PARASITIC CASTRATION & ZOMBIE CRABS

From hairworms to cordyceps, the Zombie Research Society has studied a number of terrifying and deadly parasites. But a PhD student at the University of Alaska Fairbanks School of Fisheries and Ocean Sciences has recently unleashed an important new thesis regarding an otherwise overlooked and nearly forgotten horror; Briarosaccus callosus.

Practically ignored and unstudied since an outbreak among Alaskan crabs in the 1980s, this parasitic barnacle can actually control, castrate, and feminize its host! Briarosaccus callosus eventually influences their behavior with the sole purpose of infecting others with its larvae, creating what marine biologist Leah Sloan refers to as “zombie crabs.”

Parasitic barnacles can influence the behavior and morphology of host crabs to favor the production of their own larvae. For example, infected crabs will groom the parasite’s externa as if it was their own egg sac, and pump their abdomens to assist with parasite larval release. In addition, many rhizocephalan species cause feminization of male crabs. Despite the physiological, morphological, and behavioral changes these parasites cause in the host, no one has ever determined how the parasite “takes control” of its host and manipulates its behavior.

Because males crabs that carry the parasite are much smaller and can easily be mistaken for females, government regulations require that fishermen actually throw the infected crabs back into the water, propagating the population of the parasite itself. But thanks to the research of Leah Sloan, this new focus on Briarosaccus callosus may eventually help us prepare and better understand the potential source of a future zombie-like parasite!

For additional details please read the original thesis titled “King crabs: Environmental effects on their parasitic castrator (Briarosaccus callosus), metabolic effects of B. callosus, and practical applications of fishery log books” via the University of Alaska Fairbanks. You can also read or listen to this great report online by KRBD reporter Leila Kheiry.