Population dynamics of the philometrid nematode Margolisianum bulbosum in the southern flounder Paralichthys lethostigma (Pisces: Paralichthyidae) in South Carolina, USA.

This is the first report of the philometrid nematode Margolisianum bulbosum Blaylock and Overstreet, 1999 from the southern flounder Paralichthys lethostigma on the east coast of the USA. Observation of adult female worms was used as an indication of the parasite's presence in the fish. Adult females were found only in P. lethostigma >50 mm total length. The overall prevalence was 74%, with a mean intensity of 5 female nematodes per parasitized fish. Infected flounders were found throughout the year with a statistically significant decrease in intensity in the winter months. Neither salinity, water temperature, fish gender nor fish age were found to influence either prevalence or intensity of infection in the flounder. While larvigerous (gravid) females were found throughout the year, the significant decrease in their occurrence during the summer through fall, in concert with an observed decrease in intensity of infection during the winter, indicated that the life cycle of this philometrid species is likely to be annual.