New haemoglobin genotypes in Atlantic cod, Gadus morhua: Possible relation with growth Albert K. Imsland a,c, ⁎ , Atle Foss b , Gunnar Nævdal c , Torild Johansen c , Sigurd O. Stefansson c , Thor M. Jonassen d a Akvaplan-niva, Iceland Office, Akralind 4, 201 Kópavogur, Iceland b Akvaplan-niva Bergen, Postbox 2026 Nordnes, 5817 Bergen, Norway c Department of Biology, University of Bergen, High Technology Centre, 5020 Bergen, Norway d Marine Harvest Norway AS, Sandviksboder 78A, Bergen, Norway Received 9 August 2006; received in revised form 1 March 2007; accepted 1 March 2007 Available online 12 March 2007 Abstract In a preliminary study, 121 individually tagged juvenile Atlantic cod (Gadus morhua) were classified according to their haemoglobin genotypes into four groups, i.e., two main haemoglobin genotypes [Hb-I(1/2), Hb-I(2/2)] and two sub-types [Hb-I(1/2b), Hb-I(2/2b)], and reared for 3 months at 10 °C, 13 °C and T-step (fish reared at 16 °C and then subsequently moved to 13 and later to 10 °C). Overall growth rates across temperatures were 10% and 19% higher in the Hb-I(2/2b), Hb-I(1/2b) sub-types compared to corresponding Hb-I(2/2) and Hb-I(1/2) main types, respectively. Individual growth rate trajectories varied between the genotypes at all temperatures studied. Our study indicates that under certain environmental conditions higher growth in the two sub-types compared to the main genotypes could be expected. This may indicate difference in other physiological characters not studied here, but seen in previous studies, i.e., oxygen affinity and competitive performance. © 2007 Elsevier Inc. All rights reserved. Keywords: haemoglobin genotypes; sub-types; genotypic growth; Norway; temperature 1. Introduction In Atlantic cod, Gadus morhua, haemoglobin is charac- terised by at least three different main genotypes called Hb-I (1/1), Hb-I(1/2) and Hb-I(2/2) and originally described by Sick (1961). Differences in biochemical properties have been described for the genotypes. Some studies have indicated different growth properties of the Hb genotypes (Mork et al., 1984a,b; Nævdal et al., 1992; Imsland et al., 2004), although in other studies no such dependence has been found (Jørstad and Nævdal, 1994; Glover et al., 1997; Jordan et al., 2006). This discrepancy might be linked to different size investigated in the studies above. Jordan et al. (2006) speculated that the sub-type Hb-I(2/2) could represent an intrinsic “fast grower” during early life stages. The oxygen affinity of haemoglobin is higher for Hb-I(2/2) cod at low temperatures (b 10 °C) (Karpov and Novikov, 1981; Brix et al., 1998, 2004), and for Hb-I(1/1) cod, at some blood pH values, at high temperatures (N 14 °C) (Karpov and Novikov, 1981; Brix et al., 1998, 2004). The heterozygous haemoglobin type is generally found to have oxygen affinity values that are intermediate to Hb-I(1/1) and Hb-I(2/2).(Karpov and Novikov, 1980; Brix et al., 2004). This information suggests that temperature could be a selective parameter for the distribution of Atlantic cod with different haemoglobin types. Petersen and Steffensen (2003) measured the preferred temperature of the homozygous genotypes Hb-I (1/1) and Hb-I(2/2). They found that Hb-I(2/2) preferred a temperature of 8.2 ± 1.5 °C while Hb-I(1/1) cod preferred 15.4 ± 1.1 °C, and this preference was significant. These findings together with the data of Mork et al. (1984a,b), Nævdal et al. (1992) and Imsland et al. (2004) may indicate that different growth between haemoglobin genotypes at different temperature regimes could be expected. Comparative Biochemistry and Physiology, Part A 147 (2007) 955 – 960 www.elsevier.com/locate/cbpa ⁎ Corresponding author. Akvaplan-niva, Iceland Office, Akralind 4, 201 Kópavogur, Iceland. E-mail address: albert.imsland@akvaplan.niva.no (A.K. Imsland). 1095-6433/$ - see front matter © 2007 Elsevier Inc. All rights reserved. doi:10.1016/j.cbpa.2007.03.001