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Lobo JM. Hotter-is-not-better: A study on the thermal response of a winter active and nocturnal beetle. JOURNAL OF INSECT PHYSIOLOGY 2024; 153:104602. [PMID: 38142956 DOI: 10.1016/j.jinsphys.2023.104602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Revised: 12/12/2023] [Accepted: 12/19/2023] [Indexed: 12/26/2023]
Abstract
While there are numerous examples of thermogenesis processes in poikilothermic insects that maintain a stable temperature for a certain time and in certain parts of the body, there is a lack of information on ectothermic insect species capable of remaining active under "cold" conditions that would be challenging for other species. Such a thermal strategy would imply the existence of a metabolism that can operate at different temperatures without the need to increase body temperature when experiencing cold environmental conditions. This "hotter-is-not-better" thermal strategy is considered ancestral and conjectured to be linked to the origin and evolution of endothermy. In this study, we examined the thermal performance of a large-bodied dung beetle species (Chelotrupes momus) capable of being active during the winter nights in the Iberian Mediterranean region. Field and laboratory results were obtained using thermocamera records, thermocouples, data loggers and spectrometers that measured ultraviolet, visible and near-infrared wavelengths. The thermal data clearly indicated that this species can remain active at a body temperature of approximately 6 °C without the need to warm its body above ambient temperature. Comparing the spectrophotometric data of the species under study with that from other previously examined dung beetle species indicated that the exoskeleton of this particular species likely enhances the absorption of infrared radiation, thereby implying a dual role of the exoskeleton in both heat acquisition and heat dissipation. Taken together, these results suggest that this species has morphological and metabolic adaptations that enable life processes at temperatures that are typically unsuitable for most insect species in the region.
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Affiliation(s)
- Jorge M Lobo
- Departamento de Biogeografía y Cambio Global, Museo Nacional de Ciencias Naturales-CSIC, Spain.
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2
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deCastro-Arrazola I, Andrew NR, Berg MP, Curtsdotter A, Lumaret JP, Menéndez R, Moretti M, Nervo B, Nichols ES, Sánchez-Piñero F, Santos AMC, Sheldon KS, Slade EM, Hortal J. A trait-based framework for dung beetle functional ecology. J Anim Ecol 2023; 92:44-65. [PMID: 36443916 PMCID: PMC10099951 DOI: 10.1111/1365-2656.13829] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2022] [Accepted: 09/27/2022] [Indexed: 11/30/2022]
Abstract
Traits are key for understanding the environmental responses and ecological roles of organisms. Trait approaches to functional ecology are well established for plants, whereas consistent frameworks for animal groups are less developed. Here we suggest a framework for the study of the functional ecology of animals from a trait-based response-effect approach, using dung beetles as model system. Dung beetles are a key group of decomposers that are important for many ecosystem processes. The lack of a trait-based framework tailored to this group has limited the use of traits in dung beetle functional ecology. We review which dung beetle traits respond to the environment and affect ecosystem processes, covering the wide range of spatial, temporal and biological scales at which they are involved. Dung beetles show trait-based responses to variation in temperature, water, soil properties, trophic resources, light, vegetation structure, competition, predation and parasitism. Dung beetles' influence on ecosystem processes includes trait-mediated effects on nutrient cycling, bioturbation, plant growth, seed dispersal, other dung-based organisms and parasite transmission, as well as some cases of pollination and predation. We identify 66 dung beetle traits that are either response or effect traits, or both, pertaining to six main categories: morphology, feeding, reproduction, physiology, activity and movement. Several traits pertain to more than one category, in particular dung relocation behaviour during nesting or feeding. We also identify 136 trait-response and 77 trait-effect relationships in dung beetles. No response to environmental stressors nor effect over ecological processes were related with traits of a single category. This highlights the interrelationship between the traits shaping body-plans, the multi-functionality of traits, and their role linking responses to the environment and effects on the ecosystem. Despite current developments in dung beetle functional ecology, many knowledge gaps remain, and there are biases towards certain traits, functions, taxonomic groups and regions. Our framework provides the foundations for the thorough development of trait-based dung beetle ecology. It also serves as an example framework for other taxa.
