ANTARUTIU BENTHOS
131
Females with ripening eggs, especially in late August have much
lower respiratory levels than males or immature females (Wohlschlag,
1964). This may well result in different behaviour patterns between
males and mature females at this time and may well account for only
males being caught by line and trap at this period of the year.
Too little is known as yet of the possible causes of different breeding
periods in such areas as McMurdo Sound and the Adelie Coast, separated
by about 670 latitudinal nautical miles. Similar differences have been
noted for the starfish, Odontaster validus (Pearse, 1965). Sea temperature
differences are slight, but even these slight differences have been shown
to be sufficient to cause appreciable changes in the abundance of phytoplankton. Pearse (1965) has suggested that the time the shelf ice breaks
out may have more significance than temperature as such.
Wohlschlag (1964) has given a summary of his work on the physiology of Trematomus bernacchi, and has given details of his methods
in a series of papers (Wohlschlag, 1959-64). Oxygen consumption rates
increased with rising temperatures up to about 0°C and above that
decreased (Wohlschlag, 1960). On the whole throughout the year there
were only slight differences between the sexes in respiratory rates except
for a very great difference for late winter collections from very deep
water, a phenomenon which Wohlschlag considered of purely local
significance. Females in this species appear to have much faster growth
rates,and much higher survival rates than do males (Wohlschlag, 1961a),
possibly a direct correlation of their lower metabolic maintenance
requirements (Wohlschlag, 1962b). Field observations indicate that
many of the Nototheniiformes are relatively inactive in life, and
laboratory experiments bear this out. Slight artificial rises in temperature cause a tendency to swim even more slowly. Their optimum
swimming speed is obtained at the lowest possible temperatures (i.e.
those found in their normal habitat), in contrast to the results obtained
with temperate species.
Some specimens of T . bernacchi can live for long periods under sea
ice (perhaps even permanently). Specimens collected from beneath the
Koettlitz Glacier at Heald Island are paler coloured than fish from open
waters, or from under the annual ice sheet. These fishes from deep
water appear to have a significantly lower metabolism than those from
areas with good light penetration.
5. General Antarctic fish physiology
Work has begun to try to determine something of the modifications
in these fishes which are of adaptive significance for cold conditions.
131
Females with ripening eggs, especially in late August have much
lower respiratory levels than males or immature females (Wohlschlag,
1964). This may well result in different behaviour patterns between
males and mature females at this time and may well account for only
males being caught by line and trap at this period of the year.
Too little is known as yet of the possible causes of different breeding
periods in such areas as McMurdo Sound and the Adelie Coast, separated
by about 670 latitudinal nautical miles. Similar differences have been
noted for the starfish, Odontaster validus (Pearse, 1965). Sea temperature
differences are slight, but even these slight differences have been shown
to be sufficient to cause appreciable changes in the abundance of phytoplankton. Pearse (1965) has suggested that the time the shelf ice breaks
out may have more significance than temperature as such.
Wohlschlag (1964) has given a summary of his work on the physiology of Trematomus bernacchi, and has given details of his methods
in a series of papers (Wohlschlag, 1959-64). Oxygen consumption rates
increased with rising temperatures up to about 0°C and above that
decreased (Wohlschlag, 1960). On the whole throughout the year there
were only slight differences between the sexes in respiratory rates except
for a very great difference for late winter collections from very deep
water, a phenomenon which Wohlschlag considered of purely local
significance. Females in this species appear to have much faster growth
rates,and much higher survival rates than do males (Wohlschlag, 1961a),
possibly a direct correlation of their lower metabolic maintenance
requirements (Wohlschlag, 1962b). Field observations indicate that
many of the Nototheniiformes are relatively inactive in life, and
laboratory experiments bear this out. Slight artificial rises in temperature cause a tendency to swim even more slowly. Their optimum
swimming speed is obtained at the lowest possible temperatures (i.e.
those found in their normal habitat), in contrast to the results obtained
with temperate species.
Some specimens of T . bernacchi can live for long periods under sea
ice (perhaps even permanently). Specimens collected from beneath the
Koettlitz Glacier at Heald Island are paler coloured than fish from open
waters, or from under the annual ice sheet. These fishes from deep
water appear to have a significantly lower metabolism than those from
areas with good light penetration.
5. General Antarctic fish physiology
Work has begun to try to determine something of the modifications
in these fishes which are of adaptive significance for cold conditions.