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Leukocyte profile of the helmeted manakin, Antilophia galeata (Passeriformes: Pipridae) in a Cerrado forest fragment

ABSTRACT

Changes in the amounts and proportions of leukocytes, known as leucocyte profiles, have been documented for several bird species and have been used to measure stress levels in these animals. The present work ascertained the biological and ecological attributes that influence the leukocyte profile of Antilophia galeata (Lichtenstein, 1823), the helmeted manakin. This species has been deemed useful in ecological studies because it responds to environmental changes. Blood samples drawn from 89 individuals of A. galeata captured in a Cerrado forest fragment were subjected to analysis under optical microscopy to identify and quantify leukocytes and micronuclei. The number of lymphocytes was greater for males, non-reproductive individuals and individuals infected with ticks. None of the leukocyte components differed in relation to age, molting or body condition index. The amount of micronuclei was correlated with values for total leukocytes, H/L ratio, heterophils, basophils and monocytes. The results suggest that reproduction may be an immunosuppressive factor for the species, producing sexual differences in lymphocyte availability. In addition, biomarkers of genotoxic damage (micronuclei) were related to the amount of leukocytes, indicating that individuals may be sensitive to environmental disturbances. Leukocyte profiles can be considered a useful tool for addressing ecological questions that are relevant to the conservation of species in degraded environments.

KEY WORDS:
Avian hematology; Brazilian birds; micronuclei; stress; white blood cells

INTRODUCTION

Various biological and physiological parameters can be used to assess stress in birds, including hematological exams such as the evaluation of leukocyte profiles (Davis et al. 2008Davis AK, Maney DL, Maerz JC (2008) The use of leukocyte profiles to measure stress in vertebrates: a review for ecologists. Functional Ecology 22: 760-772. https://doi.org/10.1111/j.1365-2435.2008.01467.x
https://doi.org/10.1111/j.1365-2435.2008...
). Leukocyte profiles are determined by differential leukocyte counts and represent a major component of the vertebrate immune system, comprising various cell types that provide protection against pathogens and stressors (Campbell 2015Campbell TW (2015) Exotic animal hematology and cytology. John Wiley & Sons, New Jersey, 402 pp. https://doi.org/10.1002/9781118993705
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).

Avian leukocytes can be classified into granulocytes and agranulocytes or mononuclear cells. The former include basophils, eosinophils and heterophils, while the latter include lymphocytes and monocytes (Campbell 2004Campbell TW (2004) Hematology of birds. In: Thrall MA (Ed) Veterinary hematology and clinical chemistry. Lippincott Williams & Wilkins, Philadelphia, 225-257., Fernandes et al. 2013Fernandes DC, Eto SF, Claudiano GS, Marcusso PF, Loureiro BA (2013) Biologia do sistema imune de aves. Ensaios e Ciência: Ciências Biológicas, Agrárias e da Saúde 17: 131-140.). Lymphocytes undergo maturation in lymphoid organs, such as the thymus or bursa of Frabricius, and are responsible for acquired or adaptive immunity with the production of antibodies and specific responses to pathogens (Campbell 2015Campbell TW (2015) Exotic animal hematology and cytology. John Wiley & Sons, New Jersey, 402 pp. https://doi.org/10.1002/9781118993705
https://doi.org/10.1002/9781118993705...
). Heterophils, eosinophils, basophils and monocytes act primarily on innate immunity, which is the first line of immune defense (Davison et al. 2008Davison F, Kaspers B, Schat KA, Kaiser P (2008) Avian Immunology. Academic Press, Oxford, 481 pp.). Bird heterophils are equivalent to the mammalian neutrophils and are the major phagocytic cells involved in the inflammatory response, attacking bacteria through chemotaxis, opsonization, phagocytosis, and lysis (Cândido 2008Cândido MV (2008) Hematologia, bioquímica sérica e nutrição em aves: Cracidae. PhD Thesis, Curitiba, Universidade Federal do Paraná. http://hdl.handle.net/1884/16089
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, Capitelli and Crosta 2013Capitelli R, Crosta L (2013) Overview of psittacine blood analysis and comparative retrospective study of clinical diagnosis, hematology and blood chemistry in selected psittacine species. Veterinary Clinics of North America: Exotic Animal Practice 16: 71-120. https://doi.org/10.1016/j.cvex.2012.10.002
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). The functions of eosinophils and basinophils in birds are uncertain, but both may play a role in hypersensitivity reactions, while eosinophils may also act against parasitic infections (Kiesecker 2002Kiesecker JM (2002) Synergism between trematode infection and pesticide exposure: a link to amphibian deformities in nature? Proceedings of the National Academy of Sciences 99: 9900-9904. https://doi.org/10.1073/pnas.152098899
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, Mitchell and Johns 2008Mitchell EB, Johns J (2008) Avian hematology and related disorders. Veterinary Clinics of North America: Exotic Animal Practice 11: 501-522. https://doi.org/10.1016/j.cvex.2008.03.004
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). Monocytes phagocytize and degrade microorganisms, abnormal cells and cellular debris (Campbell 2015Campbell TW (2015) Exotic animal hematology and cytology. John Wiley & Sons, New Jersey, 402 pp. https://doi.org/10.1002/9781118993705
https://doi.org/10.1002/9781118993705...
).

Heterophils and lymphocytes together make up approximately 80% of the leukocytes of birds and their amounts and proportions can change according to variation in corticosteroid concentrations (Davis et al. 2008Davis AK, Maney DL, Maerz JC (2008) The use of leukocyte profiles to measure stress in vertebrates: a review for ecologists. Functional Ecology 22: 760-772. https://doi.org/10.1111/j.1365-2435.2008.01467.x
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, Wojczulanis-Jakubas et al. 2015Jakubas D, Wojczulanis-Jakubas K, Kośmicka A (2015) Factors affecting leucocyte profiles in the little auk, a small Arctic seabird. Journal of Ornithology 156: 101-111. https://doi.org/10.1007/s10336-014-1101-5
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). When present at high levels, these hormones promote greater recruitment of heterophils in relation to lymphocytes, thereby increasing the H/L ratio, which characterizes the leukocyte stress profile (Gross and Siegel 1983Gross WB, Siegel HS (1983) Evaluation of the heterophil/lymphocyte ratio as a measure of stress in chickens. Avian Diseases 27: 972-979. https://doi.org/10.2307/1590198
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, Davis et al. 2008Davis AK, Maney DL, Maerz JC (2008) The use of leukocyte profiles to measure stress in vertebrates: a review for ecologists. Functional Ecology 22: 760-772. https://doi.org/10.1111/j.1365-2435.2008.01467.x
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). This adjustment in the proportions of heterophils and lymphocytes occurs during stressful periods, when individuals tend to suppress one component of the immune system while enhancing another (Apanius 1998Apanius V (1998) Ontogeny of immune function. In: Starck JM, Ricklefs RE (Eds) Avian growth and development: evolution within the altricial-precocial spectrum. Oxford University Press, Oxford, 203-222.), as demonstrated by experiments with laboratory animals using exogenous treatment with synthetic glucocorticoids (Dhabhar et al. 1995Dhabhar FS, Miller AH, Mcewen BS, Spencer RL (1995) Effects of stress on immune cell distribution - dynamics and hormonal mechanisms. Journal of Immunology 154: 5511-5527. https://www.jimmunol.org/content/154/10/5511
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).