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Affiliation(s)
- Indradatta deCastro-Arrazola
- Germans Cabot Franciscans 48, Bunyola, Spain.,Departamento de Zoología, Facultad de Ciencias, Universidad de Granada, Granada, Spain
| | - Nigel R Andrew
- Insect Ecology Lab, Natural History Museum, University of New England, Armidale, New South Wales, Australia
| | - Matty P Berg
- Department of Ecological Science, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands.,Groningen Institute for Evolutionary Life Sciences, University of Groningen, Groningen, The Netherlands
| | - Alva Curtsdotter
- Insect Ecology Lab, Natural History Museum, University of New England, Armidale, New South Wales, Australia
| | | | - Rosa Menéndez
- Lancaster Environment Centre, Lancaster University, Lancaster, UK
| | - Marco Moretti
- Biodiversity and Conservation Biology, Swiss Federal Research Institute WSL, Birmensdorf, Switzerland
| | - Beatrice Nervo
- Department of Life Sciences and Systems Biology, University of Torino, Torino, Italy
| | | | | | - Ana M C Santos
- Terrestrial Ecology Group (TEG-UAM), Departamento de Ecología, Universidad Autónoma de Madrid, Madrid, Spain.,Centro de Investigación en Biodiversidad y Cambio Global (CIBC-UAM), Universidad Autónoma de Madrid, Madrid, Spain
| | - Kimberly S Sheldon
- Department of Ecology & Evolutionary Biology, University of Tennessee, Knoxville, Tennessee, United States
| | - Eleanor M Slade
- Asian School of the Environment, Nanyang Technological University, Singapore, Singapore
| | - Joaquín Hortal
- Department of Biogeography and Global Change, Museo Nacional de Ciencias Naturales (MNCN-CSIC), Madrid, Spain.,Departamento de Ecologia, Instituto de Ciências Biológicas, Universidade Federal de Goiás, Goiânia, Brazil.,cE3c - Centre for Ecology, Evolution and Environmental Changes, Faculdade de Ciências da Universidade de Lisboa, Lisbon, Portugal
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3
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Ospina-Rozo L, Subbiah J, Seago A, Stuart-Fox D. Pretty Cool Beetles: Can Manipulation of Visible and Near-Infrared Sunlight Prevent Overheating? Integr Org Biol 2022; 4:obac036. [PMID: 36110288 PMCID: PMC9470487 DOI: 10.1093/iob/obac036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2022] [Revised: 07/09/2022] [Accepted: 08/04/2022] [Indexed: 11/21/2022] Open
Abstract
Passive thermoregulation is an important strategy to prevent overheating in thermally challenging environments. Can the diversity of optical properties found in Christmas beetles (Rutelinae) be an advantage to keep cool? We measured changes in temperature of the elytra of 26 species of Christmas beetles, exclusively due to direct radiation from a solar simulator in visible (VIS: 400–700 nm) and near infrared (NIR: 700–1700 nm) wavebands. Then, we evaluated if the optical properties of elytra could predict their steady state temperature and heating rates, while controlling for size. We found that higher absorptivity increases the heating rate and final steady state of the beetle elytra in a biologically significant range (3 to 5°C). There was substantial variation in the absorptivity of Christmas beetle elytra; and this variation was achieved by different combinations of reflectivity and transmissivity in both VIS and NIR. Size was an important factor predicting the change in temperature of the elytra after 5 min (steady state) but not maximum heating rate. Lastly, we show that the presence of the elytra covering the body of the beetle can reduce heating of the body itself. We propose that beetle elytra can act as a semi-insulating layer to enable passive thermoregulation through high reflectivity of elytra, resulting in low absorptivity of solar radiation. Alternatively, if beetle elytra absorb a high proportion of solar radiation, they may reduce heat transfer from the elytra to the body through behavioral or physiological mechanisms.
