Looking for Loxo

It may be a Saturday, but today had a work day format: get up at 6:45am, work in the field all day, and get off at 4pm. However, I wasn't doing work in the biogeochemistry department! I was helping out the invasions lab with a survey of introduced parasites on native mud crabs in Chesapeake Bay! 

Part of being here is taking full advantage of this amazing opportunity I have been given. And the entire Smithsonian Institution, including the SERC, encourages everyone here to reach out of their comfort zone and out of their specific niche. So, when an email went out last week asking for volunteers to help the invasions lab this weekend, I signed up right away, and got excited to spend the day with the crabs!  
 
So, before I jump right into what I did all day, I'm going describe the big picture concept of the entire project. An invasive parasite is attacking native White Fingered mud crabs in Chesapeake Bay. The parasite Loxothylacus panopaei (nickname Loxo) is a barnacle with a highly evolved life cycle, perfectly structured to be a crab parasite. This parasite's female larvae are free swimming, then attach themselves to the crab's abdomen by burying themselves into the crab's carapace.  Once inside the larvae undergoes a series of physiological and morphological changes, and in the process assumes control over the host crab, controlling major functions such as molting and reproduction. After a while, the larvae becomes an adult and forms small reproductive bodies that protrude from the crab, as indicated by the arrow in the picture above. A free swimming male larvae then fertilizes these eggs, and once fertilized thousands of baby larvae are released from the crab. Loxo completely destroys the crab's ability to reproduce because the crab is parasitized and tricked into caring for Loxo's larvae by the parasite.

Thus, today we surveyed for crabs, they will be taken back to the lab at SERC to be examined under the microscope for any indications of the Loxo parasite. At each site, there was four crab condos (they are condos, not traps because the crabs can go in and out as they please) filled with oyster shells to attract the crabs. The condo was removed from its place on the bay bottom, emptied into a sieve, then we manually sorted through the sieve for crabs.
There were other marine animals too, like eels, shrimp, fish, and anthropoda. Once, we found all the crabs in that condo, we filled it back up with oyster shells, and redeployed it. Then began the next one. We got a good rhythm going. The crab I'm holding is one of the larger ones, the smallest ones were only 2mm big! 

The crabs we collected today were put in ethanol to preserve them and taken back to SERC to be sexed, measured, and examined for the Loxo parasite under a microscope.This study is connected to another one on the West coast of the United States, where mud crabs are also present. There is concern that the Loxo parasite could spread to the West Coast, so investigations here concerning Loxo will be useful in lessening the effect of the Loxo when it makes its way over, or even preventing the parasite from going to the West Coast to begin with.

It is amazing that a small parasite can cause so much damage to a crab! Even with their tough exoskeleton, crabs are not invincible; this parasite makes its way into the crab, attacks the crab, then controls it. The mechanisms of this control is not fully known. I am fascinated about this study, especially how this mechanism works. 

The video below was made by the invasions and crab labs at SERC last year to describe this experiment, possible causes for Loxo presence in certain areas including temperature and/or salinity, and possible repercussions in the future for the crab populations and the entire Chesapeake Bay ecosystems.