To determine whether an attenuated stress response is a general feature of
Antarctic fish or is dependent on ecotype, the capacity for catecholamine s
ynthesis within the head kidney and plasma levels of the primary stress hor
mones (catecholamines and cortisol) were determined in species with a range
of activity patterns. Tyrosine hydroxylase (TH) activities were similar in
both sluggish (Gobionotothen gibberifons, 153+/-22 nmol g(-1) h(-1), mean
+/- S.E.M.) and active (Notothenia rossii, 185+/-39 nmol g(-1) h(-1), Disso
stichus mawsoni, 128+/-31 nmol g(-1) h(-1)) pelagic nototheniids, but only
30% of those in Atlantic cod (Gadus morhua, 393+/-88 nmol g(-1) h(-1)) at t
he same temperature, TH activities were even lower in white-blooded channic
hthyids (Chaenocephalus aceratus, 74+/-16 nmol g(-1) h(-1) and Champsocepha
lus gunnari, 53+/-17 nmol g(-1) h(-1)), although values in Chionodraco rast
rospinosus were similar to red-blooded species (178+/-45 nmol g(-1) h(-1)),
Circulating catecholamine levels were extremely high in all species after
fishing stress, with adrenaline levels 3-4 times higher than noradrenaline
levels. Cortisol levels remained low, ranging from 1.33+/-0.58 ng ml(-1) in
Champsocephalus gunnari to 44.9+/-25.0 ng ml(-1) in Dissostichus mawsoni.
These data suggest that depressed catecholamine synthesis is typical of Ant
arctic fish regardless of life style, although they are able to release ext
ensive stores from the chromaffin tissue under conditions of extreme trauma
. Cortisol does not appear to be an important primary stress hormone in the
se species.