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Affiliation(s)
- Laura Ospina-Rozo
- School of Biosciences, University of Melbourne , Building 147, Parkville Victoria 3010, Australia
| | - Jegadesan Subbiah
- School of Chemistry, Bio21 Institute - University of Melbourne , 30 Flemington Road, Victoria 3010, Australia
| | - Ainsley Seago
- Carnegie Museum of Natural History , 4400 Forbes Ave, Pittsburgh PA 15213, USA
| | - Devi Stuart-Fox
- School of Biosciences, University of Melbourne , Building 147, Parkville Victoria 3010, Australia
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Cuesta E, Lobo JM. Can the spectrophotometric response of the elytra explain environmental preferences? A study in seven Onthophagus species (Coleoptera, Scarabaeidae). JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2021; 225:112348. [PMID: 34742032 DOI: 10.1016/j.jphotobiol.2021.112348] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Revised: 09/13/2021] [Accepted: 10/29/2021] [Indexed: 11/16/2022]
Abstract
Beetles are the most successful and diversified animal taxa characterized by the possession of an external pair of sclerotized wings (elytra). Managing electromagnetic radiations could be one of the functions of the exoskeleton. We studied the spectrophotometric response to ultraviolet, visible, and near-infrared radiations of the elytra of seven closely related and sympatric Onthophagus species to examine if the environmental preferences of these species could be associated with the spectrophotometric behaviour of their elytra. Our results indicated that sibling species can drastically differ in their environmental preferences but not in their spectrophotometric responses. However, our results corroborated that there are interspecific differences in the spectrophotometric characteristics of the elytra, which are mainly explained by morphological features. Among the examined morphological variables, darkness seems to be especially relevant as it facilitates the absorbance and obstructs the transmittance of visible and near-infrared radiations.
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Affiliation(s)
- Eva Cuesta
- Department of Biogeography and Global Change, Museo Nacional de Ciencias Naturales (C.S.I.C.), Madrid, Spain; Escuela Internacional de Doctorado, Universidad Rey Juan Carlos, Móstoles, Madrid, Spain
| | - Jorge M Lobo
- Department of Biogeography and Global Change, Museo Nacional de Ciencias Naturales (C.S.I.C.), Madrid, Spain.
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Wang LY, Franklin AM, Black JR, Stuart-Fox D. Heating rates are more strongly influenced by near-infrared than visible reflectance in beetles. J Exp Biol 2021; 224:272113. [PMID: 34494652 DOI: 10.1242/jeb.242898] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Accepted: 08/31/2021] [Indexed: 11/20/2022]
Abstract
Adaptations to control heat transfer through the integument are a key component of temperature regulation in animals. However, there remain significant gaps in our understanding of how different optical and morphological properties of the integument affect heating rates. To address these gaps, we examined the effect of reflectivity in both ultraviolet-visible and near-infrared wavelengths, surface rugosity (roughness), effective area (area subjected to illumination) and cuticle thickness on radiative heat gain in jewel beetles (Buprestidae). We measured heating rate using a solar simulator to mimic natural sunlight, a thermal chamber to control the effects of conduction and convection, and optical filters to isolate different wavelengths. We found that effective area and reflectivity predicted heating rate. The thermal effect of reflectivity was driven by variation in near-infrared rather than ultraviolet-visible reflectivity. By contrast, cuticle thickness and surface rugosity had no detectable effect. Our results provide empirical evidence that near-infrared reflectivity has an important effect on radiative heat gain. Modulating reflectance of near-infrared wavelengths of light may be a more widespread adaptation to control heat gain than previously appreciated.
