Effects of fasting on temporal changes in plasma concentrations of sex steroids, growth hormone and insulin‐like growth factor I, and reproductive investment in Arctic charr

Abstract

Proportions of maturing fish and reproductive output [egg size, relative fecundity, spermatocrit and gonado-somatic index (I G )] were studied in repeat-spawning (þ4 year old) male and female Arctic charr Salvelinus alpinus, subjected to periods of fasting. Groups of individually tagged Arctic charr were fasted for c. 3, 6, 7 and 9 months, from November 1998. In the period February to November 1999, size (fork length and mass), specific growth rate (G), condition factor (K) and plasma concentrations of growth hormone (GH), insulin-like growth factor I (IGF-I), oestradiol-17b (E 2 ; females) and 11-ketotestosterone (11KT; males), were monitored monthly. Maturing fish in each group started to gain mass soon after food was made available, and both sexes reached the highest K and G c. 2 months after the onset of feeding. The fasting regimes resulted in different growth patterns during spring and summer when energy stores are normally replenished in Arctic charr, and K prior to the breeding season was significantly higher in the groups fasted for 3 and 6 months compared to the groups fasted for 7 and 9 months. There were significant positive correlations between K during the period prior to the breeding season and reproductive output in terms of the I G , spermatocrit and relative fecundity. There was, however, no clear relationship between the length of starvation and the proportion of maturing fish. Likewise, no clear relationships were found between reproductive development and plasma levels of GH and IGF-I, although both showed marked seasonal changes, being 'down-regulated' during winter months and 'up-regulated' throughout summer months. # 2004 The Fisheries Society of the British Isles

Effect of diet and ration on the relationship between plasma GH and IGF-1 concentrations in Arctic charr, Salvelinus alpinus (L.)

“…The decrease in plasma IGF‐1 concentrations after 5 weeks of food deprivation in Arctic charr is consistent with observations in several other fish species during fasting or starvation (Niu, Pérez‐Sánchez & Le Bail 1993; Pérez‐Sánchez et al 1994a, b; Baños, Planas, Gutiérrez & Navarro 1999; Uchida et al 2003; Frantzen et al 2004; Pierce et al 2005). The timing of the changes is also in line with other similar studies, where changes in plasma IGF‐1 concentrations were only detected after several weeks of food deprivation.…”

“…The food deprivation suppression of plasma GH concentration that was observed in the present study is in accord with a similar study of Arctic charr by Frantzen et al (2004); however, in that study, fish were fed after an over‐wintering fast. Plasma GH levels in the re‐fed fish increased significantly within the first month, and hormone levels in the food‐deprived fish were significantly lower than the fed animals between February and May (Frantzen et al 2004). Plasma GH concentrations were also found to decline in fasting fish during the approach to the spring downstream migration to seawater in repeat migrants of anadromous Arctic charr (Aas‐Hansen, Vijayan, Johnsen, Cameron & Jørgensen 2004).…”

“…As such, these observed feeding and growth rhythms may be biologically significant in enabling charr to exploit periods of high feed availability. The response of plasma GH levels to food deprivation in the present study, and that of Frantzen et al (2004), may reflect the response of a species that is well adapted to long periods of fasting. These findings contrast with studies in other taxa of salmonid fish in which plasma GH concentrations were found to increase with food deprivation (see ‘’ for references).…”

Effects of Partial and Full Feed Restriction on the Plasma Levels of Thyroid Hormones and Testicular Activity in the Male Air-breathing Catfish, Clarias gariepinus during Different Phases of the Breeding Cycle

“…While there is a general awareness on the effects of fasting/starvation on fecundity, GSI, sexual maturation and temporal changes in the plasma concentrations of sex steroids in several temperate zone fish species like Amago salmon (Oncorhynchus masou ishikawae), Atlantic cod (Gadus morhua), perch (Macquaria ambigua), Atlantic salmon (Salmo salar), and Arctic charr, Salvelinus alpinus (Silverstein and Shimma, 1994;Karlsen et al, 1995;Collins and Anderson, 1999;Duston and Saunders, 1999;Frantzen et al, 2004), there is scarcity of information on the effects of partial and full feed restriction on the testicular activity of fish species in tropical/sub-tropical region with particular reference to different phases of the annual breeding cycle.…”

“…In fishes, food deprivation suppresses the plasma T 4 and T 3 levels, reduces thyroid tissue sensitivity to thyroid stimulating hormone (TSH), causes a reduction in 5'-monodeiodinase and eliminates the plasma thyroid hormone daily patterns (Eales et al, 1981;Flood and Eales, 1983;Shields and Eales, 1986;Cerda-Reverter et al, 1996;Power et al, 2000;Gaylord et al, 2001). Besides thyroid hormones, starvation has also been reported to affect reproductive function in different fish species (Silverstein and Shimma, 1994;Karlsen et al, 1995;Collins and Anderson, 1999;Duston and Saunders, 1999;Frantzen et al, 2004). However, these reports on the effects of feed restriction on the thyroid hormones and gonadal activity are limited to only a few temperate zone fish species and without any reference to the phases of the annual breeding cycle when the studies were conducted.…”