|Vol. 9 (No. 1), pp. 1–27, 2016||doi:10.5047/absm.2016.00901.0001|
Field Science Center for Northern Biosphere and Graduate School of Environmental Science
North 9 West 9, Kita-ku, Sapporo, Hokkaido 060-0809, Japan
(Received on January 22, 2016; Accepted on June 20, 2016; Online published on December 30, 2016)
Abstract: Salmon are recognized for their amazing abilities to precisely migrate thousands of kilometers from their feeding habitat in the ocean to their natal stream for reproduction, but many mysteries are still unsolved in the mechanisms of imprinting and homing migration. Physiological mechanisms of imprinting and homing migration of Pacific salmon were investigated using three different research approaches. Homing behavior of adult chum salmon from the Bering Sea to Hokkaido as well as lacustrine sockeye salmon and masu salmon in Lake Toya (serves as a model ocean) were examined using physiological biotelemetry techniques, demonstrating that salmon can navigate in open water using different sensory systems. Hormone profiles in the brain-pituitary-thyroid and brain-pituitary-gonad axes were analyzed in chum salmon and sockeye salmon during their imprinting and homing migration, suggesting that thyrotropin-releasing hormone and salmon gonadotropin-releasing hormone in the brain are involved in imprinting and homing migration, respectively. The olfactory memory formation and retrieval of Pacific salmon were investigated using several neurophysiological techniques, suggesting that long-term stability of dissolved free amino acid compositions in natal streams are crucial for olfactory imprinting and homing, and N-methyl-d-aspartate receptor can be a useful molecular marker for olfactory memory formation and retrieval. These topics are discussed with physiological mechanisms of imprinting and homing migration of Pacific salmon.
Keywords: Pacific salmon, imprinting, homing, migration, physiological mechanisms, biotelemetry, endocrinology, olfaction, neurophysiology
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