Preliminary report of occurrence of Corynosoma spp. (Acanthocephala: Polymorphidae) in Southern Caspian sprat (Clupeonella grimmi)

In recent years, there has been a steady decline in the populations of clupeid fish in the Caspian Sea which has been attributed to factors such as overfishing and introduced invasive species of jellyfish. Very little is known about the diseases and possible health impacts of infectious agents such as parasites on the population of these important fish in the Caspian Sea. The aim of this study was to determine if infection with parasites can have adverse impacts on fish health and population. Sixty fish were collected, measured for weight and length, aged, and then examined for presence of Acanthocephala. Ages were recorded, as well as length and weight data for each age category and the number of acanthocephalan parasites. The internal organs, including the liver, ovary, and testis, were subjected to histopathological examination. Ninety percent of fish were found to be infected with acanthocephalan parasites, identified as Corynosoma strumosum. Fish data including the number of parasites, age, length, and weight showed that there was no significant difference in length and weight between different age groups, e.g., between 2 and 6 years old, suggesting that those fish may not grow fully as they age. There were several granuloma of different sizes in the liver and gonads, indicating the occurrence of a chronic inflammation. It is known that large numbers of granuloma may disturb the normal function of the liver and gonads and if associated with long term infection this may cause sterility, affecting the population numbers. Further research, with targeted aims, is needed to understand the impact of infection with acanthocephala on this fish and to determine the causative agents of the histopathological changes observed in the present study.