Neuropeptide FF indirectly affects testicular morphogenesis and functions in medaka.

Testicular morphogenesis and functions are considered to be under the control of neural and endocrine systems. However, the available literature is mainly limited to mammals, and it remains unclear how they are regulated in teleost species. Here, we demonstrated that neuropeptide FF (NPFF) in the brain is responsible for the follicle-stimulating hormone expression in the pituitary, which facilitates the testicular morphogenesis and androgen synthesis, and subsequently contributes to successful spermatogenesis. The present findings give us important insights into the neuroendocrine regulatory mechanisms underlying the testicular morphogenesis and functions in teleosts.

Morphological analysis of the cerebellum and its efferent system in a basal actinopterygian fish, Polypterus senegalus.

Although all vertebrate cerebella contain granule cells, Purkinje cells, and efferent neurons, the cellular arrangement and neural circuitry are highly diverse. In amniotes, cerebellar efferent neurons form clusters, deep cerebellar nuclei, lie deep in the cerebellum, and receive synaptic inputs from Purkinje cells but not granule cells. However, in the cerebellum of teleosts, the efferent neurons, called eurydendroid cells, lie near the cell bodies of Purkinje cells and receive inputs both from axons of Purkinje cells and granule cell parallel fibers. It is largely unknown how the cerebellar structure evolved in ray-finned fish (actinopterygians). To address this issue, we analyzed the cerebellum of a bichir Polypterus senegalus, one of the most basal actinopterygians. We found that the cell bodies of Purkinje cells are not aligned in a layer; incoming climbing fibers terminate mainly on the basal portion of Purkinje cells, revealing that the Polypterus cerebellum has unique features among vertebrate cerebella. Retrograde labeling and marker analyses of the efferent neurons revealed that their cell bodies lie in restricted granular areas but not as deep cerebellar nuclei in the cerebellar white matter. The efferent neurons have long dendrites like eurydendroid cells, although they do not reach the molecular layer. Our findings suggest that the efferent system of the bichir cerebellum has intermediate features between teleosts and amniote vertebrates, and provides a model to understand the basis generating diversity in actinopterygian cerebella.