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Egg size-dependent expression of growth hormone receptor accompanies compensatory growth in fish


Segers, F H I D; Berishvili, G; Taborsky, B (2012). Egg size-dependent expression of growth hormone receptor accompanies compensatory growth in fish. Proceedings of the Royal Society B: Biological Sciences, 279(1728):592-600.

Abstract

Large egg size usually boosts offspring survival, but mothers have to trade off egg size against egg number. Therefore, females often produce smaller eggs when environmental conditions for offspring are favourable, which is subsequently compensated for by accelerated juvenile growth. How this rapid growth is modulated on a molecular level is still unclear. As the somatotropic axis is a key regulator of early growth in vertebrates, we investigated the effect of egg size on three key genes belonging to this axis, at different ontogenetic stages in a mouthbrooding cichlid (Simochromis pleurospilus). The expression levels of one of them, the growth hormone receptor (GHR), were significantly higher in large than in small eggs, but remarkably, this pattern was reversed after hatching: young originating from small eggs had significantly higher GHR expression levels as yolk sac larvae and as juveniles. GHR expression in yolk sac larvae was positively correlated with juvenile growth rate and correspondingly fish originating from small eggs grew faster. This enabled them to catch up fully in size within eight weeks with conspecifics from larger eggs. This is the first evidence for a potential link between egg size, an important maternal effect, and offspring gene expression, which mediates an adaptive adjustment in a relevant hormonal axis.

Abstract

Large egg size usually boosts offspring survival, but mothers have to trade off egg size against egg number. Therefore, females often produce smaller eggs when environmental conditions for offspring are favourable, which is subsequently compensated for by accelerated juvenile growth. How this rapid growth is modulated on a molecular level is still unclear. As the somatotropic axis is a key regulator of early growth in vertebrates, we investigated the effect of egg size on three key genes belonging to this axis, at different ontogenetic stages in a mouthbrooding cichlid (Simochromis pleurospilus). The expression levels of one of them, the growth hormone receptor (GHR), were significantly higher in large than in small eggs, but remarkably, this pattern was reversed after hatching: young originating from small eggs had significantly higher GHR expression levels as yolk sac larvae and as juveniles. GHR expression in yolk sac larvae was positively correlated with juvenile growth rate and correspondingly fish originating from small eggs grew faster. This enabled them to catch up fully in size within eight weeks with conspecifics from larger eggs. This is the first evidence for a potential link between egg size, an important maternal effect, and offspring gene expression, which mediates an adaptive adjustment in a relevant hormonal axis.

Citations

13 citations in Web of Science®
13 citations in Scopus®
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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > Institute of Anatomy
Dewey Decimal Classification:570 Life sciences; biology
610 Medicine & health
Language:English
Date:7 February 2012
Deposited On:12 Jan 2012 08:06
Last Modified:05 Apr 2016 15:20
Publisher:Royal Society of London
ISSN:0962-8452
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.1098/rspb.2011.1104
PubMed ID:21752823

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