9780521861724htl 1..2

correction to relate temperature to zero Kelvin, used in biochemical kinetics

theory (Hochachka & Somero, 2002 )). They initially suggested that these plots

would produce lines with universal slopes and intercepts. Thus, egg-hatch

times should share a common slope and intercept, as should egg-to-adult

times. However, Gilloolyet al.(2003) have since acknowledged that intercepts

are non-universal, stating ‘In our model, the coefficientaallows for variation in

intercepts with metabolic rate B 0 , and hence for differences in development

times depending on which taxa, environmental conditions and developmental

stages are measured’. Variability in the intercepts of development timesversus

temperature have been explored further by Hirst and Lo ́pez-Urrutia ( 2006 ). Using

marine plankton and nekton groups as a case study, with data compiled from

the copepods, chaetognaths, appendicularians, cephalopods, fish, euphausiids

and mysids, they found that although differences are often taxonomically

based, other factors can be important too. Specifically, after allowing for tem-

perature and mass, a significant proportion of the variability that remains in

egg-hatch times can be accounted for by the vulnerability (mortality) of the eggs.

Eggs that are protected in some way, such as carried by the female, laid in

Weight (W, g)

10 –8 10 –7 10 –6 10 –5 10 –4 10 –3 10 –2 10 –1 100101102103104105106107108

Mortality rate (

β, d

–1

)

10 –5

10 –4

10 –3

10 –2

10 –1

100

101

Fish eggs, juveniles and adults

Marine mammals

Other pelagic invertebrates

Copepods – sac spawners

Copepods – broadcast eggs

Copepods – broadcast post-hatch

Figure 3.5Mortality rates (b,d^1 ) as a function of body dry mass (W, g ind^1 ) for pelagic

invertebrates (excluding copepods) and the eggs, juveniles and adults of fish, and marine

mammals (from McGurk 1986 ). Regression through these data is given by a dotted line

log 10 b¼0.325log 10 W2.086 (r^2 ¼0.826, p<0.001). Predicted relationships from Hirst

and Kiørboe ( 2002 ) are given for broadcast eggs (solid line), broadcasters post-hatch and

sac spawners (dashed line). For broadcasters post-hatch and sac spawners body masses are

taken as adult masses, whereas for the broadcast eggs egg masses are used. All copepod

data corrected to 15 8 C using a Q 10 value of 2.0. Figure adapted from Hirst and Kiørboe

(2002).

48 D. ATKINSON AND A. G. HIRST