202 H
.I. Daly, L.S. Peck J. Exp. Mar. Biol. Ecol. 245 2000 197 –214
After a further 48 h acclimation time, respiration trials were carried out every 3 days for 9 days. The specimens were then transferred to 08C, but both died within 24 h of
transfer. Body mass and volume were recorded at the beginning and end of the trials. Specimens usually remained inactive during trials but on occasion showed some
increased activity in arm movements, which was noted. Trials where considerable activity, such as jetting, was recorded were abandoned.
Throughout the experiment the E . cirrhosa were not fed. The exact time that the
specimens last fed before respiration trials began is unknown, but, assuming that they fed regularly in the wild, it would have been approximately 4 days prior to experimenta-
tion. Attempts were made to provide live food Carcinus maenas at the start of the trial to establish a known feeding time, but this proved unsuccessful due to high prey
mortality during transportation.
The joule has been used here as the energy unit, and the conversion factor to calories is 1 calorie54.184 J Schmidt-Nielsen, 1991.
3. Results
The cumulative food consumption for the P . charcoti specimens varied in relation to
21
body size Fig. 2. The mean feeding rates over the trial were 31.44 mg day dry mass
Fig. 2. Cumulative food consumption C mg dry wt for Pareledone charcoti feeding on Mytilus edulis over the 50 days when measurements were taken.
H .I. Daly, L.S. Peck J. Exp. Mar. Biol. Ecol. 245 2000 197 –214
203
Fig. 3. Growth for Pareledone charcoti, as wet mass g increase excluding water released from the mantle cavity or web.
21 21
for specimen 1, 22.78 mg day dry mass for specimen 2 and 14.23 mg day
dry mass for specimen 3.
The growth of the three specimens over the trial was very small Fig. 3. The period over which growth was recorded in the P
. charcoti specimens was relatively brief up to 120 days, and the best fit to the observed growth over this period was linear. The slope
of the regression line for each specimen was positive. When each slope was tested for significance of difference from zero, the slope for specimen 1 was significantly different
from zero t 510.79, p ,0.001, while the slopes for specimens 2 and 3 were not t 52.00, p .0.05 and t 51.76, p .0.05, respectively. These results indicate that growth
by specimens 2 and 3 over the trial was very slow. Instantaneous growth rates G, expressed as the percent increase in body mass per day, were calculated from the
equation:
ln W 2 ln W
2 1
]]]] G 5
3 100 t 2 t
2 1
where W and W are body weights at times t and t , respectively Forsythe and Van
1 2
1 2
Heukelem, 1987. Daily growth rates were 0.13 for specimen 1, 0.08 for specimen 2 and 0.12 for specimen 3.
Respiration rates either decreased gradually with time specimens 1 and 2, or
204 H
.I. Daly, L.S. Peck J. Exp. Mar. Biol. Ecol. 245 2000 197 –214
21
Fig. 4. Respiration rate R mg O h for Pareledone charcoti with increasing time after last feeding event.
2 21
Points labelled with the respiration in mg O h indicate trials where increased activity of the specimen was
2
recorded.
remained constant specimens 3 Fig. 4. Activity was recorded as low in most trials, and on the occasions where increased activity was noted Fig. 4, there was not a
noticeable elevation in metabolism. The mean respiration rates for P . charcoti are shown
in Table 1, which includes comparative values from O’Dor and Wells 1987 for temperate and tropical octopods. All values were calculated for a standard sized animal
of 1 kg wet mass using a scaling coefficient 0.75, obtained as a mean of the exponents for octopods listed in O’Dor and Wells 1987. The respiration rates listed are for
inactive animals.
Nitrogen excretion increased with specimen size Fig. 5. The mean excretion rates
21 21
recorded were 0.170 S.D.50.007 mg atoms NH -N g h
for specimen 1, 0.167
3 21
21
S.D.50.004 mg atoms NH -N g h
for specimen 2 and 0.203 S.D.50.055 mg
3 21
21
atoms NH -N g h
for specimen 3.
