Caracterização morfológica da epiderme do bagre neotropical Pimelodella cf. vittata (Osteichthyes: Ostariophysi: Siluriformes: Heptapteridae) com ênfase nas células claviformes.

Abstract

The epidermis of Ostariophyi fish is composed by three basic cell types: epidermal, mucus and club cells. These latter cells are associated with the production of a secretion with distinct function and chemical composition. Morphological analyses of the epidermis of the catfish Pimelodella cf. vittata indicated the presence of club cells and epidermal cells. The club cells occur in the epidermis middle layer representing the largest cells of the epithelium. They are elongated and globular. The cytoplasm is poor in organelles and rich in a fibrillar secretion not encapsulated in vesicles. The observed organelles (endoplasmic reticulum, Golgi apparatus, mitochondria and polirribosomes), are located in the perinuclear region, while the remainder of the cytoplasm is filled with a fibrillar material. Occasionally, large vacuoles occur in the cytoplasmic periphery. The club cells present, in general, two nuclei with irregular shape, evident nucleolus, central loose chromatin and condensed chromatin in the periphery. By histochemistry analyses, it was detected protein composition in the cytoplasm and absence of carbohydrates. These morphological and histochemical characteristics are similar to those described for the majority of the Ostariophysi. The epidermal cells differ from that described in the literature, being described here in three distinct cell types: surface, abundant and dense one. These types have never been noted before. There was no evidence of mucus cells in P. cf. vittata, typical cells found in all Ostariophysi studied. The present study corroborates the data about club cell morphology in Ostariophysi and detects significant differences in the epidermis composition and epidermal cells structure of P. cf. vittata when compared to the literature.