Roy E. Weber

Temperature alters the respiratory surface area of crucian carp Carassius carassius and goldfish Carassius auratus

SUMMARY We have previously found that the gills of crucian carp Carassius carassius living in normoxic (aerated) water lack protruding lamellae, the primary site of O2 uptake in fish, and that exposing them to hypoxia increases the respiratory surface area of the gills ∼7.5-fold. We here examine whether this morphological change is triggered by temperature. We acclimated crucian carp to 10, 15, 20 and 25°C for 1 month, and investigated gill morphology, oxygen consumption and the critical oxygen concentration at the different temperatures. As expected, oxygen consumption increased with temperature. Also at 25°C an increase in the respiratory surface area, similar to that seen in hypoxia, occurred. This coincided with a reduced critical oxygen concentration. We also found that the rate of this transformation increased with rising temperature. Goldfish Carassius auratus, a close relative to crucian carp, previously kept at 25°C, were exposed to 15°C and 7.5°C. At 7.5°C the respiratory surface area of its gills was reduced by development of an interlamellar cell mass as found in normoxic crucian carp kept at 10-20°C. Thus, both species alter the respiratory surface area in response to temperature. Rather than being a graded change, the results suggest that the alteration of gill morphology is triggered at a given temperature. Oxygen-binding data reveal very high oxygen affinities of crucian carp haemoglobins, particularly at high pH and low temperature, which may be prerequisites for the reduced gill respiratory surface area at low temperatures. As ambient oxygen and temperature can both induce the remodelling of the gills, the response appears primarily to be an adaptation to the oxygen demand of the fish.

The biology of hagfishes

Evolution, taxonomy and ecology development and pathology the integument and associated glands supporting tissues the muscular system the respiratory system the cardiovascular system the blood and immune system the uro-genital system the endocrine system the nervous system sensory organs.

Evolutionary and functional insights into the mechanism underlying high-altitude adaptation of deer mouse hemoglobin

Adaptive modifications of heteromeric proteins may involve genetically based changes in single subunit polypeptides or parallel changes in multiple genes that encode distinct, interacting subunits. Here we investigate these possibilities by conducting a combined evolutionary and functional analysis of duplicated globin genes in natural populations of deer mice (Peromyscus maniculatus) that are adapted to different elevational zones. A multilocus analysis of nucleotide polymorphism and linkage disequilibrium revealed that high-altitude adaptation of deer mouse hemoglobin involves parallel functional differentiation at multiple unlinked gene duplicates: two α-globin paralogs on chromosome 8 and two β-globin paralogs on chromosome 1. Differences in O2-binding affinity of the alternative β-chain hemoglobin isoforms were entirely attributable to allelic differences in sensitivity to 2,3-diphosphoglycerate (DPG), an allosteric cofactor that stabilizes the low-affinity, deoxygenated conformation of the hemoglobin tetramer. The two-locus β-globin haplotype that predominates at high altitude is associated with suppressed DPG-sensitivity (and hence, increased hemoglobin-O2 affinity), which enhances pulmonary O2 loading under hypoxia. The discovery that allelic differences in DPG-sensitivity contribute to adaptive variation in hemoglobin–O2 affinity illustrates the value of integrating evolutionary analyses of sequence variation with mechanistic appraisals of protein function. Investigation into the functional significance of the deer mouse β-globin polymorphism was motivated by the results of population genetic analyses which revealed evidence for a history of divergent selection between elevational zones. The experimental measures of O2-binding properties corroborated the tests of selection by demonstrating a functional difference between the products of alternative alleles.

Respiratory adaptations in carp blood influences of hypoxia, red cell organic phosphates, divalent cations and CO2 on hemoglobin-oxygen affinity

SummaryThis study concerns the adaptation of oxygen transporting function of carp blood to environment hypoxia, tracing the roles played by erythrocytic cofactors, inorganic cations, carbon dioxide and hemoglobin multiplicity.Carp acclimated to hypoxia (

Functional adaptation and its molecular basis in vertebrate hemoglobins, neuroglobins and cytoglobins

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1 - Hemoglobin Structure and Function

∼30 mmHg) display striking increases in blood oxygen affinity compared to normoxic (

Respiratory properties of blood in awake and estivating lungfish, Protopterus amphibius☆

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