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Pronounced seasonal rhythms in plasma somatolactin levels in rainbow trout

Rand-Weaver, M.; Pottinger, T.G.; Sumpter, J.P.. 1995 Pronounced seasonal rhythms in plasma somatolactin levels in rainbow trout. Journal of Endocrinology, 146 (1). 113-119. 10.1677/joe.0.1460113

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Abstract/Summary

The aim of this study was to establish whether there are seasonal or age-related changes in circulating levels of somatolactin (SL) in rainbow trout (Onchorhynchus mykiss). SL levels were determined in blood sampled at monthly intervals over a 2-year period from a population of rainbow trout maintained under a natural daylength and temperature regime (North-West England, latitude 54°20′ N). SL levels displayed a distinct circannual cycle, with peak levels in summer (17–20 μg/l) and lowest levels occurring in winter (0.2–2 μg/l). This variation in SL levels was closely correlated with water temperature (P<0.001) but was out of phase with changes in daylength. Plasma SL levels were significantly higher in both mature male and female fish compared with immature fish. Plasma prolactin levels were determined to provide information on a hormone structurally related to SL, and also because mammalian prolactin is known to show distinct seasonal cycles. However, trout prolactin, in contrast to SL, did not show a pronounced seasonal pattern, although prolactin levels were significantly, but inversely, correlated with water temperature (P<0.001).

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1677/joe.0.1460113
CEH Sections: _ Pre-2000 sections
ISSN: 0022-0795
Additional Keywords: somatolactin, prolactin, rainbow trout, phenology, circannual cycle, daylength
NORA Subject Terms: Zoology
Biology and Microbiology
Date made live: 03 Aug 2015 10:51 +0 (UTC)
URI: http://nora.nerc.ac.uk/id/eprint/510962

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