3 21
Production of faeces were at the rates of 2.742, 2.700 and 1.950 mg day dry mass
for specimens 1, 2 and 3, respectively, over a period of around 80 days. The rates of production of faeces for specimens 1 and 2 were very similar although specimen 1 had a
21
higher mean consumption rate, 31.440 mg day dry mass compared to 22.781 mg
21
day dry mass for specimen 2. Faeces from specimen 1 may have broken up quickly in
the tank before it could be collected, possibly by movement of the octopus, and may be underestimated.
Using mean V O and ammonia excretion rates, the atomic O:N ratio for each P
.
2
charcoti specimen was calculated. O:N ratios did not vary significantly throughout the
H .I. Daly, L.S. Peck J. Exp. Mar. Biol. Ecol. 245 2000 197 –214
205 Table 1
Respiration rates calculated for three Pareledone charcoti specimens and comparative mean values from O’Dor and Wells 1987 for a standard sized animal of 1 kg wet mass
a
Species Wet body
Temperature Respiration rate
Source
21 21
mass g 8C
mg O kg h
2
Pareledone charcoti 73
10.82 Present study
51 11.59
Present study 29
8.05 Present study
Eledone cirrhosa 312
4.5 18.53
Present study E
. cirrhosa 312
11 40.58
Present study Octopus dofleini
9600 11
70.41 1
Bathypolypus arcticus 3
13 46.80
2 E
. cirrhosa 564
18 61.37
3 Octopus briareus
345 20
45.64 4
Octopus vulgaris 817
21 84.07
5 O
. vulgaris 42
22 73.40
6 Octopus cyanea
1000 25
125.71 7
O . briareus
348 30
99.94 4
a
Sources: 1 Johansen 1965, 2 O’Dor unpublished from O’Dor and Wells 1987, 3 Milne pers. commun. 1981, 4 Borer and Lane 1971, 5 Wells et al. 1983, 6 Wells and Wells 1995, 7 Van
Heukelem 1976.
21
Fig. 5. Ammonia excretion rate, U mg atoms NH -N h for Pareledone charcoti
, in relation to calculated
3
specimen dry weights.
206 H
.I. Daly, L.S. Peck J. Exp. Mar. Biol. Ecol. 245 2000 197 –214 Table 2
21 a
Components of the energy balance equation for Pareledone charcoti in J day mW, for mean dry mass
Parameter Specimen 1
Specimen 2 Specimen 3
9.51 g dry mass 6.87 g dry mass
4.01 g dry mass C
723.51 8.37 524.23 6.07
327.59 3.79 R
496.08 5.74 405.96 4.70
184.76 2.14
24 24
24
U 0.029 3.39310
0.022 2.57310 0.018 2.04310
F 21.39 0.25
21.06 0.24 15.21 0.18
P 1 G 279.48 3.23
101.00 1.17 103.43 1.20
Scope for growth: C 2 R 1 U 1 F
206.01 2.38 97.19 1.12
127.61 1.48 Difference between P 1 G
and scope for growth 73.47 0.85
3.81 0.04 224.18 0.28
a
The mean dry mass of P . charcoti specimens were estimated using data for Pareledone turqueti.
trial and were 24.6 range 22–27 for specimen 1, 27.2 range 24–30 for specimen 2 and 13.3 range 9–19 for specimen 3.
The previous results for C, R, U, F and P 1 G were used in the construction of an energy budget for each of the P
. charcoti specimens using conversion factors detailed below, and results are listed in Tables 2 and 3.
Energetic input from consumption C was calculated using the conversion 23.01
21
J mg dry mass M
. edulis flesh quoted in Thompson and Bayne 1974. The coefficient
21
used to determine the energetic cost of respiration R, was 13.598 J mg O . This was
2
based on fuelling metabolism using the relative percentage of protein, carbohydrate and lipid present in the M
. edulis Giese, 1969, which were fed to the P. charcoti. The
21 21
values 13.347 J mg O for protein respiration, 14.770 J mg
O for carbohydrate
2 2
21
respiration and 13.723 J mg O
for lipid respiration from Brafield and Llewellyn
2
1982 were used for the calculation. In calculating the amount of energy lost through excretion of nitrogenous waste
21
products U , the coefficient 288.278 J mol Brafield and Soloman, 1972 was used.
