1
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Cooper CE, Withers PC. Implications of heat exchange for a free-living endangered marsupial determined by non-invasive thermal imaging. J Exp Biol 2024; 227:jeb246301. [PMID: 38206870 DOI: 10.1242/jeb.246301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2023] [Accepted: 11/06/2023] [Indexed: 01/13/2024]
Abstract
We used thermal imagining and heat balance modelling to examine the thermal ecology of wild mammals, using the diurnal marsupial numbat (Myrmecobius fasciatus) as a model. Body surface temperature was measured using infra-red thermography at environmental wet and dry bulb temperatures of 11.7-29°C and 16.4-49.3°C, respectively; surface temperature varied for different body parts and with environmental temperature. Radiative and convective heat exchange varied markedly with environmental conditions and for various body surfaces reflecting their shapes, surface areas and projected areas. Both the anterior and posterior dorsolateral body areas functioned as thermal windows. Numbats in the shade had lower rates of solar radiative heat gain but non-solar avenues for radiative heat gain were substantial. Radiative gain was higher for black and lower for white stripes, but overall, the stripes had no thermal role. Total heat gain was generally positive (<4 to >20 W) and often greatly exceeded metabolic heat production (3-6 W). Our heat balance model indicates that high environmental heat loads limit foraging in open areas to as little as 10 min and that climate change may extend periods of inactivity, with implications for future conservation and management. We conclude that non-invasive thermal imaging is informative for modelling heat balance of free-living mammals.
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Affiliation(s)
- Christine E Cooper
- School of Molecular and Life Sciences, Curtin University, Perth, WA 6845, Australia
- School of Biological Sciences, University of Western Australia, Perth, WA 6009,Australia
| | - Philip C Withers
- School of Molecular and Life Sciences, Curtin University, Perth, WA 6845, Australia
- School of Biological Sciences, University of Western Australia, Perth, WA 6009,Australia
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2
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Taylor GI, Dodwell P, Gascoigne A, Gianoutsos M, Morris S, Shayan R, Fogg QA. Thermoregulation, Not Just Camouflage: The Unique Vasculature of Giraffe Patches. A Cadaver Study with Clinical Implications. Plast Reconstr Surg 2023; 152:669-680. [PMID: 36790779 DOI: 10.1097/prs.0000000000010301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
Abstract
BACKGROUND Serendipitously, a dead giraffe provided opportunity to study its vascular anatomy. Comparative animal studies have revealed important information for designing new flaps and new microsurgical techniques. So, do giraffe's patches support a thermal window concept, do animals with similar markings and habitat have a similar thermoregulatory role, and could results offer new insight into human thermoregulation and free tissue transfer? METHODS Previously described lead-oxide arterial-only injection studies, of a single giraffe, zebra, Africa wild dog, and spotted jaguar, all with wire-encircled pigmented patches; and archival human, pig, dog, cat, and rabbit studies, were compared. RESULTS Each giraffe patch was supplied by just a single artery (angiosome) averaging 0.9 mm diameter, that divided near its center and sent dense, long, parallel, radiating spoke-wheel branches averaging 0.62 mm diameter to the patch margin, continuing as reduced-caliber choke anastomoses averaging 0.8 mm to link adjacent patch angiosomes. Uniquely arranged large veins, with an average of 1.66 mm, encircled the patches in the pale skin paralleled by arteriae comitantes averaging 0.22 mm. These arteries, connected to patch angiosomes, filled the veins intermittently by means of arteriovenous (A-V) shunts averaging 0.12 mm in diameter of magnitude never seen before in any species studied. None of the other three animals had angiosome territories matching their pigmented fur, or significant A-V filling. CONCLUSIONS This study supports the "thermostatic" concept of the giraffe skin patches, with A-V shunts playing a major role. It affirms the need for further studies of these shunts in human thermoregulation and other flow regulations in physiology, pathology, and free tissue transfer.
