Variations in growth in haemoglobin genotypes of Atlantic cod (original) (raw)
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New haemoglobin genotypes in Atlantic cod, Gadus morhua: Possible relation with growth
Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 2007
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.
Aquaculture, 2006
The effect of temperature on growth and feed utilization was studied over 56 days in Atlantic cod of different haemoglobin subtypes [designated Hb-I(1/1), Hb-I(1/2), and Hb-I(2/2)]. The fish, held in triplicate tanks, were reared at 6 and 14°C (mean initial body weight, 218 and 212 g, respectively). These temperatures are close to the preferred temperatures of Hb-I(2/2) (8.2°C) and Hb-I(1/1) (15.4°C). Temperature had a significant effect on SGR, with cod of all haemoglobin variants growing best at 14°C (P b 0.05). There was no significant effect of Hb-I ⁎ subtype on SGR. Since cod of type Hb-I(2/2) had a higher SGR at 14°C than at 6°C this suggests that the temperature preferendum may not provide a good indicator of optimum growth temperature. Significant differences between the Hb-I ⁎ variants were detected in several nutritional indicators. At 14°C, the feed efficiency was poorer in the Hb-I(1/2) cod (0.99 ± 0.08) than in the Hb-I(1/1) and Hb-I(2/2) fish (1.35 ± 0.05 and 1.52 ± 0.07, respectively). Energy retention was significantly lower in the Hb-I(1/2) fish (19.5 ± 3.7%) than in the Hb-I(2/2) fish (43.8 ± 1.8%) at 14°C. Regardless of the Hb-I ⁎ subtype, retention of macronutrients and conversion efficiencies were better in fish reared at 6 than 14°C.
Physiological and …, 2009
Hemoglobin (Hb) polymorphism in cod is associated with temperature-related differences in biogeographical distribution, and several authors have suggested that functional characteristics of the various hemoglobin isoforms (HbIs) directly influence phenotypic traits such as growth rate. However, no study has directly examined whether Hb genotype translates into physiological differences at the whole animal level. Thus, we generated a family of juvenile Atlantic cod consisting of all three main Hb genotypes (HbI-1/1, HbI-2/2, and HbI-1/2) by crossing a single pair of heterozygous parents, and we compared their metabolic and cortisol responses to an acute thermal challenge (10ЊC to their critical thermal maximum [CTM] or 22ЊC, respectively) and tolerance of graded hypoxia. There were no differences in routine metabolism (at 10ЊC), maximum metabolic rate, metabolic scope, CTM (overall mean 22.9Њ ע), or resting and poststress plasma cortisol levels among 0.2ЊC Hb genotypes. Further, although the HbI-1/1 fish grew more (by 15%-30% during the first 9 mo) when reared at 10Њ ע and had a slightly enhanced hypoxia tolerance at 10ЊC (e.g., 1ЊC the critical O 2 levels for HbI-1/1, HbI-2/2, and HbI-1/2 cod were , , and 35.56% ע 1.24% 40.56% ע 1.99% 40.20% ע air saturation, respectively), these results are contradic-1.19% tory to expectations based on HbI functional properties. Thus, our findings (1) do not support previous assumptions that growth rate differences among cod Hb genotypes result from a more efficient use of the oxygen supply-that is, reduced standard metabolic rates and/or increased metabolic capacityand (2) suggest that in juvenile cod, there is no selective advantage to having a particular Hb genotype with regards to the capacity to withstand ecologically relevant environmental challenges.
Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 2013
Haemoglobin polymorphism in cod (Gadus morhua L) has been investigated throughout the last 50 years. Field studies have shed light on the geographic distribution of the two common alleles (HbI 1 and HbI 2 ), and laboratory studies have shown effects of genotype on physiological traits such as growth, reproduction and hypoxia tolerance. The geographic distribution of alleles shows a correlation with temperature, with increasing frequency of HbI 1 in warmer areas. This is likely due to temperature-related differences in oxygen affinity of the three genotypes. We provide a general ecological introduction to cod haemoglobin polymorphism and a detailed discussion of physiological studies, particularly laboratory growth studies. Although differences in oxygen uptake are almost certainly a contributory mechanism to observed differences in traits such as growth rate, many other environmental, behavioural and social factors may also contribute, making it difficult to quantify the effect of HbI either experimentally or in the field.
