Behavioral alterations in GH transgenic common carp may explain enhanced competitive feeding ability Ming Duan a,1 , Tanglin Zhang a, ⁎, Wei Hu a , Zhongjie Li a , L. Fredrik Sundström c , Tingbing Zhu a,b , Chengrong Zhong a,b , Zuoyan Zhu a a State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China b Graduate University of Chinese Academy of Sciences, Beijing 100049, China c Department of Animal Ecology/Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, SE-752 72 Uppsala, Sweden abstract article info Article history: Received 13 January 2011 Received in revised form 1 April 2011 Accepted 5 April 2011 Available online 14 April 2011 Keywords: Transgene Growth hormone (GH) Foraging Competition Growth Common carp Cyprinus carpio The aim of the present study was to clarify the role of GH transgenesis and its production in social interactions in juvenile common carp Cyprinus carpio. With food pellets provided sequentially, the serum GH levels and behavioral effects were measured in 14 pairs of size-matched ‘all-fish’ GH-transgenic and non-transgenic common carp. In six consecutive observations during 3 days, transgenic fish had a higher movement level as well as a higher social status, being 2.69 times as aggressive, two minutes before and after the 10-min feeding session compared to non-transgenic fish. Transgenic fish also were more than 1.74 times as likely to consume each pellet. During the 8-day experiment, transgenic fish had 4.09 times higher specific growth rate in body weight as well as 6.36 times higher serum GH level than the non-transgenic fish. These results show that GH transgenesis promotes over-expression of GH and alters behaviors in juvenile common carp, thereby increasing their ability to compete and gain food resources, presumably to meet a higher intrinsic growth rate, which gives direct evidence for the GH-induced elevation in feeding competitive ability of GH-transgenic common carp. Understanding these relationships would not only help evaluating potential ecological effects of the escaped/released transgenic fishes, but also help using potential aquaculture of this growth-enhanced strain. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Both the use of growth hormone (GH) treatment (McLean and Donaldson, 1993) and altered GH gene expression by transgenesis (Devlin et al., 1994; Gross et al., 1992; Zhu et al., 1985) can increase the growth rate in fishes, which provides a key biotechnological opportunity to increase global aquaculture production efficiency and yield (Devlin et al., 2006). However, commercial transgenic fish derived from non-fish gene constructs and ‘all-fish’ constructs raises public concerns about bio-safety and bio-ethics (Kapuscinski et al., 2007; Nam et al., 2008). Recently, ‘all-fish’ gene transfer has been presented and recommended to aquaculture (Nam et al., 2001). In ‘all- fish’ GH-transgenic fish, all constructs are derived from fish including the promoter, enhancer and coding sequence. GH-transgenic strains would not only be adopted for use in commercial aquaculture in near future, but also provide useful model systems for studying the consequences of growth enhancement from genetic, physiological and ecological standpoints (Devlin et al., 2006; Nam et al., 2008). GH is a major promoter of post-natal growth and has a key role in the metabolism and regulating the use of nutrients in tissue synthesis of vertebrates (Jönsson et al., 2003; Steele and Evock-Clover, 1993). In teleosts, the growth-promoting effects of GH are well documented (Devlin et al., 2006; Jönsson and Björnsson, 2002; McLean and Donaldson, 1993). Behavioral effects of GH administration in normal fish include increased competitive feeding ability, higher physical activity, increased aggression and decreased risk sensitivity (Jönsson and Björnsson, 2002). This supports the hypothesis that GH-treatment increases metabolic demands and feeding motivation, which in turn increases appetite and competitive ability. Similarly, GH-transgenic salmons can possess elevated chronic levels of GH (Devlin et al., 2000), which results in increased ability to compete for contested food resources (i.e., point food resources, Devlin et al., 1999), higher locomotion and more risk-taking (Abrahams and Sutterlin, 1999; Sundström et al., 2003), in addition to a feeding motivation (Sundström et al., 2004a). Similar results were also found in GH-transgenic common carp Cyprinus carpio reared in ponds and aquaria, which can possess higher and constant serum GH levels (Zhong et al., 2009), which results in elevated ability to compete for limited food resources (i.e., clumped food resources, Duan et al., 2009), besides a higher food conversion efficiency (Fu et al., 2007) and increased feeding motivation (Duan et al., Aquaculture 317 (2011) 175–181 ⁎ Corresponding author. Tel.: +86 27 6878 0369; fax: +86 27 6878 0063. E-mail address: tlzhang@ihb.ac.cn (T. Zhang). 1 Present address: Key Laboratory of Marine and Estuarine Fisheries Resources and Ecology, Ministry of Agriculture, East China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Shanghai 200090, China. 0044-8486/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.aquaculture.2011.04.013 Contents lists available at ScienceDirect Aquaculture journal homepage: www.elsevier.com/locate/aqua-online