[Seasonal variations of the ultimobranchial body of the turtle (Pseudemys scripta)].

Ultrastructural seasonal cyclic aspects of ultimobranchial body (C.U.B.) in fresh turtles (Pseudemys scripta) are studied. The C.U.B. consists of follicles and cords. The cord cells are characterized by many secretory granules measuring approximately 180 nm with variable feature and electron density. These granules are localized in the cytoplasm close to basal laminae. The follicular cells, on the contrary, present few and large secretory granules, glycogen particles, bundle of filaments and a scarcely developing Golgi apparatus and granular endoplasmic reticulum. The apical and follicular cytoplasmatic membrane is provided with small number of cilia and short microvilli. Seasonal cellular variations are described clearly in the winter (february-march) specimens of ultimobranchial body, these are characterized by more cord aspects and few follicles. The only cord cells present significant ultrastructural changes, represented by more glycogen particles, middle and wide lipid droplets and poor presecretory granules in Golgi zone. These morphological elements orient to a parallelism with the C cells of hibernant animals (Azzali 1967, Frink and Coll.) and the chief cells of parathyroid gland of the self turtle species as by our previous study.