Haemoglobin genotypes in cod (Gadus morhua L): Their geographic distribution and physiological significance

Abstract

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.

Otoliths as individual indicators: a reappraisal of the link between fish physiology and otolith characteristics

“…A classic example is the different haemoglobin genotypes in Atlantic cod (Ross et al 2013). Temperature preference has been shown to vary between haemoglobin genotypes and relate to differences in oxygen affinity between genotypes.…”

Comparative Transcripto me Analysis Depicts Candidate Genes Involved in Skin Color Differentiation in Red Tilapia

“…Fish belongs to poikilothermic animals whose body temperature varies with the environmental temperature [3]. It is well known that water temperature affects the survival, growth, metabolism, reproduction of sh [4]. Tilapia is a warm-water sh with a temperature tolerance of 6-42 °C, but the tolerance to low temperature is in uenced by water quality, sh age and health status [5].…”

ATP-induced reversed thermal sensitivity of O2 binding in both major hemoglobin polymorphs of the non-endothermic Atlantic cod, Gadus morhua

“…Environmental temperature has been referred to as the ecological master factor that profoundly affects the life of all ectotherms, where high, stable body temperatures independent of the environment cannot be achieved by metabolic means (Brett, 1971;Brown et al, 2004;Ross et al, 2013). This particularly applies to aquatic ectotherms such as fishes, where the large volume and heat capacity of water ventilated across their gills tends to equilibrate body temperature with that of the environment (Fry, 1967).…”

“…Concerns about the fate of aquatic ectotherms such as Atlantic cod in an age of climate change has sparked renewed interest in the underlying mechanisms that allow some species or populations to tolerate higher temperatures than others (Pörtner, 2001;Pörtner and Farrell, 2008;Eliason et al, 2011;Anttila et al, 2013). One of the few known and most frequently discussed genetic differences between southern, warm-water and northern, cold-water stocks of Atlantic cod that involves a component of the cardio-respiratory O 2 supply cascade is the polymorphism of HbI, the major haemoglobin (Hb) type expressed in the red blood cells (RBCs) of juvenile and adult Atlantic cod (reviewed by Andersen, 2012;Ross et al, 2013). Searching for selectively neutral genetic markers of population structure of North East Atlantic fish species and using agar gel electrophoresis, Sick (1961) described a minor (HbII) and a polymorphic major (HbI) Hb component in blood of Atlantic cod.…”