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Affiliation(s)
- G Ian Taylor
- From the Department of Anatomy and Physiology, University of Melbourne
- Reconstructive Plastic Surgery Unit, Royal Melbourne Hospital
| | - Prue Dodwell
- From the Department of Anatomy and Physiology, University of Melbourne
- Reconstructive Plastic Surgery Unit, Royal Melbourne Hospital
| | - Adam Gascoigne
- From the Department of Anatomy and Physiology, University of Melbourne
- Reconstructive Plastic Surgery Unit, Royal Melbourne Hospital
| | - Mark Gianoutsos
- From the Department of Anatomy and Physiology, University of Melbourne
- Craniofacial and Plastic Surgery Research Unit, Prince of Wales and Sydney Children's Hospital and University of New South Wales
| | - Steve Morris
- From the Department of Anatomy and Physiology, University of Melbourne
- Division of Plastic Surgery, Faculty of Medicine, Dalhousie University
| | - Ramin Shayan
- From the Department of Anatomy and Physiology, University of Melbourne
- Reconstructive Plastic Surgery Unit, Royal Melbourne Hospital
| | - Quentin A Fogg
- From the Department of Anatomy and Physiology, University of Melbourne
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3
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Brandon AA, Almeida D, Powder KE. Neural crest cells as a source of microevolutionary variation. Semin Cell Dev Biol 2023; 145:42-51. [PMID: 35718684 PMCID: PMC10482117 DOI: 10.1016/j.semcdb.2022.06.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Revised: 05/03/2022] [Accepted: 06/03/2022] [Indexed: 11/28/2022]
Abstract
Vertebrates have some of the most complex and diverse features in animals, from varied craniofacial morphologies to colorful pigmentation patterns and elaborate social behaviors. All of these traits have their developmental origins in a multipotent embryonic lineage of neural crest cells. This "fourth germ layer" is a vertebrate innovation and the source of a wide range of adult cell types. While others have discussed the role of neural crest cells in human disease and animal domestication, less is known about their role in contributing to adaptive changes in wild populations. Here, we review how variation in the development of neural crest cells and their derivatives generates considerable phenotypic diversity in nature. We focus on the broad span of traits under natural and sexual selection whose variation may originate in the neural crest, with emphasis on behavioral factors such as intraspecies communication that are often overlooked. In all, we encourage the integration of evolutionary ecology with developmental biology and molecular genetics to gain a more complete understanding of the role of this single cell type in trait covariation, evolutionary trajectories, and vertebrate diversity.
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Affiliation(s)
- A Allyson Brandon
- Department of Biological Sciences, Clemson University, Clemson, SC 29634, USA
| | - Daniela Almeida
- Department of Biological Sciences, Clemson University, Clemson, SC 29634, USA
| | - Kara E Powder
- Department of Biological Sciences, Clemson University, Clemson, SC 29634, USA.
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4
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Kang H, Zsoldos RR, Sole-Guitart A, Narayan E, Cawdell-Smith AJ, Gaughan JB. Heat stress in horses: a literature review. INTERNATIONAL JOURNAL OF BIOMETEOROLOGY 2023; 67:957-973. [PMID: 37060454 DOI: 10.1007/s00484-023-02467-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Revised: 03/21/2023] [Accepted: 03/28/2023] [Indexed: 06/15/2023]
Abstract
Healthy adult horses can balance accumulation and dissipation of body heat to maintain their body temperature between 37.5 and 38.5 °C, when they are in their thermoneutral zone (5 to 25 °C). However, under some circumstances, such as following strenuous exercise under hot, or hot and humid conditions, the accumulation of body heat exceeds dissipation and horses can suffer from heat stress. Prolonged or severe heat stress can lead to anhidrosis, heat stroke, or brain damage in the horse. To ameliorate the negative effects of high heat load in the body, early detection of heat stress and immediate human intervention is required to reduce the horse's elevated body temperature in a timely manner. Body temperature measurement and deviations from the normal range are used to detect heat stress. Rectal temperature is the most commonly used method to monitor body temperature in horses, but other body temperature monitoring technologies, percutaneous thermal sensing microchips or infrared thermometry, are currently being studied for routine monitoring of the body temperature of horses as a more practical alternative. When heat stress is detected, horses can be cooled down by cool water application, air movement over the horse (e.g., fans), or a combination of these. The early detection of heat stress and the use of the most effective cooling methods is important to improve the welfare of heat stressed horses.