Evidence has shown that the leukocyte profiles of birds differ between males and females, since sex hormones act as important modulators of the immune response: testosterone is immunosuppressive and estrogen is immune-enhancing (Campo and Davila 2002Campo JL, Davila SG (2002) Estimation of heritability for heterophil: lymphocyte ratio in chickens by restricted maximum likelihood: effects of age, sex, and crossing. Poultry Science 81: 1448-1453. https://doi.org/10.1093/ps/81.10.1448
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, Charles-Smith et al. 2014Charles-Smith LE, Rutledge ME, Meek CJ, Baine K, Massey E, Ellsaesser LN, Degernes LA (2014) Hematologic parameters and hemoparasites of nonmigratory Canada geese (Branta canadensis) from Greensboro, North Carolina, USA. Journal of Avian Medicine and Surgery 28(1): 16-23. https://doi.org/10.1647/2012-072
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, Foo et al. 2016Foo YZ, Nakagawa S, Rhodes G, Simmons LW (2016) The effects of sex hormones on immune function: a meta-analysis. Biological Reviews 92: 551-571. https://doi.org/10.1111/brv.12243
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, Roved et al. 2017Roved J, Westerdahl H, Hasselquist D (2017) Sex differences in immune responses: hormonal effects, antagonistic selection, and evolutionary consequences. Hormones and Behavior 88: 95-105. https://doi.org/10.1016/j.yhbeh.2016.11.017
https://doi.org/10.1016/j.yhbeh.2016.11....
). Since young birds have yet to undergo sexual maturation, their leukocyte profiles may differ from those of adults. In addition, there are reports of higher H/L ratios during reproduction; that is, an indication of greater stress during the reproductive period, since, for both sexes, reproduction involves high energetic demands (Wojczulanis-Jakubas et al. 2015Wojczulanis-Jakubas K, Jakubas D, Chastel O, Kulaszewicz I (2015) A big storm in a small body: seasonal changes in body mass, hormone concentrations and leukocyte profile in the little auk (Alle alle). Polar Biology 38: 1203-12. https://doi.org/10.1007/s00300-015-1687-y
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, Frigerio et al. 2017Frigerio D, Ludwig SC, Hemetsberger J, Kotrschal K, Wascher CA (2017) Social and environmental factors modulate leucocyte profiles in free-living greylag geese (Anser anser). PeerJ 5: e2792. https://doi.org/10.1016/j.cbpa.2010.02.012
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) such as during incubation and parental care, egg production for females and defense of territories for males (Saino et al. 2002Saino N, Incagli M, Martinelli R, Møller AP (2002) Immune response of male barn swallows in relation to parental effort, corticosterone plasma levels, and sexual ornamentation. Behavior Ecology 13: 69-174. https://doi.org/10.1093/beheco/13.2.169
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, Greenman et al. 2005Greenman CG, Martin LB, Hau M (2005) Reproductive state, but not testosterone, reduces immune function in male house sparrows (Passer domesticus). Physiological and Biochemical Zoology 78: 60-68. https://doi.org/10.1086/425194
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).

Birds undergo other stressors that may influence their leukocyte profile, such as parasitism, food shortage and molting, among others. Lüdtke et al. (2013Lüdtke B, Moser I, Santiago-Alarcon D, Fischer M, Kalko EK, Schaefer HM, Renner SC (2013) Associations of forest type, parasitism and body condition of two european passerines, Fringilla coelebs and Sylvia atricapilla. Plos One 8: e81395. https://doi.org/10.1371/journal.pone.0081395
https://doi.org/10.1371/journal.pone.008...
) found that the H/L ratio is significantly higher in individuals of the Eurasian blackcap, Sylvia atricapilla (Linnaeus, 1758), infected with hemoparasites. Palacios et al. (2017Palacios MJ, Valera F, Colominas-Ciuró R, Barbosa A (2017) Cellular and humoral immunity in two highly demanding energetic life stages: reproduction and moulting in the chinstrap penguin. Journal of Ornithology 159: 283-290. https://doi.org/10.1007/s10336-017-1499-7
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) observed that molting individuals of the chinstrap penguin, Pygoscelis antarctica (J.R. Forster, 1781), have a greater proportion of leukocytes. Machado-Filho et al. (2010Machado-Filho RA, Balsamão GM, Marini MÂ (2010) Seasonal differences in immune profiles and body conditions of migratory and permanent resident neotropical flycatchers. The Condor 112: 579-590. https://doi.org/10.1525/cond.2010.090146
https://doi.org/10.1525/cond.2010.090146...
) found that individuals of the plain-crested elaenia, Elaenia cristata Pelzeln, 1868, had higher H/L ratios during the dry season in a savannah environment, which the authors attributed to stress due to scarcity of food. Other studies have recorded changes in the leukocyte profiles of birds in relation to environmental disturbances, such as pollution. Eeva et al. (2005Eeva T, Hasselquist D, Langefors Å, Tummeleht L, Nikinmaa M, Ilmonen P (2005) Pollution related effects on immune function and stress in a free-living population of pied flycatcher Ficedula hypoleuca. Journal of Avian Biology 36: 405-412. https://doi.org/10.1111/j.0908-8857.2005.03449.x
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) observed that individuals of the European pied flycatcher, Ficedula hypoleuca (Pallas, 1764), sampled in an area contaminated with copper, had higher H/L ratios. Bauerová et al. (2017Bauerová P, Vinklerová J, Hraníček J, Čorba V, Vojtek L, Svobodová J, Vinkler M (2017) Associations of urban environmental pollution with health-related physiological traits in a free-living bird species. Science of the Total Environment 601: 1556-1565. https://doi.org/10.1016/j.scitotenv.2017.05.276
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) revealed a positive correlation between H/L ratio and the amount of lead, cadmium, copper and chromium present in the plumage of the Eurasian great tit, Parus major Linnaeus, 1758.

