Figure 1.
Map of Cameroon showing the distribution of the low altitude (LA) and high altitude (HA) Aphyosemion species.
Altitudes below 350 m are in white, above 350 m in yellow. ,The LA species are almost exclusively present below 350 m (black dots), the HA species above 350 m (in blue). The arrows show where the animals were collected for the current study. Photos by Olivier Buisson (A. ahli, A. cameronense and A. exiguum) and Alf Persson (A. splendopleure).
Table 1.
Mean (± SD) mass of killifish studied at each of three acclimation temperatures (19, 25 and 28°C).
Figure 2.
Mean (± SE) rates of oxygen uptake in wild-caught individuals of two species of killifish, A. ahli from low altitude (left column) or A. exiguum from high altitude (right column), at three different acclimation temperatures. In each panel, data are for fish placed into respirometers at 1630 either fasted (white symbols) or when fed 5% of their body mass as live Artemia (black symbols). Rates of oxygen uptake are corrected to a body mass of 350 mg, n = 6 in all cases. See text for further details.
Figure 3.
Specific dynamic action (SDA), expressed as rates of oxygen uptake, in two species of killifish, A. ahli from low altitude (LA, upper panel) or A. exiguum from high altitude (HA, lower panel), at three different acclimation temperatures, 19°C (white), 25°C (grey) and 28°C (black). The SDA was calculated as the net difference in oxygen uptake between animals that were either fasted, or fed 5% of their body mass as Artemia (see Figure 2). Values are means of n = 6 individuals from each species, rates are corrected to a body mass of 350 mg. Standard error bars are not shown to ease reading of the figure, but were approximately 10% of the mean value in all cases.
Table 2.
Mean (± SE) routine metabolic rate (RMR) at three acclimation temperatures in four groups of killifish.
Figure 4.
Reaction norms for mean (± SE) peak oxygen uptake rate during the specific dynamic action (Mo2-peak) as a function of acclimation temperature in four groups of killifish.
Each group comprised a species pair from either low altitude (A. splendopleure and A. ahli), with both an F0 generation (white squares) and an F1 generation (grey squares), or from high altitude (A. cameronense and A. exiguum), with both an F0 generation (white circles) and an F1 generation (grey circles). F0 generation were captured in the wild, F1 generation were bred in captivity. Rates of oxygen uptake are corrected to a body mass of 350 mg, n = between 5 and 7. Two-way ANOVA found a significant effect of temperature (F = 6.064, d.f. = 2, P = 0.003) but not of group (F = 0.926, d.f. = 3, P = 0.430) or their interaction (F = 0.241, d.f. = 6, P = 0.962). This was due to higher overall peak at 25°C than at 19°C, although individual groups did not show significant effects (see Text S8 for details).
Figure 5.
Reaction norms for mean (± SE) time required to reach peak oxygen uptake during the specific dynamic action (Tpeak) as a function of acclimation temperature in four groups of killifish.
Each group comprised a species pair from either low altitude (A. splendopleure and A. ahli), with both an F0 generation (white squares) and an F1 generation (grey squares), or from high altitude (A. cameronense and A. exiguum), with both an F0 generation (white circles) and an F1 generation (grey circles). F0 generation were captured in the wild, F1 generation were bred in captivity, n = between 5 and 7. A 2-way ANOVA on log 10 transformed values found no effect of group (df = 3, F = 0.849, P = 0.470), but a significant effect of temperature (df = 2, F = 6.652, P = 0.002) and their interaction (df = 6, F = 6.015, P<0.001). Overall Tpeak was lower at 25°C than at 19 or 28°C. At 19 and 28°C, a similar letter superscript indicates no significant difference among group means for that temperature. Within a group, † indicates a difference between 19 and 25°C, § indicates a difference between 19 and 28°C, ‡ indicates a significant difference between 25 and 28°C (see Text S9 for details).
Figure 6.
Reaction norms for mean (± SE) time required to complete the specific dynamic action response (TSDA) as a function of acclimation temperature in four groups of killifish.
Each group comprised a species pair from either low altitude (A. splendopleure and A. ahli), with both an F0 generation (white squares) and an F1 generation (grey squares), or from high altitude (A. cameronense and A. exiguum), with both an F0 generation (white circles) and an F1 generation (grey circles). F0 generation were captured in the wild, F1 generation were bred in captivity, n = between 5 and 7. A 2-way ANOVA found no effect of group (df = 3, F = 0.676, P = 0.568) or temperature (df = 2, F = 2.064, P = 0.131) but a significant interaction (df = 6, F = 12.695, P<0.001). At 19 and 28°C, a similar letter superscript indicates no significant difference among group means. Within a group, † indicates a difference between 19 and 25°C, § indicates a difference between 19 and 28°C, ‡ indicates a significant difference between 25 and 28°C (see Text S10 for details).
Table 3.
Mean (± SE) SDA coefficient, following consumption of 5% body mass as Artemia, at three acclimation temperatures in four groups of killifish.
Table 4.
Mean (± SE) appetite at three acclimation temperatures in four species of killifish, comprising an F0 generation of A. ahli and F1 generation of A. splendopleure from low altitude, or an F0 generation of A. exiguum and an F1 generation of A. cameronense from high altitude.