660 Invasive Stink Bugs and Related Species (Pentatomoidea)
2012). Although no obvious fitness defects were observed after symbiont elimination in a Hawaiian
population of Nezara viridula (Prado et al. 2006), the gut symbiont was essential in a Japanese popula-
tion in which aposymbiotic individuals rarely reached adulthood (Tada et al. 2011).
14.2.3 Effect of High Temperature on Pentatomid Symbiosis
In their study on the impact of high temperatures and egg surface sterilization on Nezara viridula’s
nymphal development rate and reproductive performance, Prado et al. (2009) showed that the symbiont’s
maintenance is affected by both treatments. They detected the symbiont in 100, 84, and 8.3% of the
untreated control insects at 20, 25, and 30°C, respectively. In insects originating from surface sterilized
egg masses, the symbionts were detected in only one of 21 insects at 25°C. Nymphs and adults from ster-
ilized egg masses at 20°C lived longer, but the time taken to reach adulthood was longer, and the females
never laid eggs. Mean generation time was remarkably longer at 20°C than at 25 and 30°C, regardless
of surface sterilization. Additionally, the pre-oviposition period and number of eggs were significantly
different between the surface sterilized and control treatments only at 20°C. The results of the study by
Prado et al. (2009) emphasized that not only egg surface sterilization but also higher temperature (30°C)
have an impact on the maintenance of symbionts and negatively affect the host’s development and repro-
duction in N. viridula.
Prado and Almeida (2009b) demonstrated in an allied species, Chinavia hilaris (Say) (formerly known
as Acrosternum hilare), that developmental time, survival, and reproductive parameters were negatively
affected by egg surface sterilization. However, no such effects were observed in Murgantia histrionica
(Hahn) (Prado and Almeida 2009b). Prado et al. (2010) demonstrated that C. hilaris and M. histrionica
lost their gut symbionts within two generations when the insects were reared at 30°C. In addition, sur-
vival and reproductive rates of both C. hilaris and M. histrionica reared at 30°C were lower than those
reared at 25°C. Based on these results, it is assumed that the decrease in host fitness is linked with,
and potentially mediated by, symbiont loss at 30°C (Prado et al. 2010). In pentatomid insects, these
crypt-associated symbionts probably play an important role in stink bug adaptation to climate change.
Although not well documented, this unique style of transmission (i.e., egg smearing with excrement) in
which symbionts live for a certain period on the egg surface, might be notable because the transmis-
sion mechanism may allow environmental factors such as climate change to interfere with symbiont
transmission/acquisition, which could lead to serious fitness defects in stink bug hosts.
AB C2 mm HG 0.5 mm 10 μmM4 M2M3M1FIGURE 14.3 (See color insert.) Microbial symbiosis in Nezara viridula. (A) Dissected midgut. Abbreviations: M1,
midgut first section; M2, midgut second section; M3, midgut third section; M4, midgut fourth section with crypts (sym-
biotic organ); HG, hindgut. (B) Enlarged image of midgut crypts. Arrowheads indicate crypts. (C) Symbiotic bacteria of
N. viridula (phase contrast microscopy).