Monthly variation in the morphological characteristics of Trichodina sp. (Ciliophora: Peritrichida) found on whiting Merlangius merlangus euxinus

to determine the existence and extent of seasonal variation in morphological characteristics of trichodina sp., sixty whiting merlangius merlangus euxinus were sampled monthly for one year, from the eastern black sea coast of turkey, using a line and hook. strong seasonal morphological variations were detected; the denticle span, blade length and ray length showed significant seasonal variation, especially in june. the timing of primary production in the black sea and the changes in cellular organelles suggested a negative relationship between the body diameter of trichodinids and food availability in the surrounding environment.