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Lehmann P, Javal M, Plessis AD, Terblanche JS. Using µCT in live larvae of a large wood-boring beetle to study tracheal oxygen supply during development. JOURNAL OF INSECT PHYSIOLOGY 2021; 130:104199. [PMID: 33549568 DOI: 10.1016/j.jinsphys.2021.104199] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Revised: 01/15/2021] [Accepted: 02/01/2021] [Indexed: 06/12/2023]
Abstract
How respiratory structures vary with, or are constrained by, an animal's environment is of central importance to diverse evolutionary and comparative physiology hypotheses. To date, quantifying insect respiratory structures and their variation has remained challenging due to their microscopic size, hence only a handful of species have been examined. Several methods for imaging insect respiratory systems are available, in many cases however, the analytical process is lethal, destructive, time consuming and labour intensive. Here, we explore and test a different approach to measuring tracheal volume using X-ray micro-tomography (µCT) scanning (at 15 µm resolution) on living, sedated larvae of the cerambycid beetle Cacosceles newmannii across a range of body sizes at two points in development. We provide novel data on resistance of the larvae to the radiation dose absorbed during µCT scanning, repeatability of imaging analyses both within and between time-points and, structural tracheal trait differences provided by different image segmentation methods. By comparing how tracheal dimension (reflecting metabolic supply) and basal metabolic rate (reflecting metabolic demand) increase with mass, we show that tracheal oxygen supply capacity increases during development at a comparable, or even higher rate than metabolic demand. Given that abundant gas delivery capacity in the insect respiratory system may be costly (due to e.g. oxygen toxicity or space restrictions), there are probably balancing factors requiring such a capacity that are not linked to direct tissue oxygen demand and that have not been thoroughly elucidated to date, including CO2 efflux. Our study provides methodological insights and novel biological data on key issues in rapidly quantifying insect respiratory anatomy on live insects.
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Affiliation(s)
- Philipp Lehmann
- Centre for Invasion Biology, Department of Conservation Ecology and Entomology, Stellenbosch University, Stellenbosch, South Africa; Department of Zoology, Stockholm University, Sweden.
| | - Marion Javal
- Centre for Invasion Biology, Department of Conservation Ecology and Entomology, Stellenbosch University, Stellenbosch, South Africa
| | - Anton Du Plessis
- CT Scanner Facility, Central Analytical Facilities, Stellenbosch University, Stellenbosch, South Africa
| | - John S Terblanche
- Centre for Invasion Biology, Department of Conservation Ecology and Entomology, Stellenbosch University, Stellenbosch, South Africa
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Kivelä SM, Davis RB, Esperk T, Gotthard K, Mutanen M, Valdma D, Tammaru T. Comparative analysis of larval growth in Lepidoptera reveals instar‐level constraints. Funct Ecol 2020. [DOI: 10.1111/1365-2435.13556] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- Sami M. Kivelä
- Department of Zoology Institute of Ecology and Earth Sciences University of Tartu Tartu Estonia
| | - Robert B. Davis
- Department of Zoology Institute of Ecology and Earth Sciences University of Tartu Tartu Estonia
| | - Toomas Esperk
- Department of Zoology Institute of Ecology and Earth Sciences University of Tartu Tartu Estonia
| | - Karl Gotthard
- Department of Zoology Stockholm University Stockholm Sweden
| | - Marko Mutanen
- Department of Ecology and Genetics University of Oulu Oulu Finland
| | - Daniel Valdma
- Department of Zoology Institute of Ecology and Earth Sciences University of Tartu Tartu Estonia
| | - Toomas Tammaru
- Department of Zoology Institute of Ecology and Earth Sciences University of Tartu Tartu Estonia
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Javal M, Thomas S, Lehmann P, Barton MG, Conlong DE, Du Plessis A, Terblanche JS. The Effect of Oxygen Limitation on a Xylophagous Insect's Heat Tolerance Is Influenced by Life-Stage Through Variation in Aerobic Scope and Respiratory Anatomy. Front Physiol 2019; 10:1426. [PMID: 31824337 PMCID: PMC6879455 DOI: 10.3389/fphys.2019.01426] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Accepted: 11/04/2019] [Indexed: 12/21/2022] Open
Abstract