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Affiliation(s)
- Hyungsuk Kang
- School of Agriculture and Food Sciences, The University of Queensland, Gatton, QLD, 4343, Australia.
| | - Rebeka R Zsoldos
- School of Agriculture and Food Sciences, The University of Queensland, Gatton, QLD, 4343, Australia
| | - Albert Sole-Guitart
- School of Veterinary Science, The University of Queensland, Gatton, QLD, 4343, Australia
| | - Edward Narayan
- School of Agriculture and Food Sciences, The University of Queensland, Gatton, QLD, 4343, Australia
| | - A Judith Cawdell-Smith
- School of Agriculture and Food Sciences, The University of Queensland, Gatton, QLD, 4343, Australia
| | - John B Gaughan
- School of Agriculture and Food Sciences, The University of Queensland, Gatton, QLD, 4343, Australia
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5
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Száz D, Takács P, Egri Á, Horváth G. Blood-seeking horseflies prefer vessel-imitating temperature gradients on host-mimicking targets: Experimental corroboration of a new explanation of the visual unattractiveness of zebras to tabanids. Int J Parasitol 2023; 53:1-11. [PMID: 36356641 DOI: 10.1016/j.ijpara.2022.10.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Revised: 10/05/2022] [Accepted: 10/07/2022] [Indexed: 11/09/2022]
Abstract
Several hypotheses tried to explain the advantages of zebra stripes. According to the most recent explanation, since the borderlines of sunlit white and black stripes can hamper thermal vessel detection by blood-seeking female horseflies, striped host animals are unattractive to these parasites which prefer hosts with a homogeneous coat, on which the temperature gradients above blood vessels can be detected more easily. This hypothesis has been tested in a field experiment with horseflies walking on a grey barrel with thin black stripes which were slightly warmer than their grey surroundings in sunshine, while in shade both areas had practically the same temperature. To eliminate the multiple (optical and thermal) cues of this test target, we repeated this experiment with improved test surfaces: we attracted horseflies by water- or host-imitating homogeneous black test surfaces, beneath which a heatable wire ran. When heated, this invisible and mechanically impalpable wire imitated thermally the slightly warmer subsurface blood vessels, otherwise it was thermally imperceptible. We measured the times spent by landed and walking horseflies on the test surface parts with and without underlying heated or unheated wire. We found that walking female and male horseflies had no preference for any (wired or wireless) area of the water-imitating horizontal plane test surface on the ground, independent of the temperature (heated or unheated) of the underlying wire. These horseflies looked for water, rather than a host. On the other hand, in the case of host-imitating test surfaces, female horseflies preferred the thin surface regions above the wire only if it was heated and thus warmer than its surroundings. This behaviour can be explained exclusively with the higher temperature of the wire given the lack of other sensorial cues. Our results prove the thermal vessel recognition of female horseflies and support the idea that sunlit zebra stripes impede the thermal detection of a host's vessels by blood-seeking horseflies, the consequence of which is the visual (non-thermal) unattractiveness of zebras to horseflies.
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Affiliation(s)
- Dénes Száz
- Department of Biological Physics, ELTE Eötvös Loránd University, H-1117 Budapest, Pázmány sétány 1, Hungary
| | - Péter Takács
- Department of Biological Physics, ELTE Eötvös Loránd University, H-1117 Budapest, Pázmány sétány 1, Hungary
| | - Ádám Egri
- Institute of Aquatic Ecology, Centre for Ecological Research, H-1113 Budapest, Karolina út 29-31, Hungary
| | - Gábor Horváth
- Department of Biological Physics, ELTE Eötvös Loránd University, H-1117 Budapest, Pázmány sétány 1, Hungary.
