Abstract
Research on immune response in polar fauna is gaining great importance due to different scenarios of environmental change. Total leukocyte counts in blood smears are one of the most widespread practices and provide useful information about the health status of individuals. However, there is no methodological agreement for these analyses. Total leukocyte counts can be performed at ×400 magnification in optical microscopy using 10,000 erythrocytes for standardizing. However, counting such number of erythrocytes is costly and time-consuming. Here, we describe a new technique to simplify leukocyte counts in blood smears from Antarctic wildlife based on the number of microscope fields instead of the number of erythrocytes which reduces considerably the time spent. We have counted total leukocytes using both methods in the three penguin species of the genus Pygoscelis—Adélie (P. adeliae), gentoo (P. papua), and chinstrap penguin (P. antarcticus)—and four Antarctic mammal species: crabeater seal (Lobodon carcinophaga), leopard seal (Hydrurga leptonyx), weddell seal (Leptonychotes weddellii), and southern elephant seal (Mirounga leonina) for validation. Our results show a high correlation between the total leukocyte counts using 10,000 erythrocytes or 10 microscope fields for standardizing. These results show the reliability of the latter method for counting the total number of leukocytes in different species of birds and mammals saving time and effort.
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The samples and data are available from corresponding author.
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Acknowledgements
This work is a contribution to the "PINGUCLIM" project. We much appreciate the hospitality of the Spanish Antarctic Station “Gabriel de Castilla” and the Argentinean Antarctic Stations “Esperanza,” “Primavera,” and “Carlini.” We thank the transportation by the Spanish Polar ship “Hespérides” and the Maritime Technology Unit (CSIC) and Dirección Nacional del Antártico for logistic support. We are very grateful to Martín Durante, Jorge Rossi, Maximiliano Perier, Sebastián Poljak, Julieta Cebuhar, Pablo Moscoso, and Lucas Lanusse for their invaluable assistance during the fieldwork. JMB acknowledges to Ciaran Stordy and Gloria Casabella-Herrero for their commentaries on the manuscript. We thank Dieter Piepenburg (Editor of Polar Biology), Silvia Olmastroni, and an anonymous reviewer for their comments and suggestions that improved the manuscript.
Funding
The study was funded by the Spanish Ministry of Economy and Competitiveness through projects CTM2011-24427, CTM2015-64720, and PID2019-108597 and by the Dirección Nacional del Antártico, Instituto Antártico Argentino (PICTA 2010-01).
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AB conceived and designed research. JMB and FS analyzed the data. FS, RCC, AMS, JMB, and MR analyzed samples. AB, RCC, FS, and JN performed the field work and sampling. JMB and FS wrote the initial draft and manuscript. AB, JMB, FS, RCC, and JN reviewed and participated in the commentary or revision; JMB performed the visualization and data presentation. JMB and AB administrated the project. All authors read and approved the manuscript.
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Menéndez-Blázquez, J., Soto, F., Negrete, J. et al. Leukocyte counts in blood smears of Antarctic seals and penguins: a new less time-consuming method. Polar Biol 44, 2195–2198 (2021). https://doi.org/10.1007/s00300-021-02950-0
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DOI: https://doi.org/10.1007/s00300-021-02950-0