198
R.E Robertson et aJ.
levels, even in species living in the water column. Consequently pelagic
Antarctic fishes show differences in the relative utilisation of the major
skeletal muscle masses, suggesting morphormetric adaptations
distinguishing sluggish from more active species [4].
Some striking adaptations are found among Antarctic fishes, including
the presence of antifreeze glycopeptides in the blood (see Cheng, this
Vol.) together with the development of aglomerular kidneys, and, in the
icefishes, enlarged hearts and absence of respiratory pigments [3]. In
general, rates of physiological systems are lower than found in temperate
species, and maximal power output of fast muscle in Antarctic fish at 0 °C
is only a third that of tropical species at 25°C. While the factorial scope
(the difference between resting and maximal activity) is similar for
Antarctic and tropical species, the absolute metabolic flux is significantly
less in the former [1]. This severely limits the power available for
locomotion and may explain the relative paucity of truly pelagic species in
Antarctica, although it remains unclear to what degree species from
different niches are restricted in their swimming capacity.
Despite the expanding literature on the strategies that have evolved to
cope so successfully with life in the cold, many questions remain
unresolved. In particular, much of the physiological data derives from
inshore, rather sluggish species so that at least some of the findings may
be biased by the type of species available for study, and may not be
representative of the broader Antarctic fish fauna. For example, an unusual
and possibly unique vertebrate stress response has been documented in
sluggish inshore species, where a rise in circulating catecholamines (the
classic "flight or fight" hormones) is apparently absent [5]. The aim of this
study was to examine a range of Antarctic fish species from different
niches for signs of morphometric adaptations for active locomotion. This
was achieved by scaling ventricle and locomotory muscle masses (total
skeletal and lateral and medial pectoral muscles) in a red-blooded pelagic
nototheniid as indices of the effort required to maintain an active lifestyle.
Values were compared to those obtained from benthic species, and those
obtained from fishes characterised by the absence of respiratory pigments
(channichthyids), to see if this had any effect on the scaling relationships.
Material and Methods
Various sized specimens of different species were collected from around
King George Island (62°S 58°W) and Elephant Island (61°S 55°W) on the
recent (1996-1997) RV "Polarstem" Ant XIVI2 cruise. Fish were either
caught in 30 min bottom ground trawls (grundschleppnetz) or 1 h
R.E Robertson et aJ.
levels, even in species living in the water column. Consequently pelagic
Antarctic fishes show differences in the relative utilisation of the major
skeletal muscle masses, suggesting morphormetric adaptations
distinguishing sluggish from more active species [4].
Some striking adaptations are found among Antarctic fishes, including
the presence of antifreeze glycopeptides in the blood (see Cheng, this
Vol.) together with the development of aglomerular kidneys, and, in the
icefishes, enlarged hearts and absence of respiratory pigments [3]. In
general, rates of physiological systems are lower than found in temperate
species, and maximal power output of fast muscle in Antarctic fish at 0 °C
is only a third that of tropical species at 25°C. While the factorial scope
(the difference between resting and maximal activity) is similar for
Antarctic and tropical species, the absolute metabolic flux is significantly
less in the former [1]. This severely limits the power available for
locomotion and may explain the relative paucity of truly pelagic species in
Antarctica, although it remains unclear to what degree species from
different niches are restricted in their swimming capacity.
Despite the expanding literature on the strategies that have evolved to
cope so successfully with life in the cold, many questions remain
unresolved. In particular, much of the physiological data derives from
inshore, rather sluggish species so that at least some of the findings may
be biased by the type of species available for study, and may not be
representative of the broader Antarctic fish fauna. For example, an unusual
and possibly unique vertebrate stress response has been documented in
sluggish inshore species, where a rise in circulating catecholamines (the
classic "flight or fight" hormones) is apparently absent [5]. The aim of this
study was to examine a range of Antarctic fish species from different
niches for signs of morphometric adaptations for active locomotion. This
was achieved by scaling ventricle and locomotory muscle masses (total
skeletal and lateral and medial pectoral muscles) in a red-blooded pelagic
nototheniid as indices of the effort required to maintain an active lifestyle.
Values were compared to those obtained from benthic species, and those
obtained from fishes characterised by the absence of respiratory pigments
(channichthyids), to see if this had any effect on the scaling relationships.
Material and Methods
Various sized specimens of different species were collected from around
King George Island (62°S 58°W) and Elephant Island (61°S 55°W) on the
recent (1996-1997) RV "Polarstem" Ant XIVI2 cruise. Fish were either
caught in 30 min bottom ground trawls (grundschleppnetz) or 1 h