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6
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Morandi K, Lindholm AK, Lee DE, Bond ML. Phenotypic matching by spot pattern potentially mediates female giraffe social associations. J Zool (1987) 2022. [DOI: 10.1111/jzo.13009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- K. Morandi
- Department of Evolutionary Biology and Environmental Studies University of Zurich Zurich Switzerland
| | - A. K. Lindholm
- Department of Evolutionary Biology and Environmental Studies University of Zurich Zurich Switzerland
| | - D. E. Lee
- Wild Nature Institute Concord NH USA
- Department of Biology Pennsylvania State University University Park PA USA
| | - M. L. Bond
- Department of Evolutionary Biology and Environmental Studies University of Zurich Zurich Switzerland
- Wild Nature Institute Concord NH USA
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7
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Biomimetic Design for Building Energy Efficiency 2021. Biomimetics (Basel) 2022; 7:biomimetics7030106. [PMID: 35997426 PMCID: PMC9397081 DOI: 10.3390/biomimetics7030106] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Accepted: 07/25/2022] [Indexed: 11/17/2022] Open
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8
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Takács P, Száz D, Vincze M, Slíz-Balogh J, Horváth G. Sunlit zebra stripes may confuse the thermal perception of blood vessels causing the visual unattractiveness of zebras to horseflies. Sci Rep 2022; 12:10871. [PMID: 35927437 PMCID: PMC9352684 DOI: 10.1038/s41598-022-14619-7] [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: 02/12/2022] [Accepted: 06/09/2022] [Indexed: 11/09/2022] Open
Abstract
Multiple hypotheses have been proposed for possible functions of zebra stripes. The most thoroughly experimentally supported advantage of zebra stripes is their visual unattractiveness to horseflies (tabanids) and tsetse flies. We propose here a plausible hypothesis why biting horseflies avoid host animals with striped pelages: in sunshine the temperature gradients of the skin above the slightly warmer blood vessels are difficult to distinguish from the temperature gradients induced by the hairs at the borderlines of warmer black and cooler white stripes. To test this hypothesis, we performed a field experiment with tabanids walking on a host-imitating grey test target with vessel-mimicking thin black stripes which were slightly warmer than their grey surroundings in sunshine, while under shady conditions both areas had practically the same temperature as demonstrated by thermography. We found that horseflies spend more time walking on thin black stripes than surrounding grey areas as expected by chance, but only when the substrate is sunlit. This is because the black stripes are warmer than the surrounding grey areas in the sun, but not in the shade. This is consistent with the flies' well-documented attraction to warmer temperatures and provides indirect support for the proposed hypothesis. The frequent false vessel locations at the numerous black-white borderlines, the subsequent painful bitings with unsuccessful blood-sucking attempts and the host's fly-repellent reactions enhance considerably the chance that horseflies cannot evade host responses and are swatted by them. To eliminate this risk, a good evolutionary strategy was the avoidance of striped (and spotted) host animals.
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Affiliation(s)
- Péter Takács
- Department of Biological Physics, ELTE Eötvös Loránd University, Pázmány sétány 1, Budapest, 1117, Hungary
| | - Dénes Száz
- Department of Biological Physics, ELTE Eötvös Loránd University, Pázmány sétány 1, Budapest, 1117, Hungary
| | - Miklós Vincze
- MTA-ELTE Theoretical Physics Research Group, ELTE Eötvös Loránd University, Pázmány sétány 1, Budapest, 1117, Hungary
| | - Judit Slíz-Balogh
- Department of Biological Physics, ELTE Eötvös Loránd University, Pázmány sétány 1, Budapest, 1117, Hungary
| | - Gábor Horváth
- Department of Biological Physics, ELTE Eötvös Loránd University, Pázmány sétány 1, Budapest, 1117, Hungary.
