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Hunting ­Zombie Crabs

Citizen scientists join the search for other life forms

With summer comes longing for adventure. Motivated to engage with nature and be a part of something bigger, I signed up to study the parasite Loxo and mud crabs at Smithsonian Environmental Research Center.
    Small by any standard, the white-fingered mud crab, aka Atlantic mud crab, is “small as a flea” or large as an inch, according to Smithsonian scientist Alison Cawood. This small crustacean plays a large part in our Bay’s ecosystem. A key indicator species, it preys on oysters, barnacles and worms, at the same time serving as a snack for birds, fish and other critters.
    It is also the unwilling host of a “bodysnatching parasite,” an invasive species called Loxothylacus panopaei. A pointy headed member of the barnacle family, Cawood explains, Loxo burrows into the mud crab during its molt, when it’s most vulnerable, and hijacks its body. It does this dastardly deed by injecting fewer than 200 cells into the crab’s nervous system. Once in, these cells take over. The crab becomes “a barnacle in a crab suit.” Loxo even uses the crab to carry its offspring, parasitic larvae, in its external sack.
    With a five-minute instructional how-to and tiny forceps, our group of 12 pull mud crabs out of small milk crates filled with mud and oyster shells, all gathered from sample sites on the Rhodes River. The result of our intricate game of I Spy is a jar full of lively crabs to be further studied for zombification by scientists and lab-certified volunteers.
    Our final task is to check another team’s milk crate remains for missed mud crabs. These crabs would be not only examined for the virus but also cataloged by number and size for another ongoing study.
    We volunteers were the subject of that second study, our accuracy factored with age, time spent, educational level and previous field study experience. This is important for Smithsonian Environmental Research Center, which depends on some 6,000 hours annually of volunteer research in its ongoing studies.
    If you take the time to get scientific this summer, you will learn odd things and find it rewarding. For upcoming opportunities for citizen scientists, check Bay Weekly’s 8 Days a Week.