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Affiliation(s)
- Lu-Yi Wang
- School of Biosciences, The University of Melbourne, Melbourne, VIC 3010, Australia
| | - Amanda M Franklin
- School of Biosciences, The University of Melbourne, Melbourne, VIC 3010, Australia
| | - Jay R Black
- School of Geography, Earth and Atmospheric Sciences, The University of Melbourne, Melbourne, VIC 3010, Australia
| | - Devi Stuart-Fox
- School of Biosciences, The University of Melbourne, Melbourne, VIC 3010, Australia
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Lobo JM, Cuesta E. Seasonal variation in the diel activity of a dung beetle assemblage. PeerJ 2021; 9:e11786. [PMID: 34306833 PMCID: PMC8280883 DOI: 10.7717/peerj.11786] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Accepted: 06/24/2021] [Indexed: 11/20/2022] Open
Abstract
The seasonal and diel variations of dung beetle species were studied in an Iberian mid-mountain locality to examine the interaction between these two temporal rhythms. We assume that a seasonal variation in the diel activity would support the notion that both rhythms may assist in achieving a quick and flexible response when the climatic conditions change. Data coming from 4,104 pitfall traps placed during 15 sampling periods and totalling 30 daily sampling cycles were analysed using circular statistics and General Linear Models. A wide variety of seasonal patterns are observed, highlighting those species with a clear unimodal or spring-autumn bimodal seasonal pattern. However, a midday diel pattern is the norm in most of the species, except in the case of those exhibiting a high body weight that prefer dusk or night periods. We hypothesize that most of the dung beetle species fly at noon to promote the passive heating of their muscle activity and minimize the metabolic energy expenditure. Results only partially support the seasonal variation in diel activity. Diel preferences are mainly manifested at the time of the year in which the abundance is greater. Approximately two-thirds of the considered species exhibit a similar diel activity along their seasonal active period. As consequence, a significant portion of the dung beetle species currently inhabiting Mediterranean mid-mountains are not able to use the daily variation in climatic conditions to limit the inconveniences of climate change.
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Affiliation(s)
- Jorge M. Lobo
- Department of Biogeography and Global Change, Museo Nacional de Ciencias Naturales (C.S.I.C.), Madrid, Spain
| | - Eva Cuesta
- Department of Biogeography and Global Change, Museo Nacional de Ciencias Naturales (C.S.I.C.), Madrid, Spain
- Escuela Internacional de Doctorado, Universidad Rey Juan Carlos, Móstoles, Madrid, Spain
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Cuesta E, Lobo JM. Visible and near-infrared radiation may be transmitted or absorbed differently by beetle elytra according to habitat preference. PeerJ 2019; 7:e8104. [PMID: 31788360 PMCID: PMC6882417 DOI: 10.7717/peerj.8104] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Accepted: 10/25/2019] [Indexed: 11/20/2022] Open
Abstract
Background The exoskeleton of an insect could be an important factor in the success of its evolutionary process. This reaches its maximum expression in beetles, which constitute the most diversified animal taxon. The involvement in the management of environmental radiation could be one of the most important functions of the exoskeleton due to the passive contributions to the thermoregulation of body temperature. We study whether the elytra of two sympatric and closely related beetle species respond differentially to the radiation of distinct wavelengths in agreement with their ecological preferences. Methods Onthophagus coenobita (Herbst) and O. medius (Kugelaan) occupy different habitats and environmental conditions (shaded vs. unshaded from solar radiation). The potential adaptive variations to thermoregulation under these different ecological conditions were studied using the responses of their exoskeletons to radiation of different wavelengths (ultraviolet, visible and near-infrared). For these two species, the amounts of the three wavelengths that were reflected, transmitted or absorbed by the exoskeleton were measured using of a spectrophotometer. In addition, the darkness and thickness of the elytra were examined to determine whether these two features influence the management of radiation by the exoskeleton. Results Both species differ in the management of visible and near-infrared radiation. In agreement with habitat preferences, the species inhabiting shaded conditions would allow infrared and visible radiation to penetrate the elytra more easily to heat internal body parts, while the elytra of the heliophilous species would have increased absorbance of these same types of radiation. An increase in body size (and therefore in elytron thickness) and the quantity of dark spots may serve as barriers against exogenous heat gain. However, the maintenance of between-species differences independent of the effects of these two morphological features led us to suspect that an unconsidered elytron characteristic may also be affecting these differences. Discussion The results of the involvement of the exoskeleton thickness and spots in the thermoregulation of insects opens new research lines to obtain a better understanding of the function of the exoskeleton as a passive thermoregulation mechanism in Coleoptera.