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9
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Numerical Assessment of Zebra-Stripes-Based Strategies in Buildings Energy Performance: A Case Study under Tropical Climate. Biomimetics (Basel) 2022; 7:biomimetics7010014. [PMID: 35076478 PMCID: PMC8788459 DOI: 10.3390/biomimetics7010014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 12/31/2021] [Accepted: 01/05/2022] [Indexed: 02/01/2023] Open
Abstract
Urban growth has increased the risk of over-heating both in the microclimate and inside buildings, affecting thermal comfort and energy efficiency. That is why this research aims to evaluate the energy performance of buildings in terms of thermal comfort (operative temperature (OP) levels, satisfied hours of natural ventilation SHNV, thermal lag), and energy efficiency (roof heat gains and surface temperatures) in an urban area in Panama City, using superficial-heat-dissipation biomimetic strategies. Two case studies, a base case and a proposed case, were evaluated using the Designbuilder software through dynamic simulation. The proposed case is based on a combined biomimetic strategy; the reflective characteristics of the Saharan ant applied as a coating on the roofs through a segmented pattern such as the Zebra’s stripes (one section with coating, and another without). Results showed that the OP decreased from 8 to 10 °C for the entire urban zone throughout the year. A reduction of 3.13% corresponding to 8790 kWh per year was achieved for cooling energy consumption. A difference of 5 °C in external surface temperature was obtained, having a lower temperature in which the biomimetic strategy was applied. Besides, it was evidenced that a contrasted-reflectivity-stripes pitched roof performed better than a fully reflective roof. Thus, the functionality of Zebra stripes, together with the reflective characteristics of the Saharan ant, provide better performance for buildings’ thermal regulation and energy needs for cooling.
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10
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Pereszlényi Á, Száz D, Jánosi IM, Horváth G. A new argument against cooling by convective air eddies formed above sunlit zebra stripes. Sci Rep 2021; 11:15797. [PMID: 34349136 PMCID: PMC8339008 DOI: 10.1038/s41598-021-95105-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Accepted: 07/15/2021] [Indexed: 11/22/2022] Open
Abstract
There is a long-lasting debate about the possible functions of zebra stripes. According to one hypothesis, periodical convective air eddies form over sunlit zebra stripes which cool the body. However, the formation of such eddies has not been experimentally studied. Using schlieren imaging in the laboratory, we found: downwelling air streams do not form above the white stripes of light-heated smooth or hairy striped surfaces. The influence of stripes on the air stream formation (facilitating upwelling streams and hindering horizontal stream drift) is negligible higher than 1–2 cm above the surface. In calm weather, upwelling air streams might form above sunlit zebra stripes, however they are blown off by the weakest wind, or even by the slowest movement of the zebra. These results forcefully contradict the thermoregulation hypothesis involving air eddies.
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Affiliation(s)
- Ádám Pereszlényi
- Department of Biological Physics, ELTE Eötvös Loránd University, Pázmány sétány 1, 1117, Budapest, Hungary.,Deutsches Meeresmuseum, Katharinenberg 14-20, 18437, Stralsund, Germany
| | - Dénes Száz
- Department of Biological Physics, ELTE Eötvös Loránd University, Pázmány sétány 1, 1117, Budapest, Hungary.,Department of Physics, ELTE Eötvös Loránd University, BDPK, 9700, Szombathely, Hungary
| | - Imre M Jánosi
- Department of Water and Environmental Policy, University of Public Service, Ludovika tér 1, 1083, Budapest, Hungary.,Max Planck Institute for Physics of Complex Systems, Nöthnitzer Strasse 38, 01187, Dresden, Germany
| | - Gábor Horváth
- Department of Biological Physics, ELTE Eötvös Loránd University, Pázmány sétány 1, 1117, Budapest, Hungary.
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11
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Larison B, Kaelin CB, Harrigan R, Henegar C, Rubenstein DI, Kamath P, Aschenborn O, Smith TB, Barsh GS. Population structure, inbreeding and stripe pattern abnormalities in plains zebras. Mol Ecol 2020; 30:379-390. [PMID: 33174253 DOI: 10.1111/mec.15728] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 10/23/2020] [Accepted: 10/30/2020] [Indexed: 01/14/2023]
Abstract
One of the most iconic wild equids, the plains zebra occupies a broad region of sub-Saharan Africa and exhibits a wide range of phenotypic diversity in stripe patterns that have been used to classify multiple subspecies. After decades of relative stability, albeit with a loss of at least one recognized subspecies, the total population of plains zebras has undergone an approximate 25% decline since 2002. Individuals with abnormal stripe patterns have been recognized in recent years but the extent to which their appearance is related to demography and/or genetics is unclear. Investigating population genetic health and genetic structure are essential for developing effective strategies for plains zebra conservation. We collected DNA from 140 plains zebra, including seven with abnormal stripe patterns, from nine locations across the range of plains zebra, and analyzed data from restriction site-associated and whole genome sequencing (RAD-seq, WGS) libraries to better understand the relationships between population structure, genetic diversity, inbreeding, and abnormal phenotypes. We found that genetic structure did not coincide with described subspecific variation, but did distinguish geographic regions in which anthropogenic habitat fragmentation is associated with reduced gene flow and increased evidence of inbreeding, especially in certain parts of East Africa. Further, zebras with abnormal striping exhibited increased levels of inbreeding relative to normally striped individuals from the same populations. Our results point to a genetic cause of stripe pattern abnormalities, and dramatic evidence of the consequences of habitat fragmentation.