Another alteration evidenced in hematological examinations is the presence of erythrocyte micronuclei, which has been associated with anthropic influences (Baesse et al. 2015Baesse CQ, Tolentino VCM, Silva AM, Silva AA, Ferreira GA, Paniago LPM, Nepomuceno JC, Melo C (2015) Micronucleus as biomarker of genotoxicity in birds from Brazilian Cerrado. Ecotoxicology and Environmental Safety 115: 223-228. https://doi.org/10.1016/j.ecoenv.2015.02.024
https://doi.org/10.1016/j.ecoenv.2015.02...
, 2019Baesse CQ, Tolentino VCM, Morelli S, Melo C (2019) Effect of urbanization on the micronucleus frequency in birds from forest fragments. Ecotoxicology and Environmental Safety 171: 631-637. https://doi.org/10.1016/j.ecoenv.2019.01.026
https://doi.org/10.1016/j.ecoenv.2019.01...
, Martínez-Haro et al. 2017Martínez-Haro M, Balderas-Plata MA, Pereda-Solís ME, Arellano-Aguilar RO, Hernández-Millán CL (2017) Anthropogenic influence on blood biomarkers of stress and genotoxicity of the burrowing owl (Athene Cunicularia). Biodiversity & Endangered Species Journal 5: 1-4. https://doi.org/10.4172/2332-2543.1000196
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). Micronuclei are small, round structures located in the cytoplasm. They have chromatic characteristics similar to those of the principal nucleus (Gattás et al. 1992Gattás GJF, Longatto Filho A, Maeda MYS (1992) Identificação de micronúcleos (MN) em células de colo uterino de pacientes assintomáticas: correlação dos métodos de Papanicolau e Feulgen-fastgreen. Folha Médica 104: 57-59.). Their shape is due to factors or events that interfere with the structure or function of the mitotic apparatus, which produces failures in the incorporation of chromosomes or chromosomal fragments in the principal nucleus (Fenech et al. 2006Fenech M, Bolognessi C, Kirsch-Volders M, Bonassi S, Zeiger E, Knesmüller S, Holland N (2006) Harmonisation of the micronucleus assay in human buccal cells - a human micronucleus (HUMN) project (www.humn.org) initiative commencing in 2007. Mutagenesis 22: 3-4. https://doi:10.1093/mutage/gel056
https://doi:10.1093/mutage/gel056...
, Thomas et al. 2009Thomas P, Holland N, Bolognesi C, Kirsch-Volders M, Bonassi S, Zeiger E, et al. (2009) Buccal micronucleus cytome assay. Nature Protocols 4: 825-837. https://doi.org/10.1038/nprot.2009.53
https://doi.org/10.1038/nprot.2009.53...
). Micronuclei reflect chromosomal damage and, therefore, can act as biomarkers of genotoxicity (Hitoshi et al. 2003Hitoshi I, Ying T, Toru Y (2003) Influence of gender, age and lifestyle factors on micronuclei frequency in healthy Japanese populations. Journal of Occupational Health 45: 179-181. https://doi.org/10.1539/joh.45.179
https://doi.org/10.1539/joh.45.179...
, Baesse et al. 2015Baesse CQ, Tolentino VCM, Silva AM, Silva AA, Ferreira GA, Paniago LPM, Nepomuceno JC, Melo C (2015) Micronucleus as biomarker of genotoxicity in birds from Brazilian Cerrado. Ecotoxicology and Environmental Safety 115: 223-228. https://doi.org/10.1016/j.ecoenv.2015.02.024
https://doi.org/10.1016/j.ecoenv.2015.02...
, 2019Baesse CQ, Tolentino VCM, Morelli S, Melo C (2019) Effect of urbanization on the micronucleus frequency in birds from forest fragments. Ecotoxicology and Environmental Safety 171: 631-637. https://doi.org/10.1016/j.ecoenv.2019.01.026
https://doi.org/10.1016/j.ecoenv.2019.01...
). Analysis of micronuclei can be used as an efficient method to assess mutagenicity of, and sensitivity to, environmental contaminants (Wolf et al. 2002Wolf T, Niehaus-Rolf C, Luepke N (2002) Some new methodological aspects of the hen’s egg test. Mutation Research 514: 59-76. https://doi.org/10.1016/S1383-5718(01)00317-5
https://doi.org/10.1016/S1383-5718(01)00...
, Baesse et al. 2019Baesse CQ, Tolentino VCM, Morelli S, Melo C (2019) Effect of urbanization on the micronucleus frequency in birds from forest fragments. Ecotoxicology and Environmental Safety 171: 631-637. https://doi.org/10.1016/j.ecoenv.2019.01.026
https://doi.org/10.1016/j.ecoenv.2019.01...
). Micronuclei and the H/L ratio can be viewed as relatively independent indicators of stress, and any association between the two would lend support to their use as physiological stress indicators. Furthermore, assessing two relatively independent stress indicators provides a far more comprehensive view of an animal’s physiological stress profile than examining just one single indicator.

Few studies have documented the leukocyte components in Brazilian bird species, and the influence of stressful situations on them (Machado-Filho et al. 2010Machado-Filho RA, Balsamão GM, Marini MÂ (2010) Seasonal differences in immune profiles and body conditions of migratory and permanent resident neotropical flycatchers. The Condor 112: 579-590. https://doi.org/10.1525/cond.2010.090146
https://doi.org/10.1525/cond.2010.090146...
, Lobato et al. 2011Lobato DN, Braga ÉM, Belo NDO, Antonini Y (2011) Hematological and parasitological health conditions of the Pale-breasted Thrush (Turdus leucomelas) (Passeriformes: Turdidae) in southeastern Brazil. Zoologia 28(6): 771-776. https://doi.org/10.1590/S1984-46702011000600010
https://doi.org/10.1590/S1984-4670201100...
). Brazil harbors one of the richest avifauna in the world with approximately 2,000 described species (Piacentini et al. 2015Piacentini VQ, Aleixo A, Agnev CE, Maurício GN, Pacheco J, Bravo GA, et al. (2015). Annotated checklist of the birds of Brazil by the Brazilian Ornithological Records Committee. Revista Brasileira de Ornitologia 3: 90-298. http://www.revbrasilornitol.com.br/BJO/article/view/1263
http://www.revbrasilornitol.com.br/BJO/a...
). The present study examined a population of the helmeted manakin, Antilophia galeata (Lichtenstein, 1823), a piprid passeriforme endemic to the Cerrado, and which inhabits the understory of riparian forests. The species can be found in preserved areas such as conservation units, and in altered sites, including urban environments such as city parks (Franchin and Marçal-Júnior 2004Franchin AG, Marçal-Júnior O (2004) A riqueza da avifauna no Parque Municipal do Sabiá, zona urbana de Uberlândia (MG) Biotemas 17: 179-202. https://doi.org/10.5007/%25x
https://doi.org/10.5007/%25x...
, Valadão et al. 2006Valadão RM, Franchin AG, Marçal-Júnior O (2006) A avifauna no Parque Municipal Victório Siquierolli, zona urbana de Uberlândia (MG). Biotemas 19: 81-91. https://doi.org/10.5007/%25x
https://doi.org/10.5007/%25x...
, Silva and Melo 2011Silva AM, Melo C (2011) Frugivory and seed dispersal by the helmeted manakin (Antilophia galeata) in forests of Brazilian Cerrado. Ornitología Neotropical 22: 69-77.). The species is monogamous and mostly frugivorous, sometimes incorporating invertebrates in its diet (Silva and Melo 2011Silva AM, Melo C (2011) Frugivory and seed dispersal by the helmeted manakin (Antilophia galeata) in forests of Brazilian Cerrado. Ornitología Neotropical 22: 69-77., Dantas 2013Dantas T (2013) Ciclos anuais em aves de ambiente florestal: muda de penas e reprodução. PhD Thesis, Uberlândia, Brazil, Universidade Federal de Uberlândia. https://repositorio.ufu.br/handle/123456789/13391
https://repositorio.ufu.br/handle/123456...
). Adult males have black plumage with red feathers on top of the head. Adult females and juveniles of both sexes have a discrete greenish plumage throughout the body (Marini 1992Marini MA (1992) Notes on the breeding and reproductive biology of the helmeted manakin. The Wilson Bulletin 104: 168-173. https://www.jstor.org/stable/4163127
https://www.jstor.org/stable/4163127...
, Sick 1997Sick H (1997) Ornitologia brasileira: uma introdução. Editora Nova Fronteira, Rio de Janeiro, 912 pp.).

