1. The saccus vasculosus of fish is a sensor of seasonal changes in day length.
- Author
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Nakane Y, Ikegami K, Iigo M, Ono H, Takeda K, Takahashi D, Uesaka M, Kimijima M, Hashimoto R, Arai N, Suga T, Kosuge K, Abe T, Maeda R, Senga T, Amiya N, Azuma T, Amano M, Abe H, Yamamoto N, and Yoshimura T
- Subjects
- Animal Structures cytology, Animal Structures ultrastructure, Animals, Autoradiography, Brain metabolism, Cells, Cultured, Fishes genetics, Gene Expression Regulation, Male, Multigene Family, Reproduction genetics, Rhodopsin genetics, Rhodopsin metabolism, Signal Transduction genetics, Testis growth & development, Testis metabolism, Animal Structures physiology, Fishes anatomy & histology, Fishes physiology, Photoperiod, Seasons
- Abstract
The pars tuberalis of the pituitary gland is the regulatory hub for seasonal reproduction in birds and mammals. Although fish also exhibit robust seasonal responses, they do not possess an anatomically distinct pars tuberalis. Here we report that the saccus vasculosus of fish is a seasonal sensor. We observe expression of key genes regulating seasonal reproduction and rhodopsin family genes in the saccus vasculosus of masu salmon. Immunohistochemical studies demonstrate that all of these genes are expressed in the coronet cells of the saccus vasculosus, suggesting the existence of a photoperiodic signalling pathway from light input to neuroendocrine output. In addition, isolated saccus vasculosus has the capacity to respond to photoperiodic signals, and its removal abolishes photoperiodic response of the gonad. Although the physiological role of the saccus vasculosus has been a mystery for several centuries, our findings indicate that the saccus vasculosus acts as a sensor of seasonal changes in day length in fish.
- Published
- 2013
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