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Affiliation(s)
- Brenda Larison
- Department of Ecology and Evolutionary Biology, UCLA, Los Angeles, CA, USA.,Center for Tropical Research, Institute of the Environment and Sustainability, UCLA, Los Angeles, CA, USA
| | - Christopher B Kaelin
- HudsonAlpha Institute for Biotechnology, Huntsville, AL, USA.,Department of Genetics, Stanford University, Stanford, CA, USA
| | - Ryan Harrigan
- Department of Ecology and Evolutionary Biology, UCLA, Los Angeles, CA, USA.,Center for Tropical Research, Institute of the Environment and Sustainability, UCLA, Los Angeles, CA, USA
| | | | - Daniel I Rubenstein
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA
| | - Pauline Kamath
- School of Food and Agriculture, University of Maine, Orono, ME, USA
| | - Ortwin Aschenborn
- School of Veterinary Medicine, University of Namibia, Neudamm Windhoek, Namibia
| | - Thomas B Smith
- Department of Ecology and Evolutionary Biology, UCLA, Los Angeles, CA, USA.,Center for Tropical Research, Institute of the Environment and Sustainability, UCLA, Los Angeles, CA, USA
| | - Gregory S Barsh
- HudsonAlpha Institute for Biotechnology, Huntsville, AL, USA.,Department of Genetics, Stanford University, Stanford, CA, USA
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12
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How MJ, Gonzales D, Irwin A, Caro T. Zebra stripes, tabanid biting flies and the aperture effect. Proc Biol Sci 2020; 287:20201521. [PMID: 32811316 PMCID: PMC7482270 DOI: 10.1098/rspb.2020.1521] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
Of all hypotheses advanced for why zebras have stripes, avoidance of biting fly attack receives by far the most support, yet the mechanisms by which stripes thwart landings are not yet understood. A logical and popular hypothesis is that stripes interfere with optic flow patterns needed by flying insects to execute controlled landings. This could occur through disrupting the radial symmetry of optic flow via the aperture effect (i.e. generation of false motion cues by straight edges), or through spatio-temporal aliasing (i.e. misregistration of repeated features) of evenly spaced stripes. By recording and reconstructing tabanid fly behaviour around horses wearing differently patterned rugs, we could tease out these hypotheses using realistic target stimuli. We found that flies avoided landing on, flew faster near, and did not approach as close to striped and checked rugs compared to grey. Our observations that flies avoided checked patterns in a similar way to stripes refutes the hypothesis that stripes disrupt optic flow via the aperture effect, which critically demands parallel striped patterns. Our data narrow the menu of fly-equid visual interactions that form the basis for the extraordinary colouration of zebras.