The helmeted manakin has been considered useful in ecology studies because it is territorial, dependent on the forest environment and is sensitive to the effects of disturbances, being a species that can show responses to environment changes (Silva and Melo 2011Silva AM, Melo C (2011) Frugivory and seed dispersal by the helmeted manakin (Antilophia galeata) in forests of Brazilian Cerrado. Ornitología Neotropical 22: 69-77., Gonçalves 2012Gonçalves VF (2012) Assimetria flutuante em aves de ambientes florestais no Cerrado mineiro. PhD Thesis, Uberlândia, Brazil, Universidade Federal de Uberlândia. https://repositorio.ufu.br/handle/123456789/13366
https://repositorio.ufu.br/handle/123456...
, Dantas 2013Dantas T (2013) Ciclos anuais em aves de ambiente florestal: muda de penas e reprodução. PhD Thesis, Uberlândia, Brazil, Universidade Federal de Uberlândia. https://repositorio.ufu.br/handle/123456789/13391
https://repositorio.ufu.br/handle/123456...
, Teles 2013Teles DRF (2013) Condição corporal de aves em Fragmento de Mata Estacional Semidecidual do Triângulo Mineiro, Brasil. PhD Thesis, Uberlândia, Brazil, Universidade Federal de Uberlândia. https://repositorio.ufu.br/handle/123456789/13386
https://repositorio.ufu.br/handle/123456...
, Baesse et al. 2015Baesse CQ, Tolentino VCM, Silva AM, Silva AA, Ferreira GA, Paniago LPM, Nepomuceno JC, Melo C (2015) Micronucleus as biomarker of genotoxicity in birds from Brazilian Cerrado. Ecotoxicology and Environmental Safety 115: 223-228. https://doi.org/10.1016/j.ecoenv.2015.02.024
https://doi.org/10.1016/j.ecoenv.2015.02...
, 2019Baesse CQ, Tolentino VCM, Morelli S, Melo C (2019) Effect of urbanization on the micronucleus frequency in birds from forest fragments. Ecotoxicology and Environmental Safety 171: 631-637. https://doi.org/10.1016/j.ecoenv.2019.01.026
https://doi.org/10.1016/j.ecoenv.2019.01...
, Paniago 2016Paniago LPM (2016) Aspectos ecológicos de Antilophia galeata (Passeriformes: Pipridae) e seu potencial em biomonitoramento e conservação. PhD Thesis, Uberlândia, Brazil, Universidade Federal de Uberlândia. https://repositorio.ufu.br/handle/123456789/18775
https://repositorio.ufu.br/handle/123456...
). The present study proposed to examine the leukocyte profile of a population of A. galeata and to associate it with biological and ecological attributes of the species. The hypotheses tested are that the leukocyte stress profile should predominate in: (i) males, because they are territorial and aggressive and this behavior is associated with increased levels of the immunosuppressive hormone testosterone; (ii) juveniles, possibly due to greater sensitivity to stress; (iii) individuals of both sexes in the reproductive period, because of the high energy demands; (iv) individuals of both sexes during molting, since the renewal of feathers requires a lot of energy; (v) individuals infested with ticks, since the exploitive action of these parasites can cause stress in birds. It is also expected that individuals in poor body condition and with a greater quantity of micronuclei would display a leukocyte stress profile.

MATERIAL AND METHODS

The study was carried out in a Cerrado forest fragment at the Fazenda Experimental do Glória (18°57’03”S; 48°12’22”W), in the municipality of Uberlândia, Minas Gerais, Brazil. The fragment encompasses 30 ha composed of seasonal semideciduous forest with gallery forest at is lower limit and abrupt transitions at artificial borders with pastures at the upper and lateral limits (Lopes 2010Lopes SF (2010) Padrões florísticos e estruturais das Florestas Estacionais Semideciduais do Triângulo Mineiro, MG. PhD Thesis, Uberlândia, Brazil, Universidade Federal de Uberlândia. https://repositorio.ufu.br/handle/123456789/13258
https://repositorio.ufu.br/handle/123456...
). The forest is adjacent to the highway BR 050, which is heavily trafficked by motor vehicles (Baesse et al. 2019Baesse CQ, Tolentino VCM, Morelli S, Melo C (2019) Effect of urbanization on the micronucleus frequency in birds from forest fragments. Ecotoxicology and Environmental Safety 171: 631-637. https://doi.org/10.1016/j.ecoenv.2019.01.026
https://doi.org/10.1016/j.ecoenv.2019.01...
). The climate of the region is Aw type, according to the climatic classification of Köppen, with a dry season (April-September) and a rainy season (October-March). Annual rainfall is around 1,500 mm, while the mean temperature is 22 °C (Rosa et al. 1991Rosa R, Lima SC, Assunção WL (1991) Abordagem preliminar das condições climáticas de Uberlândia (MG). Sociedade & Natureza 3: 91-108.).

Seven field campaigns of five days each were undertaken from June 2013 to December 2015. Birds were captured using 20 to 25 mist nets (12 m long x 3 m high) exposed on trails between 6:30 am and 5:00 pm. The nets were checked at intervals of approximately 30 minutes. When birds were found they were removed and placed in clothe bags for subsequent screening. Individuals were weighed in the bags using a hand dynamometer (Pesola®), with the weight of the bag then being subtracted. The tarsal length of each bird was measured using a digital caliper (Lotus®). Individuals were identified and banded with metal bands provided by Center for Research and Conservation of Wild Birds (CEMAVE/ICMBio - Authorization: 3730, Registry: 359076).

The reproductive stage of the captured birds was determined by the presence of an incubation patch; when the abdominal region lacks feathers and has thin, wrinkled skin with a darker coloration due to increased vascularization (Cemave 1994Centro Nacional de Pesquisa e Conservação das Aves Silvestres (1994) Manual de anilhamento de aves silvestres. CEMAVE, Instituto Brasileiro do Meio Ambiente e dos Recursos Naturais Renováveis, , Brasília, 2nd ed., 148 pp. http://www.icmbio.gov.br/cemave/downloads/finish/7-sna/13-manual-de-anilhamento-de-aves-silvestres.html
http://www.icmbio.gov.br/cemave/download...
). The feathers covering the abdominal region were blown to allow visualization of the incubation patch and determine its presence. In addition, feathers from other regions of the body (head, neck, back) were blown to detect the presence of ticks and molting (appearance of new feathers).