Temperature has a profound impact on insect fitness and performance via metabolic, enzymatic or chemical reaction rate effects. However, oxygen availability can interact with these thermal responses in complex and often poorly understood ways, especially in hypoxia-adapted species. Here we test the hypothesis that thermal limits are reduced under low oxygen availability - such as might happen when key life-stages reside within plants - but also extend this test to attempt to explain that the magnitude of the effect of hypoxia depends on variation in key respiration-related parameters such as aerobic scope and respiratory morphology. Using two life-stages of a xylophagous cerambycid beetle, Cacosceles (Zelogenes) newmannii we assessed oxygen-limitation effects on metabolic performance and thermal limits. We complement these physiological assessments with high-resolution 3D (micro-computed tomography scan) morphometry in both life-stages. Results showed that although larvae and adults have similar critical thermal maxima (CTmax) under normoxia, hypoxia reduces metabolic rate in adults to a greater extent than it does in larvae, thus reducing aerobic scope in the former far more markedly. In separate experiments, we also show that adults defend a tracheal oxygen (critical) setpoint more consistently than do larvae, indicated by switching between discontinuous gas exchange cycles (DGC) and continuous respiratory patterns under experimentally manipulated oxygen levels. These effects can be explained by the fact that the volume of respiratory anatomy is positively correlated with body mass in adults but is apparently size-invariant in larvae. Thus, the two life-stages of C. newmannii display key differences in respiratory structure and function that can explain the magnitude of the effect of hypoxia on upper thermal limits.
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Affiliation(s)
- Marion Javal
- Department of Conservation Ecology & Entomology, Faculty of AgriSciences, Centre for Invasion Biology, Stellenbosch University, Stellenbosch, South Africa
| | - Saskia Thomas
- Department of Conservation Ecology & Entomology, Faculty of AgriSciences, Centre for Invasion Biology, Stellenbosch University, Stellenbosch, South Africa
| | - Philipp Lehmann
- Department of Conservation Ecology & Entomology, Faculty of AgriSciences, Centre for Invasion Biology, Stellenbosch University, Stellenbosch, South Africa
- Department of Zoology, Stockholm University, Stockholm, Sweden
| | - Madeleine G. Barton
- Department of Conservation Ecology & Entomology, Faculty of AgriSciences, Centre for Invasion Biology, Stellenbosch University, Stellenbosch, South Africa
| | - Desmond E. Conlong
- Department of Conservation Ecology & Entomology, Faculty of AgriSciences, Centre for Invasion Biology, Stellenbosch University, Stellenbosch, South Africa
- South African Sugarcane Research Institute, Mount Edgecombe, South Africa
| | - Anton Du Plessis
- CT Scanner Facility, Central Analytical Facilities, Stellenbosch University, Stellenbosch, South Africa
- Physics Department, Stellenbosch University, Stellenbosch, South Africa
| | - John S. Terblanche
- Department of Conservation Ecology & Entomology, Faculty of AgriSciences, Centre for Invasion Biology, Stellenbosch University, Stellenbosch, South Africa
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Kivelä SM, Gotthard K, Lehmann P. Developmental plasticity in metabolism but not in energy reserve accumulation in a seasonally polyphenic butterfly. ACTA ACUST UNITED AC 2019; 222:jeb.202150. [PMID: 31138637 DOI: 10.1242/jeb.202150] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Accepted: 05/19/2019] [Indexed: 01/25/2023]
Abstract
The evolution of seasonal polyphenisms (discrete phenotypes in different annual generations) associated with alternative developmental pathways of diapause (overwintering) and direct development is favoured in temperate insects. Seasonal life history polyphenisms are common and include faster growth and development under direct development than in diapause. However, the physiological underpinnings of this difference remain poorly known despite its significance for understanding the evolution of polyphenisms. We measured respiration and metabolic rates through the penultimate and final larval instars in the butterfly Pieris napi and show that directly developing larvae grew and developed faster and had a higher metabolic rate than larvae entering pupal diapause. The metabolic divergence appeared only in the final instar, that is, after induction of the developmental pathway that takes place in the penultimate instar in P. napi. The accumulation of fat reserves during the final larval instar was similar under diapause and direct development, which was unexpected as diapause is predicted to select for exaggerated reserve accumulation. This suggests that overwinter survival in diapause does not require larger energy reserves than direct development, likely because of metabolic suppression in diapause pupae. The results, nevertheless, demonstrate that physiological changes coincide with the divergence of life histories between the alternative developmental pathways, thus elucidating the proximate basis of seasonal life history polyphenisms.