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Affiliation(s)
- Martin J How
- School of Biological Sciences, University of Bristol, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
| | - Dunia Gonzales
- School of Biological Sciences, University of Bristol, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
| | - Alison Irwin
- School of Biological Sciences, University of Bristol, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
| | - Tim Caro
- School of Biological Sciences, University of Bristol, 24 Tyndall Avenue, Bristol BS8 1TQ, UK.,Center for Population Biology, University of California, Davis, CA 95616, USA
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13
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Why do biting horseflies prefer warmer hosts? tabanids can escape easier from warmer targets. PLoS One 2020; 15:e0233038. [PMID: 32401816 PMCID: PMC7219777 DOI: 10.1371/journal.pone.0233038] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2020] [Accepted: 04/26/2020] [Indexed: 11/21/2022] Open
Abstract
Blood-sucking horseflies (tabanids) prefer warmer (sunlit, darker) host animals and generally attack them in sunshine, the reason for which was unknown until now. Recently, it was hypothesized that blood-seeking female tabanids prefer elevated temperatures, because their wing muscles are quicker and their nervous system functions better at a warmer body temperature brought about by warmer microclimate, and thus they can more successfully avoid the host’s parasite-repelling reactions by prompt takeoffs. To test this hypothesis, we studied in field experiments the success rate of escape reactions of tabanids that landed on black targets as a function of the target temperature, and measured the surface temperature of differently coloured horses with thermography. We found that the escape success of tabanids decreased with decreasing target temperature, that is escape success is driven by temperature. Our results explain the behaviour of biting horseflies that they prefer warmer hosts against colder ones. Since in sunshine the darker the host the warmer its body surface, our results also explain why horseflies prefer sunlit dark (brown, black) hosts against bright (beige, white) ones, and why these parasites attack their hosts usually in sunshine, rather than under shaded conditions.
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14
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Horváth G, Pereszlényi Á, Tóth T, Polgár S, Jánosi IM. Attractiveness of thermally different, uniformly black targets to horseflies: Tabanus tergestinus prefers sunlit warm shiny dark targets. ROYAL SOCIETY OPEN SCIENCE 2019; 6:191119. [PMID: 31824718 PMCID: PMC6837212 DOI: 10.1098/rsos.191119] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/25/2019] [Accepted: 09/23/2019] [Indexed: 06/10/2023]
Abstract
From a large distance tabanid flies may find their host animal by means of its shape, size, motion, odour, radiance and degree of polarization of host-reflected light. After alighting on the host, tabanids may use their mechano-, thermo-, hygro- and chemoreceptors to sense the substrate characteristics. Female tabanids prefer to attack sunlit against shady dark host animals, or dark against bright hosts for a blood meal, the exact reasons for which are unknown. Since sunlit darker surfaces are warmer than shady ones or sunlit/shady brighter surfaces, the differences in surface temperatures of dark and bright as well as sunlit and shady hosts may partly explain their different attractiveness to tabanids. We tested this observed warmth preference in field experiments, where we compared the attractiveness to tabanids (Tabanus tergestinus) of a warm and a cold shiny black barrel imitating dark hosts with the same optical characteristics. Using imaging polarimetry, thermography and Schlieren imaging, we measured the optical and thermal characteristics of both barrels and their small-scale models. We recorded the number of landings on these targets and measured the time periods spent on them. Our study revealed that T. tergestinus tabanid flies prefer sunlit warm shiny black targets against sunlit or shady cold ones with the same optical characteristics. These results support our new hypothesis that a blood-seeking female tabanid prefers elevated temperatures, partly because her wing muscles are more rapid and her nervous system functions better (due to faster conduction velocities and synaptic transmission of signals) in a warmer microclimate, and thus, she can avoid the parasite-repelling reactions of host animals by a prompt take-off.
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Affiliation(s)
- Gábor Horváth
- Environmental Optics Laboratory, Department of Biological Physics, ELTE Eötvös Loránd University, 1117 Budapest, Pázmány sétány 1, Hungary
| | - Ádám Pereszlényi
- Environmental Optics Laboratory, Department of Biological Physics, ELTE Eötvös Loránd University, 1117 Budapest, Pázmány sétány 1, Hungary
- Hungarian Natural History Museum, Department of Zoology, Bird Collection, 1083 Budapest, Ludovika tér 2-6, Hungary
| | - Tímea Tóth
- Environmental Optics Laboratory, Department of Biological Physics, ELTE Eötvös Loránd University, 1117 Budapest, Pázmány sétány 1, Hungary
| | - Szabolcs Polgár
- Environmental Optics Laboratory, Department of Biological Physics, ELTE Eötvös Loránd University, 1117 Budapest, Pázmány sétány 1, Hungary
| | - Imre M. Jánosi
- Department of Physics of Complex Systems, ELTE Eötvös Loránd University, 1117 Budapest, Pázmány sétány 1, Hungary
- Max Planck Institute for the Physics of Complex Systems, Nöthnitzer Strasse 38, 01187 Dresden, Germany
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