Balaenophilus: More than a turtle bully?

            Badillo et al. (2006) expanded on what little is already known about Balaenophilus, specifically questioning the status of Balenophilus unisetus and Balaenophilus umigamecolus as parasites and not commensalists. The study looked at B. unisetus and B. umigamecolus in host species that were taken from their natural habitat. Badillo et al. (2006) examined 20 fin whales (Balaenoptera physalus) that were captured off of Northwest Spain. The sample group was examined for signs of B. unisetus and heavy infections of the parasite on the baleen plates of the whales were found. The study also examined 52 Caretta caretta that were caught off the Mediterannean coast of Spain for B. umigamecolus.

            Individuals of B. unisetus had visible food pellets in their guts that were examined and were determined to have baleen tissue, and they also stained positive for keratin. There was evidence that B. unisetus found on whales at other locations may also be eating keratin because gut contents found partially digested unicellular algae and plastids (Badillo et al., 2006). Baleen plates of whales are composed of nonliving tissue that grows continuously and is easily pulled up by B. unisetus without causing harm to the host. This indicates that there is a possibility that the parasite is actually a commensal, but that was not conclusive from this study.  It is a possibility that the parasite consumes more than one food source, especially considering that Harpacticoids have a history of eating a variety of substances.

            The investigation into B. umigamecolus was much more definitive in classifying the organism as a parasite. There were no food pellets found in the gut, so no immunohistochemistry analyses could be run on the food pellets for keratin. Immunohistochemsitry analyses run on the stomach turned up negative for any trace signs of keratin, indicating that B. umigamecolus is a parasite (Badillo et al., 2006). The only sign of feeding were two individuals with tissue in their mouths that was identified to be C. caretta tissue.

More interesting than the status of B. umigamecolus is the effects that were seen and the locations that it was found in. The parasites were found primarily on the soft tissue of the turtles, at the hinge region between limb scales. There was a correlation between the parasitemia and the host reaction. Individual hosts with around 600 or more parasites had a mild reaction in the first few layers of skin that consisted of more fibroblasts, perivascular lymphoid infiltrates and aggregating granulocytes (Badillo et al., 2006). There was even a single individual with several skin lesions that were reported by the authors, but no reasoning was given. I expect the infected C. caretta had a long term infection or a compromised immune system that made the pathology much more apparent.

Badillo et al. (2006) expanded on the species description of Balaenophilus umigamecolus that was done by Ogawa et al. in 1997. Ogawa et al. (1997) discovered B. umigamecolus and gave a detailed description of morphological characteristics that identified it as a separate species from B. unisetus. There was no detail into the diet of either species, and that is something that is uniquely expanded upon by Badillo et al. (2006). The investigation done by Badillo et al. (2006) provided more insight into the life cycle and pathology of B. unisetus and B. umigamecolus. The evidence that B. unisetus is capable of consuming keratin may be why the parasite lives on the baleen plates of whales and isn’t very pathogenic. The pathology that was present in C. caretta infected with B. umigamecolus showed that B. umigamecolus can be very pathogenic to its host and that there are visible and autoimmune reactions that support that.

Work Cited:

Badillo, F.J., L. Puig, F.E. Montero, J.A. Raga, F.J. Aznar. 2006. Diet of Balaenophilus spp. (Copepoda: Harpacticoida): feeding on keratin at sea? Marine Biology 151: 751 – 758.

Ogawa, K., Matsuzaki K., Misaki H. 1997. A New Species of Balaenophilus (Copepoda: Harpacticoida), an Ectoparasite of a Sea Turtle in Japan. Zoological Science 14: 691-700.