132
R. K. DELL
Morris (1966) reported that investigation of the possible effect of the
thyroid in maintaining the high metabolic rate showed no significant
results.
Somero and DeVries (1967) showed that three species of Trematomus including T . bernacchi survived supercooling to -2.5OC but that
the upper lethal temperature of 6°C is unusually low. The main site of
thermal injury appears t o be the central nervous system.
DeVries (1969) reported low blood serum freezing points from
-1.2OC to -2.O"C. No differences could be discerned between freezing
resistances of fishes from McMurdo Sound and the Antarctic Peninsula.
Glucoprotein appeared to be the main depressant factor. DeVries
(1970) summarized the work on freezing resistance in Antarctic fishes.
Fishes from deeper water in McMurdo Sound such as the zoarcid
Rhigophila dearborni DeWitt and a liparid are supercooled. They survive in this state because there is no ice present. When they are drawn
to the surface in traps during the winter, they pass through water
containing ice crystals and promptly freeze. Other fishes occurring in
the area showed a range of resistance to freezing. Some deep-water
populations differed from shallow-water populations of the same
species.
Investigation of the serum structure shows that an efficient and
complicated antifreeze substance is present. Sodium chloride is responsible for about 80% of serum freezing-point depression in temperate
fishes. In the Antarctic species of Trematomus studied, sodium chloride
accounts for less than half of the depression. The other antifreeze
substance appeared basically to be a protein containing carbohydrate.
DeVries (1970, p. 328) gave a preliminary description of its structure in
a postscript. The mechanism by which it achieves its quite spectacular
results is still unknown.
Fishes of the genus Notothenia, and one species of Trematomus
studied at the South Orkneys (Smith, 1970) proved also to be supercooled. When these fishes did freeze the indications were that " seeding " took place with the presence of ice at the gills. I n contrast to the
results on fishes studied at McMurdo Sound, depression of the freezing
point of the blood serum appeared to be largely due to sodium chloride.
Wohlschlag's work, especially on members of the Nototheniiformes,
has shown that these Antarctic fishes have a higher metabolic level than
fishes elsewhere, when compared with the same standards. The experimental work showed that these fishes have attained a very high level
of metabolic cold adaptation. Wohlschlag believes that such fishes
have a more efficient mechanism for converting energy into growth.
Robilliard and Dayton (1969) reported on the general behaviour of
R. K. DELL
Morris (1966) reported that investigation of the possible effect of the
thyroid in maintaining the high metabolic rate showed no significant
results.
Somero and DeVries (1967) showed that three species of Trematomus including T . bernacchi survived supercooling to -2.5OC but that
the upper lethal temperature of 6°C is unusually low. The main site of
thermal injury appears t o be the central nervous system.
DeVries (1969) reported low blood serum freezing points from
-1.2OC to -2.O"C. No differences could be discerned between freezing
resistances of fishes from McMurdo Sound and the Antarctic Peninsula.
Glucoprotein appeared to be the main depressant factor. DeVries
(1970) summarized the work on freezing resistance in Antarctic fishes.
Fishes from deeper water in McMurdo Sound such as the zoarcid
Rhigophila dearborni DeWitt and a liparid are supercooled. They survive in this state because there is no ice present. When they are drawn
to the surface in traps during the winter, they pass through water
containing ice crystals and promptly freeze. Other fishes occurring in
the area showed a range of resistance to freezing. Some deep-water
populations differed from shallow-water populations of the same
species.
Investigation of the serum structure shows that an efficient and
complicated antifreeze substance is present. Sodium chloride is responsible for about 80% of serum freezing-point depression in temperate
fishes. In the Antarctic species of Trematomus studied, sodium chloride
accounts for less than half of the depression. The other antifreeze
substance appeared basically to be a protein containing carbohydrate.
DeVries (1970, p. 328) gave a preliminary description of its structure in
a postscript. The mechanism by which it achieves its quite spectacular
results is still unknown.
Fishes of the genus Notothenia, and one species of Trematomus
studied at the South Orkneys (Smith, 1970) proved also to be supercooled. When these fishes did freeze the indications were that " seeding " took place with the presence of ice at the gills. I n contrast to the
results on fishes studied at McMurdo Sound, depression of the freezing
point of the blood serum appeared to be largely due to sodium chloride.
Wohlschlag's work, especially on members of the Nototheniiformes,
has shown that these Antarctic fishes have a higher metabolic level than
fishes elsewhere, when compared with the same standards. The experimental work showed that these fishes have attained a very high level
of metabolic cold adaptation. Wohlschlag believes that such fishes
have a more efficient mechanism for converting energy into growth.
Robilliard and Dayton (1969) reported on the general behaviour of