When possible, the age group (young or adult) of each individual was determined, since young birds usually have a yellowish labial commissure and the absence of, or minimal, cranial ossification. To determine sex, blood samples were colleted from all individuals of green color (05 µL of blood from the tarsal vein) with the aid of sterile disposable needles (8 × 0.3 mm) (SISBIO/ICMBio - Authorization: 44901). The collected blood samples were stored in specific kits provided by the sexing laboratory. The samples were sent to a private laboratory for molecular sexing (©Unigen Tecnologia do DNA - from São Paulo, SP, Brazil).

A drop of blood (05 µL) was collected from the tarsal vein and placed on a clean, sterile microscope slide (SISBIO/ICMBio - Authorization: 44901). With the aid of a second slide inclined at 45°, the blood was drawn across the first slide. After drying, the slides were fixed with absolute methanol while still in the field. In the laboratory the slides were stained with a solution of Giemsa (5%) and phosphate buffer (pH 5.8) for 30 minutes. The slides were then washed in distilled water, dried at room temperature and identified with the individual’s band number.

Slides were analyzed under an optical microscope with a 100x objective using immersion oil, with 200 fields per individual (100 per slide). The components of the leukocyte profile were identified according to the descriptions of Clark et al. (2009Clark P, Boardman W, Raidal S (2009) Atlas of clinical avian hematology. John Wiley & Sons, New Jersey , 184 pp.) and Campbell (2015Campbell TW (2015) Exotic animal hematology and cytology. John Wiley & Sons, New Jersey, 402 pp. https://doi.org/10.1002/9781118993705
https://doi.org/10.1002/9781118993705...
) provided in their respective atlases of avian hematology. In order to obtain total leukocyte count (TLC), the counts for each leukocyte type were summed, whereas the percentage of each type was obtained by dividing the count for each type by TLC. The H/L ratio was calculated by dividing the percentage of heterophils by the percentage of lymphocytes. All these calculations were done according to Machado-Filho et al. (2010Machado-Filho RA, Balsamão GM, Marini MÂ (2010) Seasonal differences in immune profiles and body conditions of migratory and permanent resident neotropical flycatchers. The Condor 112: 579-590. https://doi.org/10.1525/cond.2010.090146
https://doi.org/10.1525/cond.2010.090146...
).

Micronuclei analysis involved counting the number of micronuclei in each of the 5,000 erythrocytes on each slide for a total of 10,000 erythrocytes per individual (Baesse et al. 2015Baesse CQ, Tolentino VCM, Silva AM, Silva AA, Ferreira GA, Paniago LPM, Nepomuceno JC, Melo C (2015) Micronucleus as biomarker of genotoxicity in birds from Brazilian Cerrado. Ecotoxicology and Environmental Safety 115: 223-228. https://doi.org/10.1016/j.ecoenv.2015.02.024
https://doi.org/10.1016/j.ecoenv.2015.02...
). Each erythrocyte can contain one or more micronuclei, which were identified according to the criteria proposed by Wolf and Luepke (1997Wolf T, Luepke NP (1997) Formation of micronuclei in incubated hen’s eggs as ameasure of genotoxicity, Mutation Research 394: 163-175. https://doi.org/10.1016/S1383-5718(97)00136-8
https://doi.org/10.1016/S1383-5718(97)00...
).

The capacity of individuals to store resources and survive adverse situations can be evaluated by analyzing the body condition (Schulte-Hostedde et al. 2005Schultede-Hostedde AI, Zinner B, Millar JS, Hickling GJ (2005) Restitution of mass-size residuals: validating body condition indices. Ecology 86: 155-163. https://doi.org/10.1890/04-0232
https://doi.org/10.1890/04-0232...
). Body condition can be estimated by the Relative Mass Index (RMI), which was calculated by simple linear regression between the log-transformed values of right tarsus length and individual biomass. The residual values of the regression were used as RMI, with negative values representing poorer body conditions than positive values (Schulte-Hostedde et al. 2005Schultede-Hostedde AI, Zinner B, Millar JS, Hickling GJ (2005) Restitution of mass-size residuals: validating body condition indices. Ecology 86: 155-163. https://doi.org/10.1890/04-0232
https://doi.org/10.1890/04-0232...
).

Parametric tests (Student’s t test and Pearson correlation) were performed to determine whether the components of the leukocyte profile differed among the analyzed variables (sex, age, reproductive period, molting, ectoparasites, body condition and micronuclei). To meet the assumptions of the tests, percentage data (heterophils, lymphocytes, eosinophils, basophils, monocytes and H/L ratio) were transformed (arcsine of the square root), while the continuous variables (TLC and micronuclei) were log-transformed. The analyses were conducted using Systat 10.2 software with a level of significance of p < 0.05.

RESULTS

The following numbers of individuals were captured at each year of the research: 2013, 15 individuals; 2014, 14 indivi duals (eight in February and six in July); 2015, 60 individuals (25 in June, 18 in August, 12 in October and five in December). In total, 89 individuals were captured, of which 40 (44.9%) were females, 43 (48.3%) were males. It was not possible to determine the sex of six (6.74%) individuals. The sample included 58 (65.1%) adults, 14 (15.7%) juveniles and 17 (19.1%) individuals for which the development phase could not be determined. The birds for which sex and development could not be estimated were disregarded from analyses involving sexes and age groups. A total of 26 (29.2%) individuals possessed an incubation patch while 63 (70.7%) did not. Indications of molting were present in 23 (25.8%) individuals and absent in 66 (74.1%). Ticks were found infesting 17 (19.1%) individuals, while 72 (80.8%) were tick free. Micronuclei were present in 55 (61.7%) individuals and absent in 34 (38.2%).

The number of lymphocytes was greater for males (t = -2.001, df = 81, 0.049, Table 1, Fig. 1); for individuals without incubation patch (t = 2.565, df = 86, p = 0.012, Table 1, Fig. 2); and for those infested with ticks (t = -3.064, df = 86, p = 0.003, Table 1, Fig. 3). There were no differences for any of the leukocyte components with regards to age group (Table 2), molting (Table 2), and RMI (Table 3). There was a significant correlation between the number of micronuclei and TLC (r = 0.343, df = 43, p = 0.024), H/L (r = -0.273, df = 53, p = 0.044), heterophils (r = -0.335, df = 53, p = 0.012), basophils (r = 0.280, df = 53, p = 0.039) and monocytes (r = 0.277, df = 53, p = 0.041) (Table 3).

Figures 1-3
Number of lymphocytes for Antilophia galeata in relation to sex (1), presence/absence of incubation patch (2) and presence/absence of ticks (3). Boxes represent mean values while bars represent the standard error.

Table 1
Mean ± standard deviation for the components of the leukocyte profile of Antilophia galeata in relation to sex, reproductive period, and ticks. Statistically significant differences are shown in bold (t = Student’s t test, df = degrees of freedom, p = significance probability < 0.05).