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Affiliation(s)
- Sami M Kivelä
- Department of Zoology, Institute of Ecology and Earth Sciences, University of Tartu, Vanemuise 46, EE-51014 Tartu, Estonia
| | - Karl Gotthard
- Department of Zoology, Stockholm University, SE-10691 Stockholm, Sweden
| | - Philipp Lehmann
- Department of Zoology, Stockholm University, SE-10691 Stockholm, Sweden
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Peruzza L, Gerdol M, Oliphant A, Wilcockson D, Pallavicini A, Hawkins L, Thatje S, Hauton C. The consequences of daily cyclic hypoxia on a European grass shrimp: From short‐term responses to long‐term effects. Funct Ecol 2018. [DOI: 10.1111/1365-2435.13150] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- Luca Peruzza
- Ocean and Earth ScienceNational Oceanography Centre SouthamptonUniversity of Southampton Southampton UK
| | - Marco Gerdol
- Department of Life SciencesUniversity of Trieste Trieste Italy
| | - Andrew Oliphant
- Institute of Biological, Environmental and Rural SciencesAberystwyth University Aberystwyth UK
| | - David Wilcockson
- Institute of Biological, Environmental and Rural SciencesAberystwyth University Aberystwyth UK
| | | | - Lawrence Hawkins
- Ocean and Earth ScienceNational Oceanography Centre SouthamptonUniversity of Southampton Southampton UK
| | - Sven Thatje
- Ocean and Earth ScienceNational Oceanography Centre SouthamptonUniversity of Southampton Southampton UK
| | - Chris Hauton
- Ocean and Earth ScienceNational Oceanography Centre SouthamptonUniversity of Southampton Southampton UK
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Lundquist TA, Kittilson JD, Ahsan R, Greenlee KJ. The effect of within-instar development on tracheal diameter and hypoxia-inducible factors α and β in the tobacco hornworm, Manduca sexta. JOURNAL OF INSECT PHYSIOLOGY 2018; 106:199-208. [PMID: 29246704 PMCID: PMC5960420 DOI: 10.1016/j.jinsphys.2017.12.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Revised: 12/04/2017] [Accepted: 12/06/2017] [Indexed: 05/10/2023]
Abstract
As insects grow within an instar, body mass increases, often more than doubling. The increase in mass causes an increase in metabolic rate and hence oxygen demand. However, the insect tracheal system is hypothesized to increase only after molting and may be compressed as tissues grow within an instar. The increase in oxygen demand in the face of a potentially fixed or decreasing supply could result in hypoxia as insects near the end of an instar. To test these hypotheses, we first used synchrotron X-ray imaging to determine how diameters of large tracheae change within an instar and after molting to the next instar in the tobacco hornworm, Manduca sexta. Large tracheae did not increase in diameter within the first, second, third, and fourth instars, but increased upon molting. To determine if insects are hypoxic at the end of instars, we used the presence of hypoxia-inducible factors (HIFs) as an index. HIF-α and HIF-β dimerize in hypoxia and act as a transcription factor that turns on genes that will increase oxygen delivery. We sequenced both of these genes and measured their mRNA levels at the beginning and end of each larval instar. Finally, we obtained an antibody to HIF-α and measured protein expression during the same time. Both mRNA and protein levels of HIFs were increased at the end of most instars. These data support the hypothesis that some insects may experience hypoxia at the end of an instar, which could be a signal for molting. SUMMARY STATEMENT As caterpillars grow within an instar, major tracheae do not increase in size, while metabolic demand increases. At the same life stages, caterpillars increased expression of hypoxia inducible factors, suggesting that they become hypoxic near the end of an instar.
