Abstract:
Insect larvae are reported to be a major component of the simple but
highly productive trophic web found in Lake Magadi (Kenya, Africa),
which is considered to be one of the most extreme aquatic
environments on Earth. Previous studies show that fish must
display biochemical and physiological adjustments to thrive under
the extreme conditions of the lake. However, information for
invertebrates is lacking. In the present study, the occurrence of the
larval chironomid Tanytarsus minutipalpus is reported in Lake Magadi
for the first time. Additionally, changes in larval metabolism and
antioxidant defense correlated with diel variations in the extremely
hostile environmental conditions of the lake are described. Wide
variations in water temperature (20.2-29.3°C) and dissolved oxygen
content (3.2-18.6 mg O2 l
−1
) were observed at different times of day,
without significant change in water pH (10.0±0.03). Temperature and
dissolved oxygen were higher at 13:00 h (29.3±0.4°C and 18.6±
1.0 mg O2 l
−1
) and 19:00 h (29.3±0.8°C and 16.2±1.6 mg O2 l
−1
) and
lower at 01:00 h (21.1±0.1°C and 10.7±0.03 mg O2 l
−1
) and 07:00 h
(20.2±0.4°C and 3.2±0.7 mg O2 l
−1
). Significant and parallel increases
in parameters related to metabolism (cholinesterase, glucose,
cholesterol, urea, creatinine and hemoglobin) and the antioxidant
system (SOD, GPx, GR, GSH and GSSG) were observed in larvae
collected at 13:00 h. In contrast, no significant changes were observed
in pro-oxidants (ROS and NO), TOSC and oxidative damage
parameters (LPO and DNA damage). Therefore, the observed
increases in temperature and dissolved O2 content in Lake Magadi
were associated with changes in the antioxidant system of
T. minutipalpus larvae. Adjustments performed by the chironomid
larvae were efficient in maintaining body homeostasis, as well as
protecting biomolecules against oxidative damage, so that oxidative
stress did not occur. GSH-GSSG and GPx-GR systems appeared to
play an essential role in the adjustments displayed by the chironomid
larvae during the diel changes in the extreme conditions of Lake Magadi.
