L
Journal of Experimental Marine Biology and Ecology 245 2000 197–214
www.elsevier.nl locate jembe
Energy balance and cold adaptation in the octopus Pareledone charcoti
a,b , a
H.I. Daly , L.S. Peck
a
British Antarctic Survey , High Cross, Madingley Road, Cambridge CB3 0ET, UK
b
Department of Zoology , University of Aberdeen, Tillydrone Avenue, Aberdeen AB24 2TZ, Scotland, UK
Received 18 May 1999; received in revised form 23 July 1999; accepted 25 October 1999
Abstract
A complete energy balance equation is calculated for the Antarctic octopus Pareledone charcoti at 08C. Energy used in respiration, growth, and excretion of nitrogenous and faecal waste, was
recorded along with the total consumption of energy through food, for three specimens of P .
charcoti live weights: 73, 51 and 29 g. Growth rates were very slow for cephalopods, with a mean daily increase in body weight of only 0.11. Assimilation efficiencies were high, between
95.4 and 97.0, which is consistent with previous work on octopods. The respiration rate in P .
21
charcoti was low, with a mean of 2.45 mg O h for a standard animal of 150 g wet mass at 08C.
2 21
In the North Sea octopus Eledone cirrhosa, respiration rates of 9.79 mg O h at 11.58C and 4.47
2 21
mg O h at 4.58C for a standard animal of 150 g wet mass were recorded. Respiration rates
2
between P . charcoti and E. cirrhosa were compared using a combined Q
value between P .
10
charcoti at 08C and E . cirrhosa at 4.58C. This suggests that P. charcoti are respiring at a level
predicted by E . cirrhosa rates at 4.5 and 11.58C extrapolated to 08C along the curve Q
5 3, with
10
no evidence of metabolic compensation for low temperature.
2000 Elsevier Science B.V. All rights reserved.
Keywords : Energy balance; Cold adaptation; Antarctic; Octopus; Pareledone charcoti
1. Introduction
Analyses of energy utilisation in cephalopods are rare. A complete energy balance equation has been calculated for only two species of tropical octopus, Octopus cyanea
and Octopus maya Van Heukelem, 1976, with a partial energy budget constructed for
Corresponding author. Tel.: 144-1224-273-796; fax: 144-1224-272-396. E-mail address
: h.i.dalyabdn.ac.uk H.I. Daly 0022-0981 00 – see front matter
2000 Elsevier Science B.V. All rights reserved.
P I I : S 0 0 2 2 - 0 9 8 1 9 9 0 0 1 6 1 - 6
198 H
.I. Daly, L.S. Peck J. Exp. Mar. Biol. Ecol. 245 2000 197 –214
the temperate Octopus vulgaris O’Dor and Wells, 1987. Recently, energetics in cephalopods from temperate and tropical waters has been reviewed by Wells and Clarke
1996. Energy balance in cold water species has received little attention and the recent successful maintenance of live Antarctic Pareledone charcoti in the BAS aquarium in
Cambridge has provided an opportunity for a detailed study of energy balance in a polar species.
The flow of energy through an animal is normally represented by the energy balance equation:
C 5 P 1 G 1 R 1 U 1 F where C is the total consumption of energy in the food, P and G are the values of
somatic and gonadal growth, respectively, R is the energy used in respiration, U is the amount utilised in nitrogenous waste excretion and F is the energetic loss through
faeces. The component R in the equation above can be divided into several portions which describe the utilisation of energy in more detail Clarke, 1993; Wells and Clarke,
1996. Each portion of the respiratory costs involved in somatic growth R ,
S
reproductive investment R , basal metabolism R or activity R may vary
G B
A
independently with factors such as food availability or maturity. A substantial portion, termed the specific dynamic action SDA, the increase in metabolic rate associated with
feeding, may comprise the energetic cost of somatic R and gonadal R growth
S G
Clarke, 1993; Peck, 1998. These separate components of respiration highlight the potential for balancing the finite energy resource between each component, for
maximum efficiency. In cephalopods, partitioning of resources probably differs between species, with the R component comprising a greater proportion of R in squid, due to
A
their active swimming life-style, than in the more sedentary octopuses. As well as constructing an energy budget for P
. charcoti, the present study compares the respiration rates with a related species of the Eledoninae which occurs in temperate
regions, Eledone cirrhosa. Also known as the lesser octopus, E . cirrhosa, is found
around the British coastline and in the North Sea. The seasonal temperature range in the inshore North Sea is approximately 4–128C McIntyre, 1958, and specimens have been
maintained in the marine aquarium at the University of Aberdeen Zoology Department for a number of months at temperatures of 14–158C Boyle, 1981. This study compares
the respiration rates of P
. charcoti at Antarctic temperatures of around 08C, to those of E
. cirrhosa acclimated from 11.58C down to 4.58C. Extrapolation of E. cirrhosa respiration rates to 08C will allow a direct comparison between the species.
One of the most widely used indices to assess the effect of temperature change on metabolism is the Q
coefficient Schmidt-Nielsen, 1991, which is essentially a
10
measure of the temperature sensitivity of an organism. The Q value is calculated using
10
the equation Schmidt-Nielsen, 1991:
10 t 2t
2 1
R
2
] Q
5
S D
10
R
1
where R and R are the respiration rates at temperatures t and t in8C, respectively.
1 2
1 2
In general, an unstressed animal in its normal temperature range should have a Q of
10
around 2 Cossins and Bowler, 1987, as it is observed across a wide range of organisms
H .I. Daly, L.S. Peck J. Exp. Mar. Biol. Ecol. 245 2000 197 –214
199
that metabolic reactions are slowed by approximately half when ambient temperature falls by 108C. A Q
of less than 2 denotes insensitivity or acclimation to temperature
10
change and a Q of more than 2 denotes increased sensitivity, with an expected range of
10
1–3 Calow, 1981. Q calculations for E
. cirrhosa acclimated to two temperatures and
10
a combined Q including both E
. cirrhosa and P. charcoti has allowed the assessment
10
and comparison of the effects of temperature.
2. Materials and methods
