Cardiac and Locomotory Muscle Mass in Antarctic Fishes
199
benthopelagic trawls. Although the species list for the sampling region
numbered about 50, based on the outcome of the first 5 trawls it was
decided due to logistical constraints to concentrate sampling on only those
species that were frequently caught and had a good size range. Five key
species were selected from different niches: Champsocephalus gunnari
(active, pelagic channichthyid), Chaenocephalus aceratus (sluggish,
epibenthic channichthyid), Dissostichus mawsoni (active, pelagic
nototheniid), Gobionotothen gibberifrons (sluggish, benthic nototheniid),
and Notothenia rossii (relatively active, benthopelagic nototheniid).
Blunt dissection on fresh fish was performed to remove the ventricle,
spleen, and the lateral and medial pectoral muscles. These were stored
frozen (-30 DC) and accurately weighed on return to the UK. Hearts were
cut open and residual blood removed by blotting. Samples and carcasses
were transported frozen (-30 DC) back to the Alfred-Wegener Institute at
Bremerhaven, where they were weighed and further samples taken for
analysis. Muscle mass relative to total or lean (gonad free) body mass, to
avoid complication due to different stages of sexual maturity, was
examined in an allometric analysis to allow comparison with data from
inshore epibenthic or benthic Antarctic and temperate marine fish species.
Results and Discussion
The relationships between body mass and mass of total skeletal muscle,
ventricle, lateral and medial pectoral muscles are plotted in Figs. 1 to 4.
The relative masses of the ventricle, total skeletal muscle and pectoral
muscles in all five species are displayed in Table 1, along with values for
the relative mass of the spleen as a comparative non':muscle organ.
The scaling of ventricular mass showed a clear separation between
channichthyids and nototheniids that reflects the substantial reduction in
oxygen carrying capacity of the former, and the need to generate a much
higher cardiac output [6,7]. More surprising is the apparent lack of a
separation according to ecotype, i.e. C. gunnari was similar to C. aceratus
while D. mawsoni was similar to G. gibberifrons and N rossii (Fig. 1).
Interestingly, all species showed a strikingly similar allometric
relationship between total skeletal muscle mass and body mass (Fig. 2).
Other organ systems showed no consistent difference among species,
e.g. spleen mass (data not shown). As with many other perciform families,
notothenioids rely mainly on labriform locomotion (involving pectoral
muscles) using sub-carangiform locomotion (involving trunk muscle) only
during burst swimming.
199
benthopelagic trawls. Although the species list for the sampling region
numbered about 50, based on the outcome of the first 5 trawls it was
decided due to logistical constraints to concentrate sampling on only those
species that were frequently caught and had a good size range. Five key
species were selected from different niches: Champsocephalus gunnari
(active, pelagic channichthyid), Chaenocephalus aceratus (sluggish,
epibenthic channichthyid), Dissostichus mawsoni (active, pelagic
nototheniid), Gobionotothen gibberifrons (sluggish, benthic nototheniid),
and Notothenia rossii (relatively active, benthopelagic nototheniid).
Blunt dissection on fresh fish was performed to remove the ventricle,
spleen, and the lateral and medial pectoral muscles. These were stored
frozen (-30 DC) and accurately weighed on return to the UK. Hearts were
cut open and residual blood removed by blotting. Samples and carcasses
were transported frozen (-30 DC) back to the Alfred-Wegener Institute at
Bremerhaven, where they were weighed and further samples taken for
analysis. Muscle mass relative to total or lean (gonad free) body mass, to
avoid complication due to different stages of sexual maturity, was
examined in an allometric analysis to allow comparison with data from
inshore epibenthic or benthic Antarctic and temperate marine fish species.
Results and Discussion
The relationships between body mass and mass of total skeletal muscle,
ventricle, lateral and medial pectoral muscles are plotted in Figs. 1 to 4.
The relative masses of the ventricle, total skeletal muscle and pectoral
muscles in all five species are displayed in Table 1, along with values for
the relative mass of the spleen as a comparative non':muscle organ.
The scaling of ventricular mass showed a clear separation between
channichthyids and nototheniids that reflects the substantial reduction in
oxygen carrying capacity of the former, and the need to generate a much
higher cardiac output [6,7]. More surprising is the apparent lack of a
separation according to ecotype, i.e. C. gunnari was similar to C. aceratus
while D. mawsoni was similar to G. gibberifrons and N rossii (Fig. 1).
Interestingly, all species showed a strikingly similar allometric
relationship between total skeletal muscle mass and body mass (Fig. 2).
Other organ systems showed no consistent difference among species,
e.g. spleen mass (data not shown). As with many other perciform families,
notothenioids rely mainly on labriform locomotion (involving pectoral
muscles) using sub-carangiform locomotion (involving trunk muscle) only
during burst swimming.