Biology Reference
In-Depth Information
6. DIAPAUSE CAN MODIFY LARVAL/PUPAL GROWTH
Modulations of larval/pupal developmental rate are also programmed
to adjust the growth on diapause trajectory. As an example, the swallowtail
butterfly
Sericinus montelus
triggers a pupal diapause linked to the modifica-
tions of larval/pupal development. In fact, larvae slow down development
for more than 20 days upon perception of short days (“diapause-inducing”),
while they accelerate growth (
<
19 days) under long days (direct develop-
ment). Pupal growth is also modified: diapausing pupae are fatter and heavier
than developing ones (
Wang, Yang, Zhou, Zhao, & Lei, 2007
). Similarly,
the geometrid moths
Cabera exanthemata
and
Chiasmia clathrata
trigger pupal
diapause after a prolonged larval life in which the larval growth rates is lower
than those of larvae set for direct development (
Kivel¨,V¨lim¨ki, &
M¨enp¨¨, 2012; V¨lim¨ki et al., 2013
).
The nymphalid
Pararge aegeria
diapauses either as a third (penultimate)
instar larva or as a pupa, depending by photoperiod (
Nylin, Wickman, &
Wiklund, 1989; Wiklund & Friberg, 2011
). Larvae exposed to long days
(
>
17 h of light) develop directly without diapause, those reared under inter-
mediate days (14-16 h) induce pupal diapause and those perceiving short
days (
<
13 h) trigger larval diapause (
Nylin et al., 1989
). Such trajectories
reflect changes in larval/pupal growth rate since “diapausing” larvae develop
slower than developing ones and diapausing larvae develop into heavy
pupae, diapausing pupae have intermediate weight and “nondiapausing” lar-
vae develop into small pupae (
Gotthard & Berger, 2010; Nylin et al., 1989
).
In this species, diapause trajectory is also linked to the appearance of seasonal
butterfly morphs (eyespots on the dorsal side of the wings) (
Gotthard &
Berger, 2010; Van Dyc & Wiklund, 2002; Wiklund & Friberg, 2011
).
In contrast to the slowing of development in some species, diapause is
linked to a fast larval growth when larvae have to quickly reach the dormant
stage when developing in proximity of an imminent winter (i.e., late in the
season of “rapidly changing” environments) (
Gotthard, 2008
). Such a phe-
nomenon is also reported for two nymphalids,
Lasiommata maera
and
Lopinga
achine
, whose larvae hatch in late summer and diapause as half-grown larvae
in autumn. Such larvae accelerate their growth to quickly reach diapause
when exposed to short days. Once diapause ends, the modulation of devel-
opmental time is reversed: larvae resume postdiapause development, but
grow at a slower rate under short days (spring—meaning more time available
to reach pupation) and a faster one under long days (summer—meaning less
