Researchers Study Parasites in Mosquitofish Collected from Local Waters

Dominican University faculty and undergraduate students initiated a research project in fall 2004 in collaboration with Dr. Anindo Choudhury of St. Norbert College in Wisconsin and Dr. Scott Bonar of the University of Arizona to determine whether the Asian tapeworm (Bothriocephalus achelognathii) has spread from Southern to Northern California.

The Asian tapeworm has been found in tui chub in the Mojave National Preserve. This fish is included in the U.S. Fish and Wildlife Service’s list of endangered species. The parasite has also been found in the Arroyo chub near San Diego.  Currently, Dominican University has been looking for the Asian tapeworm in Gambusia affinis (mosquitofish) as part of a general study that includes several other native and non-native species of fish.  If the parasite is present, the investigators hope to determine the extent fish species are infected.   The parasite has been found throughout the Southwestern United States, and it is responsible for mass mortalities of fish in Europe. 

Although no evidence of Asian tapeworm has been discovered in Northern California, the Dominican team discovered 13 internal parasites in eight of 301 mosquitofish collected from Marin and Sonoma counties. Dr. Choudhury, who identified the parasites, currently is collaborating on this project with Drs. James Cunningham and Sibdas Ghosh, chair of Dominican’s Department of Natural Sciences and Mathematics. 

The parasites belong to three separate groups and were identified as: Octospiniferoides chandleri (Acanthocephala), metacercariae in the family Clinostomatidae (the genus and species have not yet been determined), and Clinostomum metacercaria (the species has not yet been determined). The acanthocephalan Octospiniferoides chandleri, according to Dr. Choudhury, may be non-native to the San Francisco Bay Area. Generally, acanthocephalans cause localized pathology in the gut of their hosts, but there have been rare reports of severe pathology causing death or debilitation in fishes.  It has yet to be determined whether this Octospiniferoides can shift to new hosts and cause severe problems.  The two larval forms of the family Clinostomatidae are under investigation.  Given how common clinostomatids are in some fish-eating birds and how widely distributed that family of parasites is, it is likely that mosquitofish are simply one more intermediate host in the life cycle and became infected by larval stages of clinostomatids.

Preliminary results of the study were presented at the 20th National Conference on Undergraduate Research (NCUR April 6 through April 8 at the University of North Carolina, Asheville.  Dominican undergraduate students Jan Marie Cheng, Marielle Discipulo, Nicole Fronteras, Nenna Olumba, Caitlin Sullivan, and Joyce Valencia worked on the study, along with co-principal investigators Drs. Cunningham and Ghosh.

Dominican plans to continue the study by collecting and sampling additional species of fish as well as mosquitofish from streams within the Point Reyes National Seashore and the Golden Gate National Recreation Area.  The University also plans to expand the study to streams in Southern California. “Because we do not know if the parasites of Gambusia are a threat to the native fauna, additional work needs to be done on a variety of other fish species in order to address this question,” says Dr. Choudhury.