F2 generation
Survival of F2 P. incisus females and males was reduced under
direct exposure to MHWs (F2-MHW, Table 2, Fig. 4). FPC did not affect F2
female and male survival as the F2-FPC effect was insignificant (Table
2, Fig. 4). F2-FPC did not alter the lethal effect of F2-MHW, as
indicated by an insignificant interaction of F2-MHW × F2-FPC (Table 2,
Fig. 4). Strikingly, transgenerational MHW exposure (F1-MHW × F2-MHW)
resulted in a similar female and male survival compared to the control
temperature; all were ~10% higher survival than F2-MHW
exposed females and males (F1-MHW × F2-MHW, Table 2, Fig. 4), suggesting
that lethal F2-MHW effect was ameliorated. This pattern was independent
of F1-FPC and F2-FPC (Table 2, Fig. 4). The lethal MHW effect in the
parental generation was no longer present in F2 generation when F2
copepods were returned to the control temperature (F1-MHW, Table 2, Fig.
4).
The clutch size, % females with hatched eggs and hatched nauplii from a
clutch of F2 P. incicsus were 42%, 5%, and 22% reduced in
F2-MHW (F2-MHW, Table 2, Fig. 5a-c). The F2-MHW effect was independent
of the F2-FPC as F2-MHW × F2-FPC was insignificant. Importantly, F2-MHW
was generally less intense when F1 was also exposed to MHW (F1-MHW ×
F2-MHW, Table 2, Fig. 5a-c). Parental exposure to MHW (F1-MHW) also
decreased 22% and 33% the size of clutches and hatched nauplii from a
clutch of F2 P. incisus . No F1-MHW effect on % F2 females with
hatched eggs as it was similar to the control level (F1-MHW, Table 2,
Fig. 5a-c). Overall, F2-FPC increased ~4% the clutch
size of F2 females, but this pattern was mainly driven by large clutches
of control F2-females that their parental generation was also exposed to
both MHW and FPC (F1-MHW × F1-FPC), resulting in two-, three- and
four-way interactions (Table 2, Fig. 5a). The F2-FPC effect on other
reproductive parameters was absent or minimal (F2-FPC, Table 2, Fig.
5b-d).
Overall, cumulative nauplii and faecals of F2 copepods decreased by 40
and 32% in MHW, respectively (F2-MHW, Table 2, Fig. 5d,e). Parental
exposure to MHW (F1-MHW) also resulted in lower cumulative nauplii and
faecals than the control copepods (F1-MHW, Fig. 5b-e). F2-MHW induced
reductions in cumulative nauplii, and faecals were ~12%
less strong in F2 copepods whose parental generation was also exposed to
MHW (F1-MHW) (transgenerational effect F1-MHW × F2-MHW, Table 2, Fig.
5d,e). The F2-MHW effect was also 3-4% less strong in F1-FPC (F1-FPC ×
F2-MHW), but F1-FPC did not influence the cumulative nauplii and faecals
of copepods that were exposed to MHW for both generations (F1-MHW ×
F1-FPC × F2-MHW, Table 2, Fig. 5d,e). F2-FPC caused a minor increase
(~3-4%) in both cumulative nauplii and faecals of F2P. incisus , but only in control temperature and in F1-FPC (F2-MHW
× F2-FPC, F1-FPC × F2-FPC, F1-FPC × F2-MHW × F2-FPC, Table 2, Fig. 5e).
F2-FPC caused a slightly (~3%) stronger reduction in
cumulative faecals in F2-MHW only in copepods that were not exposed to
F1-MHW (F1-MHW × F2-MHW × F2-FPC, Table 2, Fig. 5e). Cumulative nauplii
covaried positively with the cumulative faecals (F1, 64= 30.3, P < 0.001, slope ± 1 SE = 0.68 ± 0.12).