Establishing Zebrafish as a Novel Exercise Model: Swimming Economy, Swimming-Enhanced Growth and Muscle Growth Marker Gene Expression

Abstract

BackgroundZebrafish has been largely accepted as a vertebrate multidisciplinary model but its usefulness as a model for exercise physiology has been hampered by the scarce knowledge on its swimming economy, optimal swimming speeds and cost of transport. Therefore, we have performed individual and group-wise swimming experiments to quantify swimming economy and to demonstrate the exercise effects on growth in adult zebrafish.Methodology/Principal FindingsIndividual zebrafish (n = 10) were able to swim at a critical swimming speed (Ucrit) of 0.548±0.007 m s−1 or 18.0 standard body lengths (BL) s−1. The optimal swimming speed (Uopt) at which energetic efficiency is highest was 0.396±0.019 m s−1 (13.0 BL s−1) corresponding to 72.26±0.29% of Ucrit. The cost of transport at optimal swimming speed (COTopt) was 25.23±4.03 µmol g−1 m−1. A group-wise experiment was conducted with zebrafish (n = 83) swimming at Uopt for 6 h day−1 for 5 days week−1 for 4 weeks vs. zebrafish (n = 84) that rested during this period. Swimming zebrafish increased their total body length by 5.6% and body weight by 41.1% as compared to resting fish. For the first time, a highly significant exercise-induced growth is demonstrated in adult zebrafish. Expression analysis of a set of muscle growth marker genes revealed clear regulatory roles in relation to swimming-enhanced growth for genes such as growth hormone receptor b (ghrb), insulin-like growth factor 1 receptor a (igf1ra), troponin C (stnnc), slow myosin heavy chain 1 (smyhc1), troponin I2 (tnni2), myosin heavy polypeptide 2 (myhz2) and myostatin (mstnb).Conclusions/SignificanceFrom the results of our study we can conclude that zebrafish can be used as an exercise model for enhanced growth, with implications in basic, biomedical and applied sciences, such as aquaculture.

Lactate kinetics of rainbow trout during graded exercise: Do catheters affect the cost of transport?

“…2A), as predicted by various models derived exclusively from hydrodynamic theory (Pettersson and Hedenström, 2000;Wakeman and Wohlschlag, 1981). This finding is highly consistent with empirical observations made in other fish species including European sea bass (Claireaux et al, 2006), Atlantic cod (Syme et al, 2008), Pacific bonito (Sepulveda et al, 2003), several flatfish (Duthie, 1982) and zebrafish (Palstra et al, 2010). Here, optimal swimming speed (U opt =speed with minimal cost of transport) was 2.1 BL s −1 for TCOT ( Fig.…”

“…This interesting difference has been commonly reported in the fish literature. It indicates that maximal aerobic efficiency (Webb, 1971) is achieved at ~70% U crit , whereas maximal muscle efficiency occurs at ~30-40% U crit (Luna-Acosta et al, 2011;Palstra et al, 2008;Palstra et al, 2010).…”

Muscle Remodeling and the Exercise Physiology of Fish

“…Developmental differences have led to fuel use and biochemical differences between these tissue types. Red muscle exists as a wedge running along the lateral line in most species and is recruited for steady-state swimming (up to 70%Y80% of critical swimming speed (U crit )) because of its high mitochondrial content (as indexed by citrate synthase (CS) (31)) and enhanced ability to take up and oxidize fatty acids probably because of higher carnitine palmitoyltransferase I (CPT-I) activities per unit mitochondria (25,35). The larger white muscle mass makes up the bulk of the animal's trunk and is heavily recruited for burst exercise.…”

Skeletal muscle contractile function predicts activity and behaviour in zebrafish

“…Maximal speeds may be important ecologically under certain circumstances, such as when defending territories or escaping predators . However, animals under undisturbed conditions often do not move at their maximal capacity (Hasler et al, 2009;Husak, 2006;McDonald et al, 2007;Irschick and Losos, 1998;Irschick et al, 2005;Palstra et al, 2010;Wickler et al, 2000). Our data showing that voluntary speed changes linearly with maximal speed is interesting because it suggests that there is a mechanistic link between the two.…”