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Temperature-dependent melanism and phenoloxidase activity in the dimorphic sepsid fly Sepsis thoracica


Gourgoulianni, Natalia; Schäfer, Martin A; Kapun, Martin; Busso, Juan Pablo; Blanckenhorn, Wolf U (2023). Temperature-dependent melanism and phenoloxidase activity in the dimorphic sepsid fly Sepsis thoracica. Journal of Thermal Biology, 112:103473.

Abstract

Climate is changing towards both higher average temperatures and more frequent and severe heat waves. Whereas numerous studies have investigated temperature effects on animal life histories, assessments of their immune function are limited. In the size- and colour-dimorphic black scavenger (or dung) fly Sepsis thoracica (Diptera: Sepsidae), we experimentally studied how developmental temperature and larval density influence phenoloxidase (PO) activity, a key enzyme in insect pigmentation, thermoregulation, and immunity. Flies from five latitudinal European populations were raised at three developmental temperatures (18, 24, 30 °C). PO activity increased with developmental temperature differently in the sexes and the two male morphs (black and orange), altering the sigmoid relationship between melanism, i.e. colouration and fly size. PO activity further positively correlated with larval rearing density, potentially because of higher risks of pathogen infection or greater developmental stress following stronger resource competition. Populations varied somewhat in PO activity, body size and colouration, however with no clear latitudinal pattern. Overall our results indicate that morph- and sex-specific PO activity, and thus likely immune function, in S. thoracica depends on temperature and larval density, modifying the underlying putative trade-off between immunity and body size. The strong dampening of the immune system of all morphs at cool temperatures suggests low-temperature stress in this warm-adapted species common in southern Europe. Our results also support the population density dependent prophylaxis hypothesis, which predicts higher investment in immunity when facing limited resource availability and increased pathogen infection probability.

Abstract

Climate is changing towards both higher average temperatures and more frequent and severe heat waves. Whereas numerous studies have investigated temperature effects on animal life histories, assessments of their immune function are limited. In the size- and colour-dimorphic black scavenger (or dung) fly Sepsis thoracica (Diptera: Sepsidae), we experimentally studied how developmental temperature and larval density influence phenoloxidase (PO) activity, a key enzyme in insect pigmentation, thermoregulation, and immunity. Flies from five latitudinal European populations were raised at three developmental temperatures (18, 24, 30 °C). PO activity increased with developmental temperature differently in the sexes and the two male morphs (black and orange), altering the sigmoid relationship between melanism, i.e. colouration and fly size. PO activity further positively correlated with larval rearing density, potentially because of higher risks of pathogen infection or greater developmental stress following stronger resource competition. Populations varied somewhat in PO activity, body size and colouration, however with no clear latitudinal pattern. Overall our results indicate that morph- and sex-specific PO activity, and thus likely immune function, in S. thoracica depends on temperature and larval density, modifying the underlying putative trade-off between immunity and body size. The strong dampening of the immune system of all morphs at cool temperatures suggests low-temperature stress in this warm-adapted species common in southern Europe. Our results also support the population density dependent prophylaxis hypothesis, which predicts higher investment in immunity when facing limited resource availability and increased pathogen infection probability.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute of Evolutionary Biology and Environmental Studies
Dewey Decimal Classification:570 Life sciences; biology
590 Animals (Zoology)
Scopus Subject Areas:Life Sciences > Physiology
Life Sciences > Biochemistry
Life Sciences > General Agricultural and Biological Sciences
Life Sciences > Developmental Biology
Uncontrolled Keywords:Developmental Biology, General Agricultural and Biological Sciences, Biochemistry, Physiology
Language:English
Date:1 February 2023
Deposited On:26 Feb 2023 15:02
Last Modified:30 Jan 2024 02:45
Publisher:Elsevier
ISSN:0306-4565
OA Status:Green
Publisher DOI:https://doi.org/10.1016/j.jtherbio.2023.103473
PubMed ID:36796918
Project Information:
  • : FunderUniversität Zürich
  • : Grant ID
  • : Project Title
  • : FunderSchweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung
  • : Grant ID
  • : Project Title
  • Content: Published Version
  • Language: English
  • Licence: Creative Commons: Attribution 4.0 International (CC BY 4.0)