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Affiliation(s)
- Eva Cuesta
- Department of Biogeography and Global Change, Museo Nacional de Ciencias Naturales (C.S.I.C.), Madrid, Spain.,Escuela Internacional de Doctorado, Universidad Rey Juan Carlos, Móstoles, Madrid, España
| | - Jorge M Lobo
- Department of Biogeography and Global Change, Museo Nacional de Ciencias Naturales (C.S.I.C.), Madrid, Spain
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Semmouri I, Asselman J, Van Nieuwerburgh F, Deforce D, Janssen CR, De Schamphelaere KAC. The transcriptome of the marine calanoid copepod Temora longicornis under heat stress and recovery. MARINE ENVIRONMENTAL RESEARCH 2019; 143:10-23. [PMID: 30415781 DOI: 10.1016/j.marenvres.2018.10.017] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Revised: 10/10/2018] [Accepted: 10/30/2018] [Indexed: 06/09/2023]
Abstract
Understanding the impacts of global change in zooplankton communities is crucial, as alterations in the zooplankton communities can affect entire marine ecosystems. Despite the economic and ecological importance of the calanoid copepod Temora longicornis in the Belgian part of the North Sea, molecular data is still very limited for this species. Using HiSeq Illumina sequencing, we sequenced the whole transcriptome of T. longicornis, after being exposed to realistic temperatures of 14 and 17 °C. After both an acute (1 day) and a more sustained (5 days) thermal exposure to 17 °C, we investigated gene expression differences with animals exposed to 14 °C, which may be critical for the thermal acclimation and resilience of this copepod species. We also studied the possibility of a short term stress recovery of a heat shock. A total of 179,569 transcripts were yielded, of which 44,985 putative ORF transcripts were identified. These transcripts were subsequently annotated into roughly 22,000 genes based on known sequences using Gene Ontology (GO) and KEGG databases. Temora only showed a mild response to both the temperature and the duration of the exposure. We found that the expression of 27 transcripts varied significantly with an increase in temperature of 3 °C, of which eight transcripts were differentially expressed after acute exposure only. Gene set enrichment analysis revealed that, overall, T. longicornis was more impacted by a sustained thermal exposure, rather than an immediate (acute) exposure, with two times as many enriched GO terms in the sustained treatment. We also identified several general stress responses independent of exposure time, such as modified protein synthesis, energy mobilisation, cuticle and chaperone proteins. Finally, we highlighted candidate genes of a possible recovery from heat exposure, identifying similar terms as those enriched in the heat treatments, i.e. related to for example energy metabolism, cuticle genes and extracellular matrix. The data presented in this study provides the first transcriptome available for T. longicornis which can be used for future genomic studies.
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Affiliation(s)
- Ilias Semmouri
- Ghent University, Laboratory of Environmental Toxicology and Aquatic Ecology, Faculty of Bioscience Engineering, 9000, Ghent, Belgium.
| | - Jana Asselman
- Ghent University, Laboratory of Environmental Toxicology and Aquatic Ecology, Faculty of Bioscience Engineering, 9000, Ghent, Belgium
| | - Filip Van Nieuwerburgh
- Ghent University, Laboratory of Pharmaceutical Biotechnology, Faculty of Pharmaceutical Sciences, 9000, Ghent, Belgium
| | - Dieter Deforce
- Ghent University, Laboratory of Pharmaceutical Biotechnology, Faculty of Pharmaceutical Sciences, 9000, Ghent, Belgium
| | - Colin R Janssen
- Ghent University, Laboratory of Environmental Toxicology and Aquatic Ecology, Faculty of Bioscience Engineering, 9000, Ghent, Belgium
| | - Karel A C De Schamphelaere
- Ghent University, Laboratory of Environmental Toxicology and Aquatic Ecology, Faculty of Bioscience Engineering, 9000, Ghent, Belgium
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Alves VM, Hernández MIM, Lobo JM. Elytra Absorb Ultraviolet Radiation but Transmit Infrared Radiation in Neotropical Canthon Species (Coleoptera, Scarabaeinae). Photochem Photobiol 2018; 94:532-539. [PMID: 29368396 DOI: 10.1111/php.12889] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Accepted: 12/19/2017] [Indexed: 11/28/2022]
Abstract
Strategies to deal with global radiation may be related to important aspects of species biology and ecology by reflecting, transmitting or absorbing the radiation of varying wavelengths differently. The elytra capacity to manage infrared, visible and ultraviolet radiations (from 185 to 1400 nm) was assessed with a spectrophotometric analysis in five Canthon species of dung beetles; we calculated the reflectance, transmittance and absorbance capacity of the elytra of these species. These species have different ecologies: two species preferentially inhabit forest areas (Canthon angularis and Canthon lividus lividus), two species preferentially inhabit open areas (Canthon chalybaeus and Canthon tetraodon) including agricultural crops, and one species does not present a clear habitat preference and can be found in both habitats (Canthon quinquemaculatus). All the species show a similar pattern in which the light from shorter wavelengths and higher frequencies is almost entirely absorbed by the elytra, while radiation from longer wavelengths and lower frequencies can mostly pass through the elytra. However, C. quinquemaculatus seems to have significantly higher rates of reflectance and transmittance in the visible- and near-infrared spectrum. This different pattern found in C. quinquemaculatus may be associated with its capacity to establish populations both in agricultural and forest areas.
