Urban lights keep insects awake at night
Scientists reveal how the urban-related increase in nighttime light and
heat postpones natural hibernation periods of flesh flies
Date:
August 18, 2021
Source:
Osaka City University
Summary:
New research sheds light on the effect urbanization has on the flesh
fly species Sarcophaga similis. Through a series of laboratory and
in-field experiments, scientists show that an increase in nighttime
illumination and temperature, two of the major characteristics of
urbanization, can postpone S. similis hibernation anywhere from
3 weeks to a month.
FULL STORY ==========================================================================
A new study shows how an increase in nighttime lighting (light pollution)
and heat from urban areas disturbs the hibernation periods of insects.
==========================================================================
"The study looks at a species of flesh fly called Sarcophaga similis,
but the results could be applicable to any animal species that relies on predictable environmental signals for biological processes like growth, reproductive behavior, sleep, and migration," said Assistant Professor
Ayumu Mukai of Setsunan University and lead author of the study. In collaboration with Professor Shin Goto of Osaka City University, their
findings were published in Royal Society Open Science.
A common way of exploring the ecological effects of urbanization is
to investigate changes in life cycles of species in the urban and
surrounding area. Urban warming and artificial light at night are two
of the most influential factors in this regard. As urban warming can
increase surface temperatures anywhere between 5 -- 9DEGC, species with
lower critical thermal optima, i.e. biological processes such as growth
and development that occur at lower environmental temperatures, are disproportionately affected. Due to large fluctuations throughout the day
and year, temperature can be an unreliable cue for species to determine
when to sleep, breed, migrate, etc., rendering this cue supplemental to
a biological response to seasonal changes by monitoring day length --
an ability called photoperiodism. Increased nighttime light can throw
off an insect's photoperiodism, yet few studies have focused on the
effect urban warming and artificial light at night have had on insects
in their natural habitat.
"Recognizing the conditions urbanization brings upon insects where
they actually live would be a great step forward in mitigating any
negative effects," Shin Goto said. To understand this, the team
conducted experiments indoors and outdoors. As S. similis typically
enters hibernation during autumn, laboratory hibernation was induced
in flies under two average October temperatures (20DEGC and 15DEGC),
with varying levels of illuminance to mimic bright urban to dark rural
areas. They found that the percentage of flies entering hibernation
decreased as illumination increased and as the temperature increased
from 15DEGC to 20DEGC -- suggesting the higher temperatures found in
urban areas are associated with higher nighttime illumination.
In the field, the team measured when the insects entered hibernation in
two city locations: a site with nighttime lighting at around 0.2 lux (the brightness of a full moon in a clear sky), and another with nighttime
lighting at around 6 lux, which is equivalent to a residential area or
street at night.
At sites with dark nights, most flies enter hibernation between October
and November while at sites with increased nighttime light, they did
not enter hibernation until after November. The team also compared
urban areas with illumination of about 0.2 lux with rural areas of
almost 0 lux. The percentages of flies entering hibernation in rural
areas increased from late September, around 3 weeks earlier than their
urban counterparts. Temperatures were also 2.5DEGC higher in the cities,
which is thought to be the cause for the delay in hibernation.
While these findings do suggest that nighttime lighting, which supports
our daily lives, is disrupting the seasonality of insects, "urban
environments are complex, with nighttime illumination and temperatures
varying within the same neighborhood and between different cities," Ayumu
Mukai pointed out, "and our work on a single flesh fly does not elucidate
the photoperiodic response of other insects." To understand the extent to which our cultural life influences other organisms, Shin Goto continued, "Future studies with a variety of insect species at different sites,
in cities with different climatic regions would clarify what levels
of light pollution and urban warming affect insect seasonal adaptation" ========================================================================== Story Source: Materials provided by Osaka_City_University. Note: Content
may be edited for style and length.
========================================================================== Journal Reference:
1. Ayumu Mukai, Koki Yamaguchi, Shin G. Goto. Urban warming and
artificial
light alter dormancy in the flesh fly. Royal Society Open Science,
2021; 8 (7): 210866 DOI: 10.1098/rsos.210866 ==========================================================================
Link to news story:
https://www.sciencedaily.com/releases/2021/08/210818130525.htm
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