Poecilancistrium caryophyllum and Other Trypanorhynch Cestode Plerocercoids from the Musculature of Cynoscion nebulosus and Other Sciaenid Fishes in the Gulf of Mexico

Examination of over 3,000 fish, all sciaenids, has shown that plerocercoids of Poecilancistrium caryophyllum infect Cynoscion nebulosus, Bairdiella chrysura, Sciaenops ocellata, C. arenarius, Micropogonias undulatus, and Pogonias cromis in Mississippi Sound. In addition to P. caryophyllum, a pseudophyllidean-like trypanorhynch also infected C. nebulosus and M. undulatus. Pseudogrillotia pleistacantha selectively infected large P. cromis, Pterobothrium heteracanthum infected M. undulatus, and Pterobothrium lintoni infected Menticirrhus americanus. Prevalence and intensity of infections of P. caryophyllum in C. nebulosus from Mississippi, roughly 40% of the fish each possessing an average of about two worms, compare with infections observed in fish from Texas and Louisiana. However, values for fish from Apalachee Bay, but not Tampa Bay, Florida, are about twice as high. Extensive seasonal sampling in Mississippi Sound indicates fluctuations but no clear-cut seasonal trends other than a possible relationship between infections and salinity. As C. nebulosus increases in length, the prevalence of infections, but not the intensity, increases. This finding suggests an immune response to challenge infections. No fish less than 140 mm SL and relatively few less than 250 mm SL revealed infections, suggesting either the unavailability of the intermediate host to young fish or the ultimate death of most young infected individuals. Based on condition coefficients and liver-weight analysis, no apparent detrimental effect on infected, moderately-heavy adult fish occurred. Infections primarily involve the middle of a fillet or the region adjacent to the vertebral column below the dorsal fins and cause an esthetically displeasing product and consequently depress economically the trout fishery. Relatively more male than female fish harbored worms, but the significance of that finding is questioned.