scholarly journals Involvement of hormones in olfactory imprinting and homing in chum salmon

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Hiroshi Ueda ◽  
Shingo Nakamura ◽  
Taro Nakamura ◽  
Kaoru Inada ◽  
Takashi Okubo ◽  
...  
Keyword(s):  
Gene Expression ◽  
Chum Salmon ◽  
Gene Activation ◽  
Memory Formation ◽  
Downstream Migration ◽  
Hormonal Control ◽  
Oncorhynchus Keta ◽  
Control Mechanisms ◽  
Olfactory Memory ◽  
Releasing Hormone

Abstract The olfactory hypothesis for salmon imprinting and homing to their natal stream is well known, but the endocrine hormonal control mechanisms of olfactory memory formation in juveniles and retrieval in adults remain unclear. In brains of hatchery-reared underyearling juvenile chum salmon (Oncorhynchus keta), thyrotropin-releasing hormone gene expression increased immediately after release from a hatchery into the natal stream, and the expression of the essential NR1 subunit of the N-methyl-D-aspartate receptor increased during downstream migration. Gene expression of salmon gonadotropin-releasing hormone (sGnRH) and NR1 increased in the adult chum salmon brain during homing from the Bering Sea to the natal hatchery. Thyroid hormone treatment in juveniles enhanced NR1 gene activation, and GnRHa treatment in adults improved stream odour discrimination. Olfactory memory formation during juvenile downstream migration and retrieval during adult homing migration of chum salmon might be controlled by endocrine hormones and could be clarified using NR1 as a molecular marker.

Changes in expression of neurohypophysial hormone genes during spawning migration in chum salmon, Oncorhynchus keta

1997 ◽  
Vol 18 (1) ◽  
pp. 49-55 ◽  
Author(s):  
S Hiraoka ◽  
H Ando ◽  
M Ban ◽  
H Ueda ◽  
A Urano
Keyword(s):  
Gene Expression ◽  
Northern Blot ◽  
Blot Analysis ◽  
Chum Salmon ◽  
Northern Blot Analysis ◽  
Sea Water ◽  
Spawning Migration ◽  
Oncorhynchus Keta ◽  
Males And Females ◽  
Neuroendocrine Mechanism

ABSTRACT We analyzed changes in the hypothalamic levels of vasotocin (VT) and isotocin (IT) mRNA in chum salmon during spawning migration to the Ishikari river. The fish were caught at Atsuta, a fisherman's village facing the Ishikari bay, and at Chitose, an upstream branch of the Ishikari river. The former are referred to as sea water (SW) fish, and the latter as freshwater (FW) fish. The levels of VT and IT mRNA in the forebrains were determined by quantitative Northern blot analysis using single-stranded DNA with the same mRNA sequences as the standards. Levels of VT mRNA were higher in the FW males than the FW females, although no such difference was seen in the SW fish. Changes in the levels of VT mRNA were markedly different in males and females. In the males, no significant differences were seen in the levels of VT-I and VT-II mRNA between the SW and FW fish. However, in the females, the levels of VT mRNA in the FW fish were significantly lower than those in the SW fish. Changes in the levels of IT-I and IT-II mRNA were essentially similar in the males and females. These results suggest that the control of VT gene expression is different in males and females during spawning migration, although the neuroendocrine mechanism is not known.

Phenotypic Differentiation in Seasonal Ecotypes of Chum Salmon, Oncorhynchus keta

1991 ◽  
Vol 48 (4) ◽  
pp. 661-671 ◽  
Author(s):  
Ross F. Tallman ◽  
Michael C. Healey
Keyword(s):  
Egg Size ◽  
Chum Salmon ◽  
Downstream Migration ◽  
Oncorhynchus Keta ◽  
Age At Maturity ◽  
Similar Time ◽  
Phenotypic Differentiation ◽  
Chum Salmon Oncorhynchus Keta ◽  
Spawning Stock ◽  
Autumn And Winter

We compared the reproductive environments and phenotypes of early and late season breeding stocks of chum salmon, Oncorhynchus keta, to test the hypothesis that seasonal separation has resulted in phenotypically distinct forms. These were autumn- and winter-spawning populations from Bush Creek (Vancouver Island, B.C.) and a winter-spawning stock from nearby Walker Creek. All stocks had a similar time of downstream migration of the fry. No differences were found among the Walker Creek and the autumn-spawning stock of Bush Creek in age at maturity, length composition of spawners, egg size, vertebral counts of adults and fry, and time of fry migration. The winter-spawning stock of Bush Creek differed from the other stocks in egg size and vertebral counts. Discriminant analysis of 10 morphological features of the fry revealed considerable overlap in body form among the stocks. These results do not support the hypothesis that distinct life history morphs are associated with the season of reproduction. We propose that the large amount of similarity in terms of morphology and seasonality among the populations may be the product of selection. Genetic divergence may have occurred to compensate for the environmental differences experienced during embryonic development.

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