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Affiliation(s)
- Victor M Alves
- Programa de Pós Graduação em Ecologia, Departamento de Ecologia e Zoologia, Universidade Federal de Santa Catarina, Florianópolis, Santa Catarina, Brazil
| | - Malva I M Hernández
- Programa de Pós Graduação em Ecologia, Departamento de Ecologia e Zoologia, Universidade Federal de Santa Catarina, Florianópolis, Santa Catarina, Brazil
| | - Jorge M Lobo
- Department of Biogeography and Global Change, Museo Nacional de Ciencias Naturales, CSIC, Madrid, Spain
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Amore V, Hernández MI, Carrascal LM, Lobo JM. Exoskeleton may influence the internal body temperatures of Neotropical dung beetles (Col. Scarabaeinae). PeerJ 2017; 5:e3349. [PMID: 28533987 PMCID: PMC5438579 DOI: 10.7717/peerj.3349] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Accepted: 04/24/2017] [Indexed: 11/22/2022] Open
Abstract
The insect exoskeleton is a multifunctional coat with a continuum of mechanical and structural properties constituting the barrier between electromagnetic waves and the internal body parts. This paper examines the ability of beetle exoskeleton to regulate internal body temperature considering its thermal permeability or isolation to simulated solar irradiance and infrared radiation. Seven Neotropical species of dung beetles (Coleoptera, Scarabaeinae) differing in colour, surface sculptures, size, sexual dimorphism, period of activity, guild category and altitudinal distribution were studied. Specimens were repeatedly subjected to heating trials under simulated solar irradiance and infrared radiation using a halogen neodymium bulb light with a balanced daylight spectrum and a ceramic infrared heat emitter. The volume of exoskeleton and its weight per volume unit were significantly more important for the heating rate at the beginning of the heating process than for the asymptotic maximum temperature reached at the end of the trials: larger beetles with relatively thicker exoskeletons heated more slowly. The source of radiation greatly influences the asymptotic temperature reached, but has a negligible effect in determining the rate of heat gain by beetles: they reached higher temperatures under artificial sunlight than under infrared radiation. Interspecific differences were negligible in the heating rate but had a large magnitude effect on the asymptotic temperature, only detectable under simulated sun irradiance. The fact that sun irradiance is differentially absorbed dorsally and transformed into heat among species opens the possibility that differences in dorsal exoskeleton would facilitate the heat gain under restrictive environmental temperatures below the preferred ones. The findings provided by this study support the important role played by the exoskeleton in the heating process of beetles, a cuticle able to act passively in the thermal control of body temperature without implying energetic costs and metabolic changes.
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Affiliation(s)
- Valentina Amore
- Departamento de Ecologia e Zoologia, Universidade Federal de Santa Catarina, Florianópolis, Santa Catarina, Brazil
| | - Malva I.M. Hernández
- Departamento de Ecologia e Zoologia, Universidade Federal de Santa Catarina, Florianópolis, Santa Catarina, Brazil
| | - Luis M. Carrascal
- Department of Biogeography and Global Change, Museo Nacional de Ciencias Naturales, CSIC, Madrid, Spain
| | - Jorge M. Lobo
- Department of Biogeography and Global Change, Museo Nacional de Ciencias Naturales, CSIC, Madrid, Spain
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