Monday, March 7, 2011

Crab parasites

A while back my friends and I were talking about crab parasites. We got to this topic when clarifying that the crabs I study are Chionoecetes opilio and not Pthirus pubis, the type of “crabs” that parasitize mammals.

that's not something I would advertise

We wondered what type of parasites crustaceans may come across. One is the barnacle Briarosaccus callosus, which is found in king crabs.

These nasty little rhizocephalans hijack the hosts’ reproductive process by sterilizing them, using their energy to make thousands of cyprid larvae (how scientists know these blobs are in fact barnacles), and coercing them to protect the parasitic pirates.

a scarlet king crab Lithodes couesi
host with the most!
(the red blob is the parasite)

Paralomis hirtella with its own pink-ish rhizocephalan
reported here

They almost make "crabs" sound not that bad…

Read more:
Isaeva, V. V., S. M. Dolganov, and A. I. Shukalyuk. 2005. Rhizocephalan barnacles—Parasites of commercially important crabs and other decapods. Russian Journal of Marine Biology 31: 215-220.
DOI: 10.1007/s11179-005-0075-9


  1. Ok, so the red blob labeled the "parasite" in the Tom Shirley photo- is that actually a barnacle egg-mass?!

  2. I laughed like crazy at the would be fitting at both Anderson and Lena!

  3. Hey Rhys! The red blob is the "externa" of the parasite, which includes the ovaries. The embryos develop there too. The paper (Isaeva et al., 2005) calls it, "the set of organs of the reduced adult female organism", so it's basically one big egg-mass! (The "interna" of the parasite are root-like structures that are hidden within the host.)

  4. Considering how people like to eat snow crabs, and the parasite is also a crustacean. I'd think that the flesh of the externa would be extremely similar to the snow crab itself, almost like a huge chunk of crab meat crab meat lovers eagerly break open their claws to obtain.

    While it's not crab muscle like most crab meat, it is definitely "flesh" and should be similar to the flesh of a soft shell crab that people eat whole.

    So I'm wondering if our natural revulsion re the externa and its parasite ways have made us overlook a novel way to vastly increase the productivity of the snow crab for consumption.

    Additionally, the externa also resembles the fleshy stalk of the goose barnacle which is eagerly sought after in cultures that eat them.

    1. That's an interesting idea - the parasite is, in fact, a barnacle, so you were right in that connection! The externa is, as far as I know, made up of internal organs including the ovaries. While edible (I know some people seek out crustacean roe to eat) it would be quite different from the muscle tissue of the king and snow crabs we know and love. Nevertheless, if you find a rizocephalan and cook it up, let me know how it tastes!