Only losses through ammonia excretion were considered, which were small in relation to other components in the energy balance equation. The energetic content of octopus
21
faeces F , determined by bomb calorimetry in Van Heukelem 1976 as 7.799 J mg dry mass, was used in the calculation.
21
The value 22.259 J g dry mass was used as the energy composition for octopus
tissues, combining somatic P and gonadal G growth. This figure was obtained as a
Table 3 Components of the energy budget for P
. charcoti expressed as a percentage of consumption C Parameter
Specimen 1 Specimen 2
Specimen 3 R
68.57 77.44
56.40 U
0.004 0.004
0.005 F
2.96 4.02
4.64 P 1 G
38.63 19.27
31.57 Total
110.16 100.73
92.61
H .I. Daly, L.S. Peck J. Exp. Mar. Biol. Ecol. 245 2000 197 –214
207
mean value from O . vulgaris Wissing et al., 1973 and O. cyanea Van Heukelem,
1976, based on bomb calorimetry. As no specimens of P . charcoti were available for
estimation of water content, estimates obtained from Pareledone turqueti , a similar
Antarctic species, were used to calculate dry mass Daly, 1996. Energy budgets for all three P
. charcoti specimens were approximately in balance Table 2 Each energetic component is also shown in milliwatts. The scope for growth
21
calculation underestimated the recorded growth P 1 G by 73.469 J day in specimen
21
1, overestimated it by 24.180 J day in specimen 3, and almost balanced in specimen 2,
21
underestimating by only 3.810 J day . Table 3 illustrates the results expressed as a
percentage of C and shows that the proportions calculated for each specimen were broadly consistent. Assimilation efficiency for P
. charcoti was calculated as: C 2 F
]] Assimilation efficiency 5
3 100 C
The values 97.04, 95.98 and 95.36 were obtained for specimens 1, 2 and 3, respectively.
3.1. Assessment of cold adaptation in P. charcoti by comparison with E. cirrhosa Respiration rate values for both species were corrected to standard wet animal mass of
150 g using the weight exponent 0.75 O’Dor and Wells, 1987, as this was approximately half way between the masses of the P
. charcoti and E. cirrhosa specimens used Table 4. A Q
of 3.063 was calculated for E . cirrhosa between 11.5
10
and 4.58C. As Q calculations require respiration rates at two temperatures, a value
10
could not be obtained for P . charcoti alone as respiration was only measured at one
temperature 08C. In order to compare results for P . charcoti and E. cirrhosa, a
combined Q value was calculated including the respiration rates for P
. charcoti with
10
the result for E . cirrhosa at 4.58C. This produced a Q
of 3.807. The combined
10
respiration rate data for the two species fits the curved Q relationship of 3 Fig. 6,
10
suggesting that P . charcoti respire at a rate consistent with extrapolation from E.
cirrhosa rates.
Table 4 Comparative respiration rates for individual Pareledone charcoti specimens at 08C and Eledone cirrhosa at 4.5
and 11.58C for a standard animal of 150 g wet mass Specimen
Wet body Temperature
Respiration rate
21
mass g 8C
mg O h
2
P . charcoti 1
73 2.61
P . charcoti 2
51 2.79
P . charcoti 3
29 1.94
E . cirrhosa
323 4.5
4.21 E
. cirrhosa 300
4.5 4.73
E . cirrhosa
323 11.5
11.05 E
. cirrhosa 300
11.5 8.51
208 H
.I. Daly, L.S. Peck J. Exp. Mar. Biol. Ecol. 245 2000 197 –214
Fig. 6. Comparative respiration rate for Pareledone charcoti at 08C and Eledone cirrhosa at 4.5 and 11.58C for a standard animal of 150 g wet mass. The curve, Q 53, was calculated using the mean respiration rate of
10
E . cirrhosa at 4.58C.
4. Discussion
