title: Metabolism and antioxidant defense in the larval chironomid Tanytarsus minutipalpus: adjustments to diel variations in the extreme conditions of Lake Magadi.
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 O2l-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 O2l-1) and 19:00 h (29.3±0.8°C and 16.2±1.6 mg O2l-1) and lower at 01:00 h (21.1±0.1°C and 10.7±0.03 mg O2l-1) and 07:00 h (20.2±0.4°C and 3.2±0.7 mg O2l-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 O2content 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.
authors.affiliation: Programa de Pós-Graduação em Ciências Fisiológicas: Fisiologia Animal Comparada, Instituto de Ciências Biológicas, Universidade Federal do Rio Grande, Avenida Itália km 8, Rio Grande, RS 96203-900, Brazil.
authors.forename: Lucas F
authors.identifier: http://orcid.org/0000-0002-7627-7650
authors.initials: LF
authors.lastname: Bianchini
authors.affiliation: Department of Biology, McMaster University, Hamilton, Ontario, Canada L8S 4K1.|Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4.
authors.forename: Chris M
authors.initials: CM
authors.lastname: Wood
authors.affiliation: Department of Zoology and Physiology, University of Wyoming, Laramie, WY 82071, USA.
authors.forename: Harold L
authors.initials: HL
authors.lastname: Bergman
authors.affiliation: Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4.
authors.forename: Ora E
authors.initials: OE
authors.lastname: Johannsson
authors.affiliation: Department of Biology, McMaster University, Hamilton, Ontario, Canada L8S 4K1.
authors.forename: Pierre
authors.initials: P
authors.lastname: Laurent
authors.affiliation: Department of Biology, McMaster University, Hamilton, Ontario, Canada L8S 4K1.
authors.forename: Claudine
authors.initials: C
authors.lastname: Chevalier
authors.affiliation: Department of Veterinary Anatomy and Physiology, Faculty of Veterinary Medicine and Surgery, Egerton University, P.O. Box 536 - 20115, Egerton, Kenya.
authors.forename: Mosiany L
authors.initials: ML
authors.lastname: Kisipan
authors.affiliation: Department of Biology, South Eastern Kenya University, Kitui 170-90200, Kenya.
authors.forename: Geraldine D
authors.initials: GD
authors.lastname: Kavembe
authors.affiliation: Department of Veterinary Anatomy and Physiology, University of Nairobi, P.O. Box 30197, Nairobi 00100, Kenya.
authors.forename: Michael B
authors.initials: MB
authors.lastname: Papah
authors.affiliation: EcoTox, Miami, FL 33155, USA.
authors.forename: Kevin V
authors.initials: KV
authors.lastname: Brix
authors.affiliation: SPHERE, Department of Biology, University of Antwerp, Antwerp 2020, Belgium.
authors.forename: Gudrun
authors.initials: G
authors.lastname: De Boeck
authors.affiliation: Department of Zoology, University of Johannesburg, Johannesburg 2006, South Africa.
authors.forename: John N
authors.initials: JN
authors.lastname: Maina
authors.affiliation: Department of Veterinary Anatomy and Physiology, University of Nairobi, P.O. Box 30197, Nairobi 00100, Kenya.
authors.forename: Rodi O
authors.initials: RO
authors.lastname: Ojoo
authors.affiliation: Programa de Pós-Graduação em Ciências Fisiológicas: Fisiologia Animal Comparada, Instituto de Ciências Biológicas, Universidade Federal do Rio Grande, Avenida Itália km 8, Rio Grande, RS 96203-900, Brazil adaltobianchini@furg.br.
authors.forename: Adalto
authors.initials: A
authors.lastname: Bianchini
keywords: Adjustment; Glutathione; Insect; Oxidative stress; Reactive oxygen species; Urea