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Affiliation(s)
- Taylor A Lundquist
- Department of Biological Sciences, North Dakota State University, Fargo, ND 58108-6050, United States
| | - Jeffrey D Kittilson
- Department of Biological Sciences, North Dakota State University, Fargo, ND 58108-6050, United States
| | - Rubina Ahsan
- Department of Biological Sciences, North Dakota State University, Fargo, ND 58108-6050, United States
| | - Kendra J Greenlee
- Department of Biological Sciences, North Dakota State University, Fargo, ND 58108-6050, United States.
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Kivelä SM, Viinamäki S, Keret N, Gotthard K, Hohtola E, Välimäki P. Elucidating mechanisms for insect body size: partial support for the oxygen-dependent induction of moulting hypothesis. ACTA ACUST UNITED AC 2018; 221:jeb.166157. [PMID: 29150451 DOI: 10.1242/jeb.166157] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2017] [Accepted: 11/14/2017] [Indexed: 11/20/2022]
Abstract
Body size is a key life history trait, and knowledge of its mechanistic basis is crucial in life history biology. Such knowledge is accumulating for holometabolous insects, whose growth is characterised and body size affected by moulting. According to the oxygen-dependent induction of moulting (ODIM) hypothesis, moult is induced at a critical mass at which oxygen demand of growing tissues overrides the supply from the tracheal respiratory system, which principally grows only at moults. Support for the ODIM hypothesis is controversial, partly because of a lack of proper data to explicitly test the hypothesis. The ODIM hypothesis predicts that the critical mass is positively correlated with oxygen partial pressure (PO2 ) and negatively with temperature. To resolve the controversy that surrounds the ODIM hypothesis, we rigorously test these predictions by exposing penultimate-instar Orthosia gothica (Lepidoptera: Noctuidae) larvae to temperature and moderate PO2 manipulations in a factorial experiment. The relative mass increment in the focal instar increased along with increasing PO2 , as predicted, but there was only weak suggestive evidence of the temperature effect. Probably owing to a high measurement error in the trait, the effect of PO2 on the critical mass was sex specific; high PO2 had a positive effect only in females, whereas low PO2 had a negative effect only in males. Critical mass was independent of temperature. Support for the ODIM hypothesis is partial because of only suggestive evidence of a temperature effect on moulting, but the role of oxygen in moult induction seems unambiguous. The ODIM mechanism thus seems worth considering in body size analyses.
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Affiliation(s)
- Sami M Kivelä
- Department of Zoology, Institute of Ecology and Earth Sciences, University of Tartu, Vanemuise 46, EE-51014 Tartu, Estonia
| | - Sonja Viinamäki
- Department of Ecology and Genetics, University of Oulu, PO Box 3000, 90014 University of Oulu, Oulu, Finland
| | - Netta Keret
- Department of Ecology and Genetics, University of Oulu, PO Box 3000, 90014 University of Oulu, Oulu, Finland
| | - Karl Gotthard
- Department of Zoology, Stockholm University, SE-10691 Stockholm, Sweden
| | - Esa Hohtola
- Department of Ecology and Genetics, University of Oulu, PO Box 3000, 90014 University of Oulu, Oulu, Finland
| | - Panu Välimäki
- Department of Ecology and Genetics, University of Oulu, PO Box 3000, 90014 University of Oulu, Oulu, Finland
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