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Journal of Experimental Marine Biology and Ecology 245 2000 171–182
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Relationship between specific dynamic action and protein deposition in calanoid copepods
Peter Thor
Department of Life Sciences and Chemistry , Roskilde University, PO Box 260, DK-4000 Roskilde,
Denmark Received 10 June 1999; received in revised form 20 September 1999; accepted 18 October 1999
Abstract
The link between specific dynamic action SDA and protein deposition was investigated in copepodites stage V of two calanoid copepod species, the neritic Acartia tonsa and the oceanic
Calanus finmarchicus. This was done by measuring respiration before, during, and after a specific feeding period and measuring the incorporation of carbon into proteins. These were also measured
on individuals incubated with cycloheximide, an antibiotic that inhibits protein synthesis. The cycloheximide treatment significantly diminished the magnitude of SDA in both A
. tonsa and C. finmarchicus, and inhibited carbon incorporation into protein in both species. This provides
evidence that the rate at which protein deposition takes place greatly affects the magnitude of SDA. The specific respiration rates of both starving and feeding copepods were generally higher in
A . tonsa than in C. finmarchicus. This influenced SDA, the magnitude of SDA normalised to an 8
21
h feeding period being threefold higher in A . tonsa 78.7625.7 nlO
mgC than in C
.
2 21
finmarchicus 27.5611.6 nlO mgC . This difference may arise due to differences in energy
2
allocation in the organisms of the copepodite V stage of the two species. In this stage C .
finmarchicus deposits large quantities of storage lipids, predominately wax esters, whereas A .
tonsa deposits proteins during somatic growth.
2000 Elsevier Science B.V. All rights reserved.
Keywords : Specific dynamic action; Protein deposition; Respiration; Acartia tonsa; Calanus finmarchicus;
Protein synthesis inhibitor; Energetic costs
1. Introduction
In heterotrophic organisms feeding causes an increase in metabolic rate. This has been recorded for a wide range of aquatic animals such as brachiopods Peck, 1996,
Corresponding author. E-mail address
: pthorruc.dk P. Thor 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 5 9 - 8
172 P
. Thor J. Exp. Mar. Biol. Ecol. 245 2000 171 –182
echinoderms Vahl, 1984, ascidians Petersen et al., 1995, fish and fish larvae e.g. Jobling and Davies, 1980; Kiørboe et al., 1987, molluscs Gaffney and Diehl, 1986;
Carefoot, 1987, and crustaceans Lampert, 1986; Carefoot, 1990a; Du-Preez et al., 1992 including copepods Kiørboe et al., 1985. The phenomenon, termed ‘‘specific
dynamic action’’ SDA, is the result of an elevated energy demand for the integrated physical and physiological processes of feeding. The coincidence in time of SDA and
increased filtration rate in the blue mussel Mytilus edulis led Bayne and Scullard 1977 to suggest that about 50 of the total SDA was caused by the energetic costs of
filtration. However, comparison of metabolic rates of M
. edulis feeding on inert particles and algal cells revealed that the energy required for filtering was low, constituting only a
few percent of the total energy expenditure Widdows and Hawkins, 1989. This is also thought to be true for filter-feeding crustaceans Brendelberger et al., 1986; Strickler and
Alcaraz, 1988. Indeed, despite a clear functional response of the clearance rate on the algal cell concentration there was no correlation between respiration rate and filtering
rate in Acartia tonsa Kiørboe et al., 1985. On the contrary, in feeding individuals metabolic rate varied with the rates of ingestion, assimilation and growth. Similar results
were obtained with the daphnid Daphnia magna in which a close correlation between the metabolic rate and the assimilation rate was found Lampert, 1986. Together these
observations suggested that the increase in metabolic rate is linked to the processes of assimilation and growth.
Kiørboe et al. 1985 calculated the theoretical energetic costs of absorption, assimilation, and growth in A
. tonsa using the macromolecular composition of cirriped eggs. They suggested that 50 to 74 of the measured SDA was caused by the costs of
formation of biomass, and that the costs of absorption and assimilation was responsible for 18 to 28. Thus, the formation of new biomass and the physiological processes
leading to it, appear to be the most important factors governing energy expenditure of copepods during feeding.
Different macromolecules are formed during the formation of new biomass: amino acids may be incorporated into structural protein or enzymes, fatty acids may be
incorporated into different kinds of lipids, and monosaccharides may be incorporated into polysaccharides such as chitin used in the formation of the exoskeleton Yamaoka
and Scheer, 1970. The energy demand for these processes will of course depend upon the biochemical pathways along which they occur, so formation of different macro-
molecules demands different amounts of energy. Theoretical considerations indicate that protein synthesis has the highest energy demand of the processes involved in the
formation of new biomass Grisolia and Kennedy, 1966. Direct measurements of protein synthesis and metabolic rate in larval herring, Clupea harengus, indicate that the
energetic demand for protein synthesis may account for almost 80 of the total energy consumption Houlihan et al., 1995.
The aim of my study was therefore to investigate the link between SDA and the formation of protein in calanoid copepods represented by the small neritic A
. tonsa and the larger oceanic Calanus finmarchicus. This was done by measuring respiration before,
during, and after a specific feeding period and measuring the incorporation of carbon into proteins. In an attempt to provide a direct link measurements were also made on
individuals incubated with cycloheximide, an antibiotic that inhibits protein synthesis Pestka, 1977.
P . Thor J. Exp. Mar. Biol. Ecol. 245 2000 171 –182
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2. Method
