A metabolic approach to dormancy in pelagic copepods helps explaining inter- and intra-specific variability in life-history strategies

Abstract

Dormancy (diapause) is a key life-history strategy of pelagic copepods that allows them to thrive in highly seasonal environments. Successful dormancy of copepodid stages requires the ability to store energy efficiently (for example as lipids) and to slow down the rate of mobilization of this capital during the dormant period. The physiology of lipids in copepods has been extensively reviewed; however, data about the energetics of dormancy are currently scattered throughout the literature. Thus, we conducted a meta-analysis comparing the metabolism of active and dormant copepods in 15 species that undergo dormancy as copepodids. Linear mixed-effects models showed that the metabolic rate of dormant copepods is about one-fourth of the values for actively growing copepods, a level that remains consistent across a large range of body size or environmental conditions. Based on these metabolic rates, we used a numerical modelling approach to predict dormancy duration as a function of body mass and ambient temperature, and to explain the observed range of body masses at the initiation of dormancy. Our numerical approach also provides explanations for inter-and intra-specific variability in life-history strategies, such as

Copepod Life Strategy and Population Viability in Response to Prey Timing and Temperature: Testing a New Model across Latitude, Time, and the Size Spectrum

“…Merging Coltrane 1.0 with a light-and size-based predation scheme similar to Varpe et al (2015) or Ohman and Romagnan (2015) would allow one to better test the balance of bottom-up and top-down controls on calanoid biogeography. Second, our experience constructing the Bering Sea and Disko Bay cases suggests that the greatest uncertainty in the model bioenergetics is actually not the physiology itselfempirical reviews like Saiz and Calbet (2007), Maps et al (2014), Kiørboe and Hirst (2014), and have constrained the key rates moderately well-but rather the problem of translating a prey field into a rate of ingestion. Within each of our model testbeds, the prey time series P remains subject to uncertainty in relative grazing rates on ice algae, large and small pelagic phytoplankton, and microzooplankton, despite a wealth of local observations and a history of work on this problem in Calanus specifically (Olson et al, 2006;Campbell et al, 2009, in press).…”

On the surprising lack of differences between two congeneric calanoid copepod species, Calanus finmarchicus and C. helgolandicus

“…Recently, Maps et al (2014) summarised published metabolic rates for Calanus species. In total, five papers have reported respiration rates for C. finmarchicus (Hirche, 1983;Marshall and Orr, 1958;Saumweber and Durbin, 2006;Ingvarsdóttir et al, 1999;Ikeda et al, 2001).…”

“…finmarchicus and C. helgolandicus should be very similar. In addition, Maps et al (2014) concluded that there was an almost identical inter-species pattern in allometric scaling of metabolism with body size across Calanus species. However, apparent interspecies differences in response of ingestion to temperature suggests that the energetics of each species differ, which may result in different metabolic rates.…”

“…Metabolic costs are understood to have approximately three quarter power scaling with body weight in general (Gillooly et al, 2001) and the review by Maps et al (2014) indicates that this holds for Calanus. Metabolism also increases with temperature, and this relationship follows a Q 10 relationship, i.e.…”

“…each increase in temperature of 10°C will result in respiration rates increasing by a factor of Q 10 . Therefore we use the equation Q 10 T=10 kw 0:75 to represent metabolic costs (units: lg C h À1 ), where T is temperature (°C) and with Q 10 and k being parameterised within reasonable bounds derived from the literature review contained in Maps et al (2014). Minimum and maximum published Q 10 are 2.3 (Marshall and Orr, 1958) and 3.4 (Hirche, 1983) respectively.…”