Seasonal variations in body growth rates and circulating levels of growth hormone in the goldfish,Carassius auratus

✍ Scribed by Marchant, Tracy A. ;Peter, Richard E.

• Publisher: John Wiley and Sons
• Year: 1986
• Tongue: English
• Weight: 791 KB
• Volume: 237
• Category: Article
• ISSN: 0022-104X
• DOI: 10.1002/jez.1402370209

✦ Synopsis

Several times throughout the year, changes in serum growth hormone (GH) levels over a 24-h period were determined in goldfish maintained under photoperiods and temperatures simulating natural (Edmonton) environmental conditions. In the goldfish a reproducible daily rhythm in circulating GH levels was not present at any time of the year. The average serum GH level over the daily sampling period and the instantaneous relative growth rate in goldfish sampled at the various times of the year were also determined. The highest mean daily serum GH levels were found in March and June, whereas the lowest level was found in goldfish sampled in November. Changes in mean daily serum GH levels were closely correlated to seasonal changes in daylength. The highest growth rate was found in goldfish sampled in July, whereas the lowest growth rates were found in February and March. Female goldfish exhibited a faster growth rate than male goldfish at certain times of the year, but sexual differences in growth rate were correlated with sexual differences in serum GH levels only in November when female goldfish had a higher serum GH level than male goldfish. Seasonal variations in the rate of body growth appear to be universal in teleost species found in temperate climatic zones (Ricker, '79). Variations in somatic growth rates throughout the year have been described for several teleost species, including common carp,