Newswise — Joseph Kunkel, professor of biology at the University of Massachusetts Amherst, has received a two-year, $200,000 grant from the New England Lobster Research Initiative to study shell disease in lobsters.
The disease was first identified in the 1980s, when researchers noticed spots containing a dark pigment called melanin on lobster shells. Since then, the problem has been growing, particularly in warmer waters off the coast of southern Massachusetts and Long Island Sound.
Shell disease starts when bacteria invade microscopic pores in the hard outer shell or cuticle that protects the lobster. To erode the cuticle, the bacteria must cut through the calcium-bearing minerals that make up the shell and line the pores, principally calcite. The damage activates enzymes in the cuticle that produce melanin, causing brown spots. This process, called melanization, is the lobster's attempt to wall off the attack.
Kunkel's research will focus on how shell disease affects these minerals and whether mineral destruction is involved in starting the disease. "Shell disease involves the eventual demineralization of the cuticle, but we don't know if this occurs in the early phases of the disease or where in the cuticle this process takes place," says Kunkel.
Kunkel will examine the cuticle of live lobsters with a non-invasive ion probe to locate points where the chemistry indicates the presence of bacterial attack, but visible lesions have not yet formed. "Bacteria secrete acids and use them for locomotion as well as other work," says Kunkel. "We will be looking for places that show the use of protons from acids to attack the cuticle and the release of carbon dioxide from the calcite, as well as the defensive uptake of oxygen involved in the characteristic melanization."
The mineral structure and composition of specially prepared samples will also be analyzed using the Ultrachron electron microprobe developed by Mike Jercinovic and Mike Williams of the UMass Amherst department of geosciences. After performing the analytical work, the early stages of shell disease will be mapped and related to the process of demineralization. A map of the texture of the attacked surface will also be studied with an atomic force microscope in collaboration with Lynne McLandsborough of the UMass Amherst department of food science. Kunkel is one of nine researchers who received funding from the New England Lobster Research Initiative. Other projects in the initiative will study the role of environmental factors in shell disease, the microbes involved, how the disease is transmitted and how it affects lobster physiology and populations. Results will be shared at semi-annual meetings to chart progress and encourage communication.
The New England Lobster Research Initiative is a federally funded program that is jointly administered by the National Oceanic and Atmospheric Administration's Marine Fisheries Service, the University of Rhode Island and the Rhode Island Sea Grant.
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