Sarsia, 2000
To succeed in scramble competition for food an individual fish will have to have characteristics that allow it to respond rapidly to encountered prey. A trait such as metabolic rate, which has a positive effect on oxygen consumption and growth rate, is likely to be positively correlated with the traits that determine the speed of reaction. An important factor underlying metabolic rate may be the transport efficiency of oxygen from the gills to the respiring tissue and this is mediated by the structure of the haemoglobin molecule. In cod, two structures of this molecule exist due to polymorphism at the HbI* locus. An individual cod may be homozygous (HbI*1/1 or HbI*2/2) or heterozygous (HbI*1/2). Evidence exists in the literature that HbI*2/2 fish have higher growth rate and earlier maturation and higher transport efficiency of oxygen at low temperature. However, no study has examined whether this could be associated with fish behaviour. In a study reported here we designed an experiment to test the hypothesis that fish with the HbI*2/2 genotype have a higher motivation to feed and are better competitors than individuals with the other haemoglobin genotypes and that they will eat a larger share of the prey. We use prey capture success early in a feeding trial and the rank of the first prey taken, as proxyvariables for competitive performance. Randomly chosen one-year-old cod Gadus morhua L. in small groups were tested experimentally for individual responses to prey offered sequentially. We analysed the effect on competitive performance of haemoglobin genotype, group, fish size, sex, maturation status and unobserved effects using Components of Variance Analysis, which accounts for repeated observations from the same individuals. The most successful fish were usually among the first to feed and tended to possess haemoglobin genotype HbI*2/2. Other factors such as body size, sex, stage of maturation and group also had effects which may modify the effect set by genotype. Our results suggest that the link between HbI* genotype and growth is through feeding behaviour and it supports the idea that fish with HbI*2/2 genotype are better able to support an active metabolism. The results obtained are among the first on fish that show that variation in feeding behaviour could be under genetic control.
Fish Physiology and …, 2005
The present paper describes the growth properties of juvenile Atlantic cod (Gadus morhua) reared at 7, 10, 13 and 16°C, and a group reared under ''temperature steps'' i.e. with temperature reduced successively from 16 to 13 and 10°C. Growth rate and feed conversion efficiency of juvenile Atlantic cod were significantly influenced by the interaction of temperature and fish size. Overall growth was highest in the 13°C and the T-step groups but for different reasons, as the fish at 13°C had 10% higher overall feeding intake compared to the T-step group, whereas the T-step had 8% higher feeding efficiency. After termination of the laboratory study the fish were reared in sea pens at ambient conditions for 17 months. The groups performed differently when reared at ambient conditions in the sea as the T-step group was 11.6, 11.5, 5.3 and 7.5% larger than 7, 10, 13 and 16°C, respectively in June 2005. Optimal temperature for growth and feed conversion efficiency decreased with size, indicating an ontogenetic reduction in optimum temperature for growth with increasing size. The results suggest an optimum temperature for growth of juvenile Atlantic cod in the size range 5-50 g dropping from 14.7°C for 5-10 g juvenile to 12.4°C for 40-50 g juvenile. Moreover, a broader parabolic regression curve between growth, feed conversion efficiency and temperature as size increases, indicate increased temperature tolerance with size. The study confirms that juvenile cod exhibits ontogenetic variation in temperature optimum, which might partly explain different spatial distribution of juvenile and adult cod in ocean waters. Our study also indicates a physiological mechanism that might be linked to cod migrations as cod may maximize their feeding efficiency by active thermoregulation.
Marine Ecology Progress Series, 2003
The relationship between the somatic growth rate (G) and feeding level (unfed, intermediate, and maximum rations) of age-0 juvenile cod Gadus morhua and haddock Melanogrammus aeglefinus was quantified at different temperatures. Laboratory trials were conducted using 2 sizeclasses of cod (3.6 to 5.6 cm standard length [SL], and 8.1 to 12.4 cm SL) at 5, 8, 12, and 15°C, and 1 size-class of haddock (6.0 to 9.6 cm SL) at 8 and 12°C. The shape of the growth-feeding relationship was well described by a 3-parameter asymptotic function for cod and by a linear function for haddock (R 2 range = 0.837 to 0.966). The growth rate and scope for growth were maximum at 12°C, whereas growth efficiency was greatest (26.0 to 32.2%) at temperatures between 5 and 8°C. Juvenile cod held at 15°C exhibited reduced rates and efficiencies of somatic growth compared to fish at other temperatures. Biochemical-based growth indicators for age-0 juveniles were calibrated from measurements of the amounts of RNA, DNA, and protein in white muscle samples. A multiple linear regression using RNA:DNA and temperature as independent variables explained a significant portion of the variability observed in G of juvenile cod (R 2 = 0.716) and haddock (R 2 = 0.637). This relationship may be useful in estimating recent growth of age-0 juvenile cod and haddock in the field.
Marine Biology Research, 2005
The effect of Hb-I* phenotype on white muscle lactate dehydrogenease (LDH, E. C. 1.1.1.27) activity and buffering capacity was studied in Atlantic cod ( Gadus morhua ), acclimated and measured at temperatures near their behavioral temperature preference. It was hypothesized that these conditions would optimize biochemical processes but no difference was found in LDH activity between the Hb-I* phenotype after 56 dofa cclimation to 6and 148 C. However, LDH activity was both mass-and temperature-dependent; mean activity was 162.29 / 5.0 and 275.99 / 6.4 IU g 1 wetmass (mean9 / SEM) at 6a nd 148 Cr espectively and larger fish had the highest rate of enzyme activity.W hite muscle buffer capacity was unaffected by Hb-I* phenotype but higher in cod held at 148 C.