340
G. di Prisco
crystallography and molecular modeling have allowed us to try correlating
amino acid sequence, multiplicity and oxygen binding features of
hemoglobin with ecological constraints. In collaboration with W.T. Starn
and J.J. Beintema, amino acid sequences are used as a source of
phylogenetic information on evolution. The oxygen-transport system of
nonAntarctic Bovichtidae (the most primitive notothenioid family) has
been characterized for the first time, providing further indications on
evolution. In collaboration with H.W. Detrich, we are also investigating
the status of globin genes in Hb-less icefishes and evaluating evolutionary
mechanisms leading to the Hb-less phenotype.
Antarctic Notothenioidei
Cold adaptation was developed during the last 20-30 million years of
increasing isolation south of the Polar Front, a barrier to migration in both
directions and thus a key factor for fish evolution. Antarctic fish are now
characterized by physiological and biochemical (often unique)
specializations.
The adaptive reduction in erythrocyte count and Hb content/multiplicity
in the blood of Antarctic fish counterbalances the increase in blood
viscosity produced by the subzero seawater temperature [9] with
potentially negative physiological effects (i.e. higher demand of energy
needed for circulation).
On the other hand, the coexistence of Hb-less and naturally cytopenic
red-blooded species suggests that the need for an oxygen carrier in a
stable, cold environment is reduced also in red-blooded fish. In fact,
functional incapacitation of Hb (by means of exposure to carbon
monoxide) and reduction of the hematocrit from 8-15% to <1% in
cannulated specimens of Trematomus bernacchii [9,10] caused no
discernible harm in the absence of metabolic challenges. Similar to
channichthyids, red-blooded fish can carry routinely needed oxygen
dissolved in the plasma. Our findings on globin genes in Hb-less species
(see below), suggesting that the loss of gene expression is a primitive
character (established in the ancestral channichthyid about 25 million years
ago, prior to diversification within the clade), open promising pathways for
evolutionary studies.
As clearly shown by the contributions in this volume, Notothenioidei are
by far the most thoroughly characterized group of fish in the world. For
example, our studies on their oxygen-transport system have so far been
addressed to 38 out of a total of 80 red-blooded Antarctic species. This
highly representative number encompasses all families and also two
species of nonAntarctic notothenioids.
G. di Prisco
crystallography and molecular modeling have allowed us to try correlating
amino acid sequence, multiplicity and oxygen binding features of
hemoglobin with ecological constraints. In collaboration with W.T. Starn
and J.J. Beintema, amino acid sequences are used as a source of
phylogenetic information on evolution. The oxygen-transport system of
nonAntarctic Bovichtidae (the most primitive notothenioid family) has
been characterized for the first time, providing further indications on
evolution. In collaboration with H.W. Detrich, we are also investigating
the status of globin genes in Hb-less icefishes and evaluating evolutionary
mechanisms leading to the Hb-less phenotype.
Antarctic Notothenioidei
Cold adaptation was developed during the last 20-30 million years of
increasing isolation south of the Polar Front, a barrier to migration in both
directions and thus a key factor for fish evolution. Antarctic fish are now
characterized by physiological and biochemical (often unique)
specializations.
The adaptive reduction in erythrocyte count and Hb content/multiplicity
in the blood of Antarctic fish counterbalances the increase in blood
viscosity produced by the subzero seawater temperature [9] with
potentially negative physiological effects (i.e. higher demand of energy
needed for circulation).
On the other hand, the coexistence of Hb-less and naturally cytopenic
red-blooded species suggests that the need for an oxygen carrier in a
stable, cold environment is reduced also in red-blooded fish. In fact,
functional incapacitation of Hb (by means of exposure to carbon
monoxide) and reduction of the hematocrit from 8-15% to <1% in
cannulated specimens of Trematomus bernacchii [9,10] caused no
discernible harm in the absence of metabolic challenges. Similar to
channichthyids, red-blooded fish can carry routinely needed oxygen
dissolved in the plasma. Our findings on globin genes in Hb-less species
(see below), suggesting that the loss of gene expression is a primitive
character (established in the ancestral channichthyid about 25 million years
ago, prior to diversification within the clade), open promising pathways for
evolutionary studies.
As clearly shown by the contributions in this volume, Notothenioidei are
by far the most thoroughly characterized group of fish in the world. For
example, our studies on their oxygen-transport system have so far been
addressed to 38 out of a total of 80 red-blooded Antarctic species. This
highly representative number encompasses all families and also two
species of nonAntarctic notothenioids.