The saccus vasculosus of the neotropical cichlid fish Cichlasoma dimerus: characterization, developmental studies and its response to photoperiod

SALLEMI, JULIETA EMILSE; DI YORIO, MARÍA PAULA; HERMIDA, GLADYS NOEMÍ; BRECCIA, ANDRÉS; BATTISTA, ARIADNA GABRIELA; VISSIO, PAULA GABRIELA

CELL AND TISSUE RESEARCH

SPRINGER

Año: 2024

0302-766X

The saccus vasculosus is an organ present in gnathostome fshes, located ventral to the hypothalamus and posterior to the pituitary gland, whose structure is highly variable among species. In some fshes, this organ is well-developed; however, its physiological function is still under debate. Recently, it has been proposed that this organ is a seasonal regulator of reproduction. In the present work, we examined the histology, ultrastructure, and development of the saccus vasculosus in Cichlasoma dimerus. In addition, immunohistochemical studies of proteins related to reproductive function were performed. Finally, the potential response of this organ to diferent photoperiods was explored. C. dimerus presented a well-developed saccusvasculosus consisting of a highly folded epithelium, composed of coronet and supporting cells, closely associated with blood vessels, and a highly branched lumen connected to the third ventricle. Coronet cells showed all the major characteristics described in other fsh species. In addition, some of the vesicles of the globules were positive for thyrotropin beta subunit,while luteinizing hormone beta subunit immunostaining was observed at the edge of the apical processes of some coronet cells. Furthermore, neuropeptide Y and gonadotropin inhibitory hormone innervation in the saccus vasculosus of C. dimerus were shown. Finally, animals exposed to the long photoperiod showed lower levels of thyrotropin beta and common alphasubunits expression in the saccus compared to those of animals exposed to short photoperiod. All these results support the hypothesis that the saccus vasculosus is involved in the regulation of reproductive function in fsh.