Histology, innervation and histochemistry of the UB gland in the Mexican cave fish Anoptichthys jordani Hubbs et Innes (Teleostei: Characidae).

The histomorphological investigations carried out on the ultimobranchial body of the Teleost Anoptichthys jordani Hubbs and Innes have enabled us to establish that it is an epithelial multifollicular body which lies within the transverse septum, beneath the musculature of the oesophagus and caudal to the Sinus venosus. Its parenchyma is surrounded by an extensive nerve network revealed by the Bodian silver technique. This nerve network and the occurrence of MAO activity in the ultimobranchial tissue indicate that it possesses a sympathetic innervation. The follicular epithelium sometimes acquire a pseudostratified condition in some follicles and sometimes in multistratified in others. In this latter case the presence of two main types of cell was noticed (light cells and dark cells). In these cells by the fluorescence microscopic analysis was revealed an intensely green fluorescence due to the presence of an aromatic monoamine, dopamine. This conclusion was further confirmed by the agreement between the argyrophilic cells and the fluorescent cells after silver staining. The possible partecipation of dopamine in the elaboration of polypeptide factor (calcitonin) is suggested. A notable analogy from the structural point of view to the calcitonin-producing cells of higher Vertebrates is also confirmed by the markedly argyrophilia of the main cells.