The ecological significance of certain new haematological findings in the mole and hedgehog

Quilliam, T. A.; Clarke, J. A.; Salsbury, A. J.

doi:10.1016/0300-9629(71)90150-2

Cited by 24 publications

(15 citation statements)

References 11 publications

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“…However, the Hb of this species possesses an additional external histidyl residue (δ69His; Figure 4) relative to other moles that should mitigate this effect. Finally, by stabilizing the tense (deoxy) conformation of eastern mole Hb, the δ136Gly→Glu replacement also confers a marked reduction in their whole-blood O 2 affinity (a 5-6 mm Hg increase in their P 50 ) compared to coast (see Figure 3) and European moles [1,3,4]. This reduced blood affinity would facilitate the offloading of O 2 at a relatively high PO 2 , leading to a large O 2 gradient between the plasma and tissues during burst tunnelling activities.…”

Section: Discussionmentioning

confidence: 99%

“…This reduced blood affinity would facilitate the offloading of O 2 at a relatively high PO 2 , leading to a large O 2 gradient between the plasma and tissues during burst tunnelling activities. This shift may negatively impact the O 2 saturation of eastern mole blood during periods of hypoxia, but is presumably mitigated by elevated blood hematocrit (56.4%) and Hb concentrations (19.2 g dL -1 ; Table 3) compared to coast (46.8% and 17.4 g dL -1 ; [45]), star-nosed (50.5% and 17.2 g dL -1 ; [45]), Townsend's (46.4% and 16.9 g dL -1 ; [46]) and European moles (48.7% and 17.4 g dL -1 ; [1]). Eastern moles thus present a novel category of Hbs that appear to be specifically engineered for burst activities in gas-exchange impeded burrows.…”

Section: Discussionmentioning

confidence: 99%

“…Among mammals that are adapted to hypoxic environments, only subterranean species are also obliged to breathe air with elevated concentrations of carbon dioxide [1]. Within this select group, the 25 or so species of fossorial moles (Family Talpidae) are among the few that live exclusively underground.…”

Section: Introductionmentioning

confidence: 99%

“…The high metabolic costs of burrowing, in terms of O 2 consumption and CO 2 production, are exacerbated by the obligate re-breathing of expired air while tunnelling, and may therefore require adaptive modifications in hemoglobin (Hb) function. Not surprisingly, whole blood O 2 affinity of the European mole, Talpa europaea , is much higher (its half saturation O 2 pressure or P 50 is 10-15 mm Hg lower) than those of terrestrial mammals of similar size [1,3,4]. This feature has been attributed to a reduced affinity of European mole Hb for 2,3-diphosphoglycerate (DPG) [4,5], which binds to a cluster of positively charged residues between the β-type chains and stabilizes the low affinity (deoxy) conformation of the molecule.…”

Section: Introductionmentioning

confidence: 99%

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Molecular basis of a novel adaptation to hypoxic-hypercapnia in a strictly fossorial mole

et al. 2010

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BackgroundElevated blood O2 affinity enhances survival at low O2 pressures, and is perhaps the best known and most broadly accepted evolutionary adjustment of terrestrial vertebrates to environmental hypoxia. This phenotype arises by increasing the intrinsic O2 affinity of the hemoglobin (Hb) molecule, by decreasing the intracellular concentration of allosteric effectors (e.g., 2,3-diphosphoglycerate; DPG), or by suppressing the sensitivity of Hb to these physiological cofactors.ResultsHere we report that strictly fossorial eastern moles (Scalopus aquaticus) have evolved a low O2 affinity, DPG-insensitive Hb - contrary to expectations for a mammalian species that is adapted to the chronic hypoxia and hypercapnia of subterranean burrow systems. Molecular modelling indicates that this functional shift is principally attributable to a single charge altering amino acid substitution in the β-type δ-globin chain (δ136Gly→Glu) of this species that perturbs electrostatic interactions between the dimer subunits via formation of an intra-chain salt-bridge with δ82Lys. However, this replacement also abolishes key binding sites for the red blood cell effectors Cl-, lactate and DPG (the latter of which is virtually absent from the red cells of this species) at δ82Lys, thereby markedly reducing competition for carbamate formation (CO2 binding) at the δ-chain N-termini.ConclusionsWe propose this Hb phenotype illustrates a novel mechanism for adaptively elevating the CO2 carrying capacity of eastern mole blood during burst tunnelling activities associated with subterranean habitation.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Molecular basis of a novel adaptation to hypoxic-hypercapnia in a strictly fossorial mole

et al. 2010

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“…It has been suggested that the high O 2 affinity of European mole blood (P 50 20-24mmHg) may be advantageous in loading O 2 in chronically hypoxic burrows (Bartels et al, 1969;Quilliam et al, 1971;Jelkmann et al, 1981). However, the same may not be expected for small (10-12g) semi-fossorial species such as the American shrew mole, which not only constructs shallow tunnel galleries but also frequently forages above ground (Dalquest and Orcutt, 1942).…”

Section: Oxygen Binding Propertiesmentioning

confidence: 99%

Origin and mechanism of thermal insensitivity in mole hemoglobins: a test of the ‘additional’ chloride binding site hypothesis

Signore

Stetefeld

Weber

et al. 2012

Journal of Experimental Biology

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SUMMARY The structural and evolutionary origins underlying the effect of temperature on the O2 binding properties of mammalian hemoglobins (Hbs) are poorly understood, despite their potential physiological importance. Previous work has shown that the O2 affinities of the blood of the coast mole (Scapanus orarius) and the eastern mole (Scalopus aquaticus) are significantly less sensitive to temperature changes than that of the star-nosed mole (Condylura cristata). It was suggested that this difference may arise from the binding of ‘additional’ chloride ions within a cationic pocket between residues 8His, 76Lys and 77Asn on the β-like δ-globin chains of coast and eastern mole Hbs. To test this hypothesis, we deduced the primary sequences of star-nosed mole and American shrew mole (Neurotrichus gibbsii) Hb, measured the sensitivity of these respiratory proteins to allosteric effector molecules and temperature, and calculated their overall oxygenation enthalpies (ΔH′). Here we show that the variability in ΔH′ seen among mole Hbs cannot be attributed to differential Cl– binding at δ8, δ76 and δ77, as the Cl– sensitivity of mole Hbs is unaffected by amino acid changes at this site (i.e. the proposed ‘additional’ Cl– binding site is not operational in mole Hbs). Rather, we demonstrate that the numerically low ΔH′ of coast and eastern mole Hbs results from heightened proton binding relative to other mole Hbs. Comparative sequence analysis and molecular modelling moreover suggest that this attribute evolved in a common ancestor of these two fossorial lineages and arises from the development of a salt bridge between a pair of amino acid residues (δ125His and α34Glu/Asp) that are not present in other mole Hbs.

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Comparative Mammalian Respiratory Control

Tenney

Boggs

1986

Comprehensive Physiology

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The ecological significance of certain new haematological findings in the mole and hedgehog

Cited by 24 publications

References 11 publications

Molecular basis of a novel adaptation to hypoxic-hypercapnia in a strictly fossorial mole

Molecular basis of a novel adaptation to hypoxic-hypercapnia in a strictly fossorial mole

Origin and mechanism of thermal insensitivity in mole hemoglobins: a test of the ‘additional’ chloride binding site hypothesis

Comparative Mammalian Respiratory Control

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