to common survival problems. This behavioral diversity and the variants in nervous system organization account for why I remain fascinated with biology.”

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