Table 2
Mean ± standard deviation for the components of the leukocyte profile of Antilophia galeata in relation to age groups and molting (t = Student’s t test, df = degrees of freedom, p = significance probability < 0.05, * = insufficient data for the test).

Table 3
Pearson correlations (r) between components of the leukocyte profile of Antilophia galeta and the Relative Mass Index (RMI) and the amount of micronuclei. Statistically significant correlations are shown in bold (df = degrees of freedom; p = probability of significance < 0.05).

DISCUSSION

Although the leukocyte stress profile (H/L ratio) was not correlated to any of the analyzed variables, except for micronuclei, other components of the leukocyte profile varied according to the biological and ecological attributes of the individuals. The amount of lymphocytes was significantly greater in males, contrasting with what was expected: males were expected to have decreased amounts of leucocytes, consistent with studies that have shown that testosterone is an immunosuppressive hormone (Foo et al. 2016Foo YZ, Nakagawa S, Rhodes G, Simmons LW (2016) The effects of sex hormones on immune function: a meta-analysis. Biological Reviews 92: 551-571. https://doi.org/10.1111/brv.12243
https://doi.org/10.1111/brv.12243...
, Roved et al. 2017Roved J, Westerdahl H, Hasselquist D (2017) Sex differences in immune responses: hormonal effects, antagonistic selection, and evolutionary consequences. Hormones and Behavior 88: 95-105. https://doi.org/10.1016/j.yhbeh.2016.11.017
https://doi.org/10.1016/j.yhbeh.2016.11....
). Males of A. galeata are territorial and aggressive. In order to obtain a mate, they have to exhibit themselves for the females in large arenas where they fight each other in exhibitory flights (Marçal 2017Marçal BF (2017) História natural de Antilophia galeata (Lichtenstein, 1823) (Aves: Pipridae) com ênfase na sua biologia reprodutiva. PhD Thesis, Viçosa, Brazil, Universidade Federal de Viçosa. http://www.locus.ufv.br/handle/123456789/12878
http://www.locus.ufv.br/handle/123456789...
). Studies have shown that territoriality is correlated with increased testosterone concentrations (Edler et al. 2011Edler R, Goymann W, Schwabl I, Friedl TW (2011) Experimentally elevated testosterone levels enhance courtship behaviour and territoriality but depress acquired immune response in red bishops Euplectes orix. Ibis 153:46-58. https://doi.org/10.1111/j.1474-919X.2010.01075.x
https://doi.org/10.1111/j.1474-919X.2010...
). Females, in contrast, had the lowest values of lymphocytes, suggesting that the activities that they perform, including incubation and caring for the nestlings, are more stressful (Marçal 2017Marçal BF (2017) História natural de Antilophia galeata (Lichtenstein, 1823) (Aves: Pipridae) com ênfase na sua biologia reprodutiva. PhD Thesis, Viçosa, Brazil, Universidade Federal de Viçosa. http://www.locus.ufv.br/handle/123456789/12878
http://www.locus.ufv.br/handle/123456789...
). Other studies have also shown reduced amounts of lymphocytes in female birds (Hanssen et al. 2003Hanssen SA, Folstad I, Erikstad KE (2003) Reduced immunocompetence and cost of reproduction in common eiders. Oecologia 136: 457-464. https://doi.org/10.1007/s00442-003-1282-8
https://doi.org/10.1007/s00442-003-1282-...
, 2005Hanssen SA, Hasselquist D, Folstad I, Erikstad KE (2005) Cost of reproduction in a long-lived bird: incubation effort reduces immune function and future reproduction. Proceedings of the Royal Society of London B: Biological Sciences 272: 1039-1046. https://doi.org/10.1098/rspb.2005.3057
https://doi.org/10.1098/rspb.2005.3057...
), which was attributed to an immunosuppression associated with egg incubation. In the present study, individuals in charge of an incubation patch also had reduced lymphocytes. Although this structure occurs in both sexes of A. galeata, the present study found that 72% (n=25) of the individuals in charge of an incubation patch were females.

Differences in the number of lymphocytes were also associated with the presence of ectoparasites, with individuals with ticks having higher values. The number of lymphocytes was expected to be lower in infested individuals since, according to the reviews of Kotál et al. (2015Kotál J, Langhansová H, Lieskovská J, Andersen JF, Francischetti IM, Chavakis T, et al. (2015) Modulation of host immunity by tick saliva. Journal of Proteomics 128: 58-68. https://doi.org/10.1016/j.jprot.2015.07.005
https://doi.org/10.1016/j.jprot.2015.07....
) and Wikel (2017Wikel S (2017) Tick saliva: a modulator of host defenses. In: Wikel S, Aksoy S, Dimopoulos G (Eds) Arthropod Vector: Controller of Disease Transmission. Academic Press, Oxford , 145-168. https://doi.org/10.1016/B978-0-12-805360-7.00009-5
https://doi.org/10.1016/B978-0-12-805360...
), several studies have found that proteins present in the saliva of ticks inhibit or reduce the proliferation of host lymphocytes. Of the infested individuals, 70.5% (n = 17) were males, which had a greater number of lymphocytes than females. This may be related to the absence of an immunosuppressive factor, such as incubation. Collectively, these numbers suggest that the variations in the number lymphocytes in these birds is more affected by reproduction than by the action of ticks.

Montolio et al. (2017Montolio SA, López RM, Cray C, González SL, Francisco ON, Sánchez IM, et al. (2017). Hematologic reference intervals and age effect in European Strigiformes. Veterinary Clinical Pathology 46: 483-495. https://doi.org/10.1111/vcp.12516
https://doi.org/10.1111/vcp.12516...
) suggested that age is an important biological factor that can influence hematological variables, especially in early life when growth and development occur. They also reported greater amounts of leukocytes in juvenile owls, and suggested that this may be due to the fact that young individuals have greater sensitivity of to stress (Dickens et al. 2010Dickens M, Romero LM (2010) Stress responsiveness decrease with age in precocial, juvenile chukar. The Wilson Journal of Ornithology 122: 762-766. https://doi.org/10.1676/09-185.1
https://doi.org/10.1676/09-185.1...
). Nonetheless, there are also reports in the literature of adults having higher leukocyte values than juveniles. Campo and Davila (2002Campo JL, Davila SG (2002) Estimation of heritability for heterophil: lymphocyte ratio in chickens by restricted maximum likelihood: effects of age, sex, and crossing. Poultry Science 81: 1448-1453. https://doi.org/10.1093/ps/81.10.1448
https://doi.org/10.1093/ps/81.10.1448...
) found that the leukocyte levels of Gallus gallus (Linnaeus, 1758) increased continuously from the onset of sexual maturity. Schmidt et al. (2017Schmidt EM, Paulillo AC, Santin E, Dittrich RL, Oliveira EG (2007) Hematological and serum chemistry values for the ring-necked pheasant (Phasianus colchicus): variation with sex and age. International Journal of Poultry Science 6: 137-139. https://doi.org/10.3923/ijps.2007.137.139
https://doi.org/10.3923/ijps.2007.137.13...
) found greater values for heterophils, eosinophils and monocytes in adult pheasants, Phasianus colchicus Linnaeus, 1758, which were attributed to stress from reproductive events. No differences in leukocyte components were found between the age groups in the present study, suggesting that stress related to the allocation of resources for the growth of young can be equated to stress from reproduction in adults.

Molting is considered an energy demanding process, since it producing new feathers requires energy (Hemborg and Lundberg 1998Hemborg C, Lundberg A (1998) Costs of overlapping reproduction and moult in passerine birds: an experiment with the pied flycatcher. Behavioral Ecology and Sociobiology 43: 19-23. https://doi.org/10.1007/s002650050462
https://doi.org/10.1007/s002650050462...
). Individuals undergoing molting were expected to exhibit a leukocyte stress profile. Contrasting with this expectation, no effect of molting on the leukocyte profile was found. There have been other studies supporting our findings that there is no relationship between molting and leukocyte profile (Machado-Filho et al. 2010Machado-Filho RA, Balsamão GM, Marini MÂ (2010) Seasonal differences in immune profiles and body conditions of migratory and permanent resident neotropical flycatchers. The Condor 112: 579-590. https://doi.org/10.1525/cond.2010.090146
https://doi.org/10.1525/cond.2010.090146...
, Kulaszewicz et al. 2015Kulaszewicz I, Wojczulanis-Jakubas K, Jakubas D (2015) Variation of the savi’s warbler (Locustella luscinioides) leucocyte profiles and body condition in relation to age, sex and molt. Annales Zoologici Fennici 52: 325-338. https://doi.org/10.5735/086.052.0507
https://doi.org/10.5735/086.052.0507...
, Włodarczyk et al. 2017Włodarczyk R, Podlaszczuk P, Kaczmarek K, Janiszewski T, Minias P (2017) Leukocyte profiles indicate nutritional, but not moulting stress in a migratory shorebird, the Common Snipe (Gallinago gallinago). Journal of Ornithology 1-10. https://doi.org/10.1007/s10336-017-1516-x
https://doi.org/10.1007/s10336-017-1516-...
). According to Barta et al. (2008Barta Z, Mcnamara JM, Houston AI, Weber TP, Hedenström A, Feró O (2008) Optimal molt strategies in migratory birds. Philosophical Transactions of the Royal Society B: Biological Sciences 363: 211-229. https://doi.org/10.1093/icb/icu059
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), individuals in poor nutritional status may postpone or discontinue molting. This means that individuals entering the molting period may be in relatively good condition and under low physiological stress, and that even though molting may be stressful, the negative effect it causes may be counterbalanced by the favorable status of the birds entering the process (Włodarczyk et al. 2017Włodarczyk R, Podlaszczuk P, Kaczmarek K, Janiszewski T, Minias P (2017) Leukocyte profiles indicate nutritional, but not moulting stress in a migratory shorebird, the Common Snipe (Gallinago gallinago). Journal of Ornithology 1-10. https://doi.org/10.1007/s10336-017-1516-x
https://doi.org/10.1007/s10336-017-1516-...
).

Studies have shown that nutritional status or body condition may influence the leukocyte profile of birds, and that there is a negative relationships between the H/L ratio and body condition indexes; in other words, the higher the stress, the worse the body condition, and vice versa (Plischke et al. 2010Plischke A, Quillfeldt P, Lubjuhn T, Merino S, Masello JF (2010) Leucocytes in adult burrowing parrots Cyanoliseus patagonus in the wild: variation between contrasting breeding seasons, gender, and individual condition. Journal of Ornithology 151: 347-354. https://doi.org/10.1007/s10336-009-0461-8
https://doi.org/10.1007/s10336-009-0461-...
, Gladbach et al. 2010Gladbach A, Gladbach DJ, Quillfeldt P (2010) Variations in leucocyte profiles and plasma biochemistry are related to different aspects of parental investment in male and female upland geese Chloephaga picta leucoptera. Comparative Biochemistry and Physiology, Part A: Molecular 156: 269-277. https://doi.org/10.1016/j.cbpa.2010.02.012
https://doi.org/10.1016/j.cbpa.2010.02.0...
, Krams et al. 2012Krams I, Vrublevska J, Cirule D, Kivleniece I, Krama T, Rantala MJ, et al. (2012) Heterophil/lymphocyte ratios predict the magnitude of humoral immune response to a novel antigen in great tits (Parus major). Comparative Biochemistry and Physiology , Part A: Molecular 161: 422-428 https://doi.org/10.1016/j.cbpa.2011.12.018
https://doi.org/10.1016/j.cbpa.2011.12.0...
, Jakubas et al. 2015Jakubas D, Wojczulanis-Jakubas K, Kośmicka A (2015) Factors affecting leucocyte profiles in the little auk, a small Arctic seabird. Journal of Ornithology 156: 101-111. https://doi.org/10.1007/s10336-014-1101-5
https://doi.org/10.1007/s10336-014-1101-...
, Włodarczyk et al. 2017Włodarczyk R, Podlaszczuk P, Kaczmarek K, Janiszewski T, Minias P (2017) Leukocyte profiles indicate nutritional, but not moulting stress in a migratory shorebird, the Common Snipe (Gallinago gallinago). Journal of Ornithology 1-10. https://doi.org/10.1007/s10336-017-1516-x
https://doi.org/10.1007/s10336-017-1516-...
, Zhao et al. 2017Zhao Y, Li M, Sun Y, Wu W, Kou G, Guo L, Zhao B (2017) Life-history dependent relationships between body condition and immunity, between immunity indices in male Eurasian tree sparrows. Comparative Biochemistry and Physiology , Part A: Molecular & Integrative Physiology 210: 7-13. https://doi.org/10.1016/j.cbpa.2017.05.004
https://doi.org/10.1016/j.cbpa.2017.05.0...
). However, no significant relationships were found between leukocyte components and body condition in the present study. It may be that the absence of such a relationship is indicative of insufficient stress to alter body condition, as previous studies also suggested (Ewenson et al. 2001Ewenson FL, Zann RA, Lannery GR (2001) Body condition and immune response in wild zebra finches: effects of capture, confinement and captive-rearing. Naturwissenschaften 88: 391-394. https://doi.org/10.1007/s001140100250
https://doi.org/10.1007/s001140100250...
, Greenman et al. 2005Greenman CG, Martin LB, Hau M (2005) Reproductive state, but not testosterone, reduces immune function in male house sparrows (Passer domesticus). Physiological and Biochemical Zoology 78: 60-68. https://doi.org/10.1086/425194
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, Owen and Moore 2006Owen JC, Moore FR (2006) Seasonal differences in immunological condition of three species of thrushes. Condor 108: 389-398. https://doi.org/10.1650/0010-5422(2006)108[389:SDIICO]2.0.CO,2
https://doi.org/10.1650/0010-5422(2006)1...
, Machado-Filho et al. 2010Machado-Filho RA, Balsamão GM, Marini MÂ (2010) Seasonal differences in immune profiles and body conditions of migratory and permanent resident neotropical flycatchers. The Condor 112: 579-590. https://doi.org/10.1525/cond.2010.090146
https://doi.org/10.1525/cond.2010.090146...
).

Significant positive correlations were found between the quantity of micronuclei and TLC, percentage of basophils and percentage of monocytes. The formation of micronuclei occurs through spontaneous chromosomal changes or environmental disturbances, with findings of increased micronuclei levels due to anthropization (Pereira et al. 2013Pereira BB, Campos EO, Morelli S (2013) In situ biomonitoring of the genotoxic effects of vehicular pollution in Uberlândia, Brazil, using a Tradescantia micronucleus assay. Ecotoxicology and Environmental Safety 87: 17-22. https://doi.org/10.1016/j.ecoenv.2012.10.003
https://doi.org/10.1016/j.ecoenv.2012.10...
, Baesse et al. 2015Baesse CQ, Tolentino VCM, Silva AM, Silva AA, Ferreira GA, Paniago LPM, Nepomuceno JC, Melo C (2015) Micronucleus as biomarker of genotoxicity in birds from Brazilian Cerrado. Ecotoxicology and Environmental Safety 115: 223-228. https://doi.org/10.1016/j.ecoenv.2015.02.024
https://doi.org/10.1016/j.ecoenv.2015.02...
, Martinez-Haro et al. 2017Martínez-Haro M, Balderas-Plata MA, Pereda-Solís ME, Arellano-Aguilar RO, Hernández-Millán CL (2017) Anthropogenic influence on blood biomarkers of stress and genotoxicity of the burrowing owl (Athene Cunicularia). Biodiversity & Endangered Species Journal 5: 1-4. https://doi.org/10.4172/2332-2543.1000196
https://doi.org/10.4172/2332-2543.100019...
). Environmental changes also exert an influence on the leukocyte profile, as there are records of associations between heavy metal pollution and increased H/L ratio for various species of birds (Eeva et al. 2005Eeva T, Hasselquist D, Langefors Å, Tummeleht L, Nikinmaa M, Ilmonen P (2005) Pollution related effects on immune function and stress in a free-living population of pied flycatcher Ficedula hypoleuca. Journal of Avian Biology 36: 405-412. https://doi.org/10.1111/j.0908-8857.2005.03449.x
https://doi.org/10.1111/j.0908-8857.2005...
, Bauerová et al. 2017Bauerová P, Vinklerová J, Hraníček J, Čorba V, Vojtek L, Svobodová J, Vinkler M (2017) Associations of urban environmental pollution with health-related physiological traits in a free-living bird species. Science of the Total Environment 601: 1556-1565. https://doi.org/10.1016/j.scitotenv.2017.05.276
https://doi.org/10.1016/j.scitotenv.2017...
). The relationships found in the present study between micronuclei and leukocytes may be attributed to a common stressor, such as air pollution, since birds easily absorb gasses or particles present in the air, when accumulating a large volume of air in their body for flight (Brown et al. 1997Brown RE, Brain JD, Wang N (1997) The avian respiratory system: a unique model for studies of respiratory toxicosis and for monitoring air quality. Environmental Health Perspectives 105: 188-200. https://doi.org/10.1289/ehp.97105188
https://doi.org/10.1289/ehp.97105188...
). Furthermore, in the region of the present study, Baesse et al. (2019Baesse CQ, Tolentino VCM, Morelli S, Melo C (2019) Effect of urbanization on the micronucleus frequency in birds from forest fragments. Ecotoxicology and Environmental Safety 171: 631-637. https://doi.org/10.1016/j.ecoenv.2019.01.026
https://doi.org/10.1016/j.ecoenv.2019.01...
) found that birds living in forest areas near to the city presented higher micronuclei frequency as a function of the greater exposure to emission of gases originating from the heavy vehicular traffic.

Although TLC, basophil and monocyte percentages correlated positively with micronuclei in the present study, heterophil percentage and H/L ratio were negatively correlated with micronuclei quantity. Heterophils are the primary cells that proliferate during acute inflammatory responses (Harmon 1998Harmon BG (1998) Avian heterophils in inflammation and disease resistance. Poultry Science 77: 972-977. https://doi.org/10.1093/ps/77.7.972
https://doi.org/10.1093/ps/77.7.972...
), while erythrocyte turnover can take 25 to 45 days in birds (Jones 2015Jones MP (2015) Avian hematology. Veterinary Clinics: exotic animal practice 18: 51-61. https://doi.org/10.1016/j.cvex.2014.09.012
https://doi.org/10.1016/j.cvex.2014.09.0...
). Thus, it is probable that when erythrocytes containing micronuclei appear, heterophils have already passed through their highest peaks and, consequently, also the highest H/L ratios, suggesting that although the stressor may be the same, different responses to the stress may manifest at different times. However, the relationships between micronuclei and leukocytes in birds are not yet well described and understood, and more studies are needed to clarify them.

The present study was the first to examine the leukocyte profile of A. galeata, and to determine the aspects of the species’ biology and ecology that influence the leukocytes produced by these birds. Certain components of the leukocyte profile were shown to vary in relation to certain characteristics and life periods of A. galeata. The results suggest that reproduction may be an immunosuppressive factor for the species, thereby producing sexual differences in lymphocyte availability for individuals. Furthermore, biomarkers of genotoxic damage (miocronuclei) were correlated with the H/L ratio, indicating that individuals may be sensitive to environmental disturbances. In this way, it can be concluded that leukocyte profiles are a useful tool for answering ecological questions that can be applied to the conservation of species in degraded environments.

ACKNOWLEDGEMENTS

We declare that all proceedings performed with the birds have followed and respected the international rules of animals well-being by means of the parameters required from Animal Ethics Committee. We are grateful to the members of the Laboratório de Ornitologia e Bioacústica (Universidade Federal de Uberlândia - UFU) for their field assistance and to the Programa de Pós-graduação em Ecologia e Conservação de Recursos Naturais (UFU) for their continued support. This work was supported by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (Finance Code 001), the Fundação de Amparo à Pesquisa do Estado de Minas Gerais (APQ-01654-12) and the Conselho Nacional de Desenvolvimento Científico e Tecnológico (PELD 403733/2012-0).

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Publication Notes

  • Available online:

    December 23, 2020
  • Zoobank Register:

    http://zoobank.org/276689CD-9863-4D3D-B27C-4CF7556D5AA6
  • Publisher:

    © 2020 Sociedade Brasileira de Zoologia. Published by Pensoft Publishers at https://zoologia.pensoft.net

Edited by

Editorial responsibility:

Luís Fábio Silveira

Publication Dates

  • Publication in this collection
    18 Jan 2021
  • Date of issue
    2020

History

  • Received
    09 Sept 2019
  • Accepted
    25 Sept 2020
  • Published
    23 Dec 2020
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