2016 Volunteer for a Survey of Introduced Parasites on Native Mud Crabs in Chesapeake Bay 

June 10-12, June 17-19, August 19-21, and August 26-28
Registration Required!

Project Description

The reproductive bodies of the Loxothylacus panopaei parasite protruding from the abdomen of a White-fingered Mud Crab.

An introduced parasite is affecting native mud crabs in Chesapeake Bay. The parasite Loxothylacus panopaei (Loxo for short) is a type of barnacle that is exceptionally modified, with a highly evolved life cycle tailored for its life as a crab parasite. Loxo larvae are free-swimming. Female larva infect recently molted crabs by burying into the carapace. Once inside she undergoes a series of physiological and morphological changes and assumes control over the host crab, controlling major functions such as molting and reproduction. After a time Loxo grows into a reproducing adult and forms small sacs (reproductive bodies) that emerge through the abdomen of the crab, usually after the crab molts. After fertilization by a free-swimming male Loxo, the sacs are filled with of thousands of larvae that are released into the water to seek out a new crab host. This process eliminates the crab’s ability to reproduce and results in the crab caring for the developing larvae of the parasite. Both male and female crabs are parasitized and both are tricked into caring for the larval parasites.

Loxo are native to the Gulf of Mexico, the Caribbean, and parts of Florida and parasitize several species of mud crabs throughout this range. The first discovery of the parasite in Chesapeake Bay was in 1964 on the native White-fingered Mud Crab (Rhithropanopeus harrisii) in the York River. The parasite is now common in much of the Bay, but the population and abundance varies greatly between years. Mud crabs are easily transported with oysters, and Loxo was likely transported to the Chesapeake with mud crabs caught up in shipments of oysters from the Gulf of Mexico.

SERC volunteer Donald Mitchel Brumsted dumps a crab collector on the sorting screen. Photo by Monaca Noble

Intern Kristin Maglies and SERC biologist Jessica Morris sorting through the oyster shell picking out all of the mud crabs. Photo by Monaca Noble

Researchers at the Smithsonian Environmental Research Center (SERC) having been studying the prevalence of Loxo in populations of the White-fingered Mud Crab, R. harrisii, since the 1990s in hopes of understanding how this introduced parasite affects the mud crab population. The White-fingered Mud Crab is native to and abundant in Chesapeake Bay. Starting in 2003, Dr Gregory Ruiz and others have collected mud crabs every summer from many sites in Maryland including sites near Oxford, Broomes Island, Deale, Galesville, and SERC.

Volunteers will come to SERC, Oxford, or Broomes Island to hand-collect crabs from habitat collectors, or crab condos, which are small plastic crates filled with dead oyster shells that sit on the surface of the sediment. These crates stay in the water for two months, during which time mud crabs take up residence between the oyster shells. After two months, each crate is pulled up and the crabs are hand-collected from the oyster shell habitat. Back in the laboratory SERC staff will measure, sex, and examine the crabs for outward signs of the Loxo parasite.

Volunteer Information

Collection will take place during two weekends in June (June 10-12 and 17-19) and two weekends in August (August 19-21 and 26-28). We can accommodate 15 volunteers per day. We prefer volunteers 16 years old or older, younger volunteers are welcome with parental supervision, but please note this project is not appropriate for young children. Volunteers will be separated into two teams. Each team will collect crabs from at least two crab collectors. 

What to bring: Please bring a lunch if volunteering all day, water will be provided. Ware clothing that can get damp and muddy. We will not to in the water, but you can still get your feet wet. Be prepared to be outside. Bring rain gear, we will not work in heavy rain, but will work in light drizzle. 

Transportation is not provided and unfortunately their is no public transportation to SERC or our other survey locations. Fridays we will meet at either the Cooperative Oxford Lab or the Patuxent Environmental & Aquatic Research Laboratory (PEARL). We will be at the SERC dock on the weekends and will meet at the Reed Education Center for oriantation. 



Watch the video below for an inside look at the Loxo parasite:

Summary